Bulk aging odor question

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rbmorris

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I have 30 gallons of Cab Sauv in a 30 flex tank with french oak staves. The wine is with in less than an inch of the top of the tank. It has been aging since early November. I drew a sample today from the sampling valve and it smells and tastes great. I opened the top of the tank and I noticed what I thought smelled like mildew or green apples. I drew a sample from the top and it indeed smelled like green apples. The taste was similar to the sample taken from the middle of the tank. I also notice sediment in the sample from the top.

Have any of you experienced this? Any ideas of what I should do? this is my first time making this quantity of wine and also the first time in a flex tank. The sample from the sample valve is great and probably the best cab I have ever made, I don't want to risk losing the entire 30 gallons.
 
You got something else to rack into? Since this is the tanks maiden voyage I wouldn’t feel comfortable leaving it go without inspecting. (Bought new or used?)
If nothing else transferring out will have a nice byproduct of airing the wine out while you figure out what the heck is goin on with the tank.
 
I have two tanks, both are new. I considered racking and may do just that. I also thought about carefully taking wine off the top and then racking from the bottom. Topping will be necessary but better that than losing 30 gallons.
 
Green apple seems to be an unusual odor. Some initial thoughts ....

Has the wine completed MLF? This would allow you to load it up with sulfites for protection from oxidation.

Is the wine sitting on significant lees? Then racking it off may clean up the odor but I've found that odors from excessive lees result in H2S production which you certainly won't mistake for green apple.

Have you been able to keep the headspace purged of air? I keep a CO2 tank with a spray gun attachment handy for purging out air.

Since gravity will clarify the wine from the top down, are you actually tasting the cleaner portion of the wine and better able to identify aromas in the wine? If it is not green apple then:
* Is it bell pepper, indicating some unripeness or lack of sun exposure on the grapes? Not much you can do with that now other than mask with more oak. Adding some untoasted oak granules during fermentation can help reduce the "green" aromas.
* Is it ethyl acetate (fingernail polish)? When it is very dilute you can get a light fruitiness out of it (which isn't unappealing to be honest). If this is the case though, you need to prevent further oxidation with sulfites and purging out the headspace of air.
* I presume it is not vinegar? A dilute amount of acetic acid will also present itself as a off-fruity aroma. If so, prevent further oxidation with sulfites and purging out the headspace of air.

It is good you are monitoring your wine aging and noting issues that are not right. Identification is sometimes more difficult. Usually the resolution comes back to preventing oxidation through sulfite dosing and displacement of air, or if that is not the issue then those steps will not hurt either.
 
When someone says apples, the first thing that comes to mind is acetaldehyde. This usually indicates air is getting in somehow, especially if you notice the odor at the top. I would check the seal on the lid as well as the bung. Are you using the threaded bung with an airlock? I have several Flextanks and I use a food grade grease on the threads and o-rings/gasket of the cap and bung; this helps to ensure a better seal as well as easy removal.
 
Thanks for all the advice. I wondered about acetaldehyde. I never thought about the o-rings and gaskets not providing a good seal.

I'm gonna try to save it. Since the samples from the bottom still smell and taste great I'm going to try to rack it from the bottom. Luckily I have a 3 gallon carboy of the same wine to use to top up. Also plan to get argon.

Again, thanks for the help.
 
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