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Cold soaking must now smells of acetone

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we5inelgr

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Hi all,

I've got about 10 gallons of petite sirah must, grapes from our home vineyard, sitting at 65 F in a stainless steel tank in a cold box since last Sunday (about 5 days now).

All equipment that's been in contact with the grapes / must (aside from the bypass loppers) were sterilized using potassium metabisulfite (52.8 g / gal). The punchdown tool, every time it's been used has been sterilized (for 5 minutes) prior to use.

I've kept the must SO2 level at 50 ppm (+/- 5 ppm), via an initial addition of potassium metabisulfite, and a follow up.

The must smelled fine until today. Now, it's giving off an acetone / fingernail polish remover smell.

I was planing on starting primary fermentation either tomorrow or sunday.

Now, I'm wondering what's going on with the ethyl acetate (??) and the acetone smell.

Any ideas why this is happening now, under those conditions?

Additionally, what, if anything, should I do now beside proceeding with primary fermentation as planed?

Should I add potassium metabisulfite to reach a level of 100 ppm (or?) and then wait a few days until the SO2 level goes back down to 50 before primary?

Thanks!

P.S. The cold box is at 65 F because I also have some Rose' fermenting and didn't want to go any colder due to the temp restrictions on that yeast.
 
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jgareri

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I might be wrong but 65f is high. I would think that the best temps would be closer to fridge tempsso there is likely a bacteria contamination.
 

stickman

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What were the condition of the grapes? Any broken or damaged berries? You probably have some wild yeast producing the ethyl acetate, you need to start the fermentation quickly with a good addition of commercial yeast. Hanseniaspora uvarum (or Kloekera apiculata) is common and can cause high levels of ethyl acetate if a high population is allowed to grow; 50ppm sulfite will not suppress them. They come in with the grapes and are present in most natural fermentations, but usually are held in check by other competing yeasts, they'll die off at 4% alcohol as other yeast (usually Saccharomyces) takes over. Hopefully the ethyl acetate level is low and once the fermentation finishes it may not be an issue, if the level is high, it will be detectable in the finished wine.
 

we5inelgr

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Thanks for the reply's, I appreciate it.

I will be using RP15 Rockpile yeast, which has a temp range of 59 - 90 F. I can put the S.S. tank in our house and just keep in the indoor temp at 80 F (typically, we're at 78 F anyway). Inoculate with more yeast than called for (10 - 20% more ??) with nutrients to get it going fast and healthy.

Does that sound about right?

Additionally, before I start the primary, should I hit the must with 100 - 150 ppm SO2 (for native yeast/bacteria) since this (theoretically) won't negatively affect the RP15 yeast and do a splash rack or two? Would this help with neutralizing what's causing this...down the line?

Or don't bother with that, just start a big healthy primary right away?
 

balatonwine

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What you are smelling is ethyl acetate and caused by bacteria (and a few indigenous yeasts). The bacteria grow in warm, oxygenated environments. To prevent such problems cold soaking is either done very cold or oxygen is removed from the must. Since SO2 is an oxidizer, that is why it is used when you cold soak at higher temperatures.

Should you add more SO2? Yes. Because the amount you used was probably not enough. But only add an appropriate amount, and don't over treat the wine either (I would not go above 75 ppm myself as that should be enough unless you had damaged fruit, then 100 ppm can be considered). So then I ask how are you measuring your ppm SO2? By equipment, or by just adding "recommended" amounts? Because, if the later, then do be sure you also check your pH as you need to add more SO2 to be as effective an oxidizer if pH increases above 3.5. And cold soaking will increase your pH value.

Also, if you did not do so already, seal off the container from the ambient air. Either a plastic cover secured with bungee cords, or if using a smaller container, put on the lid with an airlock. If the container is not so sealed, then what O2 the SO2 removed can be replenished over time from the ambient air, and an uncovered container also has more bacteria raining down on the must constantly. These are of course only really minor corrective issues, but every little bit helps. You can also play some CO2 from a tank over the must before putting on the tarp or lid to help even more.

But adding SO2 will not really remove the ethyl acetate already in the must. More SO2 is simply to prevent more from being created. Ideally, and hopefully, what is already present will be blown off during fermentation and after you do one or more "splashy" racking.
 
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Stressbaby

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...cold soaking is either done very cold or oxygen is removed from the must.
Or both. The poor man's way of doing this is to lay Sarah Wrap down right on the surface of the must, all the way to the edges and up the side of the container. I keep it 35-40F for 2-3 days.

Also, I believe that a colder, slower ferment favors ethyl acetate production so I'd think you would want to get the ferment started soon, keep it warm, and let 'er rip through pretty quickly.
 

NorCal

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I don't consider 65 degrees to be cold soaking, only asking for trouble. If you are going to treat it now, prior to inoculation, you may want to get a yeast starter in a separate untreated must going. This way, when you do inoculate (I'd do it sooner than later) that you have a massive colony going to crowd out the problem microbes. Good luck.
 

we5inelgr

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Yeah, 65 F isn't a true cold soak. Being my first vintage, and with limited tools (esp. 1 cold box), I was trying to do too many different things at a single temp (cold soak reds, ferment a rose'). Next year, I'll either add large ice blocks (in zip lock bags) while fermenting the rose' at 65 F...or ferment the rose' outside the coldbox and cold soak the reds (several varietals) around 50 - 55 F, and for no more than 3 or 4 days. Probably go with that 2nd option.

As for this batch of P.S. the first thing I did last night was to bring the SS tank (with lid) inside so that it could start warming up to 78-80 F. I then re-hydrated the PR15 yeast per the directions, adding a water / go-ferm solution per those directions to the yeast. I did both at 1.5 times the recommended amount per must volume to get a big healthy yeast addition going quickly. After ~20 minutes, I added about 1/2 volume must to the yeast and waited about 10-15 minutes (the yeast slurry temp was ~12 F higher than the must temp). Then, pitched the yeast and stirred (w/sterilized punch down tool).

This morning, there was definitely a cap (for the first time) so I punched that down and added some Fermaid-K. There were significant bubbles in the must at this point.

I noticed the finger nail polish remover smell was still present...however, it was diminished by perhaps 1/3 or so. It was never a really strong smell, but definitely noticeable. Now, it seems to be dissipating a bit.

Hopefully, this batch has been saved.

Thank you all again for your helpful suggestions!
 
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Stressbaby

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Keep us posted as you go, that's how we all learn.
 

berrycrush

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I tbought 50ppm SO2 is the stop fermentation dosage. Maybe I am wrong
 

stickman

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30 to 50 ppm so2 is considered a reasonable dose to suppress the sensitive strains of bacteria and yeast, but there are many resistant strains. For example, Kloeckera is resistant to between 70 and 100 ppm so2, and there are many other resistant strains. With microbes, it is always about what percent is suppressed or killed, 80%, 90 %, etc. Adding more than 50ppm so2 isn't really recommended unless you have good reason like poor fruit. So the amount of microbes present at the start matters, that's the primary reason for a sorting table, to remove damaged fruit that brings high microbe counts.
 

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