Antioxidants from grape stalks and marc: influence of extraction procedure on yield, purity and antioxidant power of the extracts

This study was aimed to assess the feasibility of extracting antioxidant compounds from wine-making wastes (grape stalks and marc) by solvent extraction. Together with the type of raw material it was also investigated the influence of some process parameters on final antioxidants yields and extract purity: a degreasing pre-treatment, type of solvent (ethanol or a mixture ethylacetate:water/9:1), temperature (28 or 60°C) and length of maceration (5 or 24h). Solvent and temperature were statistically influent (p<0.05), and the yields were higher with ethanol (but with lower purities) and at 60°C. Antioxidant power of the extracts was evaluated by different analytical methods. An accurate comparison of our data with many literature works about antioxidants recovery from different natural sources showed similar results and highlighted a general great variability in the extraction procedures.