I’m curious as to why does wine turn to vinegar. When the threat of this happening over, if ever, and what causes it. Is there an in depth explanation anywhere I can get?
Thanks Jane
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Dear Jane,
When you talk about how or why a wine turns to vinegar, you have to start with the acetic acid. This is the stuff that makes vinegar taste like vinegar. It’s the tang. If you had acetic acid in a jar and poured some of it into a fruit drink, it would immediately start to take on the characteristics of vinegar. It’s what makes vinegar, vinegar.
Acetic acid is made by a bacteria known as acetobacter. This bacteria is everywhere: in the air, on fruit, on grape presses, etc. When acetobacter gets into your wine it can slowly turn the alcohol into acetic acid, if left unhindered.
The key takeaway here is: if you control the acetobacter; you control the vinegar.
During a fermentation the wine is relatively safe. The gases from the fermentation help to keep acetobacter fall-out from getting into the wine must. Also, domesticated wine yeast are bred to inhibit bacterial growth, giving them the term killer yeast. It is not until the fermentation is over that caution needs to be taken.
Fortunately for us winemakers, acetobacter can be very easily destroyed before they have a chance to colonize and produce acetic acid. All it takes is the addition of sulfites in the form of either Campden Tablets, Sodium Metabisulfite or Potassium Metabisulfite. Use any of these in the wine, and the acetobacter will be very easily destroyed.
I would suggest using sulfites 24 hours before adding the wine yeast. Do not use an air-lock or lid on the fermenter during this time. You need the sulfite gases to dissipate into the air during the 24 hours, otherwise it will remain in the wine must and destroy some or all of the wine yeast when you add it. I also suggest adding sulfites just before bottling to keep the wine fresh while in the bottle. You can find more information on our blog about when to add sulfites to your wine.
Make sure you use a domesticated wine yeast to keep your fermentation clean. And, always sanitize your homemade wine equipment with a sulfite/water solution before using it.
The bottom line to the question: “why does wine turn to vinegar?” is because acetobacter was allow to grow in your wine. Stop the acetobacter, and you’ll stop the vinegar.
Happy Wine Making,
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.

At the very center of wine making is the process of fermentation. Fermentation occurs because the yeast want to consume the sugars in a wine must. As a result, the sugars are converted into both alcohol and CO2 gas by the fermentation. Normally as winemakers, we are concerned about the alcohol, but in this post we are going to change directions and talk a little about the gas.
Almost all of the CO2 produced during a fermentation dissipates into the air and goes away very quickly, but not all of it. Any liquid – wine included – has the ability to hold some CO2 gas for a period of time. It stays saturated in the wine. This CO2 gas is the same stuff that puts the fizzy in soda pop, beer and even the sparkle in sparkling wines, but when it comes to still wines we don’t want CO2 gas to do anything but be gone.

A Little Degassing Background
When I first started making wine, degassing was not even a word in the winemaker’s vocabulary. Finished homemade wines always sat around long enough in bulk glass jugs clearing and aging and whatnot, that they degassed themselves naturally with time. Wines back then needed extra time, and along with this time the wine was able to release all the CO2 gas it contained.
But things changed when 28 day and 6 week wine kits came onto the scene. These kits allowed the home winemaker to bottle their wines in a relatively short amount of time. This is not enough time for the CO2 gas to escape on its own. Because of this, the wine kit producers added the extra step of degassing in their directions they included in the kit.

How Do You Degas A Wine?
A portion of the CO2 gas can stay saturated in a wine indefinitely because the gas molecules will lightly bond with the wine, but by agitating the wine with something as simple as a stirring spoon, the gas molecules will start to release and float to the surface and dissipate. If you stir the wine long enough, all but an untraceable amount of the CO2 gas will be released. The amount of time it takes to degas a homemade wine the with a stirring spoon can vary greatly. It could take a few minutes or a few hours depending on how much CO2 is still in the wine at this point.
One way to speed up the process is to use a degassing/mixing paddle. The paddle attaches to a hand drill just like a drill bit would. This significantly reduces the amount of labor and time needed to degas a wine.
Another way of degassing a homemade wine it by putting the wine under a vacuum. This can be done with a wine preserving vacuum pump, like our Vacuvin Wine Saver or any other hand-held wine preservation system to degas the wine. By putting the vacuum pump directly over the air-lock hole of a rubber stopper, you can literally suck the CO2 gas out of a glass jug.
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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.

Hi everyone!
Last time I checked in, I think I solved the slow fermentation issue I was having with one of my wine making kits. I did this by increasing the temperature of my wine with a heating pad. The fermentation was simply too cool for the yeast to ferment. Things still moved along very slowly after that, but it eventually hit 1.000 on my wine hydrometer (after 19 days!).
I have a feeling the rest of the process is going to do incredibly slow, so if things aren’t where they should be according to the time frame set on the instructions that came with the kit, I won’t be upset. I suppose I’ll be upset if the wine starts to look or smell funny, but for now, all seems to be going OK with the exception of the time-frame of the fermentation.
….fast-forward until today….
So, it’s been 17 days since I transferred the wine over to another carboy for secondary fermentation. According to the instructions, the wine needs to be less than 0.996 on the specific gravity scale of my hydrometer in order to move forward. I anticipate that the fermentation might finish out slower than that, but who knows.
Checking the specific gravity 17 days after starting secondary fermentation, it hasn’t moved AT ALL. It’s STILL 1.000. The temperature was 66°F., just a little to cool.
To top it off, the wine tastes disgusting. Overripe fruit overload, as well as other things I just can’t really describe. I guarantee that way too much oxygen was in contact with the wine for way too long causing the wine to become oxidized – I mean it took 19 days for primary fermentation to finish for crying out loud, leaving ample time for oxygen to do it’s dirty work.
I am extremely disappointed. I don’t even know at this point if the wine is even going to continue on its own. 2.5 weeks later and no change in the specific gravity? That, and it tastes nasty (reminiscent of that mead I tried to make)? I think it’s done. Destined for the drain.
I will never forget now to at least poke my head in to check on my wine once every day to two instead of waiting until when the instructions say it’s time to move on. If I had noticed that my fermentation wasn’t getting going after 12-24 hours to begin with, I would have been able to warm the fermentation sooner and most likely save it.
I will also get in the habit of checking the temperature of the fermentation more often as well, particularly since I live in Colorado and I’m making it in a basement which does not have its own individual temperature control. After all, temperature is #1 on the list of The Top 10 Reasons of Fermentation Failure.
I may as well assume I’m always going to need a alternate heating source of some kind while I’m sending my wines through primary fermentation. That being said, if I want to increase my production and have more than one wine going at the same time, I’ll want to purchase a second (or more) heating elements to do that.
Live and learn, my friends!
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My name is Leigh Erwin, and I am a brand-spankin’ new home winemaker! E. C. Kraus has asked me to share with you my journey from a first-time dabbler to an accomplished home winemaker. From time to time I’ll be checking in with this blog and reporting my experience with you: the good, bad — and the ugly.

Most of my “fresh fruit” wines are dry. I was talking with a gentleman who also makes his own wines. He told me to double up on the sugar to sweeten my batches. Right now I have a batch of wine (brewing since mid-May). It needs to be racked again. If I add sugar to this batch now, will it start fermentation all over?
Thanks,
Marlene
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Hello Marlene,
The short answer to your question is, “yes.” Continuing to add more sugar to your wine must while it is still fermenting will contribute to more fermentation and alcohol content, not to the wine’s sweetness. When first learning how to make your own wine this can be a great area of confusion for many.
If you keep adding more and more sugar you be raising the alcohol level of the wine, but will eventually come to a point where the wine yeast can no longer ferment more alcohol.  Where that point is is something that varies greatly from one batch to the next based on a whole host of conditions. Factors such as temperature, available nutrients, the type of wine yeast, and many, many others. All of these factors sum up to either contribute or hinder the wine must’s ability to ferment.
Some factors such as available oxygen and temperature can even change over the coarse of the fermentation. This means that the fermentation can stop at some point and then start up again. For example, if the fermentation gets cooled down by weather, then warms up again. You could have a fermentation the temporarily stops for a few days.
Fortunately, there is another way to approach making a sweet wine beside adding a bunch of sugar and hoping for the best. One that is more predictable, more controlled and easy to accomplish. This is also the method that any of the wine making books you read will suggest.
The first step is to accept the fact that any sugar you add before fermentation is to contribute to the alcohol content of the wine and not its sweetness. You can follow your wine recipes suggested amount, or you can use a wine hydrometer to tell you how much sugar to add. Shoot for an alcohol range of 10% and 13% alcohol. Any wine yeast can achieve this amount under reasonable conditions.
The second step is wait until the wine’s ready to bottle before worrying about sweetness. Once the wine has fermented, cleared and ready to bottle, you can then add sugar to taste. Once you get the wine’s sweetness to where you like it, you will then add potassium sorbate. This is a wine stabilizer that will hinder the residual yeast’s ability to recolonize and support a re-fermentation.
Don’t confuse potassium sorbate with Campden tablets or sodium metabisulfite. These work differently and can not completely eliminate a chance of re-fermentation. They should be added regardless if potassium sorbate is added to the wine or not.
By going about sweetening your wine in this way you are taking charge of the wine’s sweetness and no longer are at the mercies of a wine must’s ability to ferment or not ferment. If you’d like, you can also think about it as taking control or your wine’s alcohol content – particularly if you are using a wine hydrometer to help you target an finished alcohol level.
Happy Wine Making,
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.