Influence of climatic conditions on ripening and the phenolic content of grapes from Cabernet Sauvignon, Gamza and Rubin red vine varieties

Abstract

During the period 2021-2022, the dynamics of ripening and the phenolic content of grapes from the varieties Cabernet Sauvignon, Gamza and Rubin, grown in the region of the town of Pleven, were studied. The changes in the meteorological indicators throughout the vegetation period were monitored. During the winter months, significantly low temperatures for the vine plant growth were not registered in the region. The onset of the vines’ vegetative development was in the middle (2021) or the early (2022) April. During the grapes ripening period, the dynamics of sugars and total acids were monitored. The Rubin variety showed the fastest sugar accumulation while maintaining a relatively high acidity rate. The Gamza and Cabernet Sauvignon varieties were later ripening and revealed a gradual increase in sugars and a decrease in total acids. The highest sugar accumulation in the Rubin and Gamza varieties was found in 2021, while for Cabernet Sauvignon - in the grapes from the 2022 harvest. Both the weather conditions during the year and the varietal characteristics, specifics and potential had an impact on the phenolic content in the structural elements of the cluster. The varieties had different reserves of total, flavonoid and non-flavonoid phenolic compounds, which increased in the order of berries < skins < rachis < seeds. The Rubin variety had the highest values of the studied phenolic components, followed by Cabernet Sauvignon, and the lowest were in Gamza. The anthocyanin content of the varieties changed in the same sequence. In all three varieties, the anthocyanin content in the skins was significantly higher compared to the berries.