The Release of Grape Pomace Phenolics from Alginate-Based Microbeads During Simulated Digestion In Vitro: The Influence of Coatings and Drying Method

Grape pomace is a byproduct of wineries and sustainable source of bioactive phenolic compounds. Encapsulation of phenolics with a well-chosen coating may be a promising means of delivering them to the intestine, where they can then be absorbed and exert their health-promoting properties. Ionic gelation of grape pomace extract with natural coatings (sodium alginate and its combination with maltodextrins, gelatin, chitosan, tragacanth gum, and gum arabic) was performed, and the resulting hydrogel microbeads were then air-, vacuum-, or freeze-dried to prevent their spoilage. The physicochemical characterization (size, shape, texture, and morphology) of the microbeads and the in vitro release of phenols from microbeads were studied and a good relationship between them was established. Freeze-dried microbeads showed the highest cumulative release of phenols as in the intestinal phase (23.31 – 43.27 mgGAE/gMB), followed by vacuum-dried (23.31 - 35.41 mgGAE/gMB) and air-dried (22.74 – 31.38 mgGAE/gMB), while the most suitable release dynamics in the intestinal phase were observed for alginate-based microbeads combined with gelatin (58.4 %), gum arabic (34 %) and 1.5 % w/v chitosan (15.3 %). The results highlight the importance of developing encapsulated formulations containing a natural source of bioactive compounds that can be used in various functional foods and pharmaceutical products.