Effect of Myoinositol Phosphate Esters on In Vitro and In Vivo Digestion of Protein

Effects of phytate and its hydrolysis products (myo-inositol phophate esters) on protein digestion were investigated by in vitro and in vivo procedures. Tri-, tetra-, penta-, and hexa-phosphate ester fractions, isolated from phytate hydrolysates, inhibited pepsin digestion of casein and bovine serum albumin in vitro. The inhibition ranged from 0% for the mono- and diphosphate esters to 9–14% with the hexa-phosphate ester (phytate). The phosphate ester fractions did not significantly affect trypsin digestion of the proteins. In the in vivo study, rats were fed phytate and hydrolysates thereof (mixtures of the esters above) at levels of 1–3.5% of the diet. Under the conditions of this study, neither phytate nor its hydrolysates significantly affected protein utilization or weight gain in rats.