Sulaiman
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Apples, Cider, Vinegar question
I fermented 6 kg apples in 10 litres of water using bakers yeast,
when fermentation was complete I added some vinegar 'mother' to the filtered liquid and gently aerated it.
Judging by smell there is a lot of acetic acid formed.
I used the pulp recovered from the above to start a new batch,
this time with added sugar (target=13%ABV) to increase the alchohol hence acetic acid concentration.
The fermentation started normally but soon began to smell of acetic acid.
The two fermentations are side by side so cross-contamination was anticipated, but not expected.
The 'used apples' plus sugar to ethanol fermentation stopped much too soon - two days.
Will fermentation proceed to acetic acid ?
Should I aerate the fermentation ?
Can I just combine the two fermentations and get concentrated vinegar after fermentation is complete ?
[Edited on 30-11-2018 by Sulaiman]
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Twospoons
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Production of alcohol via yeast + sugar requires anaerobic conditions, otherwise you just get CO2 and water and no alcohol.
You need alcohol to get acetic acid by the action of acetobacter + aeration.
So I doubt you can just combine the two and expect high conc vinegar - the process conditions would appear to be in opposition. It looks to me like
you have to go through a two step process.
[Edited on 30-11-2018 by Twospoons]
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AJKOER
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I would use natural (like organic) apples as the pesticides residue on the skin of the apples may not be friendly to anything (including required
bacteria).
Note, it may be cheaper with superior results just to buy apple cider vinegar commonly sold in grocery stores!
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Tsjerk
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Pesticides don't influence fermentation as fruit sold for consumption contains so little antifungals it won't hurt bakers yeast. Actually, all
antifungals are toxic to humans, so regulations on end product concentrations are strict, and definitly below active levels.
Besides that, why would his first fermentation work, but not his second if it was because of pesticides... Acetobacter is only inhibited by
antibiotics, which are not used in agriculture.
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AJKOER
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In particular, however, a copper based pesticide (for example, copper ammonium carbonate) is very toxic to many microorganism in small doses (see https://www.ncbi.nlm.nih.gov/pubmed/22030247 and also https://www.ncbi.nlm.nih.gov/pmc/articles/PMC93308/).
However, copper is better tolerated by large living entities (like people but not perhaps your pet fish), so if a few apples have a small Cu residue
not completely washed off, not a problem for people, but it could be an issue for bacteria.
The reason why the 2nd run could have failed is that the threshold for heavy metal toxicity may have been reached. A good clue, as whether this may be
the case, would be if other runs are failing also.
-----------------------------
This sort of reminds me of the case of the fish tank that had a brass connector installed. When the tank wasn't cleaned for a period of time, then
ammonia levels jumped from waste produced by the fish. The NH3 attacked the brass with the help of oxygen (from an air pump) forming a copper ammonium
complex. Then, everything living, including plants, in the fish tank died. Attempts to clean the tank, so that new fish would live, prove futile.
[Edited on 2-12-2018 by AJKOER]
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Sulaiman
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The apples are from my garden, which is 'organic' as I like eating stuff as I wander around.
I must have inadvertantly transfered the acetic acid bacteria from the first fermentation of ethanol to acetic acid
to the second fermentation of sugars to ethanol, before the sugar was consumed.
Unless I learn something new,
I will combine the two fermentations, allowing filtered atmospheric air exchange, and check on it sometime next year.
There are acetic acid bacteria that can aerobically convert sugars to acetic acid so I hope some are present.
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happyfooddance
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It will certainly be vinegar in a year or so. The best tasting vinegars however take a little more care in preparing, especially during that first
fermentation. If I were you though I would definitely try to accelerate the conversion of the sugar into alcohol, and strain everything through cloth
if you haven't already. You don't want pulp in your mix or it will produce excessive acetone and fusels.
Be on the lookout for furry growth on the surface (you don't want that). If you do get growth, all is not lost. Just place the lot of it in a pot (or
flask) with a lid and reflux briskly but not excessively (so as to minimize loss of etOH). Let cool (resist urge to lift lid) and place in clean
container with at least 20% headspace and provision for clean aeration.
Also be aware that you will go through a phase where the malic acid is converted to lactic acid. This happens with wine vinegars also but is (for
obvious reasons) especially noticeable when making apple cider vinegar. During this conversion you might get a waxy film on top (different from the
slimy film of acetobacter colony biomass) and a strong smell of cheese. Don't think that your vinegar is ruined at this point, it is a natural part of
the process.
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Sulaiman
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Thank You
I'll filter both batches asap.
Thanks for the 'cheese smell' warning
- I imagine I could throw it away as ruined.
" The best tasting vinegars however take a little more care in preparing, especially during that first fermentation."
... any recommended reading
...........................................................................................
@Twospoons: "- the process conditions would appear to be in opposition."
that's what I thought, and why I asked the question.
The second fermentation now has a gel-like layer on top which may allow the acetic acid bacteria to act aerobically at the surface while the yeast
ferments sugar anaerobically lower down - maybe.
@AJKOER: I had a lot of apples this year but they do not store well so I decided to make cider vinegar
- and started immediately without any prior research.
IF I had performed even the briefest research,
I would have fermented the filtered juice of pressed apples,
rather than a watery slurry of diced apples.
[Edited on 2-12-2018 by Sulaiman]
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Twospoons
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Frankly I think you should have stopped your fermentation at "cider". 
I made a dry sparkling cider from my own apples and crab apples one year. Most enjoyable.
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happyfooddance
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Actually one of the best sources for a comprehensive and detailed outline of vinegar porduction can be found in the book "Industrial Fermentations" in
the forum library. Page 292
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Sulaiman
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Thanks for the reference - never noticed that book.
I've downloaded it and read a little ... lots more to read ... good book.
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