SO2 Management and Yeast Inoculation Strategies (NoSO2-Spont, NoSO2Sc, SO2Sc) During Fermentation Shape the Chemical, Polyphenolic, Microbiological, and Sensory Profiles of 'Solaris' White Wine.

Consumer interest in low-SO2 white wines is increasing; however, such approaches may reduce compositional and sensory predictability. This study evaluates how three fermentation strategies-SO2 addition and Saccharomyces cerevisiae ES181 inoculation (SO2Sc), spontaneous fermentation (NoSO2-Spont), and inoculation with S. cerevisiae ES181 without SO2 addition (NoSO2Sc)-shape the chemical profile, polyphenolic composition, colour, microbiological status, and sensory perception of 'Solaris' wines relative to the must (reference). A single batch of 'Solaris' must (one press run) was split into three variants and fermented under identical temperature conditions (12 ± 0.5 °C), followed by cool ageing and natural sedimentation prior to bottling. Basic oenological parameters, selected fermentation by-products, viable yeast counts, CIE Lab colour, targeted polyphenolics (phenolic acids, flavonols, flavan-3-ols, and stilbenes), PCA of by-products, and blind sensory evaluation were assessed. The NoSO2-Spont variant showed reduced fermentation completeness (higher residual sugars and lower ethanol) and the highest volatile acidity, together with elevated glycerol and several higher alcohols, and received the lowest sensory ratings. The SO2Sc variant yielded the most controlled outcome, with the lowest volatile acidity, the brightest colour (higher L*, lower b*), and the highest sensory acceptance. The NoSO2Sc variant produced intermediate sensory scores and a higher total phenolic content; however, volatile acidity remained high and viable yeast counts were the greatest, indicating increased susceptibility to microbiological activity during extended pre-bottling handling. Overall, the SO2Sc strategy provides the greatest chemical stability and sensory acceptance, whereas low-SO2 regimes require a hurdle approach (oxygen control, residual sugar management, hygiene, and stabilisation) to limit spoilage development and post-bottling refermentation.