Use of Non-Saccharomyces Yeasts with Nitrogen Addition to Improve Fermentation of Chardonnay Having High Initial Sugar Content Due to Global Warming

Date

2024-12-20

Author

Aktuna, İpek

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The sugar content in grapes has increased due to climate change, leading to higher alcohol content in wines. Due to health issues, consumer preferences, and taxation, winemakers tend to reduce alcohol levels by using non-Saccharomyces yeasts. However, sequential inoculation with S. cerevisiae causes competition for nitrogen, which is crucial to manage effectively to prevent stuck or sluggish fermentation. Therefore, this study, firstly, monitored the effects of timing of nitrogen addition in Chardonnay must (28˚Brix) sequentially inoculated with M. pulcherrima and S. cerevisiae. Nitrogen addition on day 5 significantly reduced fermentation duration and increased glycerol production. Subsequently, this finding was applied to Chardonnay must sequentially inoculated with different non-Saccharomyces and S. cerevisiae. A 0.6-0.7% (v/v) alcohol reduction was noted with M. pulcherrima P01A016 compared to M. guillermondii, L. thermotolerans, or W. anomalus. However, these non-Saccharomyces yeasts struggled to adapt to high initial sugar content. Therefore, two M. pulcherrima strains gradually adapted to high sugar medium before inoculating Chardonnay must (28˚Brix). Alcohol levels in wines inoculated with adapted and non-adapted M. pulcherrima strains were similar. However, wines produced with adapted M. pulcherrima D11 had lower acetic acid concentrations, acting as osmoprotectants. Finally, the fermentation process of Chardonnay must with 110 or 220 mg N/L YAN addition was monitored. 220 mg N/L of YAN enhanced the population and the fermentation rate, leading to an accelerated fermentation process. Overall, this study highlights the importance of non-Saccharomyces yeasts’ ability to respond to osmotic stress in high sugar must with nitrogen addition to reduce alcohol levels.

Subject Keywords

Non-Saccharomyces, Nitrogen Addition, High Sugar Content, Chardonnay, HPLC

URI

https://hdl.handle.net/11511/113063

Collections

Graduate School of Natural and Applied Sciences, Thesis