How do pH reduction and the addition of potassium metabisulfite impact colour and the phenolic and anthocyanin profiles in red araçá (Psidium cattleianum Sabine) wine?

Abstract

This study evaluated the effect of reducing the pH of the must and adding potassium metabisulfite at different stages of the process on the physicochemical parameters, color, phenolic composition, and antioxidant activity of red araçá wines. Six beverage formulations were prepared, three using the original pH of the pulp (pH 3.0) and the other three adjusting the pH to 2.8 with citric acid. Potassium metabisulfite (K₂S₂O₅) was added to all the formulations but at different stages: 100 mg.L⁻¹ in the pre-fermentation stage (MI), 50 mg.L⁻¹ in the pre-fermentation stage + 50 mg.L⁻¹ in the post-fermentation stage (MP), and 100 mg.L⁻¹ in the post-fermentation stage (MF). The primary organic acids in red araçá wine were citric, malic, glycolic, and lactic acid. The initial pH influenced the red coloration of the CIELab color scale, with more significant effects observed in wines with an initial pH of 2.8. The MI and MP samples with an initial pH of 2.8 exhibited the highest antioxidant activity in the DPPH test, reaching 20.99 µM Trolox equivalent (TEAC).mL⁻¹ and 20.28 µM.mL⁻¹ TEAC, respectively. Fourteen phenolic compounds were identified in the red araçá wine, with gallic acid, catechin, and tyrosol being the main compounds. Furthermore, the results revealed that reducing the pH to 2.8 and adding 100 mg of K₂S₂O₅ in the pre-fermentation stage contributed significantly to a higher content of cyanidin-3-glucoside, aiding in preserving the beverage's reddish color. This study pioneered the production of fermented beverages from red araçá.