Bioaccessibility of minerals in school meals: Comparison between dialysis and solubility methods

Determinations have been made of content and bioaccessibility of Ca, Fe, Zn and Cu in 13 dishes collected from a catering service delivering to a school. Bioaccessibility was estimated by measuring the soluble or dialyzable mineral fraction resulting from in vitro gastrointestinal digestion of the meal. The analyzed dishes had mineral contents (μg/g) in the following ranges: Ca (74.1-913), Fe (2.8-17.9), Zn (2.8-13.1), Cu (0.28-1.90). Mineral solubility and dialysis percentages were as follows: Ca (1.7-96.2; 0.75-61.3), Fe (16.0-97.8; 0.23-19.0), Zn (22.6-93; 5.78-31.45), Cu (35.7-92.3; 0.66-25.0). The highest bioaccessible Ca content corresponded to fish-based dishes, while vegetables were poor sources of Ca. The lowest Fe and Zn bioaccessible percentages corresponded to vegetable-based dishes, particularly spinach omelet, whereas dishes having meat as the main ingredient exhibited the highest bioaccessible percentages. In the case of Cu, vegetable-based dishes could be considered the best sources.