Development of Semiliquid 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 semiliquid ingredients for functional foods, as an alternative to powdered GS, which needs high energy input for drying. Processing of semiliquid 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 semiliquid 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 similar to 75% for both air-dried GS and 2% GS dispersion and 59% for 10% GS dispersion. The average particle size diameters of solids in semiliquid GS ingredients were similar to those observed in commercial apple skin products. Possible applications of GS semiliquid ingredients to increase the reducing capacity of food 10 times include formulation into beverages and ice-type desserts and use in bakery products