Dialysable, soluble and fermentable calcium from beans (Phaseolus vulgaris L.) as model for in vitro assessment of the potential calcium availability

Calcium potential availability from mottled and white bean was studied by using an in vitro model which simulates the conditions existing in the small intestine and the fermentation process in the colon. Beans contained high amounts of calcium which distribution in the seed varied greatly (hull 70%, cotyledon 30%). The percentage of calcium dialysability in both bean varieties was in the range of 14%. Dehulling greatly improved calcium dialysability; when compared to whole seed, increases of up to 97% (p<0.01) were found. Calcium dialysability from the hull was very low (4–8%). Dialysable calcium and soluble calcium were not affected by cooking. Results indicated that phytate was not the main inhibitor of calcium dialysability from beans. The overall calcium dialysability from beans was mainly influenced by the calcium status in the hull. Calcium released from retentate (from 24 to 72%), during in vitro fermentation experiments indicated a substantial degradation of the undialysable High Molecular Weight (HMW) calcium complexes within the 14 h of the fermentation process.