Do the berries make it boozier?
April 11, 2006 1:41 AM   Subscribe

Does a vodka fruit infusion ferment? Is the resulting drink more alcoholic than the base distilled spirit?

If you start with a distilled alcohol (say, 40 proof vodka) and let fruit steep in it for several months, do you get more alcohol from the sugars that were in the fruit?

It was my understanding that the reason alcohol was distilled, rather than just fermented for longer with more sugar was that the yeasts doing the fermentation would be killed at a certain concentration of alcohol and the fermentation would stop. However, a chemist friend of mine insists that there are wild microorganisms in his infusions that are making more alcohol. Is he right?

Are there other factors (evaporation? dilution by the addition of a volume of fruit?) that would cause the infusion to become significantly stronger or weaker? Is there something that would make the drink seem stronger, even though the alcohol content hadn't changed?
posted by aneel to Food & Drink (14 answers total) 2 users marked this as a favorite
I think he's full of it. I used to brew beer, at at 12% alcohol the yeasts started to die.

Evaporation should work against him; alcohol will evaporate more readily than water will.

But the flavor could change, and convince him that it's more intense. A longer exposure of fruit to alcohol could increase the amount of flavor ingredients leeched out of the fruit.
posted by Steven C. Den Beste at 1:47 AM on April 11, 2006

I don't think so. Alcochol is yeast shit, and they die when there's too much of it. About the most intense fermented beverage you can directly make is wine, at about 15% alchohol. All the spirits are distilled from solutions no stronger than this.

At 40% alchohol, yeast can't live it any more, and you don't get any more alchohol. Leaving it soak a good long time will break down the fruit more, and that might change the taste, but it won't get you any drunker.
posted by Malor at 1:49 AM on April 11, 2006

*alcohol*.... sigh. The first one was a typo, and the other two are just my stupid brain insisting that there's an H where there actually isn't.
posted by Malor at 1:50 AM on April 11, 2006

Response by poster: (I mean 80 proof vodka, 40%)
posted by aneel at 1:52 AM on April 11, 2006

Um... you should ask your chemist friend why his lab equipment is sterilized in alcohol and see if a light bulb goes off in his head.
posted by junesix at 1:56 AM on April 11, 2006

As to why he thinks it's stronger, I think whatever the fruit is contributing to the spirit, it's making it "harsher" to drink and thus he's convinced there's more alcohol. For me, a shot of an 80-proof neutral spirit like vodka goes down a whole lot easier than a shot of 80-proof whiskey so it feels like there's more alcohol in the whiskey even though they're both exactly 40% alcohol.
posted by junesix at 2:05 AM on April 11, 2006

Best answer: Given that your friend didn't listen to you I doubt they will listen to random internet people, so here is some evidence, from 1947 no less.

This guy basically took ~30 strains of yeast, and stuck them with heaps of sugar and varying amounts of alcohol and then measured the amount of sugar used over time (eg new alcohol production). This is pretty much exactly the conditions your friend has. He found that at higher concentrations, little sugar was used, ergo little new alcohol was produced.

There are however a couple of yeasts there that can use ~15% of the sugar at 17% alcohol. It is unlikely this would continue to the 40% of his fine liquor.

Of course, your friend will probably argue that given the location of this study (the Microbiology Laboratory of Jos. E. Seagram and Sons, Inc.) the results are not to be trusted.
posted by scodger at 2:26 AM on April 11, 2006

Your friend is wrong, of course, but consider this: different concentrations of sugars and other ingredients in alcoholic drinks give a different feeling of drunkenness when you drink them.

There's a difference between drinking beer and drinking vodka, and a difference between drinking bourbon and coke and drinking scotch and water. The main difference is carbs.

Drinking his infused spirits probably does give a different feeling than drinking the straight spirits. But that's not because there's more alcohol.
posted by AmbroseChapel at 3:34 AM on April 11, 2006

By the way, modern American breweries (like Sam Adams and Dogfish Head) are brewing beers (with no distilling) above 15-17% ABV by using lots of different yeast strains--Sam Adams up to 25% for their Utopias 2005. See this list of strongest beers at Beer Advocate.

Of course, all of the points above are still correct. 40% is a lot higher and and there wouldn't the strains of yeast that can handle being alive with that much alcohol. Most of the baddies that can infect fermenting liquids, for one thing, don't produce very much--if any--alcohol. And you'd know if it wasn't yeast producing the alcohol, because you'd get a lot of funky off flavors.
posted by skynxnex at 6:27 AM on April 11, 2006

junesix isn't exactly correct... you need at least 60% ethanol to surface-sterilize stuff.

that said, liquor contains enough ethanol to halt the growth of pretty much any microorganism, not to mention the fact that the concentrations of necessary nutrients are far too low in the distilled spirit to support further fermentation.
posted by rxrfrx at 7:33 AM on April 11, 2006

There's a difference between drinking beer and drinking vodka, and a difference between drinking bourbon and coke and drinking scotch and water. The main difference is carbs.

Drinking his infused spirits probably does give a different feeling than drinking the straight spirits. But that's not because there's more alcohol.

So you're saying there are carbs in the infused beverage? Wouldn't that actually imply less alcohol by volume?
posted by staggernation at 9:15 AM on April 11, 2006

FYI, you can buy yeast that will produce up to 40 proof (20% ABV).

Some fruit naturally carries wild strains of yeast with them and will self-start into fermentation. Some do not. A 40% ABV environment will kill them.
posted by plinth at 9:41 AM on April 11, 2006

Response by poster: That data's great, scodger, and just the sort of thing that might convince him. Thanks. Anyone know of a similar study that determines the limit for hardier yeasts (rather than topping out at 17%)?
posted by aneel at 9:42 AM on April 11, 2006

Best answer: From 1984: High-Gravity Brewing: Effects of Nutrition on Yeast Composition, Fermentative Ability, and Alcohol Production

This study suggests that it's not so much the ethanol concentration that halts these brewing yeasts but rather a series of interrelated factors like nutritional deficiency, temperature, and osmotic pressure. I'm guessing that once the ABV hits the 20%-ish levels, the yeasts are completely killed off regardless of whether or not they can keep making ethanol.

The "turbo yeast" are special strains of Saccharomyces cerevisiae that thrive and can continue to convert sugars to ethanol in high ethanol concentration conditions.
posted by junesix at 2:23 PM on April 11, 2006

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