Saccharomyces Yeast Rehydration

Last Updated: 6/2021

Applies to: This protocol is for wineries using Saccharomyces yeast for primary fermentation. It details the importance of proper rehydration on cell viability and provides detailed steps for rehydration. This protocol is not appropriate for non-Saccharomyces yeast.

Contains video protocols in English, Spanish, and French and pdf download of procedure (English).

The Importance of Proper Rehydration

Proper yeast rehydration is one of the most important steps to ensure a strong and healthy fermentation. Normal inoculation rate for wine active dried yeast is 2 lb/1000 gal (25 g/hL). When added properly, this inoculation rate results in an initial yeast cell concentration of 3–4 million viable cells per mL of must/juice. Under favorable conditions, the initial yeast cell population will increase up to 100–150 million viable cells per mL of must/juice before growth stops and alcoholic fermentation begins. This biomass increase is critical for healthy fermentations. Higher inoculation rates are recommended on grapes that are higher maturity (higher sugar). When using a yeast rehydration nutrient such as GO-FERM™ or GO-FERM PROTECT EVOLUTION™, maintain a ratio of 1 part yeast to 1.25 parts rehydration nutrient.

Careful rehydration, attemperation, inoculation and homogenization are all important to help prevent sluggish or stuck fermentations.


This protocol is not appropriate for non-Saccharomyces yeast.

  • step 1: Suspend 2.5 lb/1000 gal (30 g/hL) of GO-FERM or GO-FERM PROTECT EVOLUTION in 20 times its weight of clean, chlorine free, 43°C(110°F) water. (For example: 2.5 lb rehydration nutrient x 20 = 50 ÷ 8.33 lb/gal water = 6 gal water.)
    • The water temperature is important for mixing of the rehydration nutrient. Due to the unique nature of GO-FERM and GO-FERM PROTECT EVOLUTION, they will not go into solution completely. This is due to the fatty acid and sterol content
    • Important: if not using a yeast rehydration nutrient, water temperature should being at 40°C (104°F) and the volume of water should be 10 times the weight of the yeast amount. This lower temperature is important, so you do not have to harm the yeast.

  • step 2: Once the temperature of the yeast rehydration nutrient solution has dropped to 40°C(104°F), add 2 lb/1000 gal (25 g/hL)* of active dried yeast. Stir gently to break up any clumps. Let suspension stand for 20 minutes, then stir gently again. Live yeast populations decline when allowed to stand for more than 30 minutes.
    • Note: Foaming is not an indicator of yeast viability.

  • step 3: Slowly (over a period of 5 minutes) combine an equal amount of the must/juice to be fermented with the yeast suspension. This will help the yeast adjust to the high sugar conditions and the cooler temperature of the must/juice and in fact this step is essential as it will help to avoid cold shock caused by a rapid temperature drop exceeding 10°C(18°F).
    • Important: This attemperation step may need repeating for very low temperature must/juice. Each attemperation step should last about 15–20 minutes.
      • For every 10°C(18°F) temperature difference between the must/juice and the yeast slurry, an attemperation step must be performed. For example, for a must/juice temperature of 20°C(68°F) and yeast slurry temperature of 40°C(104°F), two attemperation steps are required.

  • step 4: Inoculate
    • For direct inoculation of yeast post rehydration, ensure you mix the yeast slurry into the full volume of the must/juice.
    • For large tanks with long filling times add the yeast slurry to the bottom of the fermentation vessel just as you begin filling with must/juice. This is especially important when inoculating with strains that are sensitive to the competitive factor. This allows the yeast a head start over indigenous organisms.
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