Dual-layer microencapsulation of grape skin extract via spray chilling and fluid-bed coating for targeted intestinal release

This study aimed to develop an efficient and sustainable dual-layer microencapsulation system for grape skin extract, a phenolic-rich by-product of the food industry. A spray-chilling process was employed for primary encapsulation with palm oil, followed by a zein-based secondary coating to achieve targeted intestinal release and enhanced oxidative stability. The resulting microcapsules exhibited favorable physicochemical properties, including low moisture content (5.50 ± 0.08%), reduced water activity (0.38 ± 0.02), and high encapsulation efficiency (98.98 ± 1.11%). In vitro gastrointestinal assays revealed a controlled release profile, with minimal resveratrol diffusion in simulated oral and gastric phases, and a pronounced increase under intestinal conditions due to enzymatic lipid degradation. Three-way ANOVA indicated that digestion phase, coating type, and sampling time, as well as all their interactions, significantly affected resveratrol release (p < 0.01). A strong positive correlation (r = 0.91, p < 0.01) between single- and dual-layer systems demonstrated that the additional zein coating slowed the release rate while maintaining a similar release trend. During 60 days of storage, dual-coated microcapsules retained approximately 98% of their initial resveratrol at 4°C, whereas samples kept at 25°C decreased to 81%, accompanied by increased peroxide formation. Two-way ANOVA confirmed significant effects of both storage time and temperature (p < 0.01). Overall, the dual lipid–protein matrix effectively protected resveratrol against oxidative degradation and enabled targeted intestinal delivery, highlighting its potential for valorizing grape by-products as functional food ingredients.