Impact of Ultrasonic-Assisted, Glutathione-Enriched Inactive Dry Yeast Addition on the Flavor, Metabolites and Antioxidant Properties of Kiwi Wine

Ultrasonic-assisted maceration and supplementation with glutathione-enriched inactive dry yeast (g-IDY) represent promising strategies to optimize the quality of fermented fruit wines. This study systematically investigated the synergistic effects of combined ultrasonic treatment and g-IDY addition on the metabolomics, flavoromics, and antioxidant properties of kiwifruit wine (KW), using integrated 1H-NMR, GC-MS, gas chromatography–ion mobility spectrometry (GC-IMS), and radical scavenging assays. 1H-NMR analyses revealed that both individual and combined treatments significantly altered the KW metabolome, influencing the levels of amino acids, organic acids, and carbohydrates. GC-MS and GC-IMS analyses characterized numerous volatile compounds, demonstrating that the combined treatments (USL + GSH, USM + GSH, USH + GSH) particularly enhanced the concentrations of desirable fruity esters (e.g., ethyl isobutyrate) and reduced off-flavor compounds (e.g., hexanoic acid), exhibiting a clear synergistic effect beyond individual applications. Furthermore, the combined treatment significantly enhanced the antioxidant capacity of KW, as evidenced by the significantly higher scavenging activities against DPPH, hydroxyl, and superoxide anion radicals, compared to individual applications. Overall, this study sheds light on applying the synergistic treatment of ultrasonics and g-IDY as a novel technique to comprehensively enhance the flavor and functional quality of KW.