The dreaded banana smell

Discussion in 'General Wine Making Forum' started by Samthedionisian, Apr 16, 2018 at 3:15 PM.

  1. Samthedionisian

    Samthedionisian Junior

    Joined:
    Apr 8, 2018
    Messages:
    10
    Likes Received:
    0
    One of my '17 PN barrels has that unmistakable smell of bananas and its pretty blatant. I remembered vaguely that it was a bad sign so I looked it up. I do cold slow fermentations so that might be the culprit. I use 1 ton fermentation bins and use fish tank heaters to heat. Over the course of 3 weeks, give or take, it gets to 70 degrees at most, but it takes a while with this method of heating. The other possibility is amyl acetate. If that is the case how should I mitigate it? If it is because of the cold fermentation is there any remedy? I'm guessing it won't spread and will just be diluted once its blended? How can I determine what the source is?
     
  2. jgmillr1

    jgmillr1 Junior Member

    Joined:
    Jun 13, 2017
    Messages:
    150
    Likes Received:
    57
    If you are only noting this in one of your barrels and not the rest, then that points to just that one barrel as being the source of the issue. Isoayml acetate is the ester that gives the banana aroma and figuring that acetate ion came from the presence of acetic acid, it suggests there was oxygen exposure to the wine in that barrel while it was too low on sulfites to protect against that.

    As a side note, why do you cold slow fermentations? It would make me nervous to keep the fermenting grapes in an open topped fermenter for 3 weeks. I use 1/2 ton fermenters and press as soon as I can in order to minimize risk of oxidation.
     
    JohnT likes this.
  3. Samthedionisian

    Samthedionisian Junior

    Joined:
    Apr 8, 2018
    Messages:
    10
    Likes Received:
    0
    I have been waiting until after malo to rack. When should I add so2 for the isoayml acetate if I am waiting for malo?

    If I am talking to a potential customer, I tell them it is a preferred style. If I am talking to anyone who knows anything about winemaking I tell them the truth. I have a very densely planted 4 acres of grapes to harvest as soon as I can stand to wake up at in the morning and then crush/ destem after it is dark. I am lucky if I can average 2-3 people harvesting any given day of harvest and myself being the only seasoned vineyard worker. I really have no option, its just pick pick pick until the fruit is unusable. We usually take about a month to finish. I use fish tank heaters to heat fermentations but it takes a while in a 2 ton tote. If I could afford an employee I might opt for a slightly faster fermentation though I am accustomed to this style because it is the only way I have ever done things.
     
  4. jgmillr1

    jgmillr1 Junior Member

    Joined:
    Jun 13, 2017
    Messages:
    150
    Likes Received:
    57
    Yeah, harvest season is brutal for winemakers!

    Ok, so it sounds like your fermentation bins are outside and being chilled by the air temperature? I've been able to squeeze the bins in the heated winery while they ferment so it proceeds quickly and I'm pressing in a few days. Once the vineyard starts really producing I may have to change that around some.

    The banana note (if subtly blended) may actually add pleasant complexity to the finished wine. If nothing else you can leverage it as the "terroir" of your area!

    Does the problematic barrel draw a vacuum on the bung as the wine evaporates? I use silicone bungs and they seal up the barrel well enough that I hear a "whoosh" when I open them to top off. In the short term while you wait for MLF to finish to add sulfites, you could use top off or CO2 to purge out any angle's share headspace to protect against spoilage.
     
  5. jgmillr1

    jgmillr1 Junior Member

    Joined:
    Jun 13, 2017
    Messages:
    150
    Likes Received:
    57
    I just had another thought about the source of that aroma. Is it possible one of the pieces of plastic equipment you used leached some odor? I'm wondering about that fish tank heater. I'm guessing it isn't made with food grade plastic or at least isn't designed to work in acidic liquids. Just thinking of things "outside the box" that could be at work here too. I've never gotten a banana aroma before as a defect from any winemaking. Apple aroma, yes. Fingernail polish remover, yes. VA, yes. But banana, no.
     
  6. Samthedionisian

    Samthedionisian Junior

    Joined:
    Apr 8, 2018
    Messages:
    10
    Likes Received:
    0
    Yes, I do ferment outside until it gets too cold. It all depends on the space I have to work with really. I've used the fish tank heaters for years. This banana thing hasn't come up with my pinot before. It did with riesling in like '12 or '13 but never pinot. Now Im just concerned about how to address it. I could add so2 but that would inhibit the malo. And then if I just blended it like you said it might react with the other barrels that went through malo and referment in the bottle (I'm guessing...?) Do I need to test for the acetate, determine the EXACT amount of sulphur needed to bring it to the point of having 0 free so2, so that I can then still inoculate for malo? Or would the final pre-bottling sulphur addition be enough to inhibit any malo in bottle so that then blending wouldn't be a problem?
     
  7. jgmillr1

    jgmillr1 Junior Member

    Joined:
    Jun 13, 2017
    Messages:
    150
    Likes Received:
    57
    Perhaps the best news is that since isoamyl acetate is a volatile ester, it may degrade over time as it ages. And since malo seems to degrade fruity esters anyway, that process alone may remove the aroma. When MLF is done you could pull some samples from the banana barrel and a non-banana barrel for a blending trial.

    I'm not sure if sulfites would resolve the aroma (see below) and at least it doesn't sound like anything leaching from the plastic. Here are a few references I've found in looking into this. Apparently the isoamyl acetate banana aroma can be produced by yeast (both Saccharomyces and others), influenced by grapes, and is not necessarily an indication of spoilage risk.

    1) This article describes how isoamyl acetate can form from the degradation of amino acids.
    2) There also may be a yeast selection element that contributes to the production off isoamyl acetate.
    3) This article discusses how pinot noir and pinotage are capable of producing large amounts of the isoamyl acetate during fermentation and that it does NOT necessarily require the presence of spoilage acetate.

    Perhaps you can experiment with various yeasts to see if one gives you better results than another. RC212 is nutrient-hungry and would be a good choice if your must is high in YAN.

    This is an interesting problem and a good example of how much variability there is in making wine.
     
  8. Samthedionisian

    Samthedionisian Junior

    Joined:
    Apr 8, 2018
    Messages:
    10
    Likes Received:
    0
    Thank you for the info. Perhaps the yeast is the culprit. It was a wild ferment, so I have no idea what strain of yeast it is. Hopefully you're right, and going through malo will help reduce the problem. Thanks again.
     

Share This Page