Use of hydration, germination, and α-galactosidase treatments to reduce oligosaccharides in dry beans

This investigation was done to determine an energetically feasible method to reduce bean oligosaccharides (stachyose and raffinose) for large-scale bean flour production. Michigan black, red, and navy beans (all Phaseolus vulgaris) were treated by α-galactosidase, germination, or hydration to determine treatment effects on stachyose and raffinose levels. Oligosaccharides were extracted with 70% (w/w) ethanol, and α-galactosidase was added to catalyze hydrolysis of the oligosaccharides. Enzyme treatment was for 1 h at ambient temperature (23 °C). For germination, whole beans were incubated in a germinating chamber (100% humidity, 26.7°C) for 48 h. In hydration, whole beans were soaked in excess water at ambient temperature (23°C) for 5 h. Enzyme treatment resulted in 51% ± 3.0%, 30% ± 1.9%, and 48% ± 1.9% reduction in total raffinose and stachyose for black beans, red beans, and navy beans, respectively. Germination treatment resulted in 61% ± 12%, 61% ± 1.9%, and 70% ± 2.8% reduction in total raffinose and stachyose for black beans, red beans, and navy beans, respectively. Hydrated black beans showed a loss of 33% ± 9.6%, whereas hydrated red and navy beans showed no reduction of oligosaccharides. Although germination showed the greatest reduction in bean oligosaccharides, this method may not be as cost-effective commercially as the enzyme treatment because of the time required for germination.