sluggish fermentation

Cold weather fermentation

Brrr… it’s starting to get cold outside! Especially here in New England.

In the Northeast we get the joy of experiencing four distinct seasons. Harvest time is filled with lots of excitement in the air during the warm days and cool nights… but when the warm days start to turn into cool days too, things can get a little more complicated if your wine isn’t done fermenting.

Sometimes wine season extends into winter…

As anyone who makes wine knows, the alcoholic fermentation process can create some serious heat. As long as it doesn’t get too cold outside, the heat generated from this can pretty much sustain itself without issue.

But once the alcoholic fermentation slows down and eventually ends, if the malolactic fermentation (MLF) hasn’t finished and your wine is in a pretty cold (or even cool) location, it can be difficult to get MLF to finish. A half completed MLF can pose some issues in and of itself: delayed SO2 additions, persistent fizz, and stability issues down the road.

So what can you do to ensure you have as smooth a fermentation as possible that isn’t TOO quick, yet doesn’t drag on for too long?

  1. Choose earlier ripening varieties if you live in cold regions and/or the place you ferment your wine is in a cold place like a basement/cellar.
  2. Try co-inoculation as your method of malolactic fermentation.
  3. Use space heaters as needed. These can be placed in small spaces with your barrels to prevent MLF from slowing down or even stopping entirely.
  4. Choose a fast fermenting yeast strain.

What are the potential results of making wine in cold weather?

  1. Stuck alcoholic fermentation
  2. Stuck malolactic fermentation
  3. Unintentional cold stabilization (this can be positive or negative depending on the wine and style you’re attempting) as it can affect the TA even when you don’t want the TA to move, whether upwards or downwards.

Remember to keep a careful eye on your fermentations as they happen, because you can catch sight of a slow or sluggish fermentation caused by cold weather before it’s too late. Happy fermenting, and remember to keep your aging vessels bundled up and warm enough to keep that fermentation going strong.

SOS: Sluggish/stuck fermentation

Many a winemaker has lamented the dreaded stuck fermentation. With so much to deal with during harvest time, the last thing you should be worried about is a ferment that has just up and quit. But sometimes it happens – knowing what to do when it does will be a life saver during an otherwise potentially unfortunate moment in a wine’s life. We’re here to walk you through how to handle this, what to do, and most importantly, how to do it.

stuck wine fermentation-how to make wine-musto wine grape

Step 1: Think about why it may have gotten stuck

This is going to help you moving forward, both with this wine and with future ferments. Was there too much sugar in the juice or must to begin with? Was the fermentation temperature too cool or too hot? Did you choose a yeast that doesn’t do well with high sugar levels? Were nutrient levels too low?

Considerations before restarting

  • Adding lysozyme can halt spoilage organisms which are often present in sluggish or stuck fermentations
  • Resuke can lower toxin levels that have accumulated which will give you a better chance for a healthy restart. If you add this you will rack off of it 1-2 days later.
  • Incorporate Go-Ferm and Go-Ferm Protect Evolution to ensure health of ensuing restarting fermentation
  • Carefully choose what yeast you will re-pitch with. 43, 43 Restart, Fermivin Champion, K1 (V1116), Vin 13, BC, and DV10 are great choices.

Step 2. Add a complex yeast nutrient

This is going directly into the stuck wine tank. If you think you may have a spoilage bacteria problem, this is the time you would be adding lysozyme.

Step 3. Combine equal parts stuck wine and water in another vessel

This is known as the “mother restart tank.” At this moment it will be totaling 2% of whole volume.

Step 4. Rehydrate yeast nutrient + yeast as you would when pitching yeast the first time

This is the exact same process you did during the initial yeast pitch.

Step 5. Add the yeast to the mother restart tank

As always, there should be a <18F difference between the yeast mixture and the mother restart tank liquid temperature.

Step 6. Add 10% of the stuck wine to the starter culture

Wait 20-30 minutes.

Step 7. Add 20% of the stuck wine to the starter culture

Wait 20-30 minutes.

Step 8. Repeat until the remainder of the stuck wine has been added to the mother restart tank

Don’t skimp on waiting the 20-30 minutes at each of the following steps. Give it time to acclimate!