Effects of solvent and temperature on pressurized liquid extraction of anthocyanins and total phenolics from dried red grape skin

Pressurized liquid extraction (PLE) was used to extract anthocyanins from the freeze-dried skin of a highly pigmented red wine grape with six solvents at 50 degreesC, 10.1 MPa, and 3 x 5 min extraction cycles. Temperature (from 20 to 140 degreesC in 20 degreesC increments) effects on anthocyanin recovery by acidified water and acidified 60% methanol were also studied. Acidified methanol extracted the highest levels of total monoglucosides and total anthocyanins, whereas the solvent mixture (40:40:20:0.1 methanol/acetone/water HCl) extracted the highest levels of total phenolics and total acylated anthocyanins. Acidified water extracts obtained by PLE at 80-100 degreesC had the highest levels of total monoglucosides, total acylated anthocyanins, total anthocyanins, total phenolics, and ORAC values. Acidified methanol extracts obtained by PLE at 60 degreesC had the highest levels of total monoglucosides and total anthocyanins, whereas extracts obtained at 120 degreesC had the highest levels of total phenolics. High-temperature PLE (80-100 degreesC) using acidified water, an environmentally friendly solvent, was as effective as acidified 60% methanol in extracting anthocyanins from grape skins.