A common question I get is whether or not a ferment is safe to consume. I’ve received this question so many times that I feel it’s time to make a post about it. One of the most commonly asked questions is if fermented juice is safe to drink. Here are my thoughts.

No, fermented juice is NOT safe to drink.
My response assumes you are asking because your juice spontaneously fermented. As in, you did not set out to make a fermented drink.
Instead, you bought some grape juice or pineapple juice, and it stayed in the fridge too long and now it’s bubbly and fizzy. Or maybe it’s the orange juice you’ve been drinking for the past week. You forgot to put it back in the fridge for several hours, and suddenly it’s got some bubbles and a tang.
You know that people purposefully ferment drinks to make natural, probiotic sodas, so you’re wondering if this is the same general idea.
The answer is no, it couldn’t be farther from the same thing. Your spontaneously fermented apple juice is not the same as cider, and is not safe to drink.
What happens when juice ferments spontaneously?
When juice ferments spontaneously, often it is due to contamination with bad bacteria. This is particularly the case if it is a pasteurized beverage, because all the good bacteria has already been killed.
But even a raw juice that spontaneously ferments isn’t necessarily safe to drink. It could be tainted with harmful bacteria such as E. coli or salmonella and make you very sick.
Bacteria and yeasts gobble up the sugars in the drink and release gases and ethanol. It results in a drink that is bubbly with a low alcohol content. This drink should be regarded as spoiled.
I’d avoid whether the juice was pasteurized or raw.
And when anyone asks me if “randomly” fermented drinks are safe, I will always say NO. Of course some will choose to drink them and things may turn out OK. But I would never advise it.
Drinking spontaneously fermented beverages can make you sick.
What’s the difference between a spontaneously fermented drink and a lacto-fermented drink?
Spontaneously fermented drinks are not created under any kind of controls. It is generally due to products being kept at too warm of a temperature, or not being used within the designated period of time. Generally juices recommend keeping them under refrigeration, and discarding within 7-10 days of opening.
Intentional fermentation is the complete opposite. When you intend to ferment, you put the juice in the right environment to ensure a safe end product.
Lacto-fermented drinks almost always contain a starter. If they do not, such as beet kvass, they are still fermented under controlled environments, generally with salt added to help stunt growth among harmful bacteria and allow lactic acid bacteria to flourish.
I personally also ferment beet kvass and similar ferments under anaerobic conditions, which also greatly decreases the odds of promoting the growth of bad bacteria and yeasts.
When fermenting fruit juices, I generally use a starter such as ginger bug or water kefir. These starters quickly drop the pH of the juice and crowd out any bad bacteria that may be in it. The starters help good bacteria flourish in the fermented juice, and have a preserving effect.
Even when home brewers are fermenting wine/alcohol, they will generally add something to kill the natural cultures before adding their own yeast.
What shoud you do if you accidentally drank fermented juice?
If you accidentally drank some juice that was sitting too long, then you need to somewhat play it by ear.
Rest assured that you don’t need to jump to the conclusion that you’re going to die.
Chances are that the worst that will happen is you’ll have some digestive distress, like a stomachache or diarrhea. Here are some tips for dealing with belly pain.
In some cases, you may have more serious digestive issues such as vomiting. If you have a little nausea or vomit once or twice and then feel better, then it’s safe to assume that your body did a good job of clearing the irritant.
However, if you have persistent diarrhea or vomiting and don’t seem to be getting better, you may want to consult your doctor.
chris
Wednesday 28th of June 2023
Hi -- I often buy fresh juices from Trader Joe's and while I love TJ's approach to organic/natural products, they often don't last long. Five days ago I bought the pasteurized, not-from-concentrate, refrigerated pink grapefruit juice. While unopened I noticed the bottle puffed up but otherwise perfect color and consistency. When I opened it, it basically exploded, foamed over like a beer. Tons of carbonation but otherwise perfect smell, consistency, color and taste. It tasted just like perfectly carbonated and nicely sweet pink grapefruit juice. So I drank it down with no issues. I'm wondering if all indicators are perfect, could it be just friendly yeast got into the bottle -- and thus safe?
robert bishop
Tuesday 4th of April 2023
I bought a large jar of halved peaches in juice. Sat in fridge for too long. White stuff growing on the peaches. I'm taking your advice & not considering the juice peach wine. I'm dumping it. Thank you for the info.
10 is fermented fruit juice safe to drink Ideas - Món Ăn Ngon
Thursday 26th of January 2023
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Judith
Thursday 6th of October 2022
My daughter made a Black Forest Cake for my birthday mid September, all from scratch, beautiful and delicious. This is now early October and living in SW Florida we are now in the aftermath of hurricane Ira. The Green wise organic juice was in the fridge lying on its side and when I opened it to check it out, it had been lying on it's side for a week. I was discarding things that might have spoiled and when I opened the cherry juice it let off a stream of what looked like fog and kept emmiting this fog for a long time. I put it back in the fridge with a loose lid. I smelled it and could detect no smell. Should I through it out or taste it?
Jon
Sunday 13th of March 2022
Thanks for this info. I've been unsure forever about the spoilage factors of orange juice. Now I know. When it begins to outgas and pressure releases (bottle farts) when unscrewing the lid, I've suspected spoilage but did not know if it was unsafe to drink. The fiz that comes with the gas actually has an interesting taste and sensation, like soda pop. However, I've always tended to follow the rule, "if in doubt, throw it out." Thank you for confirming my suspicions that it is a bad idea to drink. My gut thanks you as well !
Jo
Saturday 21st of May 2022
You're very welcome! I have followed the "when in doubt, thow it out" adage many times!