Oxygen and Vinegar fermentation

[West Lake]

I want to set up a linear air pump to pump air into my apple juice to
speed up fermentation when producing vinegar - I am thinking of 30
litres air per minute in a barrel of 800 litres of liquid.....lets say
keep pump on one hour per day. My question is - can the fermentation
process be over-aerated and ruin the liquid at the cider stage before
acetification takes place. Oxygen acts on the acetabacta.

thanks Linda

[Andrew Lea]

You can't make vinegar by aerating apple juice directly. It's a two
stage process. First you ferment juice to alcohol using yeast (which
needs and demands little air if any), then you convert further to acetic
acid using acetobacter and lots of air. Pumping air through juice itself
will achieve little.

But air (sparged through fine pores) can certainly be used to enhance
the second acetic fermentation. However, you may find you need to keep
the air running continuously if you plan to do this. The reason is that
the acetobacter can get adapted to high oxygen levels and can then die
off when it stops. You also need to keep the barrel at > 20C for the
bacteria to thrive.

It is possible for acetobacter to over-oxidise acetic acid to carbon
dioxide and water but you are unlikely to do this to any great extent in
any normal process.

Andrew

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Cider Workshop Website
www.ciderworkshop.com

Andrew's Website
www.cider.org.uk

[linda]

Thank you for your quick and informative response. In previous years I have
waited for the juice to ferment to cider and then in time to vinegar. Now I
am in position to create vinegar by adding fresh apple juice to my vinegar
barrels. Each barrel has heaps of mother and about 20 litres of cider
vinegar in the bottom of the barrel. I am guessing this will help
quicken the procedure. Given the conditions I have set up - do you advise
adding yeast to each of the barrels of apple juice. The apple juice has now
been in the barrels one month. Once at the cider stage I should then
aerate -but need to keep the air pump on until optimum level of acidity. Is
that right? And roughly how long is the process once the pump is engaged.
Thanks Linda

West Lake Orchards
Chilla
Beaworthy
Devon EX21 5XF

01409 221991

www.west-lake.co.uk (apple juice & cider)
www.orchardkeeperscottage.co.uk (accommodation)

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[Tim]

Are you sure you can make vinegar in that way, I thought the acetobacter
needed alcohol to convert into vinegar?

Tim

[Andrew Lea]

On 10/11/2011 18:52, linda wrote:
> Thank you for your quick and informative response. In previous years I
> have waited for the juice to ferment to cider and then in time to
> vinegar. Now I am in position to create vinegar by adding fresh apple
> juice to my vinegar barrels.

No you cannot do that. It must be allowed to go to cider first. It is a
two-step process.

> Each barrel has heaps of mother and about 20 litres of cider vinegar in the bottom of the barrel. I am guessing
> this will help quicken the procedure. Given the conditions I have set up
> - do you advise adding yeast to each of the barrels of apple juice.

Yes. You must ferment to cider separately and in separate barrels before
it meets the mother. You cannot mix yeast and mother. Their requirements
are not compatible - one is reductive and one is oxidative.

> The apple juice has now been in the barrels one month. Once at the
cider
> stage I should then aerate -but need to keep the air pump on until
> optimum level of acidity. Is that right? And roughly how long is the
> process once the pump is engaged.

Once it is cider you can introduce it to the mother. If you then aerate
it it is impossible to say how long it will take. Temperature is a key
factor. Should be between 20 - 35C. It would be a week or two I should
think. The mother will break up and you will get an acetobacter
suspension not a film. You can monitor the acidity every couple of days
by titration and then you can see how you are getting on. Remember
vinegar must be 5% acetic acid by law before you can sell it.