Dynamics of Sugars, Organic Acids, Hormones, and Antioxidants in Grape Varieties ‘Italia’ and ‘Bronx Seedless’ during Berry Development and Ripening

Grapes are a globally important fruit with significant economic value, influenced by factors such as sugar content, organic acids, hormones, and antioxidants. Understanding the dynamics of these compounds during grape development and ripening is critical for optimizing berry quality and production. This study investigates the changes in sugar, organic acids, hormones, and antioxidants in two grape varieties, ‘Italia’ and ‘Bronx Seedless’, at various growth stages (BBCH-77, BBCH-79, BBCH-81, BBCH-83, BBCH-85, and BBCH-89). Regarding sugars, significant variations were observed due to grapevine cultivar and phenological stage. ‘Bronx Seedless’ grapes consistently displayed lower sugar content than ‘Italia’ grapes, regardless of the type of sugar being examined. The BBCH-77 stage consistently exhibited lower sugar levels compared to BBCH-89. The varieties ‘Bronx Seedless’ and ‘Italia’ exhibited distinct nutritional profiles, each with their unique advantages in terms of sugar content and organic acid composition. Both varieties were rich in the primary sugar glucose and fructose, with ‘Bronx Seedless’ displaying notably high levels of the beneficial tartaric acid, enhancing its nutritional value. On the other hand, ‘Italia’ stood out for its higher concentrations of fumaric, butyric, and oxalic acids, contributing to its unique taste and health benefits. Throughout their growth stages from BBCH-77 to BBCH-89, an increase in organic acid levels was observed, peaking at the BBCH-85 stage, except for maleic acid. In terms of hormonal content, ‘Italia’ exhibited higher levels compared to ‘Bronx Seedless’. The predominant hormone, abscisic acid (ABA), alongside lower quantities of zeatin, indicated a strong physiological response to environmental and developmental cues in both varieties, with hormone levels increasing as the grapes approached maturity. Antioxidant profiles also varied between the two varieties, with ‘Italia’ consistently showing higher antioxidant levels than ‘Bronx Seedless’. Antioxidant levels consistently increased from BBCH-77 to BBCH-89. This comprehensive analysis contributes to our understanding of the complex processes underlying grape berry development and ripening, with potential implications for enhancing grape quality and refining production strategies.