Will suspiciously fizzy homemade nocino be the death of me?

July 5, 2010 1:06 PM

Why is my homemade walnut vodka infusion FIZZING after its first night? Am I going to die?

We picked a ton of unripe black walnuts in the park this weekend to try our hand at making nocino, a tasty tasty liquor. Step one involved quartering 20 or so unripe walnuts and covering them with vodka in a mason jar to infuse. (The spices and sugar go in later. Yum.) We did a first batch yesterday, and two more today.

Problem is, when we checked in on yesterday's batch to see if the walnuts had settled overnight, it fizzed like crazy as soon as we opened the jar!

Now, it seems pretty unlikely that our vodka has botulism. We've done successful vodka infusions before (pear, vanilla, kahlua, gingerbread spices) and never had a problem like this.

What could be causing the fizzing? Do we have to worry about the jars of proto-liquor exploding in our pantry? Will we die when we drink it (months down the line)?

posted by Eshkol to food & drink (15 answers total)

Neat vodka will kill anything immersed in it. You don't have to worry about an infectious infusion. Mason jars are also quite good at taking pressure, although if you're really worried just leave the band a little loose so gases can burp out while maintaining a general seal. (That's why Mason jars have separate bands and lids.)
posted by seanmpuckett at 1:16 PM on July 5, 2010

Infection is not the only concern with food spoilage. Some bacteria leave toxins--which are not killed by vodka.
posted by dirtynumbangelboy at 1:22 PM on July 5, 2010

I'm also making nocino this year, and just checked mine after reading your question to see if there was any fizziness at all, and there is not. Mine have been going for about two weeks now, so if there was going to be gassy fermentation, I'd expect to see it there - I wouldn't expect to see it in something you started yesterday, though.

If you picked the walnuts from a park (in Brooklyn, as your profile suggests), you really have no way of knowing what pesticides or fertilizers have been used on the trees. I'm all for urban foraging, but I'm not sure I'd be comfortable with infusing anything I didn't know the origins of, as the alcohol may react with any chemicals in interesting and potentially toxic ways.
posted by judith at 1:30 PM on July 5, 2010 [1 favorite]

Yes, dirtynumbangelboy has it. In particular, Clostridium botulinum, the bacterium that causes botulism, spews gas in a way that sounds suspiciously close to the fizziness you mentioned. That's why you never eat from bulging cans. I don't know if Clostridium botulinum is killed by alcohol, though.
posted by guybrush_threepwood at 1:37 PM on July 5, 2010

Botulinum is killed by air, let alone alcohol; the problem is that, as dnab says, the toxin is longer-lived than the bacterium that produced it.
posted by hattifattener at 1:48 PM on July 5, 2010

Re toxins lasting longer than bacteria - I know that, but shouldn't bacteria die in vodka before they can even produce toxins in meaningful quantity?

re park foraging - I see your point, but I also eat wood sorrel and hedge mustard from the park without fear or ill effect, so that would surprise me.

In sum, I remain confused and worried.
posted by Eshkol at 4:02 PM on July 5, 2010

I'd eat wood sorrel and hedge mustard too (and do, here in SF), but trees are different - there are all sorts of invasive parasites and disease that the parks dept work hard to protect trees from, and I would guess that the trees are treated with various chemicals for that, without consideration of food safety, since the trees are intended to be decorative rather than food supplies.

It's infinitely more likely to be bacteria than chemicals, but in either case, it's definitely not something I've ever heard as an expected part of the nocino-making process.
posted by judith at 4:20 PM on July 5, 2010

I would not be worried about chemicals. Parks don't have that much money for pesticides, and any residue would be on the outsides, and should wash off.

That said, I don't know why it's fizzing. The only promising link I could find was about CA cracking down on bars that do their own infusions in the name of public health earlier this year, but I couldn't find their rationale. Maybe if you google "rectifier license" and "ABC" you'll find their concern, but in looking through several articles I could only find bartenders pointing out that nothing survives in alcohol.
posted by ldthomps at 5:45 PM on July 5, 2010

Could you ring whoever 'administrates' the park and ask if they spray with pesticides or other chemicals?

A quick google brought this up. Might be worth a try?
posted by malibustacey9999 at 6:18 PM on July 5, 2010

Botulinum is killed by air, let alone alcohol;

It's killed by oxygen because it's an anaerobic bacteria, not because it's particularly fragile or anything. And that says nothing about it's sensitivity to ethanol. Except that by steeping the walnuts in vodka you've nicely protected them from the oxygen that would otherwise kill the bacteria.

This article shows that ethanol won't kill the spores although it will kill the dividing cells (and they got viable bacteria after dosing the spores in 90% ethanol). But the concentration of ethanol within the walnut meat could easily be low enough to let the spores start to grow now you've removed the oxygen (and this abstract suggests low concentrations will increase growth, so clearly they're not desperately sensitive). So the idea that vodka kills all doesn't necessarily apply in this case (plus we always use at least 70% ethanol in the lab for killing microbes anyway).

The thing with clostridium botulinum is that you only need a very small amount of the toxin to make you very, very sick. So if you're at all unsure (which you are) then you need to throw it out.
posted by shelleycat at 10:36 PM on July 5, 2010

Could be a chemical reaction between the alcohol and the jugolone in the black walnuts.
Here's more on jugolone
posted by cosmicbandito at 8:53 AM on July 6, 2010

Shelleycat - Oh, that's terrifying. Thank you.

Follow-up question: Does anyone know what the easiest/cheapest way to test for botulism (well, more importantly, the toxin rather than the bacteria) is? I've already sent out emails to two friends who work in biochem labs, but the hive mind might know things they won't!
posted by Eshkol at 11:40 AM on July 6, 2010

There's an obvious possibility that people are missing: the walnuts could be fermenting due to yeast. Alcohol inhibits most of yeast's competitors (but, as noted above, botulin can still survive, although not thrive), and the interiors of the walnuts might not have reached proof levels that will inhibit the yeast yet.

Not sure if there's enough food for yeast in walnuts to support them, but it's a possibility.

As for testing for botulism... feeding it to a test animal is the first thing that comes to mind. But I'd prefer starting over to sacrificing an animal, and given the alcohol level, you'd never be sure you didn't just give them alcohol poisoning.

You could put a drop of the liquid on a test slide, and look for bacteria - if they're present in any real quantity, they've been reproducing since you added the vodka. Any bacteria = bad; I wouldn't worry about the species identification (and this does mean that you might be throwing it out over harmless yeast, but a false positive is far worse than a false negative in this case!).

Culturing the critters, in order to examine them without a microscope, can be done at home, but it takes more prep than is worth it for this effort (it starts with buying HEPA filters).
posted by IAmBroom at 6:27 AM on July 7, 2010

It is obviously not fermentation by yeast. Wild yeast on walnuts won't produce fizzing in a day. High concentrations of alcohol kill yeast. That is why vodka is made with distillation.
posted by llc at 7:51 PM on July 7, 2010

Okay, it turns out that in theory I can ask the NYC Dept of Health to test for botulism. I haven't made the call yet, so I'm not sure of the cost or error rate. But if I can't test it effectively, I'm going to throw away my proto-nocino just to be on the safe side.

I hadn't considered the possibility of botulism surviving in the nut crevices - thanks for the save, shelleycat!

And here's contact info for the test, in case anyone else comes across a similar issue in the future:

BOTULISM TOXIN IN FOODS & CLINICAL SPECIMENS
This test is available on an emergency basis
24 hours a day—7 days a week

Division of Microbiology-NYC DOHMH
455 First Avenue, New York, NY 10016
TEL [phone] FAX [phone]
posted by Eshkol at 9:29 AM on July 8, 2010