Tannin contents and protein digestibility of black grams (Vigna mungo) after soaking and cooking.

The objective of this research was to ascertain the effects of soaking black grams (Cultivar AARI-5732) in different salt solutions at different temperatures and different time periods, and different methods of cooking on the tannin content and protein digestibility. Tannin content of black grams was reduced to various extents by soaking at 30 degrees and 100 degrees C for different time periods. However, soaking at 100 degrees C increased the rate of extraction and reduced the extraction time of tannins. Soaking black grams in water at 100 degrees C reduced tannins by 22.14% in 45 minutes whereas about 2.5 times more tannin was reduced after soaking in sodium bicarbonate solution with or without sodium chloride. Maximum improvement in protein digestibility was also observed after soaking black grams in sodium bicarbonate solution. Tannin contents were further reduced along with improvement in protein digestibility as a result of cooking.