Blanketing prior to yeast inoculation.

[Daniel Waksman]

Hello everyone.

I have searched but none of the topics seems to address this specific concern. I know that yeast needs oxygen to reproduce and that oxygen deprivation might lead to a stalled start, but i want to be as carefull as possible regarding oxydation. My concern is, how much is too much? I mean. Is it ok to prefill fermenters with CO2 prior to juice? Is it ok to inject CO2 along with the juice in the pump lines? Is it ok to blanket the press with a constant CO2 flow? Or by doing that will I thwarting the yeast reproduction afterwards?

Thanks so much

Daniel

[Andrew Lea]

At first sight I was very puzzled why you should want to do all this CO2 blanketing and air exclusion at the juice stage. This is not normal in cidermaking. Then I remembered that you are in a hot country and that this is the modern way people make white grape wine in hot climates, where they try hard to reduce juice oxidation to preserve varietal aromas. You have obviously been talking to the winemakers. 

I’m not at all sure that the same thing would apply to apples, even to the dessert types you will be using. Much cider aroma actually comes from oxidative breakdown of fatty acids to aroma precursor aldehydes during juice production, which are later transformed during fermentation. Most of us here have no relevant experience of CO2 blanketing at the apple juice stage. You will just have to try it and see. If you use a good inoculum of a modern cultured wine yeast, the absolute need for oxygen during the yeast growth phase is much less than it is for wild yeasts, since the cultured cells are already packed full of sterols and glycogen and don’t have the same need for extra air to build up their reserves. 

Andrew

Wittenham Hill Cider Portal
www.cider.org.uk

On 1 Dec 2021, at 16:20, Daniel Waksman <dwak...@gmail.com> wrote:

Hello everyone.

I have searched but none of the topics seems to address this specific concern. I know that yeast needs oxygen to reproduce and that oxygen deprivation might lead to a stalled start, but i want to be as carefull as possible regarding oxydation. My concern is, how much is too much? I mean. Is it ok to prefill fermenters with CO2 prior to juice? Is it ok to inject CO2 along with the juice in the pump lines? Is it ok to blanket the press with a constant CO2 flow? Or by doing that will I thwarting the yeast reproduction afterwards?

Thanks so much

Daniel

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[Daniel Waksman]

Hello Andrew!

First and foremost, thanks for your usual insightful and kind replies. 

As a matter of fact, that is exactly what happened. I have been (in the absence of more suitable local consultants) talking to winemakers to get some advice. We have very high temperatures by the harvesting season here (fluctuating between 15 and 30 degrees) so oxidation is something to be aware of. I didn't know about the benefits of oxidation so I guess my course of action will be to choose the mid ground. I will only blanket the fermenter and not the rest of the process and I will see how that turns out. I have been told that there are some acids that might prevent the adverse effects of oxidation. Which is our ground on those?

Thanks again

Best

Daniel

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[Andrew Lea]

I think it’s worth remembering that apples are not grapes.  There is certainly a general benefit to some oxidation during cider juice making. This was covered in an earlier thread this autumn. I wonder if any of our Spanish cider makers could comment? I believe they can have quite high temperatures (in the 20s) at cider making time and traditionally (AFAIK) they make no attempt to exclude oxygen. 

There are no grape or apple acids that have any specific effects on juice oxidation.  However, as a general rule, fruit grown in warmer climates has less acid than that from cool climates and may therefore benefit from acid addition for simple reasons of taste balance.  Also, the PPO enzyme is more active at high pH (low acid) so you get more browning if the acid level is low. This is probably undesirable in modern white grape wines but not so in cider where a golden colour is traditionally expected. 

You should certainly check the acidity and the pH of your fruit ideally with small samples at harvest time. 

Andrew 

Wittenham Hill Cider Portal
www.cider.org.uk

On 3 Dec 2021, at 15:36, Daniel Waksman <dwak...@gmail.com> wrote:



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[Trevor FitzJohn]

Similar higher temperatures at harvest time in Australia. 

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[Andrew Lea]

> I have been told that there are some acids that might prevent the adverse effects of oxidation.

Just a thought - I wonder if your informants mean ascorbic acid (which is not really an acid at all) and / or sulphurous acid (otherwise known as SO2). Both are antioxidants. Their acidity is incidental and not relevant to their antioxidant function.

Andrew

Wittenham Hill Cider Portal
www.cider.org.uk

[Wes Cherry]

We have started flooding the headspace of wild ferments before they show fermentation activity because a few batches have grown molds in the oxygen rich headspace.  The geosmin taint that comes from those molds is pretty objectionable.  The slow start of wild ferments seems to make this much more of an issue than with pitched culture ferments.  Since adopting this, we haven’t seen any mold/geosmin.

'//es Cherry
w...@dragonsheadcider.com
Vashon WA, USA

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[Miguel Pereda]

The issue of oxidation of apple juice and its subsequent consequences in cider, from my experience, which is that of an amateur and not of a large industry, is more related to the polyphenolic profile of the apples than to the temperature. Although obviously temperature can also play a role. In my case, I do not use CO2-based protection systems, but as I have the possibility to choose between many types of cider apples, I try to use varieties with few hydroxycinnamic acids and in small proportions, because these are a family of polyphenols that are very sensitive to the action of polyphenol oxidase. I also use slow juice extraction techniques. This avoids oxidised phenolic aromas and flavours that crush the fresh and fruity character of the cider.  That is the profile I am looking for in a natural Spanish cider style.
I also play with a certain amount of oxidation in the apple pulp by maceration for hours before pressing to prevent oxidised phenols from passing into the juice. It is a game of artisan balances. The use of CO2-based protection techniques is beyond my artisanal and self-consumption resources. I also think that the higher acid content in the must has practically no influence on oxidation phenomena. Unless the pH is so low that it inhibits PPO.

Miguel A. Pereda