Influence of phytate on in vitro digestibility of casein under physiological conditions

The phytic acid content of four different varieties of beans under different processing conditions was estimated. It was highest in red kidney (1.86-2.13%) slightly lower in pigeon (1.86-2.03%), white (1.80-1.96%) and black eyed beans (1.15-1.64%). There was no significant change in phytic acid content of beans after soaking at 25 degrees C for 22 hours. However, both soaking and cooking revealed 26-37% loss of phytic acid in all four varieties of beans. The rate of in vitro casein digestibility with and without phytic acid at concentrations found in legumes was determined at pH 8 and 37 degrees C using multienzyme technique. Addition of 5 mg Na-phytate reduced the casein digestibility up to 20% compared to the control. However, only 25% reduction of casein digestibility was observed in the presence of 25 mg of Na-phytate. Higher concentration of Na-phytate had no significant effect on the rate of casein digestibility. Data strongly suggest the formation of protein phytate complex at alkaline pH of small intestine.