Improving the Quality of Muscat Grape Juice Through Cold Maceration Using Metschnikowia pulcherrima: A Comparative Study on Phenolics, Antioxidant Activities and Volatile Profiles

Phenolic compounds in Muscat grape juice contribute to antioxidant capacity, functional properties, and sensory quality; however, conventional enzymatic maceration is often limited in efficiency and typically requires elevated temperatures. This study systematically compared pectinase-assisted heat maceration (P45-HM), low-temperature pectinase maceration (P-CM), and low-temperature maceration mediated by the psychrotolerant yeast Metschnikowia pulcherrima (Mp-CM) in Muscat grape juice. Mp-CM significantly enhanced the extraction and transformation of phenolic compounds, with total phenolic and flavonoid contents increasing by 8.01% and 13.14%, respectively, compared with P-CM, and by 27.06% and 55.28%, respectively, compared with P45-HM. Moreover, Mp-CM exhibited higher antioxidant activities, as determined by DPPH, ABTS, and FRAP assays, as well as greater sodium glycocholate-binding capacity than P-CM (p < 0.05). Correlation analysis revealed strong positive correlations between phenolic composition and biological activities. Volatile compounds were analyzed by HS-SPME-GC-MS combined with principal component analysis (PCA), demonstrating distinct aroma profiles. Mp-CM was enriched in terpenes (14.63% higher than P-CM), whereas P-CM was dominated by esters, suggesting that M. pulcherrima possesses a distinct biotransformation capacity that modulates volatile compounds potentially contributing to the characteristic Muscat aroma. These findings indicate that Mp-assisted cold maceration represents an efficient and promising biological maceration strategy for enhancing the quality of grape juice.