EFFECT OF ELECTRICAL STIMULATION 
ON CONSUMER ACCEPTANCE OF 
MUTTON FROM CLASS-AB SHEEP 
CARCASSES 
M.DAVEL 
(B.Sc. Home Economics) RD 
Mini-dissertation submitted in the School for Physiology, Nutrition and 
Consumer Sciences at the Potchefstroom University for Christian Higher 
Education in partial fulftlment of the requirements for the degree Magister 
Consumer Sciences (Foods). 
Supervisor: Prof. M.J.C. Bosman 
Assistant Supervisor: Prof. E.C. Webb 
2003 
Potchefstroom 
DEDICATION 
To Daniel-Joe who was three months old when I started my studies 
and who does not know life without it. 
To Chris for your love and support. 
To Mother for your encouragement and example. 
I 
ACKNOWLEDGEMENTS 
I would like to thank the following people who contributed to this study: 
♦ Prof. Lena Bosman for her continuous support, guidance and motivation. 
♦ Prof. Eddie Webb for his valued inputs, time and exceptional knowledge. 
♦ Mrs Elise Pienaar for all her hard work in preparing the samples and assistance during 
sensory sessions. 
♦ Helah van der Walt for her assistance in the library. 
♦ Ferdinand Postma library for assistance in obtaining literature. 
♦ Dr. Suria Ellis for the statistical analysis. 
♦ All the consumers participating in the study. Without them there would have been no 
study. 
♦ The staff at Kagiso Khulane Supervision Food Services for the motivation and 
understanding. 
♦ My family for their encouragement and endless support. 
♦ Most of all I would like to thank God for giving me the opportunity, strength, 
knowledge and perseverance to complete this study. 
II 
SUMMARY 
Background 
The inconsistency in the eating quality of meats, predominantly tenderness, is probably the most 
important problem faced by the meat industry worldwide. Consumers consider tenderness to be 
the single most important component of meat quality. An alternative for increasing meat 
tenderness and/or preventing cold shortening may exist in the form of electrical stimulation of the 
carcass shortly following slaughter. Other advantages of electrical stimulation such as increased 
shelf life, bright red colour and decreased bacterial growth are all quality characteristics 
demanded by consumers. 
Objective 
The objective of this research was to study the effect of electrical stimulation on consumer 
acceptance of, preference for and consumption intent regarding mutton of the recently introduced 
AB-class sheep carcasses. 
Methods 
A total of 22 wethers of between 45 and 50 kg live weight were selected from a homogenous 
group of Dorpers. Carcasses were divided in two groups, of which one group was electrically 
stimulated (0.4amp/h for 45sec; ES) and the other group was not electrically stimulated (NES). 
The left M longissimus dorsi samples of both groups were oven-roasted and total cooking losses 
were determined. A consumer panel rated the degree of acceptance of each cooked mutton 
sample regarding juiciness, tenderness and flavour. Overall acceptance was calculated. A 
preference test and food action rating test were also conducted. 
Results 
Results of the hedonic tests indicated that consumer acceptance regarding juiciness, tenderness, 
flavour and overall acceptability of mutton samples were not significantly influenced by the 
electrical stimulation. Samples from both the ES and NES treatments were highly acceptable to 
the consumers. No significant differences in preference were obtained. The present results 
suggest that electrical stimulation does not have a significant influence on consumer acceptance 
or preference for the AB-class mutton. Shear force values of the electrically stimulated and non-
stimulated samples also showed no significant numerical differences. The variation within shear 
force values of the electrically stimulated group of samples was, however, less than within the 
m 
non-stimulated group, indicating that electrical stimulation can successfully be applied to lessen 
variation in tenderness within class-AB. Consumption intent towards both samples was scored 
very high, which revealed a positive attitude towards both the electrically stimulated and non-
electrically stimulated class-AB mutton samples. No significant difference in the % cooking 
losses was observed between the ES and NES samples. 
Conclusion 
Electrical stimulation can be applied successfully to limit variation in tenderness of mutton within 
class-AB sheep carcasses. The class-AB mutton is of a very high quality and is highly accepted 
by consumers. 
Keywords 
Electrical stimulation, class-AB sheep, mutton, tenderness, consumer acceptance. 
IV 
OPSOMMING 
Agtergrond 
Die variasie in die eetkwaliteit van vleis, veral sagtheid, blyk die grootste probleem in die 
vleisindustrie te wees. Sagtheid is die belangrikste kwaliteitseienskap vir verbruikers. 
Elektriese stimulering van karkasse kan as alternatiewe metode gebruik word om die 
taaiheid van vleis a.g.v koelkrimping van die spierweefsel kort na die slagting te 
voorkom. Addisionele voordele van elektiese stimulering wat ook verbruikersvereistes 
is, is 'n verlengde rakleeftyd, helder rooi kleur en verlaagde bakteriele groei. 
Doel 
Die doel van die studie was om die effek van elektriese stimulering (ES) op 
verbruikersaanvaarbaarheid van die vleis van die AB-klas skaap te ondersoek. 
Metode 
'n Totaal van 22 hammels tussen 45 en 50 kg lewende massa is geselekteer vanuit 'n groep 
homogene Dorpers. Die karkasse is in twee groepe verdeel waarvan die een groep elektries 
gestimuleer (0.4amp/h vir 45 sek; ES) is. Die linker M longissimus dorsi van beide groepe is ge-
oondrooster en totale gaarmaakverliese is bepaal. 'n Verbruikerspaneel het elke gaar 
skaapvleismonster geevalueer ten opsigte van die graad van aanvaarbaarheid van die sappigheid, 
sagtheid en smaak. Algehele aanvaarbaarheid is daama bereken. 'n Voorkeur- en 
reaksieskattingstoets van elk van die twee groepe is ook bereken. 
Resultate en bespreking 
Resultate van die hedoniese toetse het aangedui dat elektriese stimulering geen betekenisvolle 
effek op die aanvaarbaarheid van die sappigheid, sagtheid, smaak of totale aanvaarbaarheid van 
die skaapvleismonsters gehad het nie. Beide die gestimuleerde en nie-gestimuleerde 
vleismonsters was vir die verbruikers hoogs aanvaarbaar. Daar was ook geen betekenisvolle 
verskil in die voorkeur vir 'n spesifieke monster nie. Die huidige resultate bewys dat elektriese 
stimulering nie 'n betekenisvolle invloed op die verbruiker se aanvaarbaarheid van en die 
voorkeur vir die AB-klas skaap het nie. Snyweerstandresultate van die elektries gestimuleerde 
(ES) groep en die nie-elektries gestimuleerde (NES) groep het geen numeries betekenisvolle 
verskille opgelewer nie. Die variasie tussen die snyweerstandwaardes binne die elektries 
gestimuleerde groep was egter laer as binne die nie-gestimuleerde groep. Hierdie resultate dui 
V 
dus daarop dat elektriese stimulering van die AB-klas skaapkarkasse sal hydra tot meer konstante 
kwaliteit en verminderde variasie in sagtheid binne die AB-klas. Die mate waartoe die 
verbruikers bereid was om beide vleismonsters te eet was baie hoog en dit dui dus op 'n positiewe 
houding teenoor beide die elektries gestimulleerde en nie-gestimuleerde AB-klas 
skaapvleismonsters. Resultate dui ook daarop dat die verbruikers nie 'n spesifieke voorkeur vir 
'n bepaalde skaapvleismonster gehad bet nie. Geen betekenisvolle verskille in die 
gaarmaakverliese van die elektries gestimuleerde en nie-elektries gestimuleerde 
skaapvleismonsters is verkty nie. 
Gevolgtrekking 
Elektriese stimulering kan suksesvol aangewend word om moontlike variasies in die sagtheid van 
die AB-klas skaap te verminder. Die AB-klas skaap is van baie hoe gehalte en is ook hoogs 
aanvaarbaar vir die verbruiker. 
Sleutelterme 
Elektriese stimulering, AB-klas skaap, skaapvleis, sagtheid, verbruikersaanvaarbaarheid. 
VI 
TABLE OF CONTENTS Page 
ACKNOWLEDGEMENTS II 
SUMMARY III 
OPSOMMING V 
LIST OF TABLES AND FIGURES X 
LIST OF ABBREVIATIONS XI 
CHAPTER 1: INTRODUCTION 1 
1.1 Background and motivation 2 
1.1.1 Electrical stimulation and its effects on meat tenderness 
1.1.2 Consumer perceptions and expectation of meat quality 
1.2 Hypothesis 4 
1.3 Aim and objective 4 
1.4 Structure of the mini-dissertation 5 
1.5 Authors' contribution 5 
1.6 References 7 
CHAPTER 2: LITERA TORE REVIEW 8 
2.1 Introduction 9 
2.2 Food Quality 9 
2.2.1 Consumers' perception and expectations of food quality 10 
2.2.2 Consumers as sensory panellists 11 
2.3 Meat quality 12 
2.4 Factors influencing meat quality with special reference to tenderness 15 
2.4.1 Age and species 16 
2.4.2 Genotype 17 
2.4.3 Type of muscle 17 
2.4.4 Feeding 18 
2.4.5 Pre-slaughter stress conditions 18 
2.4.6 Electrical stimulation 19 
2.4.7 Ageing 19 
VII 
2.5 Electrical stimulation 20 
2.5.1 History of Electrical Stimulation 21 
2.5.2 Principles of electrical stimulation 22 
• Physiology of electrical stimulation 22 
• Inconsistencies in results with electrical stimulation 23 
• Low voltage electrical stimulation versus high voltage electrical stimulation 23 
2.5.3 Effect of electrical stimulation on meat 26 
• Tenderness 26 
• Post mortem glycolysis 27 
• PH 27 
• Protease and calpastatin activity 28 
• Breed differences 28 
2.5.4 Advantages of electrical stimulation 29 
• Free iron 29 
• Colouring 29 
• Bacterial growth 29 
• Shelf life 29 
• Tenderness 29 
2.6 Classification of red meat 30 
2.6.1 Classification of sheep carcasses 31 
• Dentition 
• Age 
2.6.2 Class-AB Sheep 33 
2.7 Consumption ofred meat in South Africa 33 
2.8 Conclusion 35 
2.9 References 37 
CHAPTER 3: THE EFFECT OF ELECTRICAL STIMULATION ON 
CONSUMER ACCEPTANCE OF MUTTON FROM CLASS-AB 
SHEEP CARCASSES 43 
3.1 Abstract 44 
VIII 
3.2 Introduction 44 
3.3 Materials and methods 46 
3.4 Results and discussion 47 
3.5 Conclusion 48 
3.6 Acknowledgements 49 
3.7 References 49 
CHAPTER 4: GENERAL SUMMARY, CONCLUSIONS AND 
RECOMMENDATIONS 51 
4.1 Introduction 5? 
4.2 Summary of findings 52 
4.3 Conclusions 53 
4.4 Recommendations 54 
ADDENDUM A: Recruiting of consumers for the sensory evaluation on the acceptability of 
mutton. 
ADDENDUM B: Werwing van verbruikers vir die sintuiglike evaluering van die 
aanvaarbaarheid van skaapvleis. 
ADDENDUM C: Consumer questionnaire. 
ADDENDUM D: Verbruikersvraelys. 
ADDENDUM E: Cooking loss calculation. 
IX 
LIST OF TABLES AND FIGURES 
CHAPTER! 
Table 1: Names and role description of people involved in the study on the effect of electrical 
stimulation on the consumer acceptance of mutton from class-AB sheep carcasses. 
CHAPTER2 
Figure 1: Consumer's perception of fresh meat quality 
Table 1: Comparison of studies done to determine the effect of electrical stimulation on meat 
quality 
Table 2: South African Classification Characteristics of Beef, Lamb, Sheep and Goat Meat 
Table 3: Average age classification of sheep 
Table 4: Classification according to age and dentition of sheep 
Table 5: Percentage of animals slaughtered in each meat class in South Africa 
CHAPTER3 
Table 1: Comparison of studies done to determine the effect of electrical stimulation on meat 
quality 
Table 2: Description of consumer panel (n=229) 
Table 3: Mean (± SD) values for the acceptance of sensory attributes, shear force values and 
total cooking losses of M. longissimus dorsi samples from electrically stimulated and 
non-electrically stimulated class-AB sheep carcasses 
Figure 1: Consumer preference for electrically stimulated (ES) and non-stimulated 
(NES) class-AB mutton samples 
X 
LIST OF ABBREVIATIONS 
ES: electrically stimulated 
NES: non-electrically stimulated 
HVES: high voltage electrical stimulation 
LYES: low voltage electrical stimulation 
PM: post mortem 
WBSF: Warner Bratzler shear force 
V: volts 
XI 
CHAPTER! 
INTRODUCTION 
1 
CHAPTER 1 
INTRODUCTION 
1.1 BACKGROUND AND MOTIVATION 
The aim of this chapter is to motivate the actuality and relevance of this research to the ongoing 
debate regarding the quality and acceptability of the recently introduced class-AB mutton. This 
study was motivated by the need to determine consumer acceptance of the meat from the recently 
introduced class-AB mutton into the current South African meat classification system, in order to 
accommodate the large proportion of good quality carcasses from sheep with one or two 
permanent incisors. During the past years the Food Science Research Group in the School for 
Physiology, Nutrition and Consumer Sciences from the Potchefstroom University for Christian 
Higher Education (PU for CHE), together with the Department of Animal and Wildlife Sciences 
from the University of Pretoria, have researched numerous factors that influence the sensory 
characteristics of mutton, such as the influence of different diets on meat and carcass fat 
composition and fatty acid composition. 
The relationship between meat science, consumer studies, sensory evaluation of products as well 
as the current trend towards the production of more "natural" products presented the unique 
opportunity to address current concerns regarding meat quality. Access to a representative group 
of consumers and national and international established networks and colleagues, facilitated a 
new direction in research, namely the effect of electrical stimulation on the consumer acceptance 
of mutton from class-AB sheep carcasses. This study comprised of the evaluation of the 
acceptability of electrically stimulated and non-stimulated samples by using a consumer panel 
and the objective measurement of the samples' shear force values. 
As will be pointed out in this chapter, inconsistencies in the eating quality of meat, predominantly 
tenderness, is probably the most important problem faced by the meat industry as well as the most 
important requirement insisted on by the consumer (Morgan, 1998:10; Webb, 1998:1). 
After a general motivation for the research, an in-depth discussion on electrical stimulation, the 
class-AB sheep carcass and consumer expectations of meat quality will set the background 
against which the advantages of electrical stimulation as a possible solution to lessen 
inconsistencies in meat tenderness will be described in a literature study (Chapter 2). The 
2 
structure of the manuscript will be explained, followed by the author and co-authors ' 
contributions to the manuscript. 
1.1.1 Electrical stimulation and its effects on meat tenderness 
Meat toughness is the result of the combined effects of two intrinsic factors in muscle, namely the 
connective tissue and muscle fibre. Connective tissue includes collagen (which is inextensible 
and non-branching) and elastin (branching, elastic and yellow in colour). Animal age, muscle 
type, gender and rate of collagen synthesis are the main factors influencing collagen 
characteristics in meat. Variation in collagen characteristics (increased cross-link formation, 
heat stability and insolubility in older animals) and increased collagen concentration are 
responsible for the toughening of meat as animals age (Webb, 1998:3). Postmortem myofibrillar 
toughness is the net result of two opposing processes, namely rigor mortis (toughening process) 
and the natural tenderising process. The binding of myosin to actin is associated with an increase 
in toughness, depending on the number of cross-bridges formed. 
Tenderness is generally improved by slow chilling, electrical stimulation, ageing methods and 
calcium injection. Together with ageing, electrical stimulation contributes to the improved 
tenderness of meat, much more so than genotype or feeding (Epley, 2002:3). A consistent 
method for increasing the tenderness to a more acceptable level would transform mutton 
carcasses into a product that is highly acceptable for the consumer (Ockerman et al. , 2001: 184). 
Electrical stimulation can improve tenderness with approximately 10% and is particularly 
effective for carcasses that are inherently less tender. Electrical stimulation enhances meat 
colour, improves tenderness and blood yield, and also decreases back breaks in carcasses during 
hide removal. Low-voltage electrical stimulation is currently used to prevent cold-induced 
shortening of muscles from lean carcasses (Morgan, 1998:16), thus reducing the variation in 
tenderness within a specific group. 
Electrical stimulation promotes the activity of endogenous proteolytic enzymes, including 
cal pain. The increased cal pain activity is due to a depolarisation of the cell membrane that causes 
the release of calcium into the cell, activating calcium-dependent proteases (Kerth et al. , 
1999:2951 ). Increased carcass temperature due to the electrical stimulation stimulates the 
dilation of veins, improving the maximal bleeding of the carcass (Menday, 1979:5). 
3 
1.1.2 Consumer perception and expectations of meat quality 
Accepting a food is a dynamic process in which the relationship between the food and the 
consumer changes from one moment to the next and depends on the situation in which the 
consumer consumes the food. The determinants of acceptability can be categorised as the 
sensory characteristics of the food, the physiological state of the consumer, the socio-
psychological context of consumption and the effects of learning on all these categories (Booth, 
1981:64). Consumer perception regarding meat quality differs between age groups, with time 
and between ethnic groups. Meat tenderness is the single most important component of meat 
quality for the consumer (Webb, 1998:1). Consumers appear to pay more for guaranteed 
tenderness (Morgan, 1998:10) and have new expectations regarding meat quality due to safety 
concerns, technological progress in the meat industry and movement towards the buying of more 
natural products (Manin, 1998: S231 ). The class-AB sheep carcass (p32-33) is definitely a 
possible answer to the raising need, seeing that lambs can be left on the field for a longer period, 
produce an additional shearing and have an increased carcass weight. The meat obtained from 
this method will still be of a high quality and highly acceptable to consumers (De Bruyn, 2002:2). 
Variations in tenderness within the group can be reduced by electrical stimulation, ensuring 
consistent meat quality and consumer satisfaction. Consumers' eating satisfaction results from 
desirable flavour, juiciness and tenderness combined (Morgan, 1998: 11-14; Webb, 1998:1). 
Objective measurement of meat tenderness can never mimic the complex and multifaceted 
actions that occur during biting and chewing (Perry, 2002: 1) . Consumer expectations, 
perceptions and acceptance must therefore be the driving force behind improving meat quality. 
1.2 HYPOTHESIS 
The meat from the electrically stimulated class-AB sheep carcasses will differ significantly in 
acceptance by consumers, will be preferred to and will be consumed more often than the meat 
from non-stimulated carcasses. 
1.3 AIM AND OBJECTIVE 
The aim and objective of this mini-dissertation are: 
Aim: To investigate the effect of electrical stimulation on the consumer acceptance of, 
preference for and consumption intent of mutton from class-AB sheep carcasses. 
Objective: a.) To compare the following by means of consumer panel evaluation: 
4 
acceptance of juiciness, tenderness and flavour, 
preference for, 
and intended consumption of meat from the electrically stimulated and non-
stimulated class-AB sheep carcasses. 
b.) To compare shear force values obtained between ES and NES samples. 
c.) To determine variation in cooking loss between ES and NES samples. 
1.4 STRUCTURE OF THIS MINI-DISSERTATION 
This mini-dissertation is presented in article format. The experimental work included consumer 
assessment of the acceptance of sensory attributes and objective measurement of meat tenderness. 
This introductory chapter motivates the necessity of the research effort, outlines the objectives of 
the study and explains the structure. Chapter 2 gives an overview of the literature considered 
important for the interpretation of data from the collected information. Chapter 3 consists of a 
manuscript on the effect of electrical stimulation on the consumer acceptance of mutton from 
class-AB sheep carcasses (submitted for publication in the South African Journal of Animal 
Sciences). The questionnaire used in this study is presented as Addendum A at the end of the 
mini-dissertation. Please note that the relevant references in Chapter 3 are provided at the end of 
the chapter according to the instructions of the specific journal to which the manuscript was 
submitted. The references used in the unpublished Chapters 1 and 2 are provided according to 
the mandatory style stipulated by the PU for CHE. 
1.5 AUTHORS' CONTRIBUTIONS 
The contribution of each researcher involved in the study is given in Table 1. Also included in 
this section is a statement from the co-authors confirming their individual role in the study and 
giving their permission that the article may form part of this mini-dissertation. 
5 
Table 1: Names and role descriptions of people involved in the study of the effect of electrical 
stimulation on consumer acceptance of mutton from class-AB sheep carcasses 
Name Role in the study 
Mrs Mariana Davel Co-responsible for planning and execution of the study, as well as 
literature searches and preparation of the manuscript. 
Prof. MIC Bosman Ph.D Supervisor. Co-responsible for design, planning, approval of final 
(Food Scientist) protocol, adaptation of questionnaires, compilation of the data and 
execution of the total study. Supervised the writing of the 
manuscript. 
Prof. EC Webb Co-supervisor. Co-responsible for design, approval of final protocol 
and determination of shear force values. Responsible for obtaining 
of experimental sheep carcasses. Supervised the writing of the 
script. 
Mrs Elize Pienaar Supervised the preparation and serving of the meat samples as well 
as determination of cooking losses. 
4th Year students (Food) Assisted in the preparation of the samples for the taste panel sessions 
as well as recruitment of consumers. 
The following is a statement from the co-authors confirming their individual role in the study and 
giving their permission that the article may form part of the manuscript. 
I declare that I have approved the above mentioned article, that my role in the study, as 
indicated above, is representative of my actual contribution and that I hereby give my consent 
that it may be published as part of the mini-dissertation of Mrs M Davel for the degree Magister 
Consumer Science. 
Prof MJC Bosman 
6 
1.6 REFERENCES 
1. BOOTH, D.A. 1981. Momentary acceptance of particular foods and processes that change it. 
(In J. Solms & R.L. Hall (eds), Criteria of food acceptance. 6th edition. Zurich. Foster 
verslag). 
2. DE BRUYN, J. 2002. Proposal: Alternative description of AB-Mutton.(Original copy in 
possession of the author). 
3. EPLEY, J.E. 2002. Meat tenderness. [Web:] http://www. extension. urnn.edu/distribution 
/nutrition /DJ0856.html. [Date used: 13 October 2002]. 
4. KERTH, C.R., CAIN, T.L., JACKSON, S.P., RAMSEY, C.B. & MILLER, M.F. 1999. 
Electrical stimulation effects on tenderness of five muscles from Hampshire rambouillet 
crossbred lambs with callipyge phenotype. Journal ofA nimal Science, 77: 2951-2955 
5. MENDAY, K. 1979. Elektriese stimulering van vleis. Community Health in SA. 5-7. March. 
6. MONIN, G. 1998. Recent methods for predicting quality of whole meat. Meat Science, 
49:S231-243. 
7. MORGAN, J.B. 1998. Influence of extrinsic factors on meat tenderness. (In ZILMAX® 
Meat quality symposium, Gallagher Estates Midrand: South Africa. p. I 0-22.) 
8. OCKERMAN, H.W., YANAR, M. & YETIM, H. 2001. The effects of electrical stimulation 
on sensory and instron textural measurements of mutton tissue. Ohio State University. 
Bulletin. Research and reviews: meat. Special circular 183-02. [Web:] 
http://www.ohioline.osu.edu/sc183/sc 14a.html. [Date of access: 10 Oct. 2002] (Abstract 
from Internet) 
9. PERRY, D. 2002. Laboratories, taste panels and palatibility. [Web]: 
http://www.beef.crc.org.au/Pu b 1i cati ans/Latest Pu blicati ons/feeder2002/Sessi on6/6f.html. 
[Date of access: 7 October 2002]. 
10. WEBB, E.C. 1998. Intrinsic factors influencing meat tenderness in commercial beef 
production. (In ZILMAX® Meat quality symposium, Gallagher Estates Midrand: South 
Africa. p.1-8.). 
7 
CHAPTER2 
LITERATURE REVIEW 
8 
CHAPTER2 
LITERATURE REVIEW 
2.1 INTRODUCTION 
The inconsistency in the eating quality of meats, predominantly tenderness, is probably the most 
important problem faced by the meat industry worldwide. Consumers consider tenderness to be 
the single most important component of meat quality (Morgan, 1998:10; Webb, 1998:1). An 
alternative for increasing meat tenderness and/or preventing cold shortening may exist in the form 
of electrical stimulation of the carcass shortly following slaughter (Savell et al., 1977:702). Other 
advantages of electrical stimulation, such as increased shelf life, bright red colour and decreased 
bacterial growth, are all quality characteristics demanded by consumers (Menday, 1979:7). Red 
meat consumption has decreased dramatically over the past 30 years. Numerous factors have 
contributed to this phenomenon e.g. economical factors (increased red meat prices), consumer 
perceptions (red meat versus white meat) and misconceptions regarding the market, e.g. grading 
system of red meat (Poonyth et al., 2001:427-8). In the current South African Red Meat 
Classification System, consumers have the perception that Class-A carcasses yield the best 
quality meat and may therefore have a higher price (Bray et al., 1989:303; Webb, 1998:1). The 
demand and associated marketing of more "natural" animal products are increasing daily. This 
demand will entail the exclusion of any synthetic growth stimulants (hormones and feed 
additives) and will expose animals to a more natural (free-range) environment. An important 
consequence of this shift in animal production is in many instances the production of somewhat 
older animals, compared to those produced in more intensive systems (De Bruyn, 2002: 1) . The 
introduction of the class-AB in the Beef, Lamb & Mutton Carcass Classification System is a good 
example of adaptation to changes in the market. It is, however, necessary to inform consumers of 
the quality characteristics of the class-AB mutton and to investigate options such as electrical 
stimulation of carcasses to minimise inconsistencies in the tenderness of the class-AB mutton to 
assure consistent quality and guaranteed tenderness. 
2.2 FOOD QUALITY 
Food quality is a complex concept that is frequently measured using objective indices related to 
the nutritional, microbiological or physiochemical characteristics of the food or in terms of the 
opinions of designated experts. However, when food quality is defined in terms of "degree of 
excellence" none of these measures serves as adequate indices of food quality. It can be argued 
9 
that food quality is a consumer-based perceptual/evaluative construct that is relative to person, 
place and time (Cardello, 1995: 163). 
Food quality can be considered as both the best defined and the least well defined concept in the 
food industry. The difference depends upon who is defining it and the level at which it is 
measured. Food scientists represent only a small percentage of people concerned with food 
quality. The majority are consumers - the people whose definition of food quality drives the 
economy of the global food industry (Cardello, 1995:163). 
According to Clark (quoted by Cardello, 1995:163), the notion that food quality must be defined 
and measured from the consumer's perceptive can be traced to the earliest attempts to establish a 
scientific discipline related to food. In volume 1 of The Food Journal, published in 1870, there 
appeared a paper by H. Clarke, in which the basic proposition was put forth that food quality is a 
relative concept that is inappropriate for evaluation by anyone other than the average consumer of 
that food. As underlined by many authors, the consumer expectations and perceptions must drive 
quality improvement. Such a consumer-oriented approach is in accordance with the ISO 
definition of quality (ISO, 1992) "quality represents the totality of features and characteristics of 
a product that bear on its ability to satisfy stated or implied needs". To motivate a consumer, 
quality must be supported by a specific concrete benefit for the consumer. Food quality is not an 
inherent characteristic of the food but it is closely allied with the concept of acceptability 
(Cardello, 1995: 164; Issanchou, 1996: S5). 
2.2.1 Consumers' perceptions and expectation of food quality 
When focusing on the perceived quality by the consumer, the first question is: " Who is this 
consumer?" Many people have different role patterns and cannot be categorised in one type of 
behaviour. Perceived quality is thus dependent on a person but also on the context, i.e. on the 
circumstances in which food and consumer interact (lssanchou, 1996: S6). 
Consumers only respond to what they see and taste. They know very little, if anything, about the 
process by which food comes to them (Kahar, 2002:1). Consumer research, which involves 
consulting the consuming public about their preferences and investigating acceptable traits, is one 
way of analysing a product. But this method tells the scientist little, because people express their 
preferences for and their impressions of certain food attributes differently (Issanchou, 1996: S6; 
Kahar, 2002: 1) . 
10 
Perceived quality is determined by many factors, which can be categorised in different 
dimensions. Sensory properties contribute to a product's aesthetics, shelf life, conformance, 
performance and reliability (Civille, 1991:57). For Molnar (1995:185) their sensory qualities, 
safety, nutritional value and convenience determine the quality of food products. Molnar's model 
is, however, based on consulting experts and not consumers' judgements. Issanchou (1996:S7) 
distinguished between two types of quality attributes, experience quality attributes (including 
convenience, freshness and sensory characteristics) and credence quality attributes (including 
health, naturalness and wholesomeness that cannot be experienced directly). 
The overall quality evaluation is hypothesised to be based upon the perceptions of the product 
with regard to the quality attributes. According to Issanchou (1996:S7), personal and situational 
variables influence the formation of perceived quality judgements. A product is thus valued in 
comparison with other products and price must be considered as a key element in this value 
evaluation. It can thus be stated that perceived quality depends on the person, product and 
situation and all three aspects are changing continuously for a given population over time. 
2.2.2 Consumers as sensory panellists 
The importance of meat quality is crucial, as meat consumption tends to decline in many Western 
countries. Changes in the perception of meat quality can take place rapidly, e.g. those related to 
product safety and pathogens, whereas attitudes based on ethical and moral evaluations evolve 
slowly. Consumers' expectations appear to be a paradox for the producer. There is also a clear 
lack of consumer-oriented communication from the meat producers and the food industry. 
Communication could help to decrease the uncertainty concerning meat. Reducing uncertainty is 
a key point because consumers experience different consequences of making a wrong choice, 
especially health and financial consequences (Issanchou, 1996: S16). It is obvious that the meat 
industry is changing from being a traditionally production-led industry to being a consumer-
driven industry. This implies that methodologies developed in consumer science will have to be 
more widely used than is currently the case. 
Consumer panel testing provides valuable feedback, particularly where large numbers of samples 
are involved (Claire et al., 1993:7). Consumer taste panels are commonly used for sensory 
assessment of palatability, which is a function of assessment of the acceptance of tenderness, 
juiciness and flavour/aroma (Perry, 2002:1). The consumer is an individual who regularly 
11 
consumes the product and generally has a positive disposition towards the product (Goldman, 
1994b: 822). 
Training a panel is expensive and time-consuming and requires considerable commitment from 
the potential panel members, who must be available for training and for the duration of any 
investigation. The alternative approach is to ask consumers to judge types of food, which they eat 
themselves. Previous studies have considered consumer sensory appraisal work in two broad 
groups: food given to prepare at home or samples evaluated under controlled conditions in a 
sensory appraisal laboratory (Claire et al., 1993:7). The results obtained from consumer panels 
are trustworthy because the consumer cannot be influenced in opinion and there is no variation in 
response because a sample is only evaluated once and not over a period of time (Claire et al. , 
1993:7; Goldman, 1994a: 103). Preference tests focus on the choice of one item over another. 
It does not indicate whether any of the products are liked or disliked. Acceptance tests indicate 
how well a product is liked by consumers. A hedonic scale is used to indicate degrees of 
unacceptability to acceptability or dislike to like. From relative acceptance scores one can infer 
preference. The sample with the highest score is preferred (Meilgaard et al., 1990: 150-151 ; 
Thompson, 1988:77). These tests may appear identical, but it is possible for a consumer to show 
a strong preference for a sample but not to consume it frequently (Penfield & Campbell, 
1990:70). 
Where large numbers of samples are to be evaluated quickly, there are considerable advantages to 
consumer testing under controlled sensory laboratory conditions using hedonic rating scales. The 
major advantages of hedonic scales are simplicity, their suitability for use by a wide range of 
participants and the speed with which a large number of samples can be assessed (Claire et al. , 
1993:7). 
While sensory evaluations may be moving in the direction of more demanding and sophisticated 
approaches of situations, consumer panel testing retains its relevance in a number of situations, 
particularly where large numbers of samples must be tested (Claire et al. , 1993:8). 
2.3 MEAT QUALITY 
Consumers of meat have always been concerned with the safety and sensory quality of food, in 
particular meat. In the present century new expectations arise and are still growing. Purchasers 
12 
of any product expect an optimal quality/price relation and consistency in quality. These growing 
expectations have led to increased demands for 
• technological quality due to industrialisation in the meat industry, 
• guarantees for safety and eating quality and 
• authenticity. 
The meat industry is therefore continuously in search of new techniques to improve meat quality 
(Monin, 1998:S231). 
The free market system not only gives farmers a better opportunity to market their products but 
also expects of them to continuously deliver high quality products. The products should produce 
the highest edible yield and be of superior quality. It is, however, important that the farmer, 
market and retail organisations work together to assure that all crucial control points are 
maintained to keep the carcass quality high (Morgan, 1998:20). Total quality management should 
be applied from the production to the delivery of the end product on the consumer's plate 
(Morgan, 1998: 10). 
Meat quality needs to be defined so as to fully appreciate the needs of the consumer. Appearance, 
palatability, nutritive values, processability and shelflife contribute greatly to meat quality (Webb 
et al., 1994: 45). The current Red Meat Classification System can be confusing to the consumer, 
producer, supplier and retailer. They have the perception that a class-A carcass produces the best 
quality meat and can therefore have a higher price (Meaker, 1995:1). Although meat colour is a 
poor indicator of eating quality, most consumers make purchase decisions based on display 
colour. Consumers discriminate against meat that is not red and bright, considering it to be old or 
of poor quality (Young et al., 1999: 4 7). 
Interesting results were obtained in a study completed by Glitsch (2000: 177), who found that 
consumer perception of meat quality consists of two phases namely the stage prior to the actual 
purchase (experiences, habits) and the stage after the purchase while eating the meat (sensory 
evaluation, experiences). 
13 
Extrinsic quality Intrinsic quality Sensory characteristics 
cues cues 
Quality lables, Colour, marbling Flavour, tenderness, colour, smell 
place of purchase, (except chicken), leanness, juiciness, free of 
price, country of leanness gristle, texture 
origin 
Figure 1. Consumer's perception of fresh meat quality (Glitsch, 2000:185) 
According to Figure 1, consumers' perceptions of fresh meat quality are influenced by the 
expected quality (extrinsic and intrinsic quality cues) and perceived quality (sensory 
characteristics) (Glitsch, 2000: 185). Among meat characteristics which can be used for assessing 
meat quality in the shop for the first stage, "price" was distinctly considered to be the least helpful 
quality indicator. "Place of purchase" was one of the most important quality cues, while among 
the intrinsic factors "colour" was the most important factor. In the phase of quality evaluation 
after purchase, flavour was one of the most significant quality characteristics, while "leanness, 
texture and free of gristle" were of minor importance (Cassal, 2000: 193-4). 
Inconsistency in meat tenderness at the consumer level has been identified as one of the major 
problems facing the entire meat industry. The importance of meat tenderness to consumers and 
the meat industry is the reason that retail meat cuts are priced according to the expected 
tenderness level. Consumers' eating satisfaction results from desirable flavour, juiciness and 
tenderness combined. One must, however, keep in mind that twice as much variation exists in 
meat tenderness, when compared to the variation of juiciness and flavour (Morgan, 1998: 11-14). 
Palatability of meat and consumer taste preferences are based on three components: acceptability 
of juiciness, tenderness and flavour (Umberger et al. , 2000:2). In a study done by Schultz & 
Wahl (1981 :97), the relative importance of appearance, flavour and texture to the perceived 
quality of meat when eaten, was investigated. Consumers were asked to value appearance, 
flavour and texture according to importance. Results indicated that texture was globally rated 
14 
more important to men than women. A significant increase of importance ascribed to flavour 
with increasing of age was noted. It also appeared that young people gave little priority to 
sensory criteria, whereas older respondents declared sensory factors very important for meat 
quality. Results also indicated that texture, especially tenderness and juiciness, has a substantial 
effect on the acceptability of cuts of meat. 
2.4 FACTORS INFLUENCING MEAT QUALITY WITH SPECIAL REFERENCE TO 
TENDERNESS 
Meat tenderness can be measured or estimated either objectively (in a laboratory using an 
instrument) or subjectively (sensory analysis e.g. taste panel). Tenderness assessment by 
laboratory instruments can, not mimic the complex and multifaceted actions that occur during 
biting and chewing. Objective measurements attempt to use a number of instrumental methods 
that closely correlate with one or more of these actions. Shear force measurements measure the 
toughness caused by both the muscle fibres and connective tissue (Perry, 2002: 1) . 
Food quality in a product may be regarded as the degree of excellence of a product. Each 
consumer's needs, previous experiences and expectations will influence the perception of food 
quality. Red meat consumption has decreased dramatically over the past 30 years. Numerous 
factors have contributed to this phenomenon, e.g. economical factors (increased red meat prices), 
consumer perceptions (red meat vs white meat) and misconceptions in the market (grading 
system of red meat). In the current South African Red Meat Classification System, consumers 
have the perception that A-grade carcasses produce the best quality meat and can therefore have a 
higher price. 
Consumer demand for more "natural" animal products is increasing daily. This demand will 
entail the exclusion of any synthetic growth stimulants (hormones, feed additives etc.) and will 
expose animals to a more natural (free-range) environment. An important consequence of this 
shift in animal production is in many instances the production of somewhat older animals, 
compared to those produced in more intensive systems. In light of these changes, it is important 
that available marketing tools, e.g. the SA Carcass Classification System, support the shift in 
production systems and customer demands. The introduction of the class-AB in the Beef and 
Lamb & Mutton Carcass Classification System is a good example of adaptation to changes in the 
market. 
15 
Meat quality is a function of production, processing, value adding and cooking methods used to 
prepare the meat for consumption by the consumer. Failure of one or more links in the meat 
supply chain increases the risk of a poor eating experience for the consumer. A guarantee for 
eating quality can only be given if the factors that affect tenderness the most are controlled in the 
production chain (Thompson, 2002:295). Meat toughness is the result of the combined effect of 
connective tissue and muscle fibres. Both the connective tissue and the muscle fibres are 
responsible for physiological functioning and ultimately muscle contraction. Connective tissue 
components include collagen (inextensible and non-branching) and elastin (branching and elastic) 
(Webb, 1998:1-2). Myofibrillar toughening is the result of the binding of the main contractile 
proteins (myosin and actin), resulting in a rigor complex. The binding of actin to myosin is 
associated with an increase in toughness. The strength of the myosin/actin complex appears to 
be variable in rigor and this may affect tenderness. Post-mortem changes in skeletal muscles may 
improve meat tenderness. The post-mortem activation of calpains is initiated by an increase in 
the concentration of available activating ions (calcium). Activated calpains may form a complex 
with calpastatin, particularly at a high pH, and temporarily reduce any proteolysis. If there is a 
significant proportion of calpain when inactivation occurs, less tenderisation will occur, resulting 
in tough meat (Webb, 1998:5-7). 
Factors influencing meat quality are: 
2.4.1 Age and species 
Meat of older animals tends to be more tough (less tender) with the accruement of 
permanent incisors. This is one of the reasons why the classification system is based on 
the number of incisors (Schonfeldt et al., 1993:381). Beefis usually the most variable in 
tenderness, followed by lamb, pork and veal. The tenderness variation between species 
is due primarily to the chronological age of the animal at the time of slaughter. Beef is 
normally processed at 20 months of age, lamb at 8 months, pork at 5 months and veal at 2 
months. The decrease in tenderness with increasing age is due to the changing chemical 
constitution of collagen (gristle), the connective tissue protein found in meat. . Collagen 
becomes more complex and stronger with advancing age and is thus more resistant to 
tenderisation from moist heat cooking (Epley, 2002:2; Webb, 1998:2). It is thus the 
changes in collagen characteristics, rather than collagen concentration, that are 
responsible for the toughening of meat as animals age (Webb, 1998:2). 
16 
2.4.2 Genotype 
The heritability of tenderness in meat is approximately 45%, which means that 45% of 
the observed variation in tenderness of cooked meat is due to the genetics of the animal 
from which the meat comes (Epley, 2002:1-2). However, difference in genotype should 
not be used alone as an indicator of quality meat. Incorrect slaughtering, cooling and 
preparation methods can attribute to poor quality meat. 
2.4.3 Type of muscle 
Within any species, there is considerable variation in tenderness among muscles. The 
amount of connective tissue present is due to the function of the muscle in the live 
animal. The pH decline is faster in fast twitch glycolytic muscles, compared to slow 
twitch muscles. The fore shank will therefore have more connective tissue than the 
tender loin. The amount of stretch of the muscle is another factor influencing tenderness. 
Stretching of the muscles takes place when the carcass is being chilled. This stretching is 
due to the weight of the carcass and prevents shortening of the muscle (Epley, 2002:3; 
Webb, 1998:5). 
Skeletal muscles are composed of different fiber types, which are classified according to 
contraction characteristics and predominant metabolism of the fibres. Both these 
characteristics are involved in rigor mortis development and may be involved in its 
acceleration by electrical stimulation and muscle tensioning to tenderise meat (Walker et 
al., 1996: 1118). The M longissimus dorsi is significant in terms of its high value as a cut 
of meat and is generally used as a test muscle. However, it does not give the greatest 
response to stress. The shoulder muscles (M triceps brachii and infra spinatus) 
generally have a higher ultimate pH than the loin and it is also more affected by stress 
situations (Bray et al. , 1989:65). Deviations in the ultimate pH of meat may also result in 
two unfavourable conditions, namely PSE (pale, soft and exudative meat) and DFD 
(dark, firm and dry meat) (Webb, 1998:4). The development of PSE is usually attributed 
to an increased post mortem glycolitic rate. In muscles which developed DFD the muscle 
glycogen is already depleated before slaughter. This gives substrate for post-mortem 
glycolysis and the ultimate pH becomes higher than normal (Webb, 1998:4). Irreversible 
anaerobic glycolysis which occurs when oxygen is permanently removed from the 
muscle at death is the sequence of chemical steps by which glycogen is converted to 
17 
lactic acid. Exercise immediately before slaughter diminishes the reserves of glycogen in 
the muscle and the conversion of glycogen to lactic acid will continue until a pH is 
reached where enzymes effecting the breakdown become inactivated. In the typical 
mammalian muscles this pH is about 5.4-5.5 (Lawrie, 1998:67). The extent of 
tenderisation is critically dependant upon the net proteolysis resulting from both the 
activity and inactivation of mainly µ-calpain. Calpain activity is pH and temperature 
sensitive and increases about five-fold from pH 5.5 to 7.0. Inactivation occurs mainly at 
high temperatures, almost independently of pH. High or low temperature will lead to a 
preferential rate of inactivation of calpain and will be accompanied by muscle shortening 
(Webb, 1998:6-7). 
1.4.4 Feeding 
Animals in feedlots are removed from field grazing at an earlier stage and will have more 
tender meat than animals kept grazing in the field (Bosman et al., 1994:25; Epley, 
2002:2). This is due to the fact that the muscles of animals in feedlots are still actively 
growing and will result in more tender meat with less yellow fat. 
1.4.5 Pre-slaughter stress conditions 
All stressing conditions, such as bruising, bathing etc., should be limited before 
slaughtering. Bruising reduces the total carcass yield and stress reduces the quality and 
shelf life of the meat. Stressing, unnecessary handling and long waiting periods in the 
abattoirs may increase the presence of dark, firm and dry meat (Viljoen et al., 2002: 181 ). 
Hygienic slaughtering, processing and storage can enhance shelf life. Stressful 
conditions, e.g. undernutrition, pre-slaughter wash and depleted muscle glycogen 
reserves before slaughter, increase the ultimate pH of meat and result in low residual 
levels of glucose. This causes changes in protein structures and chemical composition 
that influence meat colour, flavour, tenderness, water-holding capacity and storage life 
(Bray et al., 1989:59; Geesink et al., 2001(b):265). 
Developments in the meat industry may have increased the incidence of pre-slaughter 
stress. The meat industry has become centralised into fewer, larger plants and animals 
have to be transported over greater distances. The larger plants often operate at higher 
speeds than smaller plants. The need to move and process animals rapidly may increase 
stress in the period immediately before slaughter (Geesink et al., 2001(b):265). 
18 
Apart from the toughening effect of stress on the ultimate pH, a toughening effect 
independent of ultimate pH has been observed in a study done by Geesink et al. 
(2001(b):266). In addition, this effect was more pronounced when low-voltage electrical 
stimulation was used to immobilise the animals, suggesting an interaction between stress 
and electrical stimulation. Stress treatment increased the percentage of muscle with a 
high ultimate pH associated with undesirable tenderness and colour characteristics (see 
p.17) (Geesink et al. , 2001(b):267). 
2.4.6 Electrical stimulation 
Together with ageing, electrical stimulation contributes to the tenderness of meat, much 
more so than genotype or feeding (Epley, 2002:3). If the muscles still contain energy and 
are cooled immediately after slaughter, meat becomes tough. The advantage of electrical 
stimulation is that after two days electrically stimulated meat will have the same 
tenderness as non-electrically stimulated meat after ten days ageing (Menday, 1979:5). 
Savell et al.(1981:1781) reported that electrical stimulation appears to increase the 
tenderness of meat if its initial tenderness would be unacceptable but it does not appear to 
affect the tenderness of meat if its initial tenderness level would be acceptable. The 
effect of electrical stimulation on tenderness improvement is not consistent throughout 
the carcass. In a study done by Savell et al. (1977:704) results indicated that electrical 
stimulation resulted in substantial improvements in tenderness in the loin region 
(longissimus muscle) while sporadic results in tenderness were observed for the leg 
region (M bicepsfemoris). This may be related to the connective tissue content of these 
muscles. On average the electrical stimulation lowered the variability in tenderness 
ratings. Electrical stimulation will accelerate the post- mortem ageing of meat but the 
actual ageing time reduction and extent of ultimate tenderisation appear to be affected by 
inherent tenderness of the meat (Savell et al. , 1981: 1781 ). 
2.4. 7 Ageing 
On completion of rigor mortis, changes take place in meat, resulting in more tender meat. 
Post- mortem ageing of meat is probably the most widely used tenderising process in the 
meat industry (Savell et al. , 1981 :1777). This holding of meat in a cooler is referred to 
as the ageing period. Lamb and pork are rarely aged, as a lack of tenderness is not 
encountered because of the relatively young age of the animals when slaughtered (Epley, 
19 
2002:4). Even if the animals/carcasses have been treated correctly before, during and 
after slaughtering, it is still very important that the processing and distribution of the meat 
should be of a high standard. 
Consumers' acceptance of meat quality is also influenced by convenience, animal 
welfare, safety, intrinsic quality cues, extrinsic factors and sensoric factors (Geesink et 
al., 2001b:265; Issanchou, 1996: Sl0-12; Lister, 1995:3; Verbeke et al., 1999:77). 
2.5 ELECTRICAL STIMULATION 
A consistent method for increasing the tenderness to a more acceptable level would transform 
mutton carcasses into a product that might be marketed through retail channels, allowing for 
increased flexibility in merchandising (Ockerman et al., 2001:184). Post-mortem technologies 
that enhance the tenderness of meat are economically important to both the processor and 
producer. As consumer satisfaction increases, sales are likely to increase. Electrical stimulation 
has provided positive results for improving meat tenderness. 
Methods of handling carcasses immediately post-mortem have been shown to affect the ultimate 
tenderness of meat. The most common problem associated with prerigor meat is "cold 
shortening," which can be controlled by physical restraint or the use of high temperature 
conditioning during the development of rigor mortis. Although these procedures have been 
shown to improve tenderness, there are production time problems with the use of high 
temperature conditioning and changes in carcass shape with the use of non-conventional carcass 
suspension, which have deterred industry application of either method (Savell et al., 1977:702). 
An alternative for increasing tenderness and/or preventing cold shortening may exist in the form 
of electrical stimulation of the carcass shortly following slaughter. Electrical stimulation would 
not disrupt product flow through a plant, requires little time and does not affect the appearance of 
the carcass (Savell et al., 1977:702). Post-mortem electrical stimulation has received 
considerable attention as a tool to improve meat quality traits such as tenderness, flavour, lean 
colour, marbling set-up and reduce dark, coarse-band formation (Lee et al., 2000:786). 
Electrical stimulation was originally used to prevent the toughening effect of cold shortening and 
to provide an additional tenderising effect (Geesink et al., 2001a:145; Lee et al., 2000:786). 
Electrical stimulation has been used to tenderise meat in the red meat industry for more than 20 
20 
years (Li et al., 1994:223). It has also been reported to be an effective method for improving 
meat tenderness in beef, lamb and goat carcasses (Kerth et al., 1999:2951; Savell et al., 1977:706; 
Savell et al., 1978:1609). The orthodox meaning is that electrical stimulation only accelerates 
post-mortem changes (Menday, 1979:5). Although the mechanism by which electrical 
stimulation improves tenderness has not been elucidated, postulations include the reduction in 
cold shortening and increased activity of acid proteases (Savell et al., 1977:705). 
2.5.1 History of electrical stimulation 
The use of electricity to increase meat tenderness is not new: Benjamin Franklin had already 
suggested its use for that purpose in 1749. In a biography of Franklin, it was reported that 
"killing turkeys electrically, with the pleasant side effect that it made them uncommonly tender, 
was the first practical application that had been found for electrical stimulation" (Lopez & 
Herbert, 1975:7). 
According to Lemisch (1961:51), Franklin stated the following in a letter in 1773 to two French 
scientists: 
"It has been observed that lightning, by rarefying and reducing into vapour the moisture 
contained in solid wood in an oak, has forcibly separated its fibres and broken it into small 
splinters. Is it not then improbable, that the same subtle matter, passing through the bodies of 
animals with rapidity, should possess sufficient force to produce an effect nearly similar? The 
flesh of animals, fresh killed in the usual matter, is firm, hard and not in a very eatable state, 
because the particles adhere too forcibly to each other. At a certain period, the cohesion is 
weakened, and, in its progress toward putrefaction, which tends to produce a total separation, 
the flesh becomes more tender or is in a state most proper to be used as our food. 
Experience alone will inform us on the requisite proportions (of electricity) for animals of 
different forms and ages. " 
Harsham and Deatherage issued patents for the electrical stimulation process in 1951. No reports 
of the research studies upon which those patents were based, were ever published in scientific or 
popular literature (Smith, 1985: 123). Scientists at Texas A & M University (TAMU) developed a 
process for tenderisation of carcasses that was ultimately called "Texas A & M Tenderstretch". 
Despite extensive research documenting its effectiveness in increasing the tenderness of beef and 
21 
lamb, the Tenderstretch process was not implemented by packers in the United States. It was the 
use of the Tenderstretch process in Australia and New Zealand to prevent toughness in rapidly 
processed (chilling and/or freezing) lamb carcasses that led to TAMU investigations of electrical 
stimulation (Smith, 1985: 122). The first report of scientific research on electrical stimulation and 
meat tenderness in New Zealand was released in 1973. Research on electrical stimulation and 
meat tenderness was initiated at the University of Florida and at Texas A & M University 
(TAMU) in 1975 and the first report of scientific research was published in 1976 (Smith, 
1985:123). TAMU studies of electrical stimulation involved field research and the development 
and implementation of specifics for commercial use. The main advancements made by the 
scientists were the identification of the proper voltage, impulse duration and number of impulses 
needed to achieve the desired changes in tenderness and meat quality indicators. The most useful 
results were those that allowed identification oflocations on the kill floor for possible installation 
of the electrical stimulator in an in-line, hand operated system for all carcasses (Smith, 1985:126). 
2.5.2 Principles of electrical stimulation 
• Physiology of electrical stimulation 
The most common post- mortem change is the reduction in muscle pH together with the 
conversion of muscle glycogen (energy) to lactic acid (Menday,1979:5). At a critical pH 
level and while the carcass is still warm due to the electrical stimulation, lysosomes in the 
muscle tissue burst and release enzymes. These enzymes are capable of breaking down 
macromolecules such as proteins and connective tissue (Menday, 1979:5). 
The increased carcass temperature ( due to the electrical stimulation) is also associated with 
increased enzyme activity. 
Electrical stimulation can promote the activity of endogenous proteolytic enzymes, including 
µ-calpain, that are instrumental in promoting the ageing effect. The increased calpain activity 
may be due to a depolarisation of the cell membrane that causes a release of calcium into the 
cell, which then activates calcium-dependent proteases (Kerth et al. , 1999:2951). 
The increased temperature of the thermal receptors in the carcass stimulates the widening of 
veins and improves the conditions for maximal bleeding of the carcass after slaughtering. 
The quick post-mortem changes lead to the stiffening of the muscles while the higher muscle 
temperatures prevent cold shrinkage, which normally leads to tough meat (Menday, 1979:5). 
22 
Post-mortem electrical stimulation has received considerable attention in the improvement of 
the meat quality traits like tenderness, flavour, lean colour, marbling set-up and reduced dark, 
coarse-band formation (Savell et al., 1979:911). There are three popular theories to explain 
how electrical stimulation improves tenderness: (1) the rapid decline of available ATP, 
which accelerates rigor onset before chilling, may reduce the effects of cold shortening, (2) 
the rapid reduction in pH while carcass temperatures are high may provide favourable 
conditions for the naturally occurring lysosomal enzymes (Unruth et al., 1986:282) and (3) 
the physical tissue disruption may also improve tenderness. One mechanism alone is not 
responsible for the beneficial effects of electrical stimulation. There is considerable evidence 
that increased tenderness results from a combination of relatively low pH and high 
temperature during the early post-mortem period (Savell et al., 1978:1606; Unruth et al., 
1986:282). 
• Inconsistencies in results with electrical stimulation 
Conversely, the voltage, frequency, duration of ES and the method of application are 
important factors influencing the degree of tenderisation (Lee et al., 2000:786). According to 
Li et al. (1994:223), inconsistencies in results obtained in studies on electrical stimulation 
may have resulted from (1) different experimental procedures such as applying electrical 
stimulation before or after scalding, and with or without specific environments, and different 
ageing methods, (2) different electrical parameters such as voltage, frequency, duty cycle and 
wave form, (3) different tenderness analysis procedures such as the shear force device or 
technique used and (4) variations in physiological properties such as genotype and body 
weight (Li et al., 1994: 223). 
• Low-voltage vs high-voltage electrical stimulation 
Concern has arisen in some circles regarding the relative effectiveness of low-voltage and 
high-voltage electrical stimulation. Research has shown that low-voltage electrical 
stimulation is similar to high-voltage electrical stimulation in terms of its effects on carcass 
quality traits, but that low-voltage electrical stimulation is not as effective as high-voltage 
electrical stimulation in improving tenderness (Smith, 1985:148). High-voltage electrical 
stimulation (HVES, 300V-1000V) has been applied to achieve a very rapid pH decline that 
results in a more desirable lean colour and improved marbling scores (Lee et al., 2000:786). 
Many researchers have also demonstrated a similar effect from low-voltage electrical 
stimulation (L VES, ca 30V) on pH decline and improvement of quality (Bouton et al., 
23 
1980:146; Eikelenboom et al., 1985:249; Hopkins et al., 2000:362). In many cases low-
voltage stimulation of lamb carcasses has not significantly reduced the shear force of cooked 
meat compared to that of non-stimulated meat. It is speculated by Hopkins et al. (2000:362) 
that the response to low-voltage electrical stimulation was determined by the history of the 
animal rather than the processing conditions. Low-voltage electrical stimulation may be 
more desirable under commercial conditions due to its practicality and safety of application 
(Geesink et al., 2001a: 145; Lee et al. , 2000:786). 
Results from a study done by Polidori et al. ( 1999: 179) indicated that the use of a low-
voltage electrical stimulation (28V, 60 Hz) accelerated the glycolytic process, resulting in a 
significant fall in pH during the first 6 h post-mortem. Tenderness was also significantly 
increased. Results in a study done by Geesink et al. (200l(a):146) indicated that even low 
electrical input during immobilisation could adequately stimulate carcasses and avoid cold 
shortening. According to Aalhus et al. (2000:51), low-voltage electrical stimulation 
accelerates the rate of pH decline, which results in brighter red coloured meat. Results from a 
study done by Hopkins et al. (2000:364) indicated that low-voltage stimulation does not 
significantly improve tenderness but caused pH to drop significantly faster than in the control 
samples. The lamb industry must investigate and adopt methods that reduce the variability 
in quality. 
24 
Table 1: Comparison of studies done to determine the effect of electrical stimulation on 
meat quality 
Eikelenboom Aalbus et Birkhold & Bouton et Hopkins et al., 
et al., 1985 al., 2000 Sams, 1993 al., 1980 2000 
LYES 85V 21V 45V 45V 
HVES 300V 440V vs 820V 1100V 
PH pH decline in Decline Significant Lower value Faster drop in ES 
both samples reduction in for II00V than in NES 
insignificant pH lb/PM than 45V carcasses 
Temperature Increased in ES Drop in 
carcasses temperature 
Sarcomerelength Shorter in control 20% shorter Shorter in Shortest in No significant 
than ES samples in control control than control difference 
than ES ES samples samples 
samples 
Shear force values Lower in Lower in Lower in No significant No significant 
stimulated stimulated stimulated differences. effect 
samples samples samples 
Cooking loss Increase in ES Significant No significant 
samples increase in ES losses 
samples 
Consumer panels HVES & LVES Higher for Lower for 
(tenderness scores) higher than LVES than 1100V than 
control samples control for 110V 
samples 
Preference Higher for ES Higher for 
samples than LVES than 
control control 
Conclusion No significant ES reduced ES tenderised HVES is a Animal history 
diffences in proportion of meat causing bigger risk influences meat 
HVES/ LVES meat rated as myofibrillar than LVES. tenderness 
meat quality tough, fragmentation Tenderness 
improved increased with 
red colour LVES 
LVES - low-voltage electrical stimulation, HVES - high-voltage electrical stimulation, ES - electrical stimulation, NES- non-
electrically stimulated, PM - post- mortem, h - hour, V- volt 
Results in the above summary indicate numerous studies done to indicate the effect of various 
rates of electrical stimulation on meat quality and consumer perceptions of that. Electrical 
stimulation varied between 21V - 1100V. The drop in pH was significantly faster in the ES 
samples than in the NES samples (Hopkins et al., 2000:365). Sarcomere lengths were 
significantly shorter in NES samples. This underlines the results obtained through the Wamer-
Bratzler measurements, indicating that ES has a definite positive effect on the tenderness of meat. 
The results of consumer feedback in the above studies, indicate that tenderness scores were 
significantly lower for high-voltage ES (HVES) than for low-voltage ES (L VES). Control 
samples (NES) scored lower than the L VES. It should be noted that other pre- and post-mortem 
factors also affect meat tenderness. It is not clear if the ageing periods in the above experiments 
were the same, and how the age of the animals in the different experiments differed? Neither is it 
clear which muscles were used. 
25 
2.5.3 Effect of electrical stimulation on meat 
• Tenderness 
Tenderness, juiciness and flavour are components of meat palatability. Although juiciness 
and flavour normally do not vary a great deal, tenderness can vary considerably from one 
meat cut to another (Epley, 2002:1) Tenderness is most probably the most important quality 
parameter affecting consumer acceptance. Tenderness has been defined as the initial 
impression of softness (Casey et al., 1990: 190). 
In its original application in New Zealand electrical stimulation was used to prevent meat 
from becoming tough. In the United States, electrical stimulation was (and still is) used to 
make meat more tender. If a lamb muscle with inherently "tough" muscle is split and one 
side (side A) is treated by the use of the New Zealand process (stimulated with a single 
impulse of high voltage low-ampere electricity, then rapidly chilled and frozen) and the other 
side (side B) is treated in the manner identified by the TAMU research group (stimulated by 
use of repetitive electrical impulses of intermediate voltage and intermediate ampere, then 
conventionally chilled), muscle from side A will still be ''tough" whereas muscle from side B 
will be ''tender" (Smith, 1985: 128; Smith et al., 1980:5). 
Shear force value is a measure of meat tenderness and is one of the most important factors in 
determining meat quality. A reduction in shear force and control of the variation in shear 
force are two of the main concerns in terms of the tenderisation of meat using electrical 
stimulation (Li et al., 1994:223). As reported by West (1982:5) electrical stimulation 
decreased shear force and brought borderline acceptability in tenderness within an acceptable 
range of tenderness. 
The inherent tenderness of meat affects its response, in terms of tenderisation, to electrical 
stimulation. The reductions in shear force for treated samples were generally large when 
control samples (from untreated sides) had high shear force requirements and small when 
control samples (from untreated sides) had low shear force requirements, suggesting that 
electrical stimulation is of greatest benefit for carcasses that would produce less tender meat 
if untreated (Savell et al. , 1977:706). This supports the hypothesis that lamb is generally 
regarded as tender, while mutton (meat from AB-, B- and C-class carcasses) could be less 
tender. 
26 
Savell et al. (1977:706) stated that the increase in tenderness observed m meat from 
electrically stimulated carcasses appears to be different for different animals. Carcasses that 
would otherwise produce tough meat benefited greatly from electrical stimulation, while 
those carcasses that would otherwise produce tender meat did not benefit from electrical 
stimulation. Electrical stimulation appears to be most effective for improving the tenderness 
of the longissimus dorsi muscle, partially effective in improving the tenderness of some 
muscle of the sirloin and relatively ineffective for improving the tenderness of almost all of 
the muscle of the chuck (Smith, 1985:138). 
Electrical stimulation can also be employed to reduce breed differences in tenderness of the 
M longissimus (Ferguson et al., 2000:267). Cuts of meat from ram lambs have been shown 
to be slightly tougher than similar cuts from wethers, as determined by Warner-Bratzler shear 
values and sensory panel scores (Mendenhall & Ercanbrack, 1979:1064). 
• Post-mortem glycolysis 
Post-mortem shortening of muscles toughens lamb if carcasses are chilled or frozen in a pre-
rigor state. To prevent this toughening, carcasses are held at about 15 °C until pre-rigor 
changes are near completion. This "conditioning" procedure introduces an undesirable delay 
in processing. Storage facilities with environmental controls must be provided, carcass 
weight loss through evaporation is increased and microbial growth is encouraged (Carse, 
1973:163). This is a costly practise in terms of labour, space and refrigeration (Walker et al., 
1996:1118). Because it is expensive to hold carcasses for the ageing period, post-mortem 
electrical stimulation has been investigated as a means to reduce the toughness (Birkhold & 
Sams, 1993:578). ES facilitates the conversion of glycogen to lactate, which results in a 
decrease in muscle pH required for the normal conversion of muscle to meat. 
• pH 
In a study done by Geesink et al. (2001(b):267) results indicated that electrical stimulation 
accelerated the pH-decline to the extent that the pH of stimulated muscles was significantly 
lower than the non-stimulated muscle up to 24 hours post-mortem. Similar results were 
obtained in a study done by Hopkins et al. (2000:364). Stress treatment resulted in a 
significant increase in pH post-mortem, which persisted as a trend up to 48 hours post-
mortem. This result indicates that the stress treatment caused some depletion of muscle 
27 
glycogen stores, resulting in a decreased lactic acid production post-mortem (Geesink et al., 
2001(b): 267; Menday, 1979:5). 
Meat pH results show a cumulative effect of stressors. Individually the stressors did not have 
a significant effect, but combined they enhanced the pH response. The importance of the 
increase in pH relates to its association with eating qualities and storage life of meat. 
Tenderness increased subsequently with the normal decrease in muscle pH (Bray et al., 
1989:65). 
• Protease activity and calpastin activity 
Bovine carcasses are usually electrically stimulated to increase tenderness and the process has 
been hypothesised to increase the activity of proteolytic enzymes (protease). The calcium-
dependent proteases, known as calpains, play a key role in the tenderisation process. These 
enzymes may degrade structural proteins in muscle cells and cause fractures and breaks in 
muscle fibres, thus enhancing meat tenderness (Ho et al., 1996:1563; Morton et al., 1997:71). 
The post mortem activation of calpains is initiated by an increase in the concentration of 
available activating ions (calcium). Activated calpains may form a complex with their 
inhibitor (calpastatin), particularly at a high pH and temporarily reduce any proteolysis 
(Webb, 1998:6). 
Electrical stimulation results in a general reduction in calpastin activity, suggesting that it 
accelerates proteolysis (Ferguson et al., 2000:267). The strong correlation between 
calpastatin and the rate of tenderisation indicates that the calpain system is closely linked to 
the proteolytic breakdown of myofibrillar proteins (Morton et al., 1999:71). Early post-
mortem electrical stimulation is used to increase meat tenderness and promotes the activity of 
some endogenous proteolytic enzymes, including µ-calpain (Ho et al., 1996: 1563). 
In a study done by Polidori et al, (1999:180) it was shown that electrical stimulation 
accelerated the glycolytic process, resulting in a significant reduction in adenosine 
triphosphate (ATP) content in the muscle (Polidori et al., 1999: 179). 
• Breed differences 
Breed differences in shear force values were reduced by electrical stimulation. The lowering 
in shear force following ageing was smaller for stimulated carcasses, compared to the 
28 
controls. This tends to reinforce the premise that electrical stimulation accelerates proteolysis 
(Ferguson et al. , 2000:268). 
2.5 4 Advantages of electrical stimulation 
• "Free Iron" 
It is speculated by Menday, (1979:7) that the electrical stimulation of carcasses stimulates the 
binding of free iron in the blood. This will lead to sufficient removal of iron during the 
bleeding period. Research in the USA indicated that consumers prefer meat with a lower 
iron-to-zink relation. Increased shelf life is predictable due to less iron, because the 
deterioration process is accelerated by iron-oxidation, which leads to the discolouring of meat 
during storage. 
• Colouring 
Another advantage of electrical stimulation is that the bleeding process is accelerated. This 
prevents the discolouration of the neck muscle, which is very common in most carcasses 
(Menday, 1979:7). 
• Bacterial growth 
According to Menday, (1979:5) bacterial growth is lower in mediums with a low iron 
content. Bloody and coloured meat therefore creates the ideal medium for bacterial growth. 
Electrical stimulation can therefore be used to prevent this situation. 
• Shelf life 
In a study done in the USA and Australia it was shown that the shelf life of electrically 
stimulated meat is longer than meat which was not stimulated. The study also indicated that 
the colour of electrically stimulated meat cuts stayed acceptable for a day longer than for non-
stimulated meat (Menday, 1979:7). 
• Tenderness 
Electrical stimulation can improve tenderness with approximately 25% and is particularly 
effective for carcasses that are inherently less tender or with little finish and low amounts of 
marbling (Morgan, 1998:15). 
29 
2.6 CLASSIFICATION OF RED MEAT 
The carcass grading system, which had been in use in South African abattoirs since 1985, was 
replaced by a carcass classification system on 26 June 1992 (South Africa, 1992: Agriculture 
Product Standards Act, 1990 (Act No. 119 of 1990)). Carcass grading implies that carcasses are 
graded in order of merit, from the most preferred to the least preferred grades. This system 
assumes that all buyers have the same preferences and needs in terms of carcass characteristics 
(SA Department of Agriculture, 2002). Where records are absent, the ages of cattle and sheep are 
commonly estimated by examining their teeth. Teeth are considered erupted when it has broken 
through the gum. The age at which animals have attained a particular pair of permanent incisors 
can be defined as the number of days from birth to the time when both incisors making up a pair 
have cut the gum (Matika et al., 2002:2). 
A classification system provides a sound basis for: 
• meat traders to describe their specific requirements m simple terms when purchasing 
carcasses; 
• utilisation in the market to indicate variety with a view to optimum consumer satisfaction; 
• utilisation to determine price differences; and 
• fixing selling price. 
(SAMIC, 1998; SA Department of Agriculture. 2002) 
30 
Table 2: South African Classification Characteristics of Beef, Lamb, Sheep and Goat Meat 
(SAMIC, 1998) 
AGE CLASS CONFORMATION CLASS 
0 Teeth A Very flat 1 
1 - 2 Teeth AB Flat 2 
3 - 6 Teeth B Medium 3 
More than 6 teeth C Round 4 
Very round 5 
FATNESS CLASS DAMAGE CLASS 
No fat 0 Slight 1 
Very lean 1 Moderate 2 
Lean 2 Severe 3 
Medium 3 
Fat 4 SEX 
Overfat 5 Only for bull and ram carcasses in the AB, B and C groups. 
Excessively overfat 6 
Table 3: Average age classes of sheep (Clayes & Rogers, 2001:6) 
Classification Age Average age 
A <11 months 6 months 
AB 11-21 months 16 months 
B 21-36 months 30 months 
C >36 months 6 years 
Although these ages indicate that animals that yield AB-carcasses could be about 10 months 
older than those that yield A-carcasses, in some instances the differences could only be one 
month. It is therefore important to inform the customer that the AB-carcasses are not coming 
from old/culled animals, but from production animals that will in most instances only be a few 
months older than the normal A-age animals. (De Bruyn, 2002: 1) . 
2.6.1 Classification of sheep carcasses 
• Classification based on dentition 
20 temporary teeth 
32 permanent teeth at maturity 
pairs of incisor teeth on the lower jaw 
31 
upper incisors missing 
cartilaginous (hard) dental pad on upper jaw. 
• Classification based on the age of sheep 
Table 4: Classification according to the age and dentition of sheep (Clayes & Rogers, 
2002: 1; Matika etal., 2002:3) 
Age Dentition Definition 
Lamb 4 pairs of incisors Lamb:Young sheep under 12 months of age, no 
permanent incisors in wear 
1 year Middle pair of incisors Hogget/Y earling: Animal between 1 & 2 years in 
age, no more than two permanent incisors in wear. 
2 years 2°0 pair of permanent incisors - Mutton: Two or more pennanent incisors in wear. 
3 years 3n1 pair of permanent incisors 
4 years 4th pair of permanent incisors 
5 years All permanent incisors close together 
6 years Incisors begin spreading apart 
7-8 years Some incisors broken 
10-12 years All incisors missing 
In Australia a sheep ceases to be a lamb as soon as the eruption of its first permanent incisor teeth 
is evident. The timing of teeth eruption is highly variable and can range from 10 - 18 months of 
age. After teeth eruption, the carcass is classified as hogget and the price paid is substantially less 
than that for lamb (Bray et al., 1989:303). A study done by the Department of Agriculture in 
Western Australia indicated that the average duration of teeth eruption was 27.4 days. Allowing 
sheep with partially erupted teeth to be classified as lambs could therefore provide producers with 
a four week period in which to market their sheep. Overall the Australian results indicated that 
meat from young sheep with partially erupted teeth was unlikely to be inferior in eating quality to 
the meat currently classified as lamb (Department of Agriculture - Western Australia, 2001: 1) . 
32 
2.6.2 Class-AB Sheep 
From the above information a definition of the class-AB would be sheep at the age of 11 - 21 
months (average age 16 months) with only 1 - 2 permanent incisors present. Although sheep is 
one of the most significant red meat sources in most countries, the native sheep breeds in 
developing countries are usually small and grow slowly (Ockerman et al., 2001 :183; South 
African Department of Agriculture, 2002). 
The sheep producers aim to raise sheep that produce heavier carcasses for a higher income. 
Therefore, old sheep are generally the animals slaughtered in developing countries. As living 
standards increase, consumers are demanding better/higher quality (more tender) meat. There are 
many factors that influence the meat quality of sheep (Sanudo & Alfonso, 1998:30), including 
tenderness and mutton flavour (Ockerman et al., 2001:183). 
In the United States of America sheep numbers have decreased from nearly 30 million head in the 
1960's to 7 million head in 2000. Total production of lamb and mutton has not declined as 
sharply, because of an increase in lamb carcass weight. From 1960 to 2000, the weight of the 
average lamb carcass increased from 22kg to 31kg. This change in carcass size is in part the 
result of improved feed management and an increase in mature size due to direct genetic selection 
and the use of large terminal sire breeds. Studies of consumer preferences indicate a lamb 
product with reduced fat and less intense flavour would be more appealing (Cockett & Snowder, 
2001 : Sl). 
The results ofresearch conducted by Tatum et al. (1978: 144) showed that the eating preferences 
of consumers were consistently in favour of meat from younger animals, due to more tender 
meat. It is well known that advanced chronological age and/or increased physiological maturity 
are usually associated with toughness of mutton and also mutton flavour (Ockerman et al., 
2001:183). As a consequence of age-associated problems with tenderness, the majority of old 
ewes are commonly sold at a low price or the tissue is used in comminated meat (Ockerman et 
al., 2001 : 183). 
2.7 CONSUMPTION OF RED MEAT IN SOUTH AFRICA 
The South African economy faced various economic adjustments over the past two decades. As a 
result, the structure and patterns of consumption have changed significantly (Poonyth et al. , 
2001:426; Traintis, 1995:459). According to Poonyth et al. (2001 :436) the red meat industry 
33 
needs to commit resources to research and develop innovative and consumer friendly items, as 
well as to recognise the fact that consumers place a higher value on their time and that the 
demand for food that requires less preparation time will increase. Price and quality will influence 
the consumer's choice (Mcllveen & Buchanan, 2001: 286). 
Per capita consumption of beef and veal has drastically decreased from 23.95kg in 1965/66 to 
12.32kg in 1999/2000 (approximately 50% reduction). The.per capita consumption of lamb 
reflects a similar pattern, namely a decrease from 7,6kg in 1965/66 to 3,8kg in 1999/2000. On 
the other hand, the per capita consumption of pork remained constant at 3kg over the same 
period. Aggregate per capita consumption of white meat, however, increased from 2,98kg in 
1965/66 to 22.91kg in 1999/2000 (Poonyth et al., 2001 : 427-8). This indicates a significant shift 
in meat consumption patterns. 
The sheep carcass is a more expensive cost item, due to its slower growth rate, lower 
reproduction rate and production under natural conditions. According to Venter and Horsthemke, 
(1999:723) generic marketing is most effective when the product is consumed by the masses at 
low prices and when consumers buy the product for the need of filling or nutritional value. 
(Venter & Horsthemke, 1999:723). If current growth in export and domestic markets continues, 
additional meat needs to be produced. Due to the shortage of available land the answer is not to 
have more sheep, but to produce heavier carcasses (http://lambplan.une.edu.au /mcpt /newsletter 
/dd14/14.htm 29/11/02). Genetic selection for increased lamb carcass weight has reduced the 
decline in the total production of lamb (http://www.oznet.ksu.edu/meatscience/column/lamb. 
14/11/02). 
In the meat industry the pressure for closer relationship or supply chain management derives from 
the needs of supermarkets for quality, consistency, reliability of supply and to ensure safety. The 
perishability of meat also contributes to the need for closer relationship in the value chain (Venter 
& Horsthemke, 1999:724-5). Technical excellence and innovation are becoming more important 
to producers who want to supply food stores with quality products. 
According to Brower (2002), 80% of all animals slaughtered in South Africa are from the A-
class, whereas only 5% of the slaughtered animals are from the AB-class. This underlines the 
trend in consumer demand for more tender meat as well as their misperception that meat other 
than the A-class will be tough and of lower quality. This trend is not only due to consumer 
34 
demand, but also to factors associated with the production system on the farm, e.g weaning, 
breeding programmes and the availability of grazing. 
Table 5: Percentage of animals slaughtered in each meat class in South Africa (Brower, 
2002) 
Class % 
A-class 80% 
AB-class 5% 
B-class 7% 
C-class 8% 
The class-AB makes provision for animals to be raised on veld to a marketable fat cover, because 
in young animals (no incisors) an acceptable fat cover is not achieved on most veld types without 
supplemental feeding (SA Department of Agriculture, 2002). 
2.8 CONCLUSION 
From the literature review it is clear that meat quality, more specifically tenderness, is influenced 
by numerous factors. The evaluation of meat tenderness is complex due to the fact that 
objective measurements can give a value, but cannot give an explanation for the value, e.g. the 
meat : fat ratio in the carcass. Subjective measurement with consumer panels may give a more 
honest opinion. 
Tenderness is one of the most important quality parameters affecting consumer acceptance. The 
problem of consumer dissatisfaction regarding meat products will only be solved when the 
problem of unacceptable variation in meat tenderness is solved. Research on the tenderness of 
electrically stimulated and non-stimulated meat indicates that the shear force values tend to be 
lower in electrically stimulated meat. Electrical stimulation can thus be used to reduce the 
percentage of meat in a population that would be unacceptable in terms of tenderness without 
electrical stimulation and thereby reducing inherited differences. 
Consumers and the meat industry demand continuous high quality products. Electrical 
stimulation of meat can be used to obtain and maintain high quality products. Good quality meat 
must, however, be used to obtain the highest quality, but electrical stimulation can contribute to 
reduce minor differences, due to genotype and the influence of pre-slaughter stress conditions. 
35 
The misconceptions amongst consumers that meat from the AB-class is of a lesser quality 
compared to the class-A, needs to be rectified. This can only be done through more intensive 
research on the class-AB, improved marketing strategies of the class-AB and educating the 
consumer on the advantages of the class-AB. Available information indicates that the class- AB 
sheep carcasses are of a very high quality regarding taste, tenderness and flavour. The class-AB 
also conforms to the most important consumer demands regarding tenderness, flavour, affordable 
prices, safety and the demand towards more "organic/natural/free-range" products. 
Electrical stimulation can be used as a tool to improve tenderness and decrease tenderness 
differences of the class-AB mutton. The effect of electrical stimulation on meat has numerous 
other advantages, such as increased shelf life and improved colour. These advantages are all 
quality characteristics demanded by consumers. 
36 
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42 
43 
CHAPTER3 
Effect of electrical stimulation on consumer acceptance of mutton from class-AB 
sheep carcasses 
M. Davel, M.J.C. Bosman 
School of Physiology, Nutrition and Consumer Sciences, Potchefstroom University for CHE, Potchefstroom, Republic 
of South Africa 
E.C. Webb# 
Department of Animal and Wildlife Sciences, Faculty of Natural and Agricultural Sciences, University of Pretoria, 
Pretoria, 0002, Republic of South Africa 
Submitted for publication in the South African Journal ofA nimal Science. 
44 
Effect of electrical stimulation on consumer acceptance of mutton from class-AB 
sheep carcasses 
M. Davel, M.J.C. Bosman 
School of Physiology, Nutrition and Consumer Sciences, Potchefstroom University for CHE, Potchefstroom, Republic 
of South Africa 
E.C. Webb# 
Department of Animal and Wildlife Sciences, Faculty of Natural and Agricultural Sciences, University of Pretoria, 
Pretoria, 0002, Republic of South Africa 
Abstract 
The inconsistency in the eating quality of meats, predominantly tenderness, is probably the most 
critical problem faced by the meat industry worldwide. Consumers consider tenderness to be the single most 
important component of meat quality. An alternative for increasing meat tenderness may exist in the form of 
electrical stimulation of the carcass shortly following slaughter. The aim of this research was to study the 
effect of electrical stimulation on the consumer acceptance of, preference for and consumption intent 
regarding mutton of the recently introduced class-AB sheep carcasses. A total of 22 wethers of class-AB, 
weighing between 45 and 50 kg, were selected from a homogenous group of Dorpers. Carcasses were 
divided in two groups, of which one group was electrically stimulated (0.4amp/h for 45sec) and the other 
group was not electrically stimulated. Samples of the left M longissimus thoracis et lumborum of both 
groups were oven roasted and a consumer panel evaluated the acceptability of the mutton regarding certain 
sensory characteristics. Three consumer sensory tests, namely the hedonic rating of the acceptability of each 
sensory attribute, a preference test and a food action rating test, were conducted in sequence. The 
acceptability of the juiciness, tenderness, flavour and overall acceptability were not significantly influenced 
by the electrical stimulation of carcasses. Samples from both the electrically stimulated and non-stimulated 
carcasses were highly acceptable to consumers. No significant differences in preference or % cooking 
losses were obtained. The present results indicate that electrical stimulation of class-AB carcasses does not 
have a significant influence on the consumer's acceptance of, nor consumption intent towards the class-AB 
mutton. The consumers revealed a positive attitude by declaring their intention to eat samples from both 
electrically stimulated and non-electrically stimulated carcasses once a week. Moreover, the variation in 
shear force values of meat samples from the electrically stimulated group was less compared to that of the 
non-stimulated group, indicating that electrical stimulation can successfully be applied to reduce the 
variation in tenderness within the class-AB mutton. 
Key words: Class AB-mutton, electrical stimulation, consumer acceptance, tenderness. 
Corresponding author.E-mail:ecwebb@postino.up.ac.za 
Introduction 
Meat quality is a complex concept that is frequently measured using objective indices related to the 
nutritional, microbiological or physiological characteristics (Cardello, 1995). As emphasised by many 
authors, the consumer expectations and perceptions must drive improvement in meat quality. According to 
Cardello (1995), the notion that meat quality must be defined and measured from the consumer's perception 
can be traced to the 1870's when H. Clark indicated that meat quality is a relative concept that is 
inappropriate for evaluation by anyone other than the average consumer. Factors influencing perceived meat 
quality are intrinsic quality cues, convenience, safety and acceptability of sensory characteristics (Schultz & 
Wahl, 1981; Umberger et al., 2000). Meat tenderness can be measured objectively (using instruments) or 
subjectively (sensory analysis e.g. taste panel). Tenderness assessment by laboratory instruments can, 
however, not mimic the complex and multifaceted actions that occur during biting and chewing (Perry, 
2002). 
Red meat consumption has decreased dramatically over the past 30 years. Numerous factors have 
contributed to this phenomenon e.g. economical factors (increased red meat prices), consumer perceptions 
(red meat vs. white meat) and misconceptions in the market (grading system of red meat) (Poonyth et al., 
45 
2001 ). In the current South African red meat classification system, consumers have the perception that class-
A carcasses produce the best quality meat and can therefore have a higher price. The introduction of the 
class-AB in the Beef and Lamb & Mutton Carcass Classification System must be used to highlight the 
unique qualities of the class-AB sheep carcass. The demand and associated marketing of more "natural" 
animal products are increasing daily. From an animal production perspective, this strategy will entail 
excluding the use of synthetic growth stimulants, anti-microbial feed additives and exposing animals to a 
more free-range environment. An important consequence of this shift in animal production is in many 
instances the production of somewhat older animals, compared to those produced in more intensive systems 
(De Bruyn, 2002). The class-AB mutton carcass can definitely be used as an answer to the increasing need, 
seeing that lambs can be left on the field for a longer period, produce an additional shearing and have an 
increased carcass weight. The quality of meat obtained from this method will still be of a high standard and 
acceptable to consumers (De Bruyn, 2002). 
Electrical stimulation can be used to reduce the percentage of meat in a population that would 
otherwise have been unacceptable in tenderness (Lee et al., 2000). Inherent differences can thus be reduced. 
Apart from the tenderising effect of electrical stimulation on meat, numerous other advantages such as an 
increased shelf life, bright red colour and reduced bacterial growth are obtained (Menday, 1979). 
Consumers and the meat industry demand consistent, high quality products. Electrical stimulation of meat 
can be used to obtain and maintain high quality products. Good quality meat must, however, be used to 
obtain the highest quality, but electrical stimulation can contribute to reduce minor differences, e.g. between 
genotypes and the influence of pre-slaughter stress conditions (Bray et al., 1989; Geesink et al., 2001; 
Viljoen et al., 2002). 
In Table 1 a summary is provided of the results obtained in numerous studies on the effect of various 
rates of electrical stimulation on meat quality and consumer perceptions. Electrical stimulation varied 
between 21 V - 11 00V. The drop in pH was significantly faster in the ES samples than in the NES samples 
(Hopkins et al., 2000). Sarcomere lengths were significantly shorter in NES samples. The results obtained 
from Wamer-Bratzler measurements, indicate that ES has a positive effect on the tenderness of meat. 
Evaluating consumer feedback in the above studies, results indicate that scores were significantly lower for 
high-voltage ES (HVES) than for low-voltage ES (LV ES). Control samples (NES) scored lower than the 
LVES. 
Table 1 Comparison of studies done to determine the effect of electrical stimulation on meat characteristics 
Eikelboom et al., Aalhus et al., 2000 Birkhold & Sams, Bouton et al., 1980 Hopkins et al., 2000 
1985 1993 
LYES 85Y 21V 45Y 45Y 
HVES 300Y 440Y vs. 820V 1100V 
pH PH decline in both Decline Significant reduction Lower value for Faster drop in ES 
samples in pH lh/PM II00V than 45Y than in NES 
Insignificant carcasses 
Temperature Increased in ES Drop in temperature 
carcasses 
Sarcomere length Shorter in control 20% shorter in Shorter in control Shortest in control No significant 
than ES samples control than ES than ES samples samples difference 
samples 
Shear force values Lower in stimulated Lower in stimulated Lower in stimulated No significant No significant effect 
samoles samoles samoles differences. 
Cooking loss Increase in ES Significant increase No significant losses 
samoles in ES samoles 
Consumer panels HVES&LYES Higher for LV ES Lower for 1 JO0Y 
(tenderness scores) higher than control than control samples than for l l0Y 
samoles 
Preference Higher for ES Higher for LYES 
samples than control than control 
Conclusion No significant ES reduced ES tenderise meat HVES is more Animal history 
diffences in HVES/ proportion of meat causing myofibrillar unsafe than LYES. influences meat 
LYES meat quality rated as tough, fragmentation LYES increased tenderness 
improved red colour tenderness. 
LVES- low-voltage electrical stimulation, H VES - high-voltage electrical stimulation, ES - electrical stimulation, NES- non-electrically stimulated, 
PM - post- mortem, h - hour, V- volt 
46 
It should be noted that other pre- and post-mortem factors also affect meat tenderness. It is not clear if 
the ageing periods in the above experiments were the same, to what extend the age of animals in different 
experiments differed and which types of muscle were used. 
The present study reports on the effect of electrical stimulation versus non-electrical stimulation on the 
tenderness of meat as well as the consumer' s acceptance of the sensory characteristics of class-AB mutton. 
Materials and methods 
Experimental design 
A total of twenty-two wethers of between 45 and 50 kg live weight (two permanent incisors to yield 
class-AB carcasses with similar fatness scores) were selected from a homogenous group of Dorpers and 
slaughtered at a commercial abattoir according normal procedures. The carcasses were randomly allocated 
to two treatments, namely, electrically stimulated (ES) and non-electrical stimulated (NES). Carcasses were 
clearly marked to indicate ES or NES. Hence, 11 wethers were subjected to the ES procedure and 11 wethers 
to the NES procedure immediately post-mortem. The carcasses in the ES treatment were electrically 
stimulated with an alternating current (ca. 20 V, 45 Hz, 45 s), eviscerated and chilled for 24 hat 2°C. The 
initial carcass temperature and pH at the beginning of cold storage were respectively ca. 30°C and 6.8, which 
decreased to an average carcass temperature of 3°C and pH of 5.8 within 12 hours post-mortem. The 
m.longissimus thoracis et lumborum were split medially, vacuum packed and frozen at - 30°C, pending 
sensory evaluation. The left m. longissimus lumborum samples were oven roasted at l 60°C until an internal 
temperature of 73°C was reached. Total cooking loss was determined according to standard procedure 
(Webb, Bosman & Casey, 1994). A consumer sensory panel evaluated the samples regarding acceptability of 
juiciness, tenderness and flavour (Webb, Bosman & Casey, 1997). Overall acceptance was calculated as the 
average of the attribute scores. Cooked samples were stored overnight in a refrigerator. The following day 
core samples were removed (2.54cm diameter, cut with the grain) and tenderness tested on an Instron Model 
1011 equipped with a Wamer-Bratzler shear blade. Five shear force measurements (N) were made on each 
core sample, by shearing across the grain of the meat. The higher the reading recorded, the greater the shear 
force required to cut through the meat and therefore the tougher the meat. 
Consumer panel 
The target population was defined as actual consumers of mutton, male and female, ages varying 
between 21 to 40+ years. The level of education varied from lower than grade 12 to tertiary education. 
Consumers took part in the consumer test conducted at a central location. One ES sample and one NES 
sample were given to the panellists to compare the acceptability of juiciness, tenderness and flavour. A 
preference test and food action rating test was also conducted. Results from each panel member were 
captured on a questionnaire and later statistically analysed. Section A on the questionnaire was designed to 
obtain demographic information about gender, age and level of education. Section B was the score sheet for 
the sensory consumer tests. 
Consumer sensory tests 
Three sensory tests were conducted in sequence. In the first test subjects had to taste and rate the 
degree of acceptance for each given mutton sample independently on juiciness, tenderness and flavour. A 5-
point hedonic scale was used (l= extremely unacceptable; 5 = extremely acceptable) (Bosman et al. , 1997). 
Overall acceptance was calculated from the attribute acceptance scores. The subjects were also asked to 
indicate whether they preferred one specific meat sample to the other and if so, which one. Consumption 
intent was determined by using a 5-point food action rating scale, with response categories ranging from 
"never eating it" (1); to "will eat it only when no other food is available" (2); to ''will eat it occasionally 
(once per month)" (3); to ''will eat it often (once per week)" (4) and "eating it every day" (5). 
Statistical analysis 
Demographic data of subjects was analysed using descriptive statistics. T-tests (p_'.S0.05) were applied 
to the hedonic attribute scores for each meat sample, using SAS (1992). Non-parametric tests were used for 
the variable consumption intent ( evaluated on a food action rating scale), which did not have equal distances 
between the different categories on the scale. Significant differences in medians within groups were 
determined by using the Wilcoxon matched pairs test, and significant differences by using the Mann-
47 
Whitney U test. A chi-square test would have been performed if the results for preference were significantly 
different. 
Results and discussion 
Consumer panel 
As indicated in Table 2 the consumer panel consisted of 229 actual consumers of mutton, of which 
43% were male and 57% female consumers. Nearly 40% of the consumers were between 21 and 30 years of 
age; only 20% were between 31 and 40 years and almost 40% were older than 40 years . Almost 70% of 
them had training after school, while the rest had only training up to grade 12. 
Table 2 Description of consumer panel (n=229) 
Gender 
A2e Male Female Total % of Total 
21 - 30 years 43 51 94 41 
31 -40 years 16 30 46 20 
>40 years 39 50 89 39 
Total 99 130 229 100 
43% 57% 100 
Acceptance, preference and intended consumption 
As indicated by the results in Table 3, electrical stimulation had no effect on any of the sensory 
acceptance criteria evaluated by the consumer panel (p>0.5) . Consumers rated both the ES and NES samples 
between 4-5 on the hedonic scale, indicating that both ES and NES samples are highly acceptable for 
consumers. Results indicated that there was no statistically significant preference amongst the consumers 
participating in this study towards the ES or NES class-AB mutton samples. According to Figure 1, the ES 
and NES samples were preferred by an equal percentage of consumers (38% ), while 24% did not prefer any 
one to the other. According to the Wilcoxon matched pair test, there was no significant difference (p = 
0.889) between the consumers' consumption intent towards the ES and NES class-AB mutton samples. 
Most of the consumers revealed a positive attitude towards both samples by declaring their intent to eat both 
samples once a week. 
11 ES I 
~ 
Figure 1 Consumer preference of electrically stimulated (ES) and non-stimulated (NES) class-AB mutton 
samples. 
48 
Table 3 Mean(± s.d.) values for the acceptance of sensory attributes, shear force values and% total cooking 
losses of M longissimus dorsi et lumborum samples from ES and NES class-AB sheep carcasses. 
Parameter NES ES p-value 
Sensory acceptance# 
Juiciness 4.2 ± 0.74 4.1 ± 0.80 0.335 
Tenderness 4.1 ± 0.84 4.1 ± 0.79 0.765 
Flavour 4.0 ± 0.83 3.9 ± 0.78 0.591 
Overall acceptance 4.1± 0.65 4.1 ± 0.64 0.372 
Shear force value 37.7 ± 10.57 32.6 ± 5.04 0.168 
(Newton) 
Total cooking loss (%) 20.2 ± 2.54 18.1 ± 2.78 0.078 
#Hedonic scale: 1 = extremely unacceptable 
5 = extremely acceptable 
Shear force evaluation 
Shear force value is a measure of meat tenderness, which is one of the most important factors that 
determine meat quality. A reduction in shear force values and control of the variation in shear values are two 
of the main concerns in tenderisation of meat using electrical stimulation (Li et al., 1994). As indicated in 
Table 3, results obtained from the Instron Warner Bratzler shear force compression test indicated that there 
were no significant differences between the ES and NES samples at the p<0.05 level. The variance between 
the standard deviations, however, indicated that the variation in the tenderness within ES samples were 
significantly less than within the NES samples (p=0.028). These results indicate that ES does have a positive 
effect on reducing the variation in meat tenderness and thus overall meat quality. Because the meat samples 
used in this study were all relatively tender as measured by the Wamer-Bratzler instrument, low-voltage 
electrical stimulation did not significantly improve the tenderness of the muscles studied (Epley, 2002; 
Webb, 1998). The type of muscle used in this study, LTL, is, however, known for its tenderness and would 
not have been significantly influenced by ES. It is possible that the tenderness of other muscles will be 
affected more positively by ES, e.g. shoulder muscles (Bray et al., 1989:65). 
Cooking loss 
As indicated in Table 3, no significant differences regarding the % total cooking losses were found 
between electrically stimulated and non-stimulated samples (p<0.05). It can therefore be assumed that 
electrical stimulation does not have a significant influence on total cooking loss. Increased cooking losses are 
associated with increased slaughter weight and carcass fatness, particularly if the fat contains large 
proportions of unsaturated fatty acids (Webb et al., 1994). 
Conclusion 
From the results obtained it is concluded that there was no significant difference between consumer 
acceptance of juiciness, tenderness, flavour and overall acceptability of the ES and NES samples from the 
class-AB mutton. Both samples were highly acceptable and consumers indicated that both the ES and NES 
class-AB mutton samples would be consumed weekly. Although shear force values indicated no significant 
differences between the ES and NES samples, variances between the standard deviations indicated that the 
variation in the tenderness within ES samples were significantly less than within the NES samples. ES can 
thus be applied in older animals or within the same group to reduce the possible variations in tenderness due 
to factors such as age, animal history, slaughtering conditions and nutrition as well as increase shelf life, 
reduce bacterial growth and enhance the red colour of meat, thus increasing the number of good quality 
carcasses available for consumption. ES can be applied successfully to reduce the variation within the class-
AB mutton group. Other post-mortem treatments should be investigated for their effectiveness in 
combination with electrical stimulation in improving the tenderness of the AB-class, limiting variation of 
tenderness within the group and assuring consistent meat quality. 
It is important to continue researching the role of the consumers' pre-conceptions, particularly in 
relation to their perception of product quality and the likely impact that this will have on future purchase and 
49 
consumption behaviour (Kerth, 1999; Mcllveen & Buchanan, 2001). The misperception amongst consumers 
regarding the quality of class-AB mutton can be addressed by using scientific results to prove the high 
quality of meat in this specific class. 
Acknowledgement 
The authors acknowledge the technical assistance rendered by Mrs E. Pienaar, 4th -year students at 
Potchefstroom University for CHE, students from the University of Pretoria, all the consumers participating 
in the taste panels, LAW Wholesale Meat Suppliers (Groblershoop, Northern Cape) and the Potchefstroom 
University for financial support. 
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49. 
CHAPTER4 
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 
51 
CHAPTER4 
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 
4.1 INTRODUCTION 
In this final chapter, a summary of the main findings from the study in this mini-dissertation will 
be presented. Since the results are discussed, interpreted, elucidated and compared to the relevant 
literature in the preceding chapters, only general conclusions will be made. This will be followed 
by general recommendations regarding the study. 
4.2 SUMMARY OF MAIN FINDINGS 
• With reference to the main objective, the results indicated that both the electrically stimulated 
(ES) and non-stimulated (NBS) mutton samples from the class-AB carcasses were highly 
acceptable to the consumers regarding juiciness, tenderness, flavour and overall acceptance. 
The consumers did not prefer the ES samples to NES samples and also revealed a positive 
attitude to both samples by declaring their intention to eat both samples once a week. 
• Meat from the class-AB mutton carcasses is highly acceptable to consumers. The 
introduction of the class-AB sheep appears to be justified, due to the limited variation in the 
acceptance of sensory characteristics and tenderness of the meat samples, regardless of the 
electrical stimulation of the carcasses. 
• According to these findings the hypothesis was rejected that the meat from the electrically 
stimulated class-AB sheep would be significantly different in terms of acceptance and 
preference by consumers and that it would be consumed more often by consumers than those 
from non-stimulated carcasses. 
• Although shear force values indicated no significant differences between the ES ans NES 
samples, the variance between the standard deviations, indicated however that the variation in 
tenderness within the ES samples was significantly less than within the NES samples. 
52 
• There were also no statistically significant differences in the % cooking losses between the 
electrically stimulated and non-stimulated meat samples from the class-AB carcasses. 
4.3 CONCLUSIONS 
Post-mortem electrical stimulation has received considerable attention as a tool to improve meat 
quality traits such as tenderness, flavour, lean colour and marbling set-up and to reduce dark, 
coarse-band formation. Electrical stimulation improves meat tenderness by reducing ATP 
( conversion of muscle glycogen to lactic acid), rapid reduction of meat pH, increasing the carcass 
temperature and the physical disruption of the tissue. 
Tenderness is one of the most important quality parameters affecting consumer acceptance. The 
problem of consumer dissatisfaction regarding meat products will only be solved when the 
problem of unacceptable variation in meat tenderness is solved. Although research on the shear 
force measurement of electrically stimulated and non-stimulated meat did not indicate that the 
shear force values decrease due to electrical stimulation of the meat, electrical stimulation can be 
used to reduce the percentage of meat in a population that would be unacceptable in tenderness 
without electrical stimulation. In that way inherited differences would be reduced. 
Consumers and the meat industry demand continuous high quality products. Electrical 
stimulation of meat can be used to obtain and maintain high quality products. Good quality meat 
must be used to obtain the highest quality, but electrical stimulation can contribute to reduce 
minor differences, due to age, genotype and influence of pre-slaughter stress conditions. 
The misconceptions among consumers that meat from the class-AB is of lesser quality than class-
A, needs to be rectified. This can only be done through more intensive research of the class-AB 
sheep and educating the consumer on the advantages of the class-AB. Information available 
indicates that the class-AB sheep carcasses are of a very high quality regarding juiciness, 
tenderness and flavour. The class-AB also conforms to most important consumer demands as 
well as new trends in the market. 
53 
Electrical stimulation can be used as a tool to decrease variances in tenderness of the class-AB 
mutton and plays an important role in improving the quality characteristics of the class-AB 
mutton carcasses, and can successfully be used to limit these inconsistencies in meat quality. 
4.4 RECOMMENDATIONS 
• Marketing "older" beef products (e.g. class-AB) to the customer does not imply a name 
change. A class-A and class-AB products are both sold as beef. With sheep, the name of 
class-AB products changes from lamb to mutton with the eruption of the first incisors. 
Despite the fact that the meat quality of the class-A and class-AB products maybe almost the 
same, consumers will discriminate against the product if the name "Mutton" is used for the 
class-AB product. This misperception can be overcome by highlighting the unique qualities 
of the class-AB mutton regarding juiciness, tenderness and flavour and by informing the 
customer that the class-AB is the best quality mutton and that it is only slightly inferior to 
lamb in tenderness. 
• It is important to continue researching the role of consumers ' preconceptions, particularly in 
relation to their perception of product quality and the likely impact that this will have on 
future purchase and consumption behaviour. 
• The misperception among consumers regarding the quality of AB-class mutton can be 
addressed by using scientific results to substantiate the meat quality of this specific class. 
• Future studies are recommended to research the possible variation in meat tenderness within 
the total class-AB mutton carcass spectrum. It can be assumed that age variation will be 
present within the class-AB mutton, due to the variation in age and number of permanent 
incisors within the group. 
• In a follow-up study the shear force values and acceptability of sensory characteristics of 
class-AB mutton should be compared to that of class-A lamb. 
54 
Potchefstroomse Universiteit 
vir Christelike Hoer Onderwys 
Potchefstroom University , 
for Christian Higher Education 
Fo unding 1889 
50 y ears of In d ependence 2001 
Private bag X6001 Potchefstroom 2520 
Tel (018) 299 1111 Fax (018) 299 2799 
http://www.puk.ac.za 
Consumer Sciences 
Tel (018) 299 2472 
Fax (018) 299 2470 
E-Mail vgemjcb@puknet.puk.ac.za 
27 February 2002 
RECRUITING OF CONSUMERS FOR THE SENSORY EVALUATION OF THE 
ACCEPTABILITY OF MUTTON 
The subject group Food Science, Master and final year students are currently busy 
with a research project regarding the effect of electrical stimulation of sheep carcasses 
on the acceptability and meat quality of the meat (mutton). 
The aim of the study is to make recommendations regarding the necessity of electrical 
stimulation on meat quality and sensory acceptability of the sheep meat (mutton) as 
motivation for inclusion of such processes as part of the after slaughtering procedures 
on sheep carcasses. 
We need 200 consumers of mutton, 18 for each session, to take part in the study 
from each of the following age groups, i.e. between 20-30 years, 31-40 and above 40 
years. The taste sessions will take only 10 minutes. 
Dates and times of taste sessions 
Dates Time Time Time 
1. Wed 10 Apr 1.1 09:30 1.2 10:30 1.3 15:00 Students - fully 
booked 
2. Wed 17 Apr 1.2 09:30 2.2 10:30 2.3 -15:00 3 sessions x 18 
each 
3. Thur 18 Apr 3.1 09:30 3.2 11 :30 3.3 15:00 3 sessions x 18 
each 
4. Wed 24Apr 4.1 09:30 4.2 11 :30 4.3 15:00 3 sessions x 18 
each 
5. Thur 25 Apr 5.1 09:30 5.2 11 :30 5.3 15:00 3 sessions x 18 
each 
If you are willing to take part in the study will you please telephone one of the following 
numbers, or send an e-mail to book for a session. 
Prof MJC Bosman 299 24 74  vgemjcb@puknet.puk.ac.za 
Mrs E Pienaar 299 2474 vgeep@puknet.puk.ac.za 
The secretary 299 2470 (o nly if no answer at 24 7 4) 
Potchefstroomse Universiteit 
vir Christelike Hoer Onderwys 
Privaatsak X6001 Potchefstroom 2520 
Tel (018) 299 1111 Faks (018) 299 2799 
O n tstaan 1 8 69 
5 0 j aar se lfstandig 2001 http://www.puk.ac.za 
Tel (018)299 2472 
Faks (018) 299 2470 
27 Februarie 2002 
WERWING VAN VERBRUIKERS VIR DIE SINTUIGLIKE EVALUERING VAN DIE 
AANV AARBAARHEID VAN SKAAPVLEIS 
Die vakgroep Voedsel,Nagraadse en Finalejaar Voedsel studente is tans besig met 'n 
navorsingprojek in verband met die effek van elektriese stimulering van 
skaapkarkasse op die aanvaarbaarheid en kwaliteit van die vleis. 
Die doel van hierdie studie is om aanbevelings in verband met die noodsaaklikheid 
van elektriese stimulering vir hoe vleiskwaliteit te maak ter motivering vir insluiting van 
sodanige prosesse as deel van naslagtingsprosedures. 
Ons benodig 200 verbruikers, 18 per sessie, pertinent bekend met skaapvleis, uit elk 
van die volgende ouderdomsgroepe, om aan hierdie studie deel te neem naamlik 
tussen 20-30 jr; 31 -40 jr en bo 40 jr. Die proesessies sal slegs 10 minute duur. 
Datums en tye vir proesessies: 
Datums Tyd Tyd Tyd 
1. Wo 10 Apr 1.1 ------- 1.2 ------- 1.3 ------- 1 sessie x 18 
(1 .1 en 1.2 vol ) 
2. Wo 17 Apr 1.2 09:30 2.2 10:30 2.3 15:00 3 sessies x 18 
benodig 
3. Do 18 April 3.1 09:30 3.2 11 :30 3.3 15:00 3 sessies x 18 
benodig 
4. Wo24April 4.1 09:30 4.2 11 :30 4.3 15:00 3 sessies x 18 
benodig 
5. Do 25 April 5.1 09:30 5.2 11 :30 5.3 15:00 3 sessies x 18 
benodig 
lndien u bereid is om aan hi~rdie studie deel te neem, sal u asseblief een van die 
ondergenoemde persone skakel of 'n e-pos stuur om vir 'n sessie te bespreek. 
Prof MJC Bosman 299 2474 vgemjcb@puknet.puk.ac.za 
Mev E Pienaar 299 24 74  vgeep@puknet.puk.ac.za 
Die sekretaresse 299 24 70 (slegs indien geen antwoord by 2474) 
CONSUMER QUESTIONNAIRE: STRICTLY CONFIDENTIAL 
QUESTIONNAIRE NO. 
SESSION NO. 
TREATMENT CODE. 
SHEEP NO. 
* Mark the appropriate square with a cross (X) 
SECTION A 
DEMOGRAPHIC INFORMATION 
1. GENDER For office 
use only 
I Male 1 
Female I 2 I D 
2. AGE 
Between 21 and 30 years 1 
Between 31 and 40 years 2 
Older than 40 years 3 D 
4. EDUCATIONAL 
QUALIFICATION 
Matric / Grade 12 1 
Deqree I Diploma 2 
D 
1 
SECTION B 
SENSORY EVALUATION OF THE ACCEPTABILITY OF MEAT SAMPLES WITH 
RESPECT TO VARIOUS CRITERIA 
• Evaluate the acceptability of the meat samples (in the specified order) with respect 
to the given criteria by marking the appropriate square with a cross. 
EXTENT OF ACCEPTABILITY 
Meat 5 4 3 2 1 Office use 
Criteria sample Extremely Acceptable Neutral Not Extremely 
codes acceptable accept- unaccept- Code 
able able 
1 
Juiciness 2 
3 
1 
Tenderness 2 
3 
1 
Flavour 2 
3 
• You have now evaluated all the samples for acceptability according to certain 
criteria 
Is one of the samples in total more acceptable than 
the others? □ 
If Yes, which one? Write down the code in the I..... ______ . 
square. □ 
• Please indicate how often you will be willing to eat each of the meat samples. 
Choose only one option under each code. 
Sample code 
305 510 Codes 
5. I will eat it very often ( every day). 5 
4. I will eat it often (1x/week). 4 
3. I will eat it occasionally (1x/month). 3 
2. I will only eat it when no other food is 2 
available. 
1. I will never eat it. 1 
Copyright reserved : Prof. MJC Bosman 
2 
VERBRUIKERSVRAELY S: STRENG VERTROULIK 
VRAELYS NO. 
SESSIE NO. 
BEHANDELINGSKODE 
SKAAP NO. 
* Merk die toepaslike blok met 'n kruisie (X) 
AFDELING A 
DEMOGRAFIESE GEGEWENS 
1. GESLAG Slegs 
vir 
kantoor 
-1~-:-o~_l:-:-------~1-:__.lge~ 
2. OUDERDOM 
Tussen 21 en 30 jaar 1 
Tussen 31 en 40 jaar 2 
Ouer as 40 iaar 3 D 
4. OPVOEDKUNDIGE 
KWALIFIKASIE 
Matriek / Graad 12 1 
Graad I Diploma 2 
D 
1 
AFDELING B 
SINTUIGLIKE EVALUERING VAN DIE AANVAARBAARHEID VAN 
VLEISMONSTERS TEN OPSIGTE VAN VERSKILLENDE KRITERIA 
• Evalueer die aanvaarbaarheid van die vleismonsters (in volgorde soos aangedui) 
ten opsigte van genoemde kriteria deur 'n kruisie in die toepaslike blokkie te maak. 
MATE VAN AANVAARBAARHEID 
5 4 3 2 1 K an t oo rqe ru, 
Kriteria Vleismon- Besonder Aanvaar- Neutraal Nie aan- Glad nie 
ster kodes aanvaar- baar vaarbaar aanvaar- Kode 
baar baar 
Sappigheid 1 
2 
3 
Sagtheid 1 
2 
3 
Smaak 1 
2 
3 
• U het nou al die monsters vir aanvaarbaarheid volgens sekere kriteria geevalueer. 
Is een van die monsters vir u in totaal meer aanvaarbaar as 
die ander? D 
lndien Ja, watter een? Skryf kode in die blokkie neer. 
• Dui asseblief aan hoe dikwels u bereid sal wees om elk van die vleismonsters te 
eet. 
Merk slegs een blokkie teenoor elke monsterkode. 
Monsterkode 
305 510 Kodes 
5. Ek sal dit baie dikwels eet (elke dag) .. 5 
4. Ek sal dit dikwels eet (1x/week). 4 
3. Ek sal dit af en toe eet (1x/maand). 3 
2. Ek sal dit slegs eet indien daar geen ander 2 
voedsel beskikbaar is nie. 
1. Ek sal dit nooit eet nie. 1 
Kopiereg voorbehou: Prof. MJC Bosman 
2 
SESSION: CONSUMERS:!~-~ 
S!ieep 510 [NES] Animal no!.__ ___ _, 
Mass raw (x) = . . . . . . . . . . . . . . . . . . . . . g 
Mass cooked (y) = . . . . . . . . . .. . . . . . . . g 
Mass loss (x-y): .......... ... .. .. . .. .. g 
% mass loss = . . . . . . . . . . . . . . . . . . . . . . % 
Cooking time: . . . . . . . . . . . . . . . . . . . . . min 
Time INTO oven .... ....... . ... . . 
Time OUT oven ...... ... .. .. .. . . 
Stand: 10 min 
Cut: 1 min 
Serve: ... ... ... .... ..... .. .. ... ...... . 
SESSION : CONSUMERS: .__I_  ____, 
Sheep 305 [ES] Animal nol~ - -~ 
Mass raw (x) = . . . . .. . . . . .. . . . . ..  . . . g 
Mass cooked (y) = . .. ... ... ... . .. ... g 
Mass loss (x-y) : ............... ....... g 
% mass loss = . . . . . . .. . . . . . . . . . . . . . . % 
Cooking time: . .. .. . . .. . . . . .. . . . . . . min 
Time INTO oven ........ . ... .. .. . 
Time OUT oven .............. . .. 
Sta rid : 10 min 
Cut · 1 min 
Serve: ............... .. . .. ... .... .... .