Troubleshooting Your Wine

The faults and flaws and their analysis and resolution presented below are from my latest book, Modern Home Winemaking, where you can find additional information should you wish to explore these further.

RESTART PROTOCOL — ALCOHOLIC FERMENTATION

The protocol to restart a stuck fermentation involves treating the problem wine with yeast hulls, e.g., Oenocell, preparing the booster yeast, which will be added to a small volume of wine (what is called a pied-de-cuve), and then adding the pied-de-cuve to the whole batch of wine. Be sure to use fresh yeast hulls as they contain fats that oxidize when exposed excessively to air and may develop an unappealing rancid taste.

Choose a strong yeast strain, such as Lalvin K1V-1116, Uvaferm 43 RESTART, or Premier Cuvée, specifically known for restarting stuck fermentations.

STEP 1:

If treating wine in a carboy or tank without grape solids, first carefully rack the wine off its lees and into another vessel while avoiding oxygen pick-up to the extent possible, and immediately add 10–20 mg/L free SO₂ (FSO2). Make sure wine temperature is in the range 20–25 °C (68–77 °F).

Add 0.1–0.25 g/L of yeast hulls, or as per your product’s instructions, while stirring thoroughly but gently, again, to minimize oxygen uptake.

Stir every 12 hours until Step 4.

STEP 2:

Take 10% of the wine volume, for example, about 2 L (½ gal) if dealing with a 23-L (6-gal) batch, and transfer to a suitably sized container. This is for preparing the pied-de-cuve.

Add and dissolve enough table sugar to raise the SG to around 1.020 (5 Brix) if it is below that. You need about 25 g/L of sugar to raise SG by 10 points (2.5 Brix).

Add complex nutrients, such as Fermaid K or Fermaid O, as per product instructions at the recommended rate. Keep wine at 20–25 °C (68–77 °F).

STEP 3:

In a separate container sufficiently large to hold more than the amount of wine drawn in Step 2 (you need to account for foaming), add the required amount of rehydration nutrients to fresh, clean (non-distilled) water, as per your product’s instructions, for example, 0.30 g/L in 20 times its weight of water at 43 °C (110 °F).

Rehydrate 0.30 g/L of your yeast strain of choice in the suspension as per your yeast rehydration instructions once the temperature of the suspension has dropped to, for example, 40 °C (104 °F).

Add about 10% of wine from the volume drawn in Step 2; for example, if you are making a 23-L (6-gal) batch and had drawn out 2 L (½ gal), then transfer about 0.2 L (200 mL) into the yeast–nutrient suspension. This is now the pied-de-cuve — it should start fermenting fairly quickly. Let cool and maintain at 20–25 °C (68–77 °F), and stir occasionally until the SG drops to 1.000 (0 Brix).

Once the pied-de-cuve SG has dropped to 1.000 (0 Brix), double the volume by adding another 10% of wine from the volume drawn in Step 2. Maintain temperature at 20–25 °C (68–77 °F) and stir occasionally. If fermentation becomes vigorous, proceed to Step 4, otherwise, double the volume again.

STEP 4:

Once the pied-de-cuve is fermenting vigorously, add to the batch of wine and stir thoroughly, add more complex nutrients at a rate midway in the recommended range for your product, and stir again thoroughly. Place an airlock on the carboy or tank. The entire batch of wine should restart fermenting and proceed to completion, i.e., SG below 0.995 (–1.5 Brix).