Nitrogen availability is an essential parameter for wine alcoholic fermentation. Moreover, recent results have shown that it plays a key role in yeast cell death in interaction with micronutrients limitations such as lipids or vitamins. Previously researchers have found that yeast cell death was triggered by starvation for a set of micronutrients, including oleic acid, ergosterol, pantothenic acid and nicotinic acid whenever the level of nitrogen was high, but not in low nitrogen conditions. In this study researchers examined the impact of the nature of the nitrogen source in the light of these previous results.
Methods and results:
- 19 Amino acids or NH4+ were added, in amounts corresponding to 354 mg/L assimilable nitrogen, to an oenological medium that was low in nitrogen and oleic acid.
- Yeast viability in function of the fermentation progress was assessed and showed differences in cell death during the alcoholic fermentation in function of the amino acid added.
- The addition of NH4+ was also tested at two different times during wine fermentation.
- The results obtained show that various nitrogen sources (amino acids, ammonium) can trigger cell death but with different intensities.
- It appears that some amino acids are preferable to others in alcoholic fermentation because they do not trigger cell death.
- The researchers also provided evidence that the timing of nitrogen addition has a strong impact on cell death in musts with micronutrient limitations: an early nitrogen addition is more likely to trigger cell death than a late addition.
Significance and impact of the study: The study, like previous studies, confirmed that addition of inorganic nitrogen (NH4+) should be delayed until the end of the exponential growth phase of the fermenting yeast. Careful consideration should also be given to the type of yeast nutrient used, with organic yeast nutrition (source of amino acids and micronutrients) being the better option under certain winemaking conditions. The results provide a novel frame for managing nitrogen supplementation of grape musts and to avoid stuck fermentation.
Reference: Duc, C., Noble, J., Tesnière, C., & Blondin, B. (2019). Occurrence of yeast cell death associated with micronutrient starvation during wine fermentation varies with nitrogen sources. OENO One, 53(3). https://doi.org/10.20870/oeno-one.2019.53.3.2408
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