How To Handle A Stuck Fermentation In Wine Making

man_looking_at_glass_of_wineI purchased 5 – 6 gallon buckets of wine juice on 10/17/13. All the juices where pH-acid balanced and inoculated with wine yeast. All completed fermenting quite quickly and have been racked to and stabilized in glass carboys, except the Sauvignon Blanc. My starting Specific Gravity (SG) for this juice was 1.080.

On 10/31/13, I racked the Sauvignon Blanc from the primary fermenter (plastic bucket) at SG 1.020 for secondary fermentation under airlock in a glass carboy as per the manufactures directions. I then checked the SG on 11/7/13 and it had dropped to 1.010. I rechecked the SG last evening (11/13/13) and it has remained unchanged at 1.010.

Is this a stuck fermentation? I really don’t want to stabilize this wine at 1.010 since it is Sauvignon Blanc and at that Specific Gravity it taste too sweet.

This wine has had a bit of a sulfur odor indicating that the yeast may be having problems fermenting this juice. Any suggestions? Pitch another package of yeast? Appreciate your help as always, thanks!

Name: Michael N.
State: Pennsylvania
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Hello Michael,

Yes, I would consider this a stuck fermentation.

The sulfur odor is the biggest clue here. This indicates that the fermentation was occurring while the wine yeast was under much stress. The yeast was not happy.

My best guess is that the amount of viable yeast in the fermentation was lacking. This can happen in one of two ways:

  1. The wine yeast pitched into the must was old or significantly compromised, or
  2. The primary fermentation was conducted under an airlock. Any yeast desperately needs air available to it in the beginning so that the colony can multiply into sufficient numbers. If an airlock is used during the primary fermentation this can not happen very well. A standard packet of wine yeast needs to multiply between 100 and 200 times itself.

One thing we do know is that as the alcohol rises the wine yeast comes under more and more stress with each additional percent. This is why most wine fermentations go a little slower and slower with each passing day. Add on top of that other stressing factors, and you can very easily end up with a stuck fermentation in wine making.

What I would do at this point would be to read over The Top 10 Reasons For Fermentation Failure that are listed on our website. If any of the 10 ring true to your situation, then go ahead and take any corrective actions necessary.

In addition, I would add a 1/2 dose of yeast nutrient. This would be 1/2 teaspoon per gallon of wine must. If you did not add any yeast nutrient when starting the fermentation, then add a full dose… 1 teaspoon per gallon. There is no down side to adding the yeast nutrient, only potential upside.

After a couple of days, if you do not observe any renewed fermentation, then I would suggest taking a more radical step by making a yeast starter and adding that to wine must. A yeast start is like repitching a grown yeast colony into the fermentation. It is the ultimate solution if active yeast numbers is the issue here.

If this does not cause the fermentation to start, then you need to strongly consider one of the other 9 reasons for a stuck fermentation listed in the above article.

Having a stuck fermentation in wine making is not a fun thing. It requires an extra effort on the winemakers part. That’s the bad news. The good news is that almost all stuck fermentations in winemaking can be remedied. It is simply a matter of identifying the underlying issue at hand.

Hope this helps you out.

Happy Winemaking,
Ed Kraus
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Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.

9 thoughts on “How To Handle A Stuck Fermentation In Wine Making

  1. My son and I have been working on a Mead and have added Potassium Sorbate too early and we feel we may have done damage to the yeasy as the fermentation has all but stopped.
    We did add yeast nutrient but nothins has happen in the last 5 to 7 days.
    Is this one of those time where we cut our losses and start new?
    Thanks
    John C

  2. I would like to thank you for the article on stuck fermentation. My husband and I have been making wine for about 15 years and have never had fermentation stop as it did in the last batch of blueberry wine we are doing now. We use you yeast starter recipe and all is going well now. Thank you so much.

  3. Regarding the stuck fermentation post, I purchased your HC Chilean Carmenere Kenridge Founders Series and the instructions state: Cover loosely with a lid or use sealed lid with fermentation lock. I have always used the sealed lid with fermentation lock because I use a space heater to keep the fermentation room at 74 degrees and this would stir up a lot of air in the basement and I want to protect the juice from wild yeast, etc. What steps should I take to insure there is enough oxygen in this instance? It seems contradictory to your reponse above! Cheers.

  4. John C, you will want to cut your losses if the fermentation was not able to complete to satisfaction. If you have a hydrometer, you can take a reading to see. If the mead is at .998 or less on the Specific Gravity scale — no-harm, no-foul. Just continue on as nothing has gone wrong. But, if the reading is at 1.010 or higher, this means that the fermentation did not complete and that the Mead is probably too sweet to be likable. If the reading is between 1.010 and .998, this means that the fermentation did not complete, but may not be to sweet to carry on. One thing I can tell you for sure is that re-starting a fermentation in a must that has has potassium sorbate added to it is extremely difficult at best.

  5. Jerry, I completely understand your concerns about wild yeast floating around. The main reason you want oxygen in the beginning of the fermentation is to promote the propagation of the yeast. You need them to multiply into a viable colony. This is what yeast want to do in the beginning of the fermentation, but need oxygen to do. Having said this, there is another solution for you. You can prestart your yeast ahead of time in a cleaner area. The can be done with a yeast start kit or something similar. Here is more info on this:

    Using Yeast Starters For Improved Fermentation
    http://www.eckraus.com/wine-making-yeast-starter/

  6. I’ve been making scratch wine for around eleven years from our own home grown fruit with a fair amount of success. What are your thoughts on this: I use a modest amount of potassium metsbisulfite to sterilize the fruit before pitching the yeast. I always bottle dry after a long period (2 years or so) in the carboy. I do not use any potassium metabisulfite to stop the wine or any potassium sorbate for conditioning. If I sweeten the wine it is done only when the wine is dispeneed. In your opinion, am I missing out on quality and flavour by doing this? I like the idea of using minimal additives.

  7. Hello Ed and team,
    I have decided to rack my fermenting must after 2 weeks of active fermentation. SG 1.080 dropped down to 1.030 within first 5 days and additional 2lb of sugar was used for 5gallons bucket to make wine stronger. After 2 more days of good fermentation all fruits were removed and bucket airlocked. Two weeks after the first day slow bubbling in airlock indicated that fermentation is close to the end. At that day I racked must into 5 Gallon carboy including most of pulp on the bottom because it was showing yeast activity. Airlocked with SG 1.015. Since that 3 days left, I do not see any progress, let looks like I have stuck fermentation. Did I shock the yeast? I was using plastic tube as usually to transfer must from bucket to carboy without splashing. What have I done wrong, please explain. Thank you.

    • Walter, it does not sound like you did anything to disrupt the process. There are many things that can cause a stuck or sluggish fermentation. Have you taken a look at the article posted below that covers the most common causes of fermentation failure?

      Top Reasons For Fermentation Failure
      http://eckraus.com/wine-making-failure/

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