Cider VA management

[David Hall]

Hey ya'll, how do you control volatile acidity? Is there a test that I can do to measure it in my ciders? When I don't know if it is high in all my ciders. But I had one tested and it was 1.9!! As far as I can tell with taste buds there is no ethyl acetate. If any knows where I can start that would be a major help.

[Andrew Lea]

VA is nearly always the result of acetic or lactic acid bacterial action during storage. Your primary defence is eliminating headspace and using SO2 correctly. This should go a long way to keeping it under control. 

The sensory effect of VA is due both to acetic acid and to ethyl acetate. They always accompany one another but in varying proportions depending on the precise organisms and pathways involved.  Ethyl acetate is much more obvious sensorially than is acetic acid, but it’s acetic acid which is always measured since it can be done by classical distillation chemistry and titration (albeit some care and laboratory experience is needed to get good results ). This can be slightly misleading and seem worse than it is if for instance you have relatively little ethyl acetate present.  Conversely many traditional perries have noticeable ethyl acetate (from bacterial breakdown of citrate) but relatively little acetic  acid. It can get quite complicated. 

1.9 grams per litre (as acetic) is on the high side for many ciders but for some ciders eg Spanish this might not be excessive and indeed may even be desirable. 

Andrew 

Wittenham Hill Cider Portal
www.cider.org.uk

On 13 Jul 2018, at 00:50, David Hall <davidh...@gmail.com> wrote:

Hey ya'll, how do you control volatile acidity? Is there a test that I can do to measure it in my ciders? When I don't know if it is high in all my ciders. But I had one tested and it was 1.9!! As far as I can tell with taste buds there is no ethyl acetate. If any knows where I can start that would be a major help.

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[luis.ga...@gmail.com]

From my understanding, VA usually come from wild ferment, especially from apiculate yeast. I guess working in an environement very clean with a low amount of saccharomyces could make the apiculate dominate your cider for a long time, which could produce a higher amount of VA then working in a less clean environment where saccharomyces population could build up faster and dominate the cider.

Does this makes sense?

Louis

[Andrew Lea]

Yes it is absolutely true that a wild primary unsulphited fermentation conducted by apiculate yeasts can also be a major source of VA, in addition to bacterial action during storage. I’m not totally sure about your cleanliness argument, though I do understand what you are trying to say about the apiculate / Saccharomyces balance.

In my reply I had somehow assumed that the poster was conducting his primary fermentation with a cultured Saccharomyces yeast, in which case VA arising from yeast is less likely. But since the poster has given us no information on his location or his processes, it is hard to be sure. Either way, in my opinion, correct use of SO2 could be a large part of the answer.

Andrew

Wittenham Hill Cider Portal
www.cider.org.uk

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[David Hall]

Thanks for the replies. We are doing primarily wild ferments along with a house culture that we pitch ML culture. We do not add back any sweetness, sulfites, and do not pasteurizes. We do also ferment all year round around 70-degree Ferhertent.   

[Andrew Lea]

I’m afraid if you do all wild ferments without any SO2 at any stage then inevitably you will run the risk of high VA’s. This is a feature of traditional low intervention cidermaking. It’s your choice really what to do about it, and that depends both on your cidermaking philosophy and the expectations of your customers. 

You can use quite low SO2 doses prior to wild yeast fermentation (say half to one quarter of the standard dose for the pH ) which will allow the beneficial organisms to develop but will control the ones you don’t want. There will also be some residual effect in storage because even bound SO2 will control lactics to some degree. This is what I do in my own cidermaking. 

But if you want to be zero sulphite at all stages, then VA is something you will just have to live with  

Andrew 

Wittenham Hill Cider Portal
www.cider.org.uk

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[David Hall]

Andrew, you have been a great help. Is there any books you would recommend or articles? Something we could possibly use to better understand the process we are seeing.

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[Miguel Pereda]

El viernes, 13 de julio de 2018, 1:50:21 (UTC+2), David Hall escribió:

Hey ya'll, how do you control volatile acidity? Is there a test that I can do to measure it in my ciders? When I don't know if it is high in all my ciders. But I had one tested and it was 1.9!! As far as I can tell with taste buds there is no ethyl acetate. If any knows where I can start that would be a major help.

 The administration of the VA of your cider is related to the style of cider that you intend to elaborate. If your intention is to make cider with sweet remains, then it is a bad idea to let the VA be noticed but, on the contrary, if your idea is to make dry cider without sugary remains it can be interesting to have a certain level of VA which will bring some structure to the cider. That's what happens with Spanish-style cider.
Keep in mind that the yeasts already produce a certain amount of acetic acid throughout the fermentation and therefore they are responsible, in part, for the VA but it is at the end of the fermentation, when the activity of the yeasts It already declines, when lactic bacteria intervene mainly and produce an increase in VA that you have to control if that is what you want.
A greeting
Miguel A. Pereda

[Andrew Lea]

 I don’t know anything that covers cider VA specifically except this Long Ashton article which is now 45 years old and should be read in that (UK) context https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1973.tb03527.x

Presumably you are familiar with the relevant winemaking literature eg http://waterhouse.ucdavis.edu/whats-in-wine/volatile-acidity

Looking at your website it seems that funky flavours and high VA are part of your USP at least for some of your product range. This chimes with the “natural winemaking” movement. I wonder if you should be talking to some of the natural winemakers in your area to see if and how they control VA in their products. 

Andrew 

Wittenham Hill Cider Portal
www.cider.org.uk

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[luis.ga...@gmail.com]

Andrew, do you know if the saccharomyces and the apiculate yeast have the same optimal temperature requirements? Im wondering if an optimal temperature should be aimed to insure an acceptable VA level in the final product.

Also, is there something that helps preventing lactic bacteria to produce VA after main fermentation has ended? Should SO2 systematicly be added at this stage or a normal 50% of standard sulfite addition before fermention should do it?

Finally, acetic acid and ethyl acetate are related and often mixed up in the term VA. Is there conditions where one is produced in a greater amount than the other or in either way (LAB or apiculate), they are produced in the same amount?

Thank you!

Louis

[David Hall]

That Is a great idea. I will check into it, I am sure there are a few near me. Thank you Andrew for the links.

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[Andrew Lea]

Louis,

I’m afraid I just don’t have the level of detail you are looking for.

But I have made some comments below.

Andrew

> On 17 Jul 2018, at 19:25, luis.ga...@gmail.com wrote:
>
> Andrew, do you know if the saccharomyces and the apiculate yeast have the same optimal temperature requirements? Im wondering if an optimal temperature should be aimed to insure an acceptable VA level in the final product.

If you mean ‘optimal’ in terms of lowest VA production, no I don’t. But if you are using monocultured Saccharomyces species, then VA is a non-problem anyway, because those yeasts have mostly been selected for low VA. If you mean wild apiculate yeasts, then you must remember that in any given fermentation there will be several species and many strains, all uncharacterised, and their VA production will vary depending on the particular yeast populations which you have. So I don’t think one can give a general rule. One thing that is known is that (some) apiculate yeasts do continue to ferment at low temperature down to 4C unlike most Saccharomyces which generally don’t function below 10C. Further, it is a tenet of most winemaking that Saccharomyces strains produce less inherent VA at the lower end of their specified temperature range. So probably, the cooler the better.

> Also, is there something that helps preventing lactic bacteria to produce VA after main fermentation has ended? Should SO2 systematicly be added at this stage or a normal 50% of standard sulfite addition before fermention should do it?

Again, please remember there are many different species and strains of wild lactic acid bacteria. It’s not one thing like a monoculture. So again it is impossible to generalise. However, lactic acid bacteria can produce acetic acid from a variety of different substrates - for instance, one is residual sugar, another is citric acid (as in perries). So the behaviour of the bacteria will depend on the exact species and strains you have, the substrates available, and also the micronutrients which the bacteria need.

One thing that is generally true though is that many lactic acid bacteria (but perhaps less so Oenococus) are sensitive to SO2 in both free and bound form. Hence even if you only ever use sulphite before yeast fermentation, you may gain some post fermentation control from bound sulphite. If you also maintain a typical flat rate of 20 ppm free sulphite for bulk cider storage, you will gain more control. As I said before, generally people making rational use of SO2 don’t get VA problems

>
> Finally, acetic acid and ethyl acetate are related and often mixed up in the term VA. Is there conditions where one is produced in a greater amount than the other or in either way (LAB or apiculate), they are produced in the same amount?

I don’t know any work that looks at this specifically, though generally acetic acid is probably present in greater amounts than the ester. And again I must repeat, in a wild situation you have many species and strains of apiculates, Saccharomyces and LAB, so you can’t easily generalise the pathways. Also, the production of acetic acid (as acetyl CoA) is a necessary precursor to the biochemical esterification of ethanol to give ethyl acetate. There may be some cases where the amount of residual acetic acid remains low and most of it is converted to the ester - I don’t know.

What is more likely is that the relative perceived contribution is actually a function of the relative sensory thresholds. For instance, the perception threshold of acetic acid in cider may be as high as 500 ppm. The perception threshold of ethyl acetate is much lower maybe 80 ppm or even less. Hence in the case of traditional perry where ethyl acetate from citrate metabolism is noticeable, it may simply be that a little goes a long way because of its relatively lower aroma threshold and the context in which you detect it.

> Thank you!
>
> Louis
>
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