44D-3 |
Evaluation of the antioxidant activity of grape juice and grape wine extracts |
G. T. KROYER, Institute of Food Chemistry & Technology, Vienna Univ. of Technology, Getreidemarkt 9, Vienna, A-1060, Austria In recent times, there is a growing interest in the food industry and in preventive health care in the development and evaluation of natural antioxidants from plant materials. Grape juice and grape wine are products from viniculture and contain considerable amounts of polyphenols which have been reported to have antioxidant activity. The objective of this study was to quantify the total polyphenols and to evaluate the antioxidative and free radical scavenging properties of different extracts of grape juice and wine of white and red grape varieties. Grape juice and wine were lyophilized and extracted individually with methanol, acetone and ethyl acetate. The content of total polyphenols were analyzed (Folin-Ciocalteau Method). The antioxidant activities were determined in terms of their Anti-Radical Power ARP (DPPH-Radical Scavenging Method) as well as their Antioxidant Activity Coefficient AAC (Beta-Carotene Bleaching Method). Lyophilized red wine and methanol extracts thereof showed the strongest antioxidative properties compared to white wine or when the other extraction solvents were used correlating with their high content of total polyphenols (5,7-8,5%). Moreover, the Anti-Radical Power was found to be most pronounced in the lyophilized samples of the red wine varieties (ARP: 48-71), whilst their methanol extracts showed the relative highest Antioxidant Activity Coefficient (AAC:193-221) which is referred to peroxidation processes. Remarkably, the Antioxidant Activity Coefficient was significantly elevated in the ethyl acetate extracts of grape juice (AAC: 239-314) with values exceeding the methanol extracts of red wine, whilst the Anti-Radical Power was relatively poor (ARP: 3-5). The presented study demonstrates the potential of appropriate extracts of grape products for use as natural antioxidant additives for food and as dietary supplements. Furthermore, these results indicate that solvent-dependent extractable substances may be effective at different stages of the autoxidation process.
Session 44D, International
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