Yeast Rehydration Is Better Than Direct Inoculation
Last updated: 9/2022
Applies to: Winemakers using or considering using yeast marketed for direct inoculation.
In recent years, the wine industry has been offered various direct inoculation yeasts that can be added directly to juice or must without rehydration. These yeast may seem attractive due to ease of use and promises of the same performance as classically rehydrated yeast. However, we have found that directly inoculated yeast may not perform the same as rehydrated yeast. Direct inoculation can result in underperforming yeast, leading to long and potentially sluggish fermentations and diminished wine aroma, flavor, and mouthfeel.
BENEFITS OF YEAST REHYDRATION
Yeast inoculation protocols that optimize yeast metabolic activities have been extensively researched. In almost all cases, yeast rehydration optimizes fermentation kinetics (implantation, lag phase length, fermentation duration) and/or sensory contribution (aroma production and conversion, mouthfeel contribution).
Yeast rehydration can improve fermentation kinetics
Yeast rehydration can decrease fermentation duration. As seen in figure 1, rehydration decreased fermentation length by 5-10 days depending on strain.
Yeast rehydration can improve aromatic expression
Yeast rehydration can improve aromas generated from yeast (esters) as well as optimize expression of aromas coming from the grapes (thiols, etc.). As seen in figure 2, in all trials rehydration improved aromatic expression even if the fermentation duration was not impacted.
WHAT ARE “DIRECT INOCULATION” YEAST?
Most commercially available yeast that are marketed for direct inoculation are not produced in any special way to prepare them for direct inoculation. Rather, they are strains produced in the standard way that have been shown to perform adequately when directly inoculated.
As seen in figure 3, other strains not marketed as direct inoculation, perform as well or better without rehydration when compared to “direct inoculation” yeast. When using Lalvin K1 (V1116) and Lalvin EC1118 without rehydration, they finished fermentation 3 days ahead of the “direct inoculation” strain.
Lallemand Oenology has shown that even strains marketed for direct inoculation perform better when rehydrated. In figure 4, “Direct Inoculation” Yeast X took 9 days longer to ferment without rehydration. Furthermore, there are many strains not marketed for direct inoculation that also perform adequately when directly inoculated. In the trial below, all strains performed better with rehydration. Even without rehydration, the Lallemand strains outperformed the rehydrated “Direct Inoculation” strain.
WHEN DOES DIRECT INOCULATION MAKE SENSE?
Direct inoculation may save time and labor during the inoculation process and there may be circumstances when these savings outweigh the risks to fermentation performance. Direct inoculation may make sense if:
- Fermentation conditions are easy (low potential alcohol, high pH, temperature control is available, adequate YAN/nutrition, optimal NTUs, hygiene of winery and cellar are good, etc)
- Quick fermentations are not important for winery logistics (tank turnover)
- The chosen commercial yeast performs adequately when directly inoculated (we recommend K1 and EC1118)
- Sensory contribution from yeast is not important (positive aromas, flavors, and mouthfeel)
To ensure efficient and complete fermentation and maximize yeast sensory contributions, we recommend that active dry yeast should be rehydrated in warm water prior to inoculation. We believe this is the best way to prevent long and potentially sluggish fermentations and maximize wine aroma, flavor, and mouthfeel.
This article was meant to discuss the benefits of rehydration and is not an in depth discussion of all the ways that yeast performance (kinetics and aromas) can be improved. Please see our Saccharomyces Yeast Rehydration protocol for more information.
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