Changes in physical and chemical characteristics of Syrah grapes in response to timing of cluster thinning

Cluster thinning was performed on vines of the Syrah variety eight days before the véraison (CTBV) and after the completion of the véraison (CTAV) in the 2019 and 2021 vegetation periods. The differences in physiological and chemical properties between the grapes were investigated to which cluster thinning was applied at two different times and those without cluster thinning. According to the research results, CTBV was more effective in the berry fresh weight, dry weight, berry volume, skin weight, skin surface, cluster width, cluster length, cluster weight, and cluster volume parameters than CTAV. Likewise, the levels of total phenolic compounds, total anthocyanins, and antioxidant capacity increased by 9%, 27%, and 30%, respectively, compared to the control group without cluster thinning. Among the phenolic compounds, trans-resveratrol showed the highest increase of 38%, and petunidin-3-glucoside increased the most (12%) among anthocyanins.