Changes in Polyphenols and Anthocyanin Pigments during Ripening of Vitis vinifera cv Maratheftiko: A Two-Year Study

The vineyard of Cyprus is comprised largely of native Vitis vinifera varieties, which are rather underexploited with regard to wine production to date. Although empirical observations concur that several of these varieties may possess a high potential for the production of quality wines, analytical data pertaining to their polyphenolic composition are scarce. This study was undertaken with the aim of providing a detailed picture of the evolution patterns of several important polyphenolic constituents during the last stages of ripening of Maratheftiko, which is one of the major native grape varieties. This study included monitoring of representative simple phenolics, flavonoids and anthocyanin pigments for two consecutive years, 2021 and 2022, to obtain a more integrated portrayal of changes occurring during the critical period prior to harvest. It was revealed that there was a very high difference in the content of almost all polyphenols considered for the harvests in 2021 and 2022. The grapes harvested in 2022 had a much higher content in catechin, but most importantly, the content in total anthocyanins was 3.91-fold higher in 2022 compared to 2021. On the other hand, trans-resveratrol was the only polyphenolic metabolite whose difference was rather marginal. In seeds, the predominant substance was catechin, which displayed pronounced fluctuations during the period examined. It was concluded that the contents of major polyphenolic metabolites in Maratheftiko grapes might exhibit large variations during the period prior to harvest, most possibly reflecting differences in the average temperature and rainfall. Thus, tight monitoring of technologically important constituents, e.g., anthocyanins, is recommended to ensure the harvest of grapes with optimal maturity.