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The use of potassium sorbate in Home Brewing

22 May 2009 3,005 views No Comment

From looking at my referrer logs and some of the questions on other website forums and blogs, there seems to be a good deal of interest in the use of potassium sorbate in home winemaking. Some of the answers I’ve seen to the questions show that there is a lack of understanding about what exactly potassium sorbate does, and when it is required.

For example, one “expert” recently responded to a question about potassium sorbate, suggesting it was necessary to add it to all wine to prevent a malolactic fermentation in the future. At a reasonable rate of addition to keep yeast from reproducing and starting a new yeast fermentation, it is still possible for lactic acid to reproduce and renew a malocatic fermentation. Indeed, winemakers are warned to not add potassium sorbate to wines that have had a malolactic fermentation in case the lactic acid bacteria become active again. Wines that have been sorbated and then undergo malolactic fermentation will end up with a very unpleasant geranium smell.

When I first began learning about how to make wine at home, I had the mistaken impression that potassium sorbate killed yeast. This is what some of the literature says or implies. However, this is simply not true. What it does do is inhibit yeast reproduction.

With this in mind, we can better understand when potassium sorbate is required and when it is not.

However, if you are new to winemaking and are following instructions of a recipe or a wine kit, and it says to add potassium sorbate to your wine, I would recommend that you do so until you have more experience and know for sure that your wine has fully fermented to dryness. Ignore for now the rest of what I’m going to write, and follow the instructions to the letter. I do not want you to have corks exploding out of the bottles due to a renewed fermentation going on after you’ve bottled your wine! Neither do the makers of the wine kits, and they don’t know for sure that you’re going to ensure your wine ferments fully, or that you know how to read a hydrometer, or that other issues might arise during the fermentation process causing the wine to not ferment fully and have just about all of the sugar consumed. That is why they instruct you to add potassium sorbate.

Having said that, what is the argument against using potassium sorbate when it is not needed? Some people claim that it can leave a “bubblegum” taste – sometimes referred to as a “wine kit” taste. I personally have never detected this, and scientific literature suggests that potassium sorbate is taste neutral. Even if it is taste neutral, I’d prefer to add as few additives as possible, so if it’s not necessary or the risk is very low, I don’t add them.

So now that we know what potassium sorbate does, when is it required and when may it be omitted?

First, it is not required when fermentation has been complete, ie. it has fermented fully dry with only a trace or zero amount of residual sugar. As long as there will be no back sweetening, there is nothing in the wine for the yeast to begin consuming to turn into alcohol and carbon dioxide. So even if there are still some viable yeast cells, they can’t do anything as far as starting up a renewed fermentation goes.

You SHOULD add potassium sorbate when:

1. You’re new to home winemaking, and you’re following instructions.

2. You’re wine is off-dry to sweet which means there is more than a trace amount of residual sugar.

3. You’ve fermented your wine dry, but you are going to sweeten it with a sugar based sweetener before bottling. This includes honey as a sweetener as well.

4. If you’re unsure.

You should also consider that potassium sorbate works better with the addition of sulfite.

For advanced winemaking, the higher the alcohol content, the lower the amount of potassium sorbate that is needed to inhibit yeast activity. In other words, if you add the amount of sorbate that comes with your wine kit accidentally before you add the yeast and ferment it, there is still a very good chance the yeast will not be affected much by that amount of sorbate and will probably reproduce and ferment your juice into wine. Of course, it’s best to try not to have accidents in the first place. But I did read recently the account of a winemaker who thought he had ruined his wine kit by accidentally putting sorbate into the juice instead of yeast. The faulty advice given to him was that his kit was ruined – however, it was not ruined and when he added yeast, they did their job fine.

The British Columbia Amateur Winemakers Association has published an article by Bill Collings which states:

“Assuming that proper levels of free SO2 are maintained and the pH’s are within the desired ranges, sorbate additions can be determined by the estimated alcohol of the wine. The following table is based upon the percentage of alcohol in the wine:”

% 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

Source: Potassium Sorbate
For those making non-kit wines, this is a handy guideline to have when the addition of potassium sorbate is required.

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