Investigating phenolic compounds, antioxidant activity, and pomological traits in highbush blueberry (Vaccinium corymbosum L.) cultivars across ripening stages

This study systematically investigated phenolic compounds, antioxidant activity, and pomological traits in five highbush blueberry (Vaccinium corymbosum L.) cultivars-"Cargo", "Ozarkblue", "Blue Ribbon", "Volar", and "Topshelf" across three distinct ripening stages (green, pink, and fully ripe). Significant cultivar-dependent variations were observed throughout fruit development. Total phenolic content declined progressively during ripening in all cultivars, with "Cargo" exhibiting the highest values at early stages. Phenolic composition shifted markedly with maturation: chlorogenic acid dominated unripe fruit (particularly in "Topshelf") and declined sharply toward ripeness, while ellagic acid and flavonoids (myricetin, quercetin, catechin) showed more stable or increasing trends. This transition reflects the biochemical shift from defense-related phenolics to color-associated compounds during fruit development. Antioxidant activity, measured by DPPH and FRAP assays, was highest in unripe fruit, with "Ozarkblue" demonstrating peak capacity. Conversely, total anthocyanin content increased dramatically during ripening, reaching maximum levels at full ripeness, with "Cargo" accumulating the highest concentrations. Pomological traits also varied considerably: "Ozarkblue" produced the largest berries (4.75 g), while "Volar" and "Topshelf" maintained higher acidity, and "Cargo" achieved superior sweetness (12.5 °Brix). Multivariate analysis confirmed that ripening stage was the primary driver of biochemical variation, while genotype determined the magnitude of these changes. These findings provide practical guidance for optimized harvest timing: early-harvested "Ozarkblue" for antioxidant-rich functional products, and fully ripe "Cargo" for anthocyanin-rich fresh market applications.