Effect of trypsin inhibitor on protein quality of black-soybean and mothbean meals

Proteins of black-soybean (Glycin max var 'kalitur') and mothbean (Vigna aconitifolius) were found to be nutritionally poorer with protein efficiency ratio (PER) values of 0.55 and 0.90, respectively, as compared to 2.66 for casein under similar conditions. Mild processing methods viz., buffer extraction and chemical acetylation in cold to free the meals of their trypsin inhibitory activities, improved the PER values to 1.54 and 1.12. Raw defatted meals fed to rats produced extensive changes in the weight and the enzyme activities of the pancreas and small intestine. They increased the activities of protease and trypsin of pancreas and small intestine, but lowered that of amylase over the control group fed on casein. Feeding of buffer-extracted and acetylated meals, however, did not affect the activities of these enzymes, indicating the involvement of trypsin inhibitors present in defatted meals. The acid and alkaline phosphatase activities of liver and small intestine were also higher in all groups compared to control and therefore, may not be linked to the presence of trypsin inhibitors. The changes produced by the defatted soybean meal were relatively greater than the defatted mothbean meal, thereby indicating a relationship between the level of trypsin inhibitor and the protein quality.