Endogenous Phytate-Degrading Enzymes Are Responsible for Phytate Reduction While Preparing Beans (Phaseolus Vulgaris)

The three dry nonprocessed bean varieties contain high amounts of phytate ranging from 9.3 to 15.9 μmol g-1 dry basis, representing 85 to 89% of total myo-inositol phosphates, while the other myo-inositol phosphates were found only in small or trace amounts. Myo-inositol phosphate concentrations were not affected by soaking in water for 15h at 25C, whereas cooking resulted in a significant reduction in phytate content (16 to 24%) with a concomitant increase in the concentrations of the lower myo-inositol phosphates. The sum of phytate and myo-inositol pentakisphosphate after soaking and cooking represents about 93% of the amount in raw beans. Therefore, preparing of beans has only a limited effect on the content of myo-inositol phosphates with inhibitory effects on mineral absorption. Phytate-degrading enzymes (phytases) were identified as responsible for phytate removal during cooking, since a good correlation between phytase activity and phytate hydrolysis was observed.