Metschnikowia pulcherrima as a Tool for Sulphite Reduction and Enhanced Volatile Retention in Noble Rot Wine Fermentation

The use of non-Saccharomyces species is gaining momentum in modern winemaking as part of broader efforts to reduce chemical inputs and adapt to climate-driven challenges. In this study, Furmint grapes were harvested at two distinct ripeness levels: an early harvest with healthy berries and a late harvest that included botrytized fruit. Two oenological protocols were compared: a conventional sulphur dioxide-based protocol and an alternative bioprotection-oriented approach that minimized SO₂ additions. Bioprotection was carried out using Metschnikowia pulcherrima, followed by sequential inoculation with Torulaspora delbrueckii and Saccharomyces cerevisiae. Grape-derived tannins (from skin and seed) were also added to inhibit oxidative enzymes such as laccase. Fermentation was monitored using standard analytical techniques, with volatile aroma profiles characterized by HS-SPME-GC-MS. Results showed that harvest timing and botrytization strongly influenced the chemical composition of the wines. Moreover, the treatment protocol had a marked effect on the final sensory profile. Wines produced with the bioprotection-oriented protocol displayed enhanced aromatic complexity, particularly through higher concentrations of esters and higher alcohols. Overall, the alternative protocol involving M. pulcherrima-based bioprotection resulted in wines with more pronounced floral and fruity notes, supporting its potential as a viable strategy for producing expressive wines under evolving climatic conditions.