Masking the bitter taste of quercetin by liposomes modified with whey protein isolate: Better to be coated or inserted?

The unsatisfactory bitterness of quercetin restricts its application to healthy food systems. In this study, whey protein isolate (WPI) inserted and coated quercetin-loaded liposomes were compared in reducing quercetin bitterness and improving the stability of quercetin-loaded liposomes. By electronic tongue and sensory evaluation, the liposomes coated by WPI (0.5–3.0 mg/mL) and inserted with WPI (0.5 mg/mL) significantly reduced the bitterness of quercetin compared to physical mixing. It was also found that the encapsulation efficiency was increased by 15.24% after insertion of WPI at 2.0 mg/mL. The environmental stability results showed that both WPI insertion and coating improved the thermal stability of the quercetin-loaded liposomes compared to the physical mixture, and the WPI coated quercetin-loaded liposomes had the best storage stability and tolerance to salt ions. In contrast, WPI insertion improved the ability of liposomes to resist against surfactant. Raman spectra and fluorescence analysis demonstrated that the modification of WPI reduced the free motion of lipid molecules and promoted the ordering at the polar headgroup area and hydrophobic core of the lipid bilayer. These findings have the potential to support the utilization of WPI modified liposomes as promising option for an efficient transportation of bitter bioactive compounds in nutraceutical and functional foods.