Hello. I am somebody who likes to make use of bounties of fruit with jams, pickles, bottling etc. At the same time I choose to completely avoid drinking alcohol. Sometimes when I try an old jar of something there is a suggestion of fermentation. Can anyone tell me, in simple terms, whether my produce is likely to become alcoholic (which is against my wishes)? Is there a simple way of telling whether something has changed to alcohol?
Probably not going to help in the presence of huge amounts of sugar - which, after all is the point of jam making - partly to sterilise the fruit with heat, partly to have so much sugar in the mix so as to kill any bugs which got in/survived the boiling (OK, the latter *should* be impossible) and to avoid fermentation.
Look for bubbles of carbon dioxide released during fermentation, it will probably smell “yeasty” as well.
To avoid fermentation make sure the sugar content is high enough and clean all the equipment thoroughly to avoid contamination with yeast.
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Thanks. This looks like a piece of kit which a home brewer would find handy. As someone who doesn’t intentionally want to brew anything, I’d be reluctant to splash out on any kit unnecessarily.
Is there any way of testing without specific equipment? And on a similar theme, what is the simple science that would explain what conditions are needed for fruit to become alcohol?
Yeast.
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There will always be yeasts around from the atmosphere, skin etc. As suggested, keep the sugar content high and yeasts (or indeed many other things) will struggle to grow. A sterilising process where you boil the fruits after bottling and sealing them will also reduce likelihood.
The sugars in fruit can be fermented by enzymes that yeasts produce, to become alcohol. Bacteria can also cause some fermentation, but may produce things other than ethanol. Conditions required: starter seed culture (yeast from fruit skins, hands etc) moderate pH (neither too acid or alkaline) neither too much nor too little sugar, moderate warmth - say 15-30 Celsius.
A Hygrometer would be useful to indicate how much alcohol and/or sugar is present in a fermenting must, but probably not useful for jams/pickled fruits.
The easiest way to check for the presence of ethanol would be the sniff test - if it smells alcoholic then it probably is. If you have a friend in a university department with some Mass Spec equipment then they could do it for you, but that’s beyond the reach of most, so just sniff & see.
Does your last sentence mean boil the bottled fruit in a saucepan of water? If so, for how long?
You need the temperature of the fruit in the jars to be even all the way through, and then it may be barely enough unless you can pressure-cook them. I’d say 30min from the time the water is at a rolling boil for 250ml jars, probably twice that for 500ml jars. You have a lot of thermal inertia to overcome, and fruit preserves will not have convection currents inside the jars to help distribute the heat.
I’d avoid using the microwave.
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It’s effectively canning the fruit. Everyone round here has bocaux and a boiler.
I use these, and then have a big fait-tout that I cook them in. Although this year I borrowed a neighbour’s boiler. I’d have to look it up but for 100% safety I think 40minutes at boiling point, and the water must be atleast 2 cm over the lids. Strangely you don’t end up with mush.
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Thanks Jane! I have the big boiler thing, never used but want to make salsa so will be back with questions as don’t want to give us botulism 
My Mum made jam most of her life but cant remember it ever turning alcoholic. I am making water kefir which does require fermentation and I will put my hydrometer in it to see but I doubt it has a worrying amount. I would be more concerned with what the sugar will do to you.
Our bodies produce about 3 to 4 grams of alcohol per day. This is equivalent to about ÂĽ of a standard alcoholic beverage. Alcohol is produced in our gastrointestinal tract through the action of bacteria and fungi (yeasts) as a by-product of carbohydrate metabolism.
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All true - but if RICROM has a religious or personal objection to the consumption of additional alcohol it seems reasonable to help out with suggestions as to how unintended fermentation might be avoided.
Yes I made that assumption too but its also funny that we make alcohol and feeding the body with sugar is unhealthy and likely to increase alcohol production, funny us humans arent we.
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Quite.
To safeguard against botulism don’t forget to put in some lemon juice, preferably out of a bottle as the acid content is generally higher.
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