Extraction and Characterization of Antioxidants from Wine By-Product (Grape Pomaces)

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Addis Ababa University


Wine grape pomace (WGP), is a valuable by-product from the winemaking industries, recognized due to its relevant polyphenolic compounds. This study investigated the potentials of wine waste in Ethiopia from red wine grape pomaces(RWGP)and white wine grape pomaces (WWGP) (Vitisvinifera L.) for extraction of antioxidants. The effect of solvent ratio, extraction time and temperature on the yield of RWGP and WWGP extract was also studied. The experimental design was employed using the Design Expert 6.0.8, three-level-three factor Central Composite Design in triplicates at the center point in the optimization study, requiring 17 experiments. The results showed that minimum and maximum extract yields were 30.23% and 52.35% for RWGP, and 20.97% and 48.56% for WWGP, respectively. Solvent ratio, extraction time and Temperature had a significant (p < 0.05) effect on the extract yields. The statistical analysis indicates that, the linear terms of solvent ratio, extraction time and temperature, had positive effect on response yield. The quadratic terms (pure quadratic terms) negatively affected the extraction yield and only AB interaction for both RWGP extract and WWGP extract had negative influence. Characterization of antioxidants was carried through the evaluation of total phenolic content (TPC), total flavonoid (TF), total anthocyanin content and scavenging capacity against 1,1-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity performed using spectrophotometer. Additionally, food applications of the obtained extract to inhibit oil oxidation were carried out according to the Shaal Oven Test compared with butylated hydroxytoluene (BHT) by measuring per oxide value (PV). Results obtained under optimum conditions were: total phenolic content 15.70-56.72 mg GAE/g extract and 10.94-50.56 mg GAE/g extract; total flavonoid 49.65 mg CE/g extract and 18.56 mg CE/g extract; total anthocyanin content 530mg/L and 14.01mg/L and DDPH radical inhibition activity42.27%-98.50% and 39%-88.23% for RWGP extract and WWGP extract, respectively .The IC50 values for RWGP extract and WWGP extract were 1.24mg/ml and 1.49mg/ml and AAR values were 0.80 and 0.67, respectively. The lower IC50 value the more potent antioxidant activity; and high value of AAR refers to high antioxidant activity. Hence, RWGP extract has more potential in antioxidant activity than WWGP extract. Inhibition test of soybean oil oxidation showed that the extract was less than BHT, since the peroxide value was higher than of the control. Key words: Red and White wine grape pomace; anthocyanins; antioxidant activity; flavonoid; phenolic compounds; yield



Red and White wine grape pomace; anthocyanins; antioxidant activity; flavonoid; phenolic compounds; yield