Fabrication of Rubus chingii Hu ellagitannins-loaded W/O and O/W emulsion gels: Structure, stability, in vitro digestion and in vivo metabolism

Tannin is the main naturally occurring phytochemicals in Rubus chingii Hu with poor digestive stability and low bioavailability. In this study, oil-in-water (O/W) and water-in-oil (W/O) emulsion gels encapsulating Rubus chingii Hu ellagitannins (RCHT) were fabricated and their structure, rheology, stability, in vitro digestion and in vivo metabolism were characterized. The W/O emulsion gel showed smaller particle size, better pH stability, thermal stability, centrifugal stability and storage stability. Regarding rheology, two emulsion gels exhibited characteristics of non-Newtonian fluids. The encapsulation efficiency of W/O emulsion gel was higher, reaching 95.46 %. The lower release rate and higher bioaccessibility of RCHT were also observed in the W/O emulsion gel. In vitro fermentation results indicated that W/O emulsion gel could promote the growth of intestinal beneficial bacteria and inhibit the growth of harmful bacteria. Metabolic kinetics in rats showed that the embedding of W/O emulsion gel greatly promoted the absorption and transformation of ellagitannins to urolithins in vivo. Thus, the W/O emulsion gel was quite suitable for the delivery of RCHT.