The evolution and antioxidant activity of polyphenol compounds in Thai fruit wines
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NO FULL TEXT AVAILABLE. Access is restricted indefinitely. ----- The principal objectives of this project were to evaluate the antioxidant activity of Thai fruit wines~ to study the evolution of polyphenol compounds and the antioxidant activity of fruit wine during winemaking~ to determine whether potassium metabisulfite (KMS) significantly affects the concentration of polyphenol compounds and the antioxidant activity of wine; and to develop and optimize HPLC methods for the determination of polyphenol compounds in Thai fruit wines. Twenty-two Thai fruit wines were evaluated for their antioxidant activity and all fruit wines were found to have a positive result on the DPPH preliminary test method. The antioxidant activity (EC₅₀) of the twenty-two fruit wines ranged between 1.44 - 29.8. Three fruit wines (ma-kiang, jambolan (wa) and mon) which are high in antioxidant activity were studied in detail for the evolution of polyphenol compounds and the development of antioxidant activity during the fermentation and ageing processes. During the fermentation, the high polyphenol content of mon wine decreased dramatically from 1480 to 854 mg/L, while the polyphenol concentration of ma-kiang· and jambolan (wa) increased from 389 to 506 mg/I and 413 to 528 mg/L, respectively. During the ageing process, there is a slight increase in the polyphenol concentration in all three fruit wines. Loss of colour can be observed during fermentation and ageing of wines. The different levels of KMS (150-250 ppm) added to the must were found to not significantly affect to the antioxidant activity and polyphenol concentration of wine at any stage of process. The developed RP-HPLC method for gallic acid, resveratrol and quercetin in fruit wine exhibited reasonable validity results. The wine sample was extracted with ethyl acetate before the analysis of HPLC. Ma-kiang and jambolan wines were found to contain a significant amount of gallic acid and quercetin.
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