Nutritional improvement of beans (Phaseolus vulgaris) by natural fermentation

The effect of natural fermentation of flour and whole beau seeds (Phaseolus vulgaris) on the content of nutrients (protein, fat, starch, dietary fiber, vitamins B-1 and B-2) and antinutritional factors (alpha-galactosides, trypsin inhibitor activity and inositol phosphates) has been studied. After fermentation, total protein content decreased (2-15%) but the in vitro protein digestibility increased (4-8%) and the fat content did not change. In fermented bean flours, fructose and sucrose decreased (67-83% and 99-100% respectively), glucose increased (175-750%) and galactose was present at the concentration 1:4 g/ml (flour:water), but when whole beans were fermented none of these soluble sugars were detected. Total starch, available starch, insoluble fiber content decreased after fermentation (5-13%, 10-24%, and 5-26%, respectively), which was less pronounced in whole fermented beans. The soluble dietary fiber decreased (61-71%). The vitamin B-1 content decreased (17-38%) and the vitamin B-2 content increased (16-35%) after fermentation. Fe, P, Mg, Ca, and K decreased and Zn content did not change after natural fermentation. In either fermented flour or whole beans, the alpha-galactosides and IP6 decreased (99-100%, 7-39% respectively); however in fermented flour beans IP5 content did not modify or decrease and IP4 content could also increase. When whole bean grains were fermented no IP5 and IP4 was detected. TIA levels and tannins content decreased (58-71% and 61-70%) after fermentation. Natural fermentation of beans has been a very effective process for increasing functionality of Phaseolus vulgaris and the whole bean fermentation is very promising due to the lower cost.