In vitro determination of calcium bioavailability of milk, dairy products and infant formulas

In this study, the aim was to determine the in vitro calcium bioavailability of different dairy products and to investigate the effect of dry matter, fat, acidity and calcium content on calcium bioavailability of the products. For this purpose, the dry matter, fat, acidity and calcium content of different kinds of milk, yogurt, cheese and infant formulas were analysed. Then, calcium bioavailability of products was determined by an in vitro method that involves simulating gastrointestinal digestion of the product with pepsin - HCl and pancreatin - biliary salts, and then measuring the fraction of element that dialyses through a membrane of a certain pore size. Each of the product groups was examined statistically and no difference was found among milk, yogurt and infant formula groups in terms of calcium bioavailability. However, there were differences among cheese kinds according to the results of the Duncan test; all cheese kinds were considerably different from each other (P < 0.05). Moreover, it was found that calcium, dry matter, fat content and acidity did not affect the calcium bioavailability (P < 0.05). According to the results of statistical analysis that was applied to all product groups, it was found that the yogurt group was different from the other products and that the acidity affected calcium bioavailability (P < 0.05).