Effect of Storage Conditions and Chemical Treatments on Firmness, in Vitro Protein Digestibility, Condensed Tannins, Phytic Acid and Divalent Cations of Cooked Black Beans (Phaseolus vulgaris)

Black beans stored at 30° or 40°C and 80% relative humidity showed marked increases in firmness and decreases in in vitro digestibility of proteins. Changes in these properties were small when beans were stored at 5°C and 50% relative humidity. The adverse effects of poor storage conditions could be practically eliminated by soaking beans in salt solutions instead of water. The changes in firmness and digestibility were accompanied by changes in the detectable concentrations of tannins and phytates. Protein digestibility appears to be reduced by interactions between protein and tannins, especially high molecular weight tannins. Concentration of these tannins is affected by poly‐phenol oxidase activity. Firmness increased and protein digestibility decreased as the phytic acid content decreased.