Development of semi-liquid ingredients from grape skins and their potential impact on the reducing capacity of model functional foods

Grape skins (GS), which can be considered as reusable coproducts of winemaking, were processed to develop semi-liquid ingredients for functional foods, as an alternative to powdered GS, which needs high energy input for drying. Processing of semi-liquid GS ingredients included blanching, dilution to obtain dispersions with 2% or 10% of dry solids, milling, homogenization and pasteurization. The individual phenolic contents and in vitro ferric ion reducing capacity (FRAP) of semi-liquid GS ingredients were compared with those of air-dried and freeze-dried GS.. With respect to freeze-dried GS, the recovery of FRAP values was ~75 % for both air-dried GS and 2% GS dispersion and 59% for 10% GS dispersion. The average particle size diameters of solids in semi-liquid GS ingredients were similar to those observed in commercial apple skin products. Possible applications of GS semi-liquid ingredients to enhance the reducing capacity of food by 10 times include formulation into beverages and ice-type dessert and use in bakery products.