Mirela Osrečak

Effect of cluster thinning on fruit composition of Vitis vinifera cv. Pinot noir (Vitis vinifera L.)

The technique of cluster thinning is being used in aim to reduce the crop load of vine in order to improve the quality of grapes. The aim of the trial was determination the optimal timimg for thinning regarding the results given from chemical analysis of the must immediately after the harvest. The experiment was conducted at the experimental station of the Faculty of Agriculture in Zagreb in 2006 and 2007 years, on cv. Pinot noir according to the random block design system. The cluster thinning was performed with 40 % intensity in three terms; immediately after the flowering period (P1), three weeks after the flowering period (P2) and with the begining of veraison (P3). The results were compared with the results of the control treatement without cluster thinning performance. The analysis of variance of given data has shown a significant difference in must composition between the terms of cluster thinning and a control treatement, and yield per vine has not been reduced with earlyer term of cluster thinning.

The effect of grape harvest date on polyphenols and anthocyanins content of different red grapes varieties

Four red grape cultivars were investigated in order to study the effect of grape harvesting date (ripening stage of the grape) on traditional indicators of maturity such as soluble solids and titratable acidity content, as well as on their total polyphenols and total anthocyanins content. Grape varieties grown in different coastal vinegrowing regions, at three different harvesting dates, and from two consecutive vintages, were examined. The results showed uncertainty of traditional indicators of maturity as the only parameter for harvest date determination, since the maximum concentration of soluble solids didn’t correlated with maximum concentration of total polyphenols and anthocyanins in the most of harvest dates. Furthermore, grapes from the third harvest date mostly didn’t have consistently higher polyphenols and anthocyanins levels, so the harvest should not be postponed unduly.