Evaluation of bioaccessibility of zeaxanthin dipalmitate from the fruits of Lycium barbarum in oil-in-water emulsions

Zeaxanthin dipalmitate (ZD) is the main constituent of carotenoids in the fully ripe fruits of Lycium barbarum. In the present study, the effect of the unsaturation degree of oil on the bioaccessibility of ZD in oil-in-water (O/W) emulsions and the bioaccessibility of ZD in the mixture of L. barbarum fruit (LF) and emulsion (LF-E) were investigated. The coarse O/W emulsions were prepared with 5 wt% oil phase and 95 wt% aqueous phase which containing 1.5 wt% lecithin and 0-0.4 wt% xanthan gum (XG). The viscosity and stability of emulsions increased with the increasing of XG concentration, and the emulsion with 0.4 wt% XG had the largest particle size, whereas XG concentration showed a limited effect on xi-potential. Furthermore, the bioaccessibility of ZD in different unsaturated degree oil emulsions were investigated by in vitro digestion. The results showed that the particle sizes of O/W emulsions decreased significantly from gastric phase to intestinal phase, whereas the xi-potential absolute values decreased in gastric phase but increased significantly in intestinal phase. Monounsaturated fatty acid-rich oil emulsions led to higher bioaccessibility compared with polyunsaturated fatty acids-rich oil emulsions, and the olive oil emulsion exhibited the highest bioaccessibility of 25.67%. Finally, the powder of LF (50% w/v) was added to the olive oil emulsion (5 wt% oil content) to investigate the effect of lipid on digestion. The bioaccessibility of ZD in LF-E increased 14.8% than that in LF. The results might facilitate the rational design of emulsions that boost the bioaccessibility of carotenoids in fruits and vegetables.