The preparation of powdered microcapsules of flavor substances should not only protect these substances from volatilization during storage but also improve their diffusion during use. This study aimed to investigate the effects of maltodextrin (MD) with different dextrose equivalent (DE) values on retention of flavor substances during storage, and the dynamic release of flavor substances during dissolution. MDs with three different DE values and whey protein isolate were mixed in a ratio of 4:1 as wall materials to encapsulate ethyl acetate, and powdered microcapsules were prepared by spray drying. It was proved that MD could reduce the diffusion of flavor substances under different relative humidity conditions through the interaction between core material and wall material. During dissolution, MD released flavor substances quickly owing to its superior solubility. The reconstituted emulsion formed after the powder dissolved in water recaptured flavor substances and made the system reach equilibrium. This study explored the mechanism of flavor release during the storage and dissolution of powder microcapsules and should help us understand the application of powder microcapsules in food systems.

Quercetin as a flavonoid polyphenol in nature has shown great anti-obesity effects. Due to its poor stability in chemical structure and low intestinal absorption, the in vivo bioavailability of quercetin is considered to be the main challenge for applications. To achieve the oral quercetin administration, chitosan was successfully trimethylated (TMC) to coat the quercetin-loaded zein nanoparticles (Zein-Q), which were designed as the core–shell structure for enhancing the intestinal absorption in this study. TMC-Zein-Q was demonstrated to protect quercetin from degradation and showed the sustained-release effect in an in vitro drug release experiment. The nanoparticles were found to reversibly open tight junctions between intestinal epithelial cells and help to increase quercetin uptake via the paracellular pathway in Caco-2 cells. In addition, the delivery system also showed stronger intestinal permeability and mucoadhesion in vivo, which improved the bioavailability of quercetin in cellular and animal experiments. After 10 weeks of intervention, TMC-Zein-Q could effectively suppress weight gain, improve serum lipid levels, and ameliorate hepatic steatosis and glucose tolerance in high-fat diet (HFD) mice by mediating the AMPK pathway. Consequently, this work successfully constructed TMC-Zein-Q for oral quercetin delivery, providing a novel and feasible strategy for the treatment of obesity via the oral route.