Microencapsulation of polyphenolic compounds recovered from red wine lees: Process optimization and nutraceutical study

Bioactive polyphenolic compounds, recovered by nanofiltration of Cabernet Sauvignon wine lees were encapsulated with maltodextrin to obtain a spray dried micro powder with enhanced nutritional value. A Central Composite Design allowed setting up optimal spray‒drying conditions using a commercial grape extract‒polyphenol as the reference polyphenolic source and considering maltodextrin concentration and the inlet temperature as independent variables. The optimized spray‒drying conditions were: maltodextrin 7 g/100 mL, inlet temperature 110 °C. These conditions were then applied to lees nanofiltrates and retentate. The obtained microcapsules were characterized according to the drying yield (62.9–82.0%), moisture (0.81–1.52%), total bioactive compounds (0.08‒0.57 mg GAE/100 mg dw), surface bioactive compounds (5.8–34.5%), microencapsulation efficiency (65.5–94.2%), polyphenols recovery (57.4–82.7%), and antioxidant activity (0.27‒0.36%). The microcapsules showed high stability and durability when subjected to accelerated aging using the stress‒heat test, as evaluated by calculating first-order rate constants of degradation of the encapsulated polyphenols and the reduction of radical scavenging capacity; stability over time was further confirmed by the reduced water activity of the micro powders (ranged 0.27–0.36). Lastly, an in‒vitro simulated digestion was performed under physiological conditions evidencing a different bioaccessibility of polyphenols among samples (ranged 50–78%) and suggesting potential for the encapsulated polyphenols to be absorbed at gastrointestinal level.