Summer conditions can reduce nitrogen availability in the soil and limit its uptake by the vine. As a result, grapes may arrive at the cellar with low levels of yeast-assimilable nitrogen (YAN). Low YAN requires careful management right from the start of alcoholic fermentation because nitrogen deficiency can:
slow fermentation kinetics
increase the risk of sluggish or stuck fermentation
promote the formation of reduced sulfur compounds such as H₂S
How the LAFFORT® Decision-Making Tool helps assess nitrogen requirements
To support this assessment, LAFFORT® has developed a new Decision-Making Tool that considers three key factors:
initial must YAN
potential alcohol
the yeast strain’s nitrogen requirements
Using a modeling graph, the tool compares the nitrogen naturally present in the must with the potential alcohol. This provides a clearer basis for planning nitrogen additions based on the specific yeast and the must's composition, rather than relying on a standard supplementation approach.
The tool also incorporates an important principle of nutrition: the more severe the deficiency, the greater the emphasis should be on organic nitrogen intake. This type of nutrient also provides vitamins and minerals, which are essential for proper cellular metabolism.
Correcting YAN is an essential step, but it is only part of the solution. The yeast must also be physiologically capable of taking up and using the nitrogen available. This is where another key factor comes into play: lipids.
Sterols and unsaturated fatty acids are crucial for maintaining the flexibility and permeability of the yeast cell membrane. This becomes increasingly important as ethanol concentrations rise during fermentation, placing greater stress on the cell membrane.
Without sufficient membrane fluidity, the yeast becomes less efficient at transporting nutrients across the membrane. This can limit nitrogen uptake even when sufficient nitrogen is present in the must.
Why yeast rehydration is the right time to supply lipids
Lipid support should begin before fermentation starts, during yeast rehydration. Using a yeast rehydration product from the SUPERSTART™ range supplies sterols and micronutrients directly to the yeast during this stage. This helps strengthen the cell membrane before the yeast is introduced into the must and exposed to the increasingly stressful conditions of alcoholic fermentation.
This approach supports the yeast's ability to:
maintain membrane function
assimilate nutrients efficiently
tolerate increasing ethanol concentrations
sustain fermentation through to completion
Using SUPERSTART™ at 20°C can simplify harvest operations
Yeast rehydration nutrients have traditionally been used in water at approximately 37°C. However, SUPERSTART™ can also be used effectively at 20°C. This provides a simpler, faster rehydration option, which can be particularly useful during harvest, when cellar teams are managing several operations simultaneously.
A complete approach to yeast nutrition
Successful yeast nutrition requires more than correcting a YAN value. Combining the LAFFORT® Decision-Making Tool with appropriate nitrogen supplementation and lipid support during rehydration addresses both sides of the equation: providing the nutrients the yeast requires and supporting its ability to assimilate them. The result is better supported yeast physiology and more reliable fermentation through to complete sugar depletion.
About the author: Dr Charlotte Vion holds a PhD in Enology from the University of Bordeaux and is currently the Product Range Manager for Nutrition and Yeast Derivatives at LAFFORT®.