engleski

Influence of grape ripeness of Rhine Riesling on the composition of polyphenolic compounds in must and wine

The aim of the study was to examine the influence of grape ripeness on the proportion of total and individual phenolic compounds in must and the wine of the white vine varieties of Rhine Riesling (Vitis vinifera L.). The research was conducted in harvests of 2007 and 2008 in Kutjevo vinegrowing region. Treatments in the experiment were different grape harvest dates (regular and late harvest) from two different positions (Mladice and Hrnjevac). The determination of individual phenolic compounds in must and wine was carried out using high performance liquid chromatography (HPLC) with UV Photodiode Array Detection, while total phenolic compounds in wine were determined by spectrophotometry. The concentration of phenolic acids and total phenols in must and wine differed significantly depending on the degree of grape ripeness. Increased grape ripeness regardless of the tested position and the year of research, the concentration of individual phenolic acids increased as well, in which process must and wines produced from the grapes from the position Hrnjevac had a higher content of gallic, trans-caftaric and caffeic acid in relation to the grapes from position Mladice. Higher degree of grape ripeness and later harvest in both years had a significant impact on reducing the concentration of flavan- 3-ol namely (+) catechin and procyanidin B2 in musts as well as in Rhine Riesling wines. The influence of tested position was determined only in concentrations of procyanidin B2, which were higher in wines obtained from grapes from the position Hrnjevac. The concentration of trans-resveratrol increased with the grape ripeness regardless of year of research on both tested positions. By late ripening process of grapes, the concentration of total phenols in wine and must increased, regardless of the position and the harvesting year. Significantly, higher concentrations of total phenols were measured at the location Hrnjevac in comparison with the location Mladice. In addition significantly larger amount of total phenols was measured in the year 2008 in relation to the year 2007.Wines obtained from later harvested grapes can be an important source of phenolic antioxidants in human diet.

Grape ripeness ; late harvest ; Phenolic compounds ; Rhine Riesling

nije evidentirano