Investigation on post-harvest processing of fruits using a Solar-Bio-energy Hybrid Dryer

Abstract

Fruits and vegetables are key sources of vitamins and minerals that are essential for a healthy diet. They are, however highly perishable, shortening their shelf life. To address this, various processing technologies such as the traditional open sun drying have been explored. This practice, however, leaves the products vulnerable to dust contamination, rodent attack and non-uniform drying. Furthermore, it is an inconsistent process that is dependent on solar availability thereby extending the drying process. This inconsistent process promotes microbial contamination, remoistening of products and reduced quality of the products. It is on this basis that a solar-bio-energy hybrid powered fruit dryer was designed and developed. The aim of this technology is to enhance the drying process through continuous drying and increased drying rates using clean energy that is easily accessible to smallholder farmers. The hybrid fruit dryer consists of a solar collector, drying chamber and bio-reactor unit. Banana fruit and Kei apple were evaluated in this study to make dried banana discs and Kei apple and banana fruit leather. The banana fruit was pretreated in lemon juice and dried in the hybrid dryer. To make the fruit leather, Kei apple was blended with banana fruit and honey then the paste was dried in the hybrid drier. The control experiment was traditional open sun drying. The ambient temperature range was between 15-38°C and the temperatures of the solar-bio-energy hybrid dryer air reached above 80°C. Air temperatures and drying rates were negatively correlated with r = -0.66, whereas relative humidity and drying rates were strongly positively correlated with r = 0.90. The solar-bio-energy hybrid dryer had a higher drying rate and efficiency compared to open sun drying and to drying the fruit without the bio reactor unit. It was also capable of drying the fruit beyond sunshine hours. The availability of this technology to rural communities would contribute to food security at household level by making processed fruits and vegetables available in-between cropping seasons. This is often referred to as hunger periods. Furthermore, this technology produces good quality value-added products that are marketable to a wider consumer catchment. It also has the potential to facilitate employment creation in rural areas and bio-entrepreneurship amongst women and the youth through the production of high-quality value-added products.