Abstract:

Effects of extraction duration, temperature, solid/liquid ratio and concentration of aqueous ethanol solution on yield of proanthocyanidins from Cabernet Sauvignon grape skin extracted individually with ethanol were studied by single factor test, as well as effects of microwave radiation duration, concentration of aqueous ethanol solution and solid/liquid ratio on yield of proanthocyanidins extracted with ethanol under the assistance of microwave. Based on the results of single factor test, the two extraction technologies were optimized by orthogonal test design. Under optimized conditions for individual ethanol extraction [temperature, 50 ℃; extraction duration, 55 min, solid/liquid ratio, 1:8.5 (g/ml); and concentration of aqueous ethanol solution, 55%], the yield of proanthocyanidins was 2.61%; under optimized conditions for microwave-assisted extraction [microwave radiation power, 320 W; microwave radiation duration 30 s; concentration of aqueous ethanol solution, 50%; and solid/liquid ratio, 1:13 (g/ml)], the yield of proanthocyanidins was 3.99%. When acidic ethanol solutions at pH 4.5 and 5.0 were used to extract proanthocyanidins by the two optimized technologies, the yields of proanthocyanidins were 2.67% and 4.11%, respectively, indicating that the addition of acid is favorable to increase the yields of proanthocyanidins.

Key words: Cabernet Sauvignon grape, skin, proanthocyanidins, extraction