Stuck Fermentation Procedures

A stuck fermentation is a fermentation that has stopped before all the available sugar in the wine has
been converted to alcohol and CO2. As fermentation progresses, sugar and nutrient supplies are
running out and alcohol levels are getting higher. It becomes harder for the yeast to do its job and
ferment your wine to completion.
How do I know if I have a stuck fermentation?

  • Taste the wine. If the wine tastes even a little bit sweet, you know that there’s sugar left.
  • Check the hydrometer readings, not the airlock activity. If you take hydrometer readings for
    three consecutive days, and the reading remains the same and is higher than 0 Brix, it’s
    probably stuck.
    Before you attempt to re-start a stuck fermentation, try these steps:
  • Move the fermenter to an area that is at room temperature (18-20°C/68-70 °F). In some cases,
    too low a temperature can cause a stuck fermentation, and bringing the temperature up may
    be enough to get it going again.
  • Open up the fermenter and rouse the yeast by stirring it with a sanitized spoon. Sometimes
    putting the yeast back in suspension will get it going again. If your fermentation is stuck, the nutrient content will be low and unable to support adequate yeast growth. In addition, the culture will require adaptation to the alcohol content of wine. Here’s an overview of the stuck fermentation procedure: First, add yeast hulls to help reduce accumulated toxins and improve the chance of a successful restart. Then, add nutrients to the wine to support yeast growth and activity. Next, you will build up a strong, healthy yeast biomass. Use a strong, vigorous yeast strain with good alcohol tolerance. We recommend Uvaferm 43 yeast.
  • Finally, add the stuck wine to the yeast biomass in stages to help the yeast adjust to the difficult conditions and alcohol level.
    Follow the procedure carefully for best results.

Equipment and Supplies

How to Re-Start a Stuck Fermentation- 1 hL (100L) or 23L

Add Yeast Hulls 40g- 1 hL (100L) or 10g- (23L) to the stuck wine 24–48 hours prior
to restarting. After 24–48 hours, rack the wine off the Yeast Hulls.

Then add Fermaid K directly to the stuck wine:

For wines stuck at 3 Brix or higher add: Fermaid K 12g/1hL or 3g/23L

For wines stuck at 1-3 Brix, reduce Fermaid K to 6g/hL or 1.4g/23L.

For wines stuck at less than 1 Brix, do not add Fermaid K.

In another clean container mix equal volumes of stuck wine and water. This should total 10% of the wine volume. This will be your Mother Restart Tank:

5L wine + 5L water (100L) or 1.15L wine + 1.15L water (23L)

Dissolve GoFerm in 20 times its weight of clean, chlorine free, 43°C (110°F) water.

Mix the solution and cool to 40°C (104°F): Go Ferm 31g + Water 625mL (100L) or 7g + 140mL (23L)

When the rehydration nutrient/water solution temperature has cooled to 40°C(104°F) about 5+ minutes, then slowly add Uvaferm 43 yeast. Stir gently to mix and avoid clumping. Let this yeast suspension stand
for 15–20 minutes.

Check the temperature of the yeast suspension. There should not be more than 10°C(18°F) difference between the yeast suspension and the diluted wine in the Mother Restart Tank.

When the temperature is within 10°C(18°F), add Uvaferm 43 yeast 25g (100L) or 6g (23L) to the Mother Restart Tank and wait 20–30 minutes. Add 10%- 10L (100L) or 2.3L (23L) of stuck wine (to the Mother Restart Tank and wait 20–30 minutes.

Then add 20%- 20L (100L) or 4.6L (23L) of stuck wine to the Mother Restart Tank
and wait 20–30 minutes. Repeat this step three more times.

Add any remaining wine to the Mother Restart Tank.

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