Liposomal encapsulation of royal jelly and its incorporation into kefir: enhancement of bioaccessibility and bioavailability

This study examined the encapsulation of royal jelly (RJ) in lecithin-based liposomes and chitosan-coated secondary liposomes to improve its stability, bioaccessibility, and antioxidant capacity. Although RJ contains valuable bioactive compounds, its oral bioavailability is limited due to its instability in the gastrointestinal tract. The formation of a secondary liposome matrix increased the liposome size and shifted the zeta potential from negative (~ –21 mV) to positive values (+ 44.2 to + 32.2 mV), confirming successful chitosan coating. Encapsulation efficiency ranged from 48.00 to 62.61% depending on RJ concentration. Simulated gastrointestinal digestion (INFOGEST protocol) showed enhanced phenolic (50.99–62.79%) and flavonoid (128.69–172.12%) bioaccessibility. When incorporated into kefir, RJ-loaded liposomes led to higher bioaccessible phenolic (TPC: 516.86) and flavonoid (TFC: 322.50) contents compared to plain kefir or kefir containing free RJ. Furthermore, Caco-2 cell assays demonstrated improved phenolic absorption (TPC: 51.17%) and antioxidant bioavailability (CUPRAC: 141.46%). Overall, liposomal encapsulation effectively protected RJ bioactives during digestion and enhanced their functional performance in a dairy matrix.