, Volume 2, Issue 2, pp 149-161
Date: 08 Nov 2008

Phenolic Content and Antioxidant Activity of Moscatel Dessert Wines from the Setúbal Region in Portugal

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Abstract

Moscatel wines from Setúbal were analyzed for their total phenolic (mean value 1,243 mg gallic acid equivalents/L), and total flavonoid (mean value 248 mg catechin/L) composition by spectrophotometric and chromatographic methods were used to quantify phenolic compounds as benzoic acids, cinnamic acids, stilbens, and some flavonoids. Antioxidant activity of the wines was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH; mean value 70.7% inhibition), ferric reducing antioxidant power (FRAP; mean value 3,098 mg of Trolox equivalents/L) and oxygen radical absorbance capacity (ORAC; mean value 10,724 μmol/L) assays. Results were analyzed using principal component analysis which allowed samples to be grouped in terms of both winemaking producer and vintage. By plotting correlation loadings, it was possible to understand which variables were responsible for sample distribution. The correlation between results obtained for variables show that, in general, total flavonoid content is a better estimation of antioxidant activity in Moscatel samples (r ORAC/flavonoids = 0.832, r FRAP/flavonoids = 0.677) than total phenolic content (r ORAC/phenolics = 0.680, r FRAP/phenolics = 0.372). No major correlations were detected for DPPH assay results (r DPPH/flavonoids = 0.283, r DPPH/phenolics = 0.271). Chromatographic profiles showed important differences among Moscatel wines. Gallic acid contents and results of antioxidant activity tests were strongly correlated (r values in the range 0.74–0.92). Correlations of the results obtained for antioxidant activity tests with contents of other phenolic compounds such as ethyl caffeate, ethyl gallate, caffeic acid, protocatechuic acid, and t-caftaric acid depend on sample and type of test employed.

Presented at the “AOAC Europe section international workshop: Enforcement of European Legislation on Food and Water: Analytical and Toxicological Aspects”, in Lisbon, April 2008, and published in abstract form.