Scott Labs Yeast Choosing Guide
Last Updated: 9/2022
Applies to: Winemakers looking for assistance in selecting and comparing Scott Labs yeast strains. This guide contains downloadable pdf choosing charts (see end of article) that characterize our yeasts by fermentation kinetics, sensory impact & recommended variety.
Selecting Yeast for Success
Every fermentation presents different opportunities and challenges. Selecting the right yeast can help ensure a successful outcome. Yeast should be selected in two steps:
1. Identify which yeast strains are compatible with fermentation conditions
Potential Alcohol
Yeast strains vary in their ability to tolerate alcohol. Alcohol (ethanol) can destabilize yeast cell membranes which interferes with sugar uptake, slows fermentation rate, and makes yeast more sensitive to other stress factors. Ensure that the chosen yeast strain has a higher alcohol tolerance than the potential alcohol of the wine, otherwise a stuck fermentation may occur.
Temperature
Yeast strains vary in their temperature tolerances. Yeast will become stressed if fermenting at the upper or lower end of the recommended range. If temperature can’t be controlled, choose a yeast with a large temperature range. When working with high potential alcohol fermentations, lower fermentation temperatures are recommended.
Yeast Assimilable Nitrogen (YAN)
Yeast strains vary in their need for yeast assimilable nitrogen (YAN). Our strains are classified as low, medium, or high nitrogen- demand. YAN can be supplemented to meet the nitrogen needs of the yeast strain using fermentation nutrients. In situations where the juice/must is particularly YAN deficient, choose a yeast strain with low nitrogen needs.
2. Compare the sensory impact of compatible yeast strains
Sensory Impact
Yeast contribute to wine aroma, flavor, and mouthfeel. They can release aromas from grapes as well as produce aromatic compounds themselves. Certain strains also produce polysaccharides and other compounds increasing mouthfeel. Select yeast with traits best suited for the intended wine style.
Avoiding Hydrogen Sulfites (H2S) and Other Sulfur Off-Odors
Yeast can produce sulfur off-odors, especially in low nutrient environments. The amount of sulfur off-odors produced varies by yeast strain and fermentation conditions. Some yeast strains have been selectively bred to produce no (or very little) H2S, even under stressful conditions.