I wish I could help you out with your off-odor issue a little bit more than I think I’ll be able to. Because you didn’t include many details about what your off odor smells like or any analysis or many winemaking details, it’s tough to diagnose from afar and help you treat this problem or help you prevent future issues.
Off-odors that were not present in the wine during aging but show up later in the bottle are often reductive sulfide issues (disulfides and mercaptans) which smell like burnt rubber or onions, Brettanomyces infections, which smell like Band-Aids or “sweaty animal,” and “corked” aromas (TCA or tri-chloranisole), which smell like wet paper, wet cardboard or a “swampy” aroma. Since I don’t know what you might be experiencing, I’m not going to launch into a treatment and prevention program for all of the above, but one or more of these are my best guesses.
Your query does, however, bring up something that might help anyone writing in — it always helps me if you can give enough relevant detail about your problem. Such details could include:
• Varietal produced
• Origin of the fruit
• Style of wine you aimed for (dry red, rosé, sweet, sparkling etc.)
• When you started to notice something was going wrong. For example, “After I racked the wine for the first time I noticed a white film growing on top of my carboy three days later.”
• A sensory description — what does your off-odor smell like? What does the film you are reporting on your carboy look like? What does your “funky” wine taste like?
• Any relevant chemical analysis or numbers you may have – Brix, pH, TA are the obvious places to start. Others that seem important to you and can also be helpful and might include: starting Brix, maximum temperature reached during fermentation, final alcohol, VA, and FSO2.
These numbers are another good way to paint me a picture of your wine at a distance. For example, if your pH is 3.95 and you are reporting a vinegar off-aroma, I’m going to say you most likely have a VA issue caused by bacteria (which thrive at high pHs). It will help me tell you what you can do about that existing batch (get the pH down by adding some acid, and adjusting the FSO2 in hopes of driving off some of that VA aroma down and stopping it from climbing again. I’ll also be able to counsel you to keep your acid levels high enough for future batches to help prevent spoilage bacteria growth.
Now, numbers aren’t everything, which is why I mentioned them last. When diagnosing a stuck fermentation, I don’t need to know the daily fermentation rate or that the residual sugar is 7.89 g/L. All I need to hear from you is that it tastes sweeter than you would like it.
It may seem like a lot of data, but concise details will help me to better diagnose your problems from a distance.