The effect of harvest time across different climatic regions on the accumulation of phenolic compounds in Marselan grapes and wines.

Harvest time is a critical determinant of grape and wine quality. This study investigated the influence of harvest time on the phenolic compounds and physicochemical properties of Marselan grapes and wines across two climatic regions during the 2022 and 2023 vintages. Five sequential harvests (S1-S5) were conducted in Shandong (warm temperate monsoon climate), whereas three (N1-N3) were implemented in Ningxia (moderate temperate continental climate). In Shandong, harvest at S4 optimized the accumulation of total phenolic content (TPC), total flavan-3-ols (TFOC), total flavonoid content (TFC) and monomeric phenolic compounds in grape skins and wines. In contrast, in Ningxia, phenolic accumulation in grape skins and wines was optimized at N1-N2; TPC, TFOC, and monomeric phenolic compounds were relatively high at N1, while total anthocyanin content (TAC) and monomeric anthocyanins remained relatively high at N2. The optimal harvest time exhibited greater interannual variability in Ningxia than in Shandong. In summary, for Marselan grapes and wines, mid-to-late delayed harvest optimized core phenolic quality in warm monsoon regions, whereas early-to-mid harvest was optimal in temperate continental regions.