The impact of heating and soaking on the in vitro enzymatic hydrolysis of protein varies in different species of tropical legumes

The effects of different thermal (raw, autoclaving or boiling for 5 and 20 min) and soaking (with or without) treatments on the degree of hydrolysis (DH) of protein were investigated for selected legumes (Canavalia brasiliensis; Lablab purpureus; pink, red and white colour hulls Vigna unguiculata). Each legume preparation underwent in vitro simulated gastrointestinal tract digestion comprising either pepsin (120 min) or pepsin/pancreatin (120/240 min) digestion. The DH was determined based on the amount of free amino groups released. Autoclaving for 5 min increased the pepsin/pancreatin DH for all the unsoaked and soaked legumes (+20% to 46% units) except Canavalia, while boiling for 5 min only increased DH for two soaked legumes (+12% to 28% units). Extending boiling from 5 to 20 min increased the DH for three soaked legumes (+5% to 29% units). In conclusion, autoclaving, in general, extensively increased the sequential pepsin/pancreatin DH, while boiling only increased it for selected legumes.