Influence of fermentation period on the chemical and functional properties, antinutritional factors, and in vitro digestibility of white lima beans flour

This study evaluated the variation in chemical and functional properties, antinutritional factors, and in vitro digestibility during the natural fermentation of white lima bean (Phaseolus lunatus) at different fermentation periods of 0, 24, 48, 72, and 96 h using standard methods. The results showed that an increase in the fermentation period resulted in a significant (p < 0.05) increase in protein and ash content, while fiber and fat content decreased with the length of fermentation. Also, there was an optimum increase by 92%, 56.39%, and 58.16% in β-carotene, vitamin B2, and vitamin B3 at 24 h fermentation. Results showed that the fermentation period increased the mineral composition except for sodium which had a slight reduction though no significant (p < 0.05) difference was observed in the fermented samples. The antinutritional factors decreased linearly as fermentation progresses from 19.05-13.26 mg/100 g, 35.29-19.05 mg/100 g, 18.00-7.15 mg/100 g, and 3.09-1.35 mg/100 g for phytate, tannins, alkaloids, and oxalate, respectively. Fermentation significantly decreased the bulk densities, and swelling index, while water and oil absorption capacity, foaming properties, and emulsion capacities increased as fermentation progresses. Furthermore, protein digestibility improved from 50.33% to 58.50% and the glycemic index (GI) increased significantly (p < 0.05) with GI values of 57.18, 62.36, 62.67, and 62.82 for 24, 48, 72, and 96 h, respectively. This implies that these are all intermediate GI foods. This study showed that fermentation periods influence the quality of lima beans and this can be used to improve nutrition especially in the rural communities and find applications in food product development. PRACTICAL APPLICATION: Lima beans are underutilized crops in comparison with other legumes. This is attributed to problems associated with digestion on consumption and its long hours in cooking described as "hard to cook" phenomenon which is reported to be attributed to the presence of significant amount of antinutrients such as tannins and phytates. The nutritional value of lima beans will be increased, along with their acceptance and consumption as food, by the reduction or inactivation of these antinutritional factors.