Vinegar Au Naturel

[JT101]

I'm not going to lie to you, I'm a purist when it comes to this stuff.

I'm sure this is possible. I want to create vinegar from fruit juice without adding sugar or yeast. I have a bucket of blackberries which I left to start fermenting with the wild yeast on them. It started to smell vinegary, so I mashed the pulp, a few days later strained it, and left it in a tub with cheesecloth over the top.

A skin keeps forming on the top (see photo), and flies keep coming out. Definitely still smells like vinegar. Today, I removed the scum on top, ran it through a sieve, and cleaned out the bucket.

The question is, what now? Should I just keep removing the film on top, or allow it to just build up this unappetising scummy layer? Perhaps I should just boil it to death, then add wine yeast? On no accounts am I adding sugar.

Surely it was common in the past to leave fruit in a barrel, and let it turn itself into vinegar??

[gregorach]

Why would you add yeast at this point? There's no real need to skim it either (the "unappetising scummy layer" is actually the bacteria which are making the vinegar), just stir it daily until you're happy with it, then filter it and heat it to over 80 deg C for 10 minutes to pasteurise it.

You'll probably find that the finished product is too acidic and will need some dilution for table use.

[grahamhobbs]

Gregorach, I'm sure you are more up on me on this, but I was under the impression that vinegar was made from 'spoiling' (sorry don't know the appropriate term) alcoholic liquids. From what JT101 implies the blackberries haven't fermented to alcohol, but have simply 'spoilt' with some unknown bacteria.

[gregorach]

There's probably several types of fermentation going on at once - there will be wild yeasts fermenting the sugars into alcohol, acetobacter fermenting the alcohol into acetic acid, and various lactobacilli fermenting both sugars and alcohol into lactic acid.

It's not the way I'd go about it right enough, but then I'm very much a "pure culture" kind of a guy...

[MKG]

There's always that possibility, Graham - but the clue is in the "smells like vinegar". You are perfectly correct in saying that vinegar must be the product of a solution already containing alcohol. The wild yeast infection, therefore, must have taken place at an early stage, followed by infection with acetobacter. And if that's the case, than Dunc has outlined exactly how to deal with it.

Only one thing concerns me. The level of sugar in the blackberries is going to be fairly low, so there's not going to be a large amount of alcohol formed and, consequently, not that much acetic acid. I'm guessing, but wine vinegar, as far as I know, is not diluted but is going to be made from wine with at least a 10% alcohol volume. The blackberries, without sugar addition, aren't going to get anywhere near that. So is the vinegar going to be "keepable"? I don't know.

Mike

Edit: OK - sugar content of blackberries is a little below 5%. So, 50 grams per kilo of fruit. To get anywhere near 10% ABV, you're going to need about 17 or 18 kilos of fruit PER GALLON. That worries me, unless someone tells me that vinegars are much less concentrated than I've previously thought they were.

[grahamhobbs]

I think before you use your 'vinegar' you need to find a way of testing its strength if you are considering using it as a preservative, as against a short-term condiment or cleaning (perhaps not with blackberries). Weak vinegars can be lethal if mistakenly used as a preservative, as in pickled onions, etc.

[gregorach]

Edit: OK - sugar content of blackberries is a little below 5%. So, 50 grams per kilo of fruit. To get anywhere near 10% ABV, you're going to need about 17 or 18 kilos of fruit PER GALLON. That worries me, unless someone tells me that vinegars are much less concentrated than I've previously thought they were.

Table vinegar is usually in the 4 - 8 % region (by volume). Not sure how that compares with the ABV, but I'm pretty sure most vinegars are diluted for table use.

As Graham points out, pickling vinegars need to be quite a bit stronger.

[MKG]

A little bit more research tells me that a sugar concentration of between 10 and 18% is ideal for vinegar making - but a gallon of pure blackberry juice will give you only 5% maximum.

JT101 - I feel that, although you'll certainly make vinegar using your method, it's going to be weak - on the other hand, Dunc thinks it will need to be diluted. There's only one way to settle that - try it when it's finished. If Dunc's right, you're home and dry. If not, you're probably going to have to boil it for a while to reduce the volume and increase the strength.

Mike

By the way, that second photo gives me the impression you have a mother developing. No matter what the outcome of this particular vinegar, that is well worth keeping alive.

[gregorach]

JT101 - I feel that, although you'll certainly make vinegar using your method, it's going to be weak - on the other hand, Dunc thinks it will need to be diluted. There's only one way to settle that - try it when it's finished. If Dunc's right, you're home and dry. If not, you're probably going to have to boil it for a while to reduce the volume and increase the strength.

I was basing that on what I've heard from people who've made vinegar from wine, so it may well not apply in this case. Probably not, given the information you've come up with so far.

[grahamhobbs]

MKG, not sure about the boiling bit to increase strength, in the back of my mind I think you have to freeze it and pick the ice cubes out. Could be completely wrong, any one want to research further ?

[MKG]

Again, Graham, you may be right. But boiling to increase strength came from the sites I got the other info from. However, there are two ways of distilling a spirit - freezing and boiling - so I don't see why that shouldn't be the case for vinegar too.

Mike

EDIT: Oh, and I just noticed "Surely it was common in the past to leave fruit in a barrel, and let it turn itself into vinegar??".

I doubt that. It was certainly common to have wine, cider or beer in a barrel - always worth much more money - but if those barrels stood around for long enough and acetobacter got in, the unavoidable result was vinegar (or alegar or whatever the proper term for cider vinegar is).

EDIT2: And alegar tweaked my thoughts a bit, so I looked it up. Although a weak "vinegar" without treatment, I found a commercial alegar - and it's concentrated to the point of resembling a balsamic one.

[gregorach]

The boiling point of acetic acid is above that of water, so boiling should work.

[Ellendra]

Save the vinegar mother, if it needs to be stronger add sugar and let it ferment some more.

Also, the fact that flies are still coming out of it makes me wonder if you have more than just vinegar growing in there!

[JT101]

Wow. I've just learned more about vinegar than I'd ever want to know! Thanks everyone, that's clear. Especially from Dunc on what action to take. In hindsight though, dunking the top layer with presumably fly eggs in it doesn't fill me with glee, but then again it's only an experiment, I can boil it to death at the end, and I've eaten insects before anyway.

So the only question remaining for me is, why does it matter if it's a weak vinegar?

I guess I was actually thinking of using it as a foodstuff. i.e. salad dressings etc.
For cleaning I'm sure that's also fine.
I guess it's just as a preservative when it may be an issue

I'll certainly continue with it for now, and post my results at the end

Cheers

[wulf]

In preserving, you are relying on the combination of ingredients and method to destroy nasty bacteria and prevent them from re-establishing. The vinegar trick uses acid to create an environment hostile to bacteria.

... and that makes me wonder if the important test of a vinegar is checking it's pH value rather than speculating whether it may be strong enough on the likely balance of sugars in the starting product?

Wulf