Posts Tagged ‘potassium sorbate’

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.

I’ve never concerned myself with Malolactic Fermentation (MLF) because all the red wines I’ve made are from kits. I did try a red wine once – where I picked up the must from a vineyard – however, they had neglected to call me ahead of time to let me know when it would be ready. By the time I had picked it up which was about four days after the grapes were harvested and crushed, a wild yeast had already fermented it. And it did not turn out well.

So I’m no expert on MLF. This evening, I was browsing the site of a self proclaimed “winemaking expert” and came across a post about adding potassium sorbate (K sorbate) to wine after it has completed fermentation. Someone commented on the post to the effect that when making dry wines, he never added potassium sorbate. The wine expert then replied that the winemaker should still be adding potassium sorbate to the wine to prevent malolactic fermentation occurring in the bottle.

Well, this is simply not true. Malolactic fermentation can most certainly occur in the presence of potassium sorbate! In fact, according to what I’ve read, not only can MLF occur after potassium sorbate has been added, when it does occur at such times, it could cause a dreadful smell in the wine.

I never add potassium sorbate to wines that I have fermented to dryness. Some suggest that sorbate can cause a “kit taste” to such wines, especially those that I am bulk aging.

On the other hand, the presence of sulfite will inhibit malolactic fermentation. All potassium sorbate does is inhibit mold and prevent yeast from renewing a fermentation.

I grew up in a tradition that some may know or understand, where on the 1st day of the week, bread and wine had much significance. I find it interesting that some that grew up in similar traditions used grape juice instead of wine and have such an intolerance toward anything with alcohol. Some years ago, I even heard a preacher rail against alcoholic beverages, claiming that “alcohol” was the excrement of yeast. Funny – he didn’t seem to mind eating bread with his grape juice on Sunday mornings – bread that had been risen with the use of yeast. And of course, one wonders how the disciples and apostles back in the day were able to preserve grape juice and keep it from turning into wine in the first place.

But that’s a matter for another blog of a different topic. Maybe I’ll start one day on Theology. This evening, I baked bread, racked wine and took specific gravity readings. It was time to add the sulphite and sorbate to the Old Vines Zinfandel that I racked back on March 6 from the primary. As I expected, there was no change in the specific gravity of this wine: 0.996.

I really like the Mexican 6 US gallon carboys. They are stouter than the other carboys I have, and seem to take about a half cup or so less in quantity so there is rarely a need to ever top up after racking from the other type of carboy. Such was the case this evening.

The Zinfandel does contain a lot of Carbon Dioxide. Part of the routine of stirring in the sorbate and sulfite includes lots of vigorous stirring. I cannot completely fill the Mexican carboy when I do this – I need to remove a good cup of wine in order to have lots of space for the inevitable foaming. I will add the fining agents that the kit came with, but not until I’ve done lots of degassing and promote the release of the CO2.

While all this was going on, I was baking the No Knead Bread. The kitchen is filled with the wonderful smells of bread baking! Perhaps tomorrow I will break bread and drink some wine. I’d have a slice tonight, but the loaf is still crackling as it cools.

Prior to all of this, the “wee man” and I recorded some specific gravity readings on a piece of paper, which I then promptly re-recorded in my log book. It will be nice to save the “wee man’s” printing and numbers though and I’ve kept copies inside my log book.

But for anyone interested in following along:

Cru Select Old Vines Grenache:

March 23/09 – Starting SG: 1.106
March 26/09: 1.054
March 27/09: 1.031

California Connoisseur Liebfraumilch:

March 25/09 – Starting SG: 1.080
March 26/09: 1.072
March 27/09: 1.060

Mystery Wine:

(Ahh.. this one is screwed up because of the stuck fermentation which I unstuck),

March 11/09 – Starting SG: 1.104
March 13/09: 1.092
March 19/09: 1.054
March 20/09: 1.046
March 21/09: 1.042
March 23/09: 1.030
March 25/09: 1.028
March 26: 1.021
March 27/09: 1.019

One of these days, I’ll start plotting these values. Might be interesting to see this graphed out.

So how was your home winemaking day?