THERMAL INACTIVATION OF LECTINS AND TRYPSIN-INHIBITOR ACTIVITY DURING STEAM PROCESSING OF DRY BEANS (PHASEOLUS-VULGARIS) AND EFFECTS ON PROTEIN-QUALITY

The effect of steam treatment on the protein quality and antinutritional factors in beans (Phaseolus vulgaris L) have been evaluated. The thermal inactivation of total and functional lectins and trypsin inhibitor activity as well as total and available lysine during steam treatment at 102, 119 and 136°C can be described by first order reaction kinetics. Inactivation of trypsin inhibitor factors occurred in two stages with different reaction rates, the initial stage having a higher rate of inactivation. The effect of steaming temperature on the rate constants can be predicted by an Arrhenius‐type relation. Part of the total lysine was lost on heating but the amount of available lysine was reduced to a greater extent. The results of the present investigation indicate that steam treatment at 119°C for 5 or 10 min seems to be a good compromise in terms of antinutritional factor inactivation and protein damage as measured by total and available lysine. Copyright © 1990 John Wiley & Sons, Ltd