Effect of Pre-fermentation Maceration on the Content of Antioxidant Compounds in Grapevine Juice

Lower antioxidant capacity of white wines is caused by a lower content of phenolic compounds. In red wine, a higher content of phenolic compounds is the result of maceration. This study deals with effects of pre-fermentation maceration on contents of some selected compounds (above all antioxidants) in juices made of grapes of white varieties 'Welschriesling', 'Green Veltliner' and 'Neuburger'. The grapevine mush was macerated for 0; 2; 4; 8; 12; 24 and 48 hours. The spectrophotometry methods was used to estimate juice antioxidant activity and content of flavanols, anthocyans, catechins, hydroxycinnamic acids and flavonols. Contents of total titratable acids and pH were estimated as well. Results of this study show increasing tendency of all parameters with length of maceration. The highest content of antioxidants were found out in the variety 'Welschriesling'. Important are increasing values of hydroxycinnamic acids. However, the main role of the phenolics acids is to contribute to the anti-oxidant capacity, the tartaric esters of hydroxycinnamic acids (particularly caftaric acid) are centrally involved in oxidation and browning reactions in white wine. Their levels increased during the whole period of maceration. In 'Welschriesling', their content increased by 74 mg·L-1. Decreasing tendency show results of titratable acids. Their contents decreased within the first 12 hours of maceration and thereafter they do not change. Longer must maceration could contribute to a decrease in contents of total titratable acids and, thus, to a better harmony of produced wine.