Encapsulation of grape seed phenolics from winemaking byproducts in hydrogel microbeads – Impact of food matrix and processing on the inhibitory activity towards α-glucosidase

Hydrogel-based encapsulation systems were developed for grape seed phenolics recovered from winemaking byproducts. Proanthocyanidins, monomeric flavanols, flavonols and anthocyanins were extracted from grape seeds with 60% ethanol. Encapsulation of solubilized grape seed phenolics in microbeads with alginate-Ca++ or alginate-chitosan-Ca++ achieved efficiency of 78 and 92%, respectively, higher than those of pure catechin and proanthocyanidins. Encapsulated phenolics showed inhibitory activity towards the brush border enzyme α-glucosidase, which was chosen as a model bioactivity assay. Grape seed phenolics were retained in the hydrogel structure after mixing of the microbeads with bovine milk or rice drink, pasteurization of these beverages to achieve 7 decimal reductions of Mycobacterium avium subsp. paratubercolosis (equivalent to 72 ◦C for 91 s) as well as after intense heat treatment of the rice beverage to achieve 7 decimal reductions of Bacillus cereus (95 ◦C for 20 min).