Gastrointestinal and colonic bioaccessibility of calcium and ferulic acid from microcapsules made with brewer spent grain arabinoxylans.

Three microcapsule formulations with 2.7, 5.5 and 10.9 g calcium 100 g solids (C1, C2, and C3, respectively) were developed using brewer spent grain arabinoxylan concentrate as wall material. The intestinal and colonic bioaccessibility of calcium and phenolic compounds were determined after in vitro gastrointestinal digestion. The level of calcium and the formation of Ca:AX complexes mediated by electrostatic interactions contributed to the construction of the microcapsule wall. It was observed that the higher calcium content increased the total calcium bioaccessibility (27.0 ± 2.4, 29.8 ± 0.2, 37.1 ± 1.0 % for C1, C2, and C3, respectively). However, the calcium level of the microcapsules decreased the total bioaccessibility of the phenolic compounds from 45 to 27 % for ferulic acid, and from 90 to 66 % for p-coumaric acid for C1 and C3, respectively. Also, the secondary metabolites of these phenolics were detected in the colonic fractions. Suitable microcapsules intendant for the supplementation of people with a calcium deficient diet, with the supply of fermentable fibres and phenolic compounds were developed.