Restarting a stuck alcoholic fermentation

Practical protocol

Why this protocol matters

A stuck alcoholic fermentation is rarely solved by simply adding more yeast.

Before restarting fermentation, the wine needs to be prepared to reduce the inhibitory conditions that caused the fermentation to stop. Medium-chain fatty acids, high alcohol, low nutrient availability and poor yeast viability can all make restart difficult.

Application: sluggish or stuck alcoholic fermentation
Main tools: Extraferm^® D’tox, Fermivin^® Champion Booster and Maxaferm^®
Protocol duration before inoculation into the tank: approximately 4 days
Purpose: detoxify the stuck wine, build an active restart culture and progressively acclimatise it before inoculation

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How to restart a stuck alcoholic fermentation (for 100hL)

Day 1: Detoxify the stuck wine

If necessary, cool the tank to 15–20 °C.
Add SO₂: 4–6 g/hL.
If total SO₂ is above 150 mg/L, add Delvozyme^® / lysozyme according to the recommended dosage.
Add Extraferm^® D’tox at 20–40 g/hL.
Treat the wine and allow it to settle.
Rack after 24 hours.

Why Extraferm D’tox?

Extraferm D’tox adsorbs inhibitory medium-chain fatty acids and other unwanted compounds that can reduce yeast viability and prevent fermentation from restarting.

Day 2: Rehydrate Fermivin Champion Booster

Use 16.5 kg sugar in 50 L water at 38 °C.
Add 3 kg Fermivin^® Champion Booster to the solution.
Leave to rehydrate for 30 minutes.

Why Champion Booster?

A restart yeast selected for difficult fermentation conditions, including high alcohol, low YAN and inhibitory environments.

Day 2: Prepare the restart inoculum

Add to the rehydrated Fermivin Champion Booster suspension:

1 L water at 20 °C
1.2 kg sugar
50 L stuck wine
Maxaferm^®: 70 g

Allow the culture to cool to 20–25 °C.

Wait until the inoculum reaches a density of 1005 maximum (approximately 24 hours).

Days 3–4: Acclimatise the restart inoculum

Step 1

Add to the inoculum:

stuck wine: 140 L
water: 70 L, room temperature
sugar: 25 kg
Maxaferm^®: 180 g

Wait approximately 24 hours, or until density reaches about 995.

Step 2

Add to the inoculum:

stuck wine: 450 L
water: 50 L, room temperature
sugar: 25 kg
Maxaferm^®: 400 g

Wait another 24 hours, or until density reaches about 995.

Final step: Restart the tank

Add the acclimatised inoculum to the tank containing the detoxified and racked stuck wine.

Why the protocol works

1. Detoxify
Extraferm^® D’tox reduces inhibitory fatty acids and improves the environment for yeast restart. Oenobrands recommends 30–40 g/hL for sluggish or stuck fermentations, with the highest dose for stuck AF.

2. Restart with the right yeast
Fermivin^® Champion Booster is used to rebuild an active yeast population under difficult fermentation conditions.

3. Acclimatise progressively
Gradual exposure to the stuck wine helps the restart population adapt to alcohol, low nutrients and the inhibitory environment before entering the full tank.