I Read Somewhere That Just One Fruit Fly...

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vinny

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Can ruin an entire commercial batch of wine.

I don't know how many gallons that would amount to, but the statement was that fruit flies have enough acetobacter on their legs that just one can turn an entire batch.

2 things.

Acetobacter needs O2 to convert ethanol to acetic acid (wine to vinegar), which we all work diligently to keep out of our wines. How likely is a wine to turn to vinegar in the short term?

Number B... Does it matter at what point the acetobactor is introduced?

I have 2 kits in primary. Both have the lids loosely fitting and a towel over the lids. I checked on them yesterday and there was one of them little [email protected]&$ on the wall of my primary half an inch above the liquid where the foam was.

Is it a matter of once introduced it just needs O2 to begin the process.

I am working on getting a rotation going, but it is pretty likely this wine will be gone in the early part of 2023, It is only my second white.
 
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Raptor99

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Acetobacter needs O2 to convert ethanol to acetic acid (wine to vinegar), which we all work diligently to keep out of our wines.

When I discovered this fact I became less concerned about acetobacter. If we limit oxygen exposure it is less likely to be a problem.
 

vinny

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@vinny I don’t buy it. I’ve seen too many videos of open vats of wine fermenting. Certainly more than one fruit fly ventured into the must. That said, I’m sure we take every precaution.
Then it's not a question of contamination and more of conditions?

It still comes down to both questions. Does the moment of contact affect reaction? Or is it simply an issue of O2 concentration after?

I tried to make apple cider vinegar from juiced apples. It's a 2 stage process. Create alcohol. convert to vinegar. After months, it tastes strongly of acetone which is the processes before acetate lacking O2. i made it in a narrow mouthed bottle not knowing. I can only assume conditions are a serious factor.
 

BigDaveK

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One of those things - I remember drosophila melanogaster from a high school science project. Yesterday's breakfast? Yeah, right...

They're also the kiss of death for kambucha, one fruit fly kills the SCOBY.

I believe oxygen control and sulfites limit the acetobacter. We just need to do what we always do.
 

VinesnBines

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I'm with crushday; I don't buy that. I had a half barrel keg of Cab Sav aging; I foolishly used a bung that I thought was breathable. It may have been breathable but a boatload of fruit flies got in. I found the bodies. I didn't count how many; I guessed maybe 15 or 20. Instead I tasted and no VA so I immediately sulfated, racked and bottled. So far so good.
 

vinny

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drosophila melanogaster
Look at you go!

From Wikipedia, drosophila melanogaster also known as the vinegar fly.

I found the bodies. I didn't count how many; I guessed maybe 15 or 20. Instead I tasted and no VA so I immediately sulfated, racked and bottled. So far so good.

I appreciate your first hand experience. At least I know I have no reason to worry with my current batch..

I understand the statement to mean that under the right conditions 1 fruit fly has the potential to turn an entire batch, not necessarily that it will. Your experience proves this is not always the case and we can mitigate or eliminate the effects of contamination.
 

Rice_Guy

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* Acetobacter needs oxygen to do its magic. That said there will be some oxygen in the carboy no matter what we do. The issue then becomes one of quantity of oxygen. A low level of acetic acid adds complexity and improves the flavor.
* we should assume that there is Acetobacter in juice which is freshly pressed, ie it is introduced into the system from the vineyard. We can assume that it just sits there if there isn't significant oxygen in the system and acetic acid never reaches taste threshold.
* industry will assume a 10 minute pasteurized pH below 4.0 juice will be commercially sterile/ no Acetobacter. Likewise there will be a kill rate measured in months for a liquid with 11% alcohol/ pH roughly 3.5/ some free SO2 and no oxygen. ,,,,, wine is a multi variable preservative system.
How likely is a wine to turn to vinegar in the short term?
Does it matter at what point the acetobactor is introduced?
 

BMarNJ

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I’m with @crushday Fall winemaking in the US means fruitflies. They come with the grapes. Do your best to keep them out, keep things clean, and use water filled s-traps after primary. But they’ll be in the primary for sure.
 

vinny

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* Acetobacter needs oxygen to do its magic. That said there will be some oxygen in the carboy no matter what we do. The issue then becomes one of quantity of oxygen. A low level of acetic acid adds complexity and improves the flavor.
* we should assume that there is Acetobacter in juice which is freshly pressed, ie it is introduced into the system from the vineyard. We can assume that it just sits there if there isn't significant oxygen in the system and acetic acid never reaches taste threshold.
* industry will assume a 10 minute pasteurized pH below 4.0 juice will be commercially sterile/ no Acetobacter. Likewise there will be a kill rate measured in months for a liquid with 11% alcohol/ pH roughly 3.5/ some free SO2 and no oxygen. ,,,,, wine is a multi variable preservative system.
\

I suppose it makes sense that it would be present to some degree, unless you were using a sterilized kit wine.

I hadn't considered it actually being one of the contributing factors to improve flavor and complexity in small amounts. Maybe it will be an ingredient to get the balance just right. 3 fruit flies per 6 gallons, not one more, never one less.
 

MHSKIBUM

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Here's an interest article I came across about one potential benefit of fruit flies landing in your fermenter: Research suggests fruit flies could be responsible for wine’s pleasant aromas – Jamie Goode's wine blog
The observation, while not definitive, gives rise to the theory that some fruit flies could add complexity to aromas. Other articles I've read say that some older wineries invite fruit flies to provide the yeast for spontaneous fermentation: Flies, Yeast, and Making Wine - Berkeley Graduate Division
and
Apparently, until modern times all wine was made via the yeast that naturally landed on grapes but the quality and alcohol content varied greatly.
If you want fruit flies gone, this is what I did:
.
 

Jim Welch

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Along the lines of what @MHSKIBUM links to, I keep several fruit fly traps in my winery at all times. I make mine from plastic water/soda bottles by cutting off the top where the upper taper begins, inverting the top portion, place it into the bottom portion and secure them together with tape. Then bait them, half with grape juice and half with apple cider vinegar adding a couple drops of liquid soap to all to decrease the liquids surface tension and preventing the flys from flying off after landing. They work pretty well.
 

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