Effects of Metschnikowia pulcherrima as a Substitute for SO2 in Pre-Fermentative Cold Maceration on Muscat Red Wine

In response to increasing safety concerns regarding the use of sulfur dioxide (SO2) in winemaking, this study investigates the efficacy of Metschnikowia pulcherrima-mediated cold maceration (Mp-CM) as a potential alternative to SO2 at industrial temperatures (10–15 °C). The analysis focused on the content of different phenolics, as well as wine color properties and aroma compounds. These parameters were compared against those obtained from CM with SO2 (SO2-CM). This study introduces and compares the phenolics, wine color properties, and volatile compounds produced by three Metschnikowia pulcherrima strains (Mp0519, Mp0516, and Mp0520 were previously isolated from Muscat Hamburg grapes in the Jieshi mountain region), revealing that the effectiveness of the treatments varied depending on the temperature and strain. At 10 °C, Mp-CM showed significantly lower phenolic (−19.23%) and flavonoid (−41.13%) content compared to SO2-CM but exhibited markedly higher anthocyanin and terpene content (+133.11% and +12.61%, respectively), with similar tannin levels. Conversely, at 15 °C, Mp-CM outperformed SO2-CM in several key metrics, including total phenolics (+17.32%), flavonoids (+83.45%), tannins (+17.05%), and anthocyanins (+54.08%), and demonstrated a significantly enhanced floral/fruity aroma intensity (+160.72%). Furthermore, Mp0520 exhibited peak levels of phenolics and esters at 10 °C, while Mp0519 reached its highest terpene level at 10 °C and total volatile at 15 °C. Notably, Mp-CM consistently displayed specific characteristics regardless of the maceration temperature, including a reduction in total volatile compounds, a suppression of ester formation, an enhancement of anthocyanin content, and an improvement of the wine’s floral aroma, with strain-specific variations observed across all evaluated parameters. This study illustrates that the Mp-CM provides distinct advantages in extracting key components from grape skins, and it has the potential to enhance wine color attributes. This positions Mp as a promising SO2 alternative for CM, contingent on strain selection and process optimization.