Yeast - Importance of Rehydrating Wine Yeast

How important is it to rehydrate the yeast before adding it to the fermenter?

Very important! Extensive research shows that the yeast cell wall is very fragile during the first few minutes of rehydration. Some of the components of the yeast are going from a dry crystalline form to a gel like state and can go through this transformation successfully if rehydrated properly (refer to our 3 easy steps rehydration protocol). With rehydration water at lower temperatures the transformation from crystalline to gel is less successful, the cell wall becomes porous and leaches out vital parts of its insides. Rehydration in 60°F water can result in a loss of 60% of the yeast viability.

Rehydration in distilled or deionized water is lethal to the yeast. The cell walls require the presence of some minerals, sodium, calcium, magnesium and or potassium, during rehydration. Tap water at 250 ppm hardness is optimum. Most tap water has enough hardness to do the job. The presence of 1/2% yeast extract, yeast hulls, autolyzed yeast or peptone in the rehydration water will give the yeast an added boost that will get it through its lag phase quicker. After the yeast cell wall has been reconstituted, the yeast returns to its normal ability to be selective.
Most fermentations should start with an inoculation of 3 - 4 million viable yeast cells per milliliter of must. A normal healthy fermentation will reach the stationary phase with a cell population up to 100 - 150 million viable yeast cells per milliliter. Because of this significant increase in biomass, it is critical that the active dried yeast gets off to a good start. Winemakers that carefully rehydrate their active dried yeast are taking a key preventative step to avoiding stuck and sluggish fermentations. Remember to use only clean 104°F tap water and please refer to our Easy 3 Steps Protocol for more information

*This content is adapted from Lalvin/Lallemand’s website for Wine Yeast - For more information and technical data visit Lalvin-Lallemand's website

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