Inositol Phosphate Content of Selected Dry Beans, Peas, and Lentils, Raw and Cooked

Abstract

Fourteen varieties of dry legumes available in local supermarkets were analyzed for inositol phosphate profile in the raw state and after cooking. Inositol tris-, tetrakis-, pentakis-, and hexakisphosphate (IP3–IP6) were determined by a HPLC procedure. The concentration of inositol phosphates in raw dry legumes did not differ significantly among three different brands. Phytic acid (IP6) concentration (per kg dry basis) ranged from 6.0 mmol in chickpeas to 14.2 mmol in black beans. Phytic acid was the predominate inositol phosphate of the total inositol phosphates determined in raw dry legumes, ranging from 77% in chickpeas and pigeon peas to 88% in black beans. The remainder of the inositol phosphates in raw, dry legumes were IP4and IP5, except lentils contained, in addition, a detectable amount of IP3. The cooked legumes all contained detectable amounts of IP3, increased amounts of both IP4and IP5, but lower amounts of IP6in comparison to the raw dry legume (differences between uncooked and cooked were statistically significant,P< 0.05). The concentration of IP6in the cooked legumes averaged 83%, ranging from 68% in red kidney beans to 86% in chickpeas, of the concentrations in the raw dry legumes. Phytic acid remained the predominate inositol phosphate in cooked legumes, averaging 68% of the total and ranging from 60% in pigeon peas to 78% in yellow split peas. Quick soak vs overnight soak of beans before cooking resulted in no difference in inositol phosphate concentration or profile of cooked beans. Although the total inositol phosphates did not differ significantly between raw and cooked dry legumes (P> 0.1), the IP6and IP5+ IP6represented a smaller percentage of the total in the cooked legumes, suggesting that cooking decreases the potential adverse impact of inositol phosphates on mineral utilization when legumes are included in the diet.