POLYPHENOLIC COMPOSITION AND FREE RADICAL SCAVENGING ACTIVITY OF RED WINES AVAILABLE IN THE LATVIAN MARKET

Abstract

Besides the medical properties, phenolic compounds represent one of the most important quality parameters of wine since they contribute to the organoleptic characteristics such as colour, astringency and bitterness. The aim of the investigation was to evaluate the phenolic composition and free radical scavenging activity of wines available in the Latvian market. Sixteen wine samples from different grape varieties and of different origin were analysed. The total phenol content was determined spectrophotometrically according to the Folin-Ciocalteou method, and the composition of phenols was detected using HPLC. The free radical scavenging activity of wine was determined using the DPPH* (2,2-diphenyl-l-l-picrylhydrazyl radical) assay. The total content of phenolic compounds in red wine samples ranged within 1569–1765 mg/l chlorogenic acid equivalents (CAE), whereas in white wine samples it was only 98.97–92.12 mg/l CAE. Free radical scavenging activity was expressed as DPPH* inhibition. The inhibition varied within 71–84 % for red, and 62 and 68 % for white wines. The content of five phenolic compounds (caffeic acid, catechin, epicatechin, gallic acid, and vanillin) was determined in all wine samples. From the identified phenolic compounds, the main in red wines were catechin (22.27–95.17 mg/l), gallic acid (13.86–60.83 mg/l), caffeic acid (0.35–13.26 mg/l). White wines contain smaller amounts of phenols; for example, the content of catechin ranged from 4.65 to 11.56 mg/l.