Cowpea inhibition of human and bovine protease activities and the effects of processing

Abstract

The inhibition of human and bovine pancreatic trypsin, chymotrypsin and total proteolytic activity of extracts from the red cowpea was studied. The thermal lability of the inhibitors was also assessed. The raw cowpea samples used had a trypsin inhibitor activity (TU) level of 14.3 mg tvpsin inhibited/g sample. Inhibition of proteolytic activity was influenced by the type and source of pancreatic enzymes. At all levels of raw cowpea extract concentration, bovine trypsin was inhibited to a significantly greater extent (P < 0.05) than was human trypsin. The most drastic inhibitory effects of raw cowpea was, howevel; observed in hydrolytic systems containing human chymotrypsin. The action of cowpea inhibitors was less pronounced (maximum of 50% inhibition) on total proteolytic activity compared to individual inhibitions of trypsin and chymotrypsin. With regards to processing effects, almost complete inactivation of inhibitors was achieved by cooking whole cowpea seeds after soaking and dehulling, while only partial inactivation occurred when raw cowpea was milled into flour before cooking. Effective control of the inhibitory activities in cowpea for maximum nutritional benefits can therefore be achieved by soaking, dehulling and cooking whole cowpea seeds