Abstract:
The study sets-out to investigate the amount of some selected class of polyphenols with cardiovascular benefits, present in red wine. The total phenolic content of the freshly opened red wine samples as determined by Folin-Ciocalteau Method (FCM) were in the range of 42-1625 mg/l Gallic Acid Equivalents (GAE) (Mean = 1084.6). Samples J and N, which were of Spanish and Portuguese origins, respectively, contained the highest concentration of 1625 mg/l GAE each, while the lowest concentration was recorded in sample C, a wine of Nigerian origin. Similarly, the total anthocyanin concentration of freshly opened wine samples was in the range of 20.5-166.7 mg/l Malvidin-3-Glucoside Equivalents (Mean = 109.4), with sample R (an American wine) containing the highest concentration. The total tannin concentration was in the range of 225-2387 mg/l Epicatechin Equivalents (Mean = 1653.1). Wine Q, a South African wine, had the highest concentration of tannin. The effect of air exposure resulted in a time-dependent decline in the total phenolic concentration of the wines, with the decline being more pronounced after 60 mins of air exposure. Red wine samples with lower phenolic concentration were found to be less affected by the reduction in total phenol due to air exposure. The maximum loss in the total phenolic concentration on air exposure was recorded in sample S (a Spanish wine), whose phenol content decreased by as much as 87.4% after 120 mins. Maximum decrease in total anthocyanin content was observed in sample A (a Spanish wine) which decreased by as much as 58.5% after 120 mins. Total tannin was found to be more stable than other polyphenolic compounds present in the samples, as the total tannin concentration showed a less significant reduction over time. Tannin concentration of sample B (an Australian wine) and sample C, decreased by as much as 22% over the course of 120 mins. A similar trend in decline was observed during cold storage between 5 - 80C after 96 hours at 24-hour intervals. Sample K lost as much as 87.6% of its total phenolic content after 96 hours. A maximum loss of 74.9% of the concentration of total anthocyanin was observed in wine C. For total tannin, a loss of 47% was observed in wine B after 120 mins. The result of the organoleptic (sensory) evaluation and the total phenolic concentration were non-significantly correlated, r = 0.29, p < 0.05. Likewise, there was a non-significant correlation between the result of the organoleptic (sensory) evaluation and the total tannin concentration, r = 0.39, p < 0.05. Total phenolic concentration and the retail price were significantly correlated, r = 0.55, p < 0.05. Similarly, Total tannin concentration and the retail price were also significantly correlated, r = 0.50, p < 0.05. Comparing the total phenolic content of the alcoholic (M = 1201.60, SD = 357.59) and non-alcoholic brands (M = 967.50, SD = 521.34), showed a non-significant difference t (18) = 0.26, p < 0.05 (p > 0.05). In conclusion, the various wine brands differed widely in their content of all classes of polyphenols tested. The polyphenols in the samples also differed in their susceptibility to oxidation during air exposure and cold storage after opening. These observations could be useful to consumers who are interested in wines because of their content of polyphenols, which are reported to offer some health benefits.