Improving enzymatic reduction of myo-inositol phosphates with inhibitory effects on mineral absorption in black beans (Phaseolus vulgaris var. Preto)

Activation of endogenous or addition of exogenous phytases during food processing gives a chance to reduce the phytate content in the final product to a nutritionally acceptable level. Optimal conditions for the endogenous phytases of black beans, this is 60C and pH 6.0 resulted in a 55% reduction in IF, after soaking and cooking. The sum of IP6 and IP5 was reduced by 54%. IP6 reduction was most extensive when black beans were soaked at 50C while adding exogenous phytases during the last 2 h of soaking. After soaking and cooking IP6 was degraded by 85% and the sum of IP6 and IP5 was reduced by 82% compared to the values in raw beans when adding Escherichia coli phytase. Using rye phytase the values were estimated to be 73% and 70%, thereby a clear accumulation of IP4 occurred. Thus, a significant improvement in reduction of myo-inositol phosphates with adverse effects on mineral bioavailability has been achieved in comparison to the usual household procedure.