In vitro bioaccessibility of iron and zinc in fortified fruit beverages

Iron and zinc bioaccessibility was estimated in the in vitro gastrointestinal digests of six different fortified fruit beverages (Fb) containing iron and/or zinc and/or skimmed milk (M). Solubility values can be used to establish trends in relative bioavailability of iron and zinc, as the first stage towards mineral bioavailability comprises solubility in the intestinal tract. FbFe, FbFeM and FbFeZnM samples showed iron bioaccessibility above 88%, differing (P < 0.05) from those of FbFeZn (53%). In turn, FbZn, FbFeZn and FbZnM samples presented higher zinc bioaccessibility (above 68%), differing (P < 0.05) from those of FbFeZnM (48%). The presence of milk-derived caseinophosphopeptides (CPPs) formed during gastrointestinal digestion in dairy samples does not increase iron or zinc bioaccessibility in FbFeM or FbZnM vs. FbFe or FbZn, but it is hypothesised that the negative interacting effect of zinc upon iron bioaccessibility when co-supplemented in these fruit beverages is overcome in the presence of CPPs, which favour iron solubility more than in the case of zinc.