Protease Inhibitors in Processed Plant Foods

Plants contain a wide variety of protein protease inhibitors. However, most is known about the serine protease (trypsin and chymotrypsin) inhibitors found in legumes, particularly soybeans. These inhibitors in unheated legume protein (a) impair the protein's nutritional quality, (b) induce pancreatic hyper-trophy in some but not all experimental animals, (c) enhance the action of chemical pancreatic carcinogens in Wistar rats but not hamsters or mice, (d) are reported to be carcinogenic to the pancreas of Wistar rats and (e) inhibit certain experimental tumors in rats, mice and hamsters. The physiological significance of the low residual protease inhibitor levels in commercially processed plant proteins and human foods prepared from such proteins remains to be resolved. Plant proteins prepared for human consumption, however, contain low levels of pro-tease inhibitor activity which are of no nutritional concern in animals or humans.