Quality of commercial wine vinegars evaluated on the basis of total polyphenol content and antioxidant properties

Abstract

Wine vinegar derived from fruit and grain contains a certain amount of phenolic compounds which are known to possess antioxidant properties. In this paper the quality of nine samples of wine vinegar commercially available in Bangkok was evaluated according to their total polyphenol content and antioxidant capacity compared to common distilled vinegar. The total polyphenol content was expressed in gallic acid equivalent, GAE (µg/ml sample) by FolinCioculteu method; while the antioxidant capacities were given as equivalent concentration of ascorbic acid (AAeq), Trolox (TLeq) and BHT (BHTeq) in µg/ml sample based on the ability to scavenge DPPH radicals and H2O2. Results showed that all wine vinegar samples evaluated contained greater levels of GAE (80.3-973.4 µg /ml) and antioxidant strength (22-3148 µg AAeq/ml, 15-2107 µg TLeq/ml and 140-19880 µg BHTeq/ml for DPPH scavenging activity and 462-15362 µg AAeq/ml, 270-8991 µg TLeq/ml and 194-6455 µg BHTeq/ml for H2O2 scavenging activity) compared to distilled vinegar. Among the nine samples of wine vinegar which were derived from different sources of fruit and grain, balsamic vinegar exhibited the strongest antioxidant capacity which correlated to the highest level of GAE. In addition, the total polyphenol content and antioxidant strength were closely correlated for the set of all the samples with r = 0.8022 for TLeq in DPPH scavenging activity and r = 0.8193 for TLeq in H2O2 scavenging activity. A close correlation between the two methods for antioxidant measurement was also observed (r = 0.9956). Moreover, the samples with darker colour tended to possess greater antioxidant strength in correlation with the higher total polyphenol content. This finding indicated that total polyphenol content and antioxidant capacity of wine vinegar products were varied depending on the source of raw materials. However, wine vinegar would be a good source of natural antioxidants compared to distilled vinegar.