The glycaemic index of muffins baked with extruded dried bean flour compared to muffins baked with whole wheat flour

Abstract

Introduction: Emphasis on using the glycaemic index (GI) in addition to carbohydrate exchange lists has led to a greater variety of foods from which to choose for the diabetic population. Breakfast is regarded as the most important meal of the day and the glycaemic response to lunch can be improved by decreasing the GI of breakfast. However, most conventional breakfast cereals and bread exhibit a high GI. Dried beans have a low GI and various processes such as cooking and canning increase GI values, but still in the low GI range. In recent years, extrusion cooking has become one of the popular new processes developed by the food industry. Extrusion provides a convenient alternative for the ingestion of dry beans in the diet. Muffins are eaten by many South Africans and may be an ideal alternative for breakfast cereals and bread, especially if the GI of the muffins is low. The aim of this study was to determine the GI of a muffin baked with extruded bean flour and compare it to the GI of a muffin baked with whole wheat flour. Subjects and methodology: The study cohort consisted of ten healthy males and ten healthy females. Subjects randomly consumed test meals of glucose (the reference), bean muffins and whole wheat muffins on different days. Each test meal provided 509 available carbohydrate as analysed by the Englyst method. Results: The GI of the muffin baked with extruded bean flour (mean 53.0%, Confidence intervals (CI): 41.7; 64.2) was not significantly different from that of the whole wheat muffin (mean 55.5%, CI: 41.8; 69.2) but still in the low to intermediate GI category. Conclusion: Extrusion of dried beans results in a fine flour with relatively no intact starch which may explain the very low resistant starch content (1.6I100g) of the muffins. The small particle size of the fine flour could further have contributed to the higher than expected GI of the bean muffin because the size of the particle is inversely related to glycaemic response. Muffins baked with extruded dried bean meal are nevertheless regarded as an excellent choice for breakfast and as part of the prudent diet. Beans have additional health benefits and are included in the South African Food Based Dietary Guidelines.