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.
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!
The Winemaker’s Think Tank: Vol 5 – Is Malocatic necessary in White Wines if it has not been inoculated?
What’s the Winemaker’s Think Tank?
Every Thursday we will post about a few frequently asked questions that our winemaker has answered. If you have a winemaking question you would like to have answered, please email us at support@juicegrape.com and we will try to get into next week’s post. Cheers! 🙂
Is Malocatic necessary in White Wines if it has not been inoculated?
When considering the stability of a white wine in preparation for bottling, sugar and microbial stability are of great importance. After fermentation, if MLF is not purposefully inoculated by the winemaker, the addition of Lysozyme may be considered as to retard any naturally present MLF bacteria from beginning to ferment. If the level of SO2 is kept up to is suggested level (contingent upon pH), the Lysozyme may not be needed as the SO2 will prevent the bacteria from fermenting. If the winemaker is trying to use a low amount of sulfites in their wine, I would suggest the use of Lysozyme to inhibit any bacterial growth.
Equally as important, is the use of sterile filtration. If the wine is processed through a sterile filter (.45µ), bacterial and yeast cells should be eliminated. This will physically prevent the bacterial spoilage of the wine. If the winemaker chooses to back sweeten the wine, this filtration will also help prevent any refermentation within the bottle. When it comes to back sweetening, I also always recommend chemical as well as physical sterilization of the wine to prevent fermentation and off aromas to develop within the bottle. Potassium sorbate may be used on any wine that has not gone through malolactic fermentation. If it is used on a wine that has undergone MLF, remaining MLF bacteria can begin to metabolize the sorbate, resulting in a strong geranium odor. In my experience, I typically add sorbate and sterile filter the wine, then bottle, without the addition of Lysozyme. I am meticulous about the level of SO2 remaining above the suggested amount , and I typically add an additional 10ppm before bottling to ensure prolonged sterility within the bottle.
While you certainly can conduct a chromatography test upon the wines to detect the presence of acid, both malic and lactic exist naturally within the grape, so the chromatography test will not be especially helpful when looking at a wine that has not gone through MLF. As long as you keep a vigilant watch upon your sulfur dioxide levels and pH, and use sorbate when sweetening, you should be fine.
We hope this information helps with your winemaking. If you have any follow up questions or winemaking questions in general, please email us at support@juicegrape.com.
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