ABSTRACTThe effects of sodium phytate and partially hydrolyzed sodium phytate (0 ‐ 82% hydrolyzed) on pepsin digestion of casein and bovine serum albumin were evaluated by an in vitro procedure using dialy‐sates of pepsin digestion over a period of 0 – 23 hr. The inhibitory effect of phytate differed with substrate and increased with dose level. At the highest phytate level, the digestion of casein and bovine serum albumin was reduced by 14% and 7%, respectively. The inhibitory effect of the phytate was inversely correlated with the degree of phytate hydrolysis. Hydrolysis for 16 hr almost eleminated the inhibitory effect of phytate.