Potassium Sorbate Myths & Facts

Postby bobsbeer » Fri Jul 25, 2014 17:34

Potassium sorbate is usually the drug of choice for most winemakers when trying to stabilise their wine at the end of fermentation. Often called wine stabiliser. So I feel an explanation of this drug might help some understand the consequences of their actions. And possibly dispel some of the myths that have built up around its use.

Myth - Potassium Sorbate kills yeast. This is completely untrue. Potassium sorbate does NOT kill yeast.

Fact - What it does do is affect the reproduction capabilities of any viable yeast colony in the wine. But even this is dependent on other factors which I will explain later.

Myth - Potassium Sorbate kills bacteria - Again untrue, but can have some effect on moulds as well as yeast.

Myth - Potassium Sorbate should ALWAYS be used in conjunction with Sodium Metabisulphite. The often quoted reason for using both together is that it prevents a geranium type odour if used on its own.

Fact - This is partly true, but can only happen if there is lactic acid present in the wine. Any wine (or cider for that matter), that has undergone Malolactic fermentation (MLF) will have lactic acid present, so potassium sorbate should not be used. When need to prevent the reaction that sorbic acid has with the lactic acid bacteria which forms geraniol, giving an undesirable geranium odour. Increasing SO2 will prevent MLF. For wines or ciders that have undergone MLF you should not use potassium sorbate for this reason.

Myth - Potassium Sorbate is used for wines I want to keep a long time. Untrue.

Fact - Adding Potassium Sorbate only has a limited effectiveness over time. Over time it breaks down into ethyl sorbate which can add undesirable notes of pineapple or celery to your wine. Many commercial wineries do not use it for that very reason. So for wines you want to keep for a few years, consider other methods, unless you are making a pineapple or celery wine of course.

So what is going on here and what is Potassium Sorbate? Potassium sorbate is the potassium salt of sorbic acid, chemical formula CH3CH=CH-CH=CH-CO2K. It is the sorbic acid that we want in our wine. However sorbic acid on its own is not very soluble in alcohol, and by the end of fermentation we will have anywhere between 10-15% alcohol. It is a very commonly used ingredient in many foods and drinks to prevent spoilage from mould and yeasts. It is an E number, designated E202.

So if it doesn't kill yeast or bacteria and breaks down fairly quickly why do we use it? As home winemakers we tend to be an impatient lot, and want to bottle our wines as soon as possible. Probably brought on by the instructions in the huge range of kits on the market today with wild claims of when it will be ready.

When we add potassium sorbate to our wine that has finished fermentation we are causing the existing yeast to stop reproduction, and those that remain will soon die from natural causes as their natural life comes to an end. But be warned that they are still converting any remaining sugar into alcohol and producing CO2. But in general not enough to cause a problem once bottled. So don't get too worried that you now have a rack full of bottle bombs. In general we don’t have the facilities to filter all the yeast from a wine, and utilise racking and or fining to get as much yeast out of the wine that we can, but there will be sufficient viable cells present that were we to add sugar to back sweeten, or other additives that contain sugar, the living cells will once again leap into action and start fermenting all over again. To prevent this we add potassium sorbate as this stops the yeast reproducing. The viable cells will ferment as has been stated above, but their life will be short and not cause a problem.

The addition of potassium sorbate isn't always necessary if your wine has been allowed to ferment fully and no other additives are being put back into the wine. And for those planning on keeping your wine for long periods to age, you should seriously consider not doing so. A fully fermented wine will not have any residual sugars for the yeast to feed on, and cannot keep producing CO2.

But if you are going to use potassium sorbate the amount you need is dependant on a number of factors. Mainly % alcohol, PH and SO2. The more alcohol present the less you need. So don’t just chuck it in and pray. Use the tools at your disposal. Below is a chart borrowed from BWCA.






% alcohol sorbate addition
10 0.20 g/l
11 0.17 g/l
12 0.135 g/l
13 0.10 g/l
14 0.07 g/l



Above I said that the use of potassium was not always used in conjunction with sodium metabisulphite (Campden Tablets). And this is true. However using it can have other benefits, not just preventing the geranium odour caused by potassium sorbate when it reacts with lactic acid to form geraniol. As we often make wines from other ingredients than grapes, but fruit and vegetables, there may be a degree of lactic acid present depending on the produce used. In grapes that have not undergone MLF the amount of lactic acid present is low and would not normally cause a problem. But many other fruits do contain amounts of lactic acid. By using campden tablets we are basically taking out a bit of insurance and preventing MLF. So probably worth using, unless you know that there is very little lactic acid. The other advantage of using campden tablets is the removal of oxygen added during the racking and degassing operation. It also adds SO2 to the wine which as stated above has an impact on the amount of potassium sorbate required.

So don’t be scared of potassium sorbate, or blindly use it when it isn't required. When you do use it, you do not need to wait for it to become effective. You can safely add potassium sorbate and carry on degassing and adding finings and not worry that it will continue fermentation. Used correctly it can make a big difference to your wines.
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Re: Potassium Sorbate Myths & Facts

Postby bobsbeer » Sat Jul 26, 2014 07:34

For some unknown reason the table in the post above isn't displaying properly. So I have copied it below.

Edit: Managed to fettle the table in the post.
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Re: Potassium Sorbate Myths & Facts

Postby StevieDS » Sat Jul 26, 2014 08:45

Some good info there :thumb:

Quick question though, if I want to back-sweeten wine how long should I wait after adding the potassium sorbate?

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Re: Potassium Sorbate Myths & Facts

Postby bobsbeer » Sat Jul 26, 2014 09:12

Assuming you have left the wine to fully ferment out, ie the SG is around .990, you can do it straight away once you have racked and cleared it. I generally use finings on my wines, and although they usually clear in a couple of days, I leave for about a week to make sure the lees have settled properly. I then rack and if required back sweeten. The potassium sorbate will stop the yeast reproducing very quickly, but you do want to get the wine as clear as possible, not just to get rid of the yeast, but for presentation reasons.
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