Action on Human Enzymes

Inhibitor activity is normally determined with commercial animal enzymes, e. g., bovine trypsin or bovine chymotrypsin. The evaluation of a potential effect of the inhibitors on human health assumes that the inhibition of human enzymes is known. Present data show that inhibitors from legumes generally inhibit human trypsin to the same extent or a little less than bovine trypsin. On the other hand, human chymotrypsin is inhibited to a much greater extent by most legumes. Ovomucoid and ovoinhibitor from egg white as well as the Kazal inhibitor from bovine pancreas do not inhibit the human enzymes. The Kunitz inhibitor from bovine pancreas inhibits human trypsin but not chymotrypsin. The data obtained greatly depend not only on the substrate used, but also on the enzyme preparation and the reaction conditions, e. g., on the ratio enzyme/inhibitor. The stability of an inhibitor as it passes through the stomach must also be taken into account in the evaluation of a potential effect (cf. Table 16.15). The Kunitz inhibitor of soybeans, for 

The inactivation of proteinase inhibitors in the course of food processing has been the subject of many studies. In general, the inhibitors are ther-molabile and can be more or less extensively inactivated by suitable heating processes. In these processes, both the starting material as well as the process parameters are of great importance (time, temperature, pressure, and water content of the sample) (Table 16.16). Steaming of soybeans for 9 minutes at 100 °C causes an 87% destraction of inhibitors (Table 16.17). 

A decrease in tbe inhibitor activity can also be achieved by soaking. A tbermal step can then follow under gentler conditions. Altbougb the processing of soybeans into protein isolates, textured protein, or meat surrogates causes a decrease in the inhibitor activity against tr)fpsin, noticeable activity can still be present (Table 16.18). Soybeans promote the growth of rats to the same extent as casein when about 90% of tbe inhibitor activity is eliminated (Table 16.19). 

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