In vitro digestion of curcumin-nanoemulsion-enriched dairy protein matrices: Impact of the type of gel structure on the bioaccessibility of curcumin

This study examined the impact of the dynamic gastric digestion of two iso-caloric dairy gels containing curcumin nanoemulsion (D3,2 = 0.187 μm) on the intestinal lipid digestion and the bioaccessibility of curcumin. The residence time in the stomach and the release of oil together with solubilized curcumin were influenced by the type of gel structure. The rennet gel restructured and became denser because of the action of pepsin and the low pH, thus slowing the outflow of both protein and oil from the gel. In contrast, the acid gel experienced rapid protein disintegration under gastric conditions and most of the chyme was emptied out of the stomach within 2 h. Similarly, the content of curcumin-enriched oil in the digesta of the acid gel was higher than that in the digesta of the rennet gel, in which the oil droplets appeared to be embedded in the gelled particles. The size of the oil droplets within the emptied gastric digesta of both gels was not significantly impacted during digestion. The rate of free fatty acid release and the concentration of curcumin during intestinal digestion were linked with the compositional profile of the gastric digesta, whereas the bioaccessibility of curcumin (85–91%) was influenced by the gel type and the gastric disintegration of the gels. This study demonstrates the influence of different gel structures on the bioaccessibility of curcumin, which could be further used to design therapeutic dairy products with health benefits. [Display omitted] •Dairy gels fortified with curcumin were prepared by acid and rennet coagulation.•The acid gel underwent faster disintegration during the gastric phase than the rennet gel.•The rennet gel formed clots that slowed the release of oil droplets and protein in the digesta.•The acid and rennet gel structures affected free fatty acid release in the intestine.•Lipid digestion of the two gels affected the bioaccessibility of curcumin in the intestine.