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Cold crash and sterile filter to stop fermentation

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GreenEnvy22

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Hi all,
I have a wine I am making for a relative. I make this most years for them, but it's always a rushed affair because we harvest in late September, and it needs to be ready for Christmas. I have no control over the timeline. I know time is the best option, and stopping fermentation isn't easy or the best method. But I don't have the time.

It's a rose (Dornfelder pressed immediately, ferments without skins), and they want it super sweet, like 1.016-1.020 at bottling).
Usually, i reserve some juice and freeze, then backsweeten after it ferments dry. We've had some issues with cloudyness/sediment, even though it's looked clear at bottling. I have run it through a 1 micron (whole house style) filter with my AIO, each time, after a few rackings, but still cloudyness appears later. I think it might be coming from the frozen sweet juice (though that was mixed in during the final filtering). I do sorbate and get my sulfites in the normal range, and we don't usually have any issue with refermentation, just cloudyness/sediment.
This year we want to try it differently. I have a spare chest freezer I had setup as a beer keezer, but is now sitting empty. So I can control temperature very well.
I can fit in a 20 gallon brute and a 7 gallon fermenting pail, which is about the volume we'd have for this.
The thought is to ferment until we approach that desired SG, then set the keezer to go down to 34-36 F, do some bentonite/chitosan/sparkloid or similar, and let it sit like that for a few weeks. Then we'd rack it out, and run through a 1 micron, then 0.35 micron filter. Then sorbate and get sulfites to around 40ppm for bottling.

Thoughts on this?
 

stickman

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Seems like it should work, but I don't think I would leave a delicate wine in a brute for a few weeks, with temperatures in the 30's the wine will pick up a full saturation of oxygen. The wine may still be fine, as some of the oxygen will be kicked out during degassing, but an enclosed vessel would be my preference if available.
 

Johnd

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Why wouldn't you just ferment dry, vacuum degas, add clearing agents, sorbate and sulfite, sweeten, put it in the cooler, then filter in a few weeks before bottling? You're using the cooler to reserve sugar, when you could just go dry and add it later...........
 

NorCal

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I'm with @Johnd on this one. I'd feel so much more confident of not having a fermentation in the bottle if I ran it dry first., cleared, sulfited, sorbate, then sweeten. Have you tried back sweetening with simple syrup to avoid cloudiness?
 

mainshipfred

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I don't believe wineries use sorbate. Their sweet wines are sterile filtered. The issue we have as home winemakers is the ability to sterile filter. I've always been told .45 micron "absolute" is what is required. I agree with not allowing the oxygen exposure but if you truly have the ability to filter to .35 microns "absolute" I don't see a problem. The key factor is absolute not nonimal filtration.
 

GreenEnvy22

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Thanks guys, I should have been more clear, it would be in carboys for the longer term cold crash, not the brute. The brute would only be for primary fermentation.
Actually, as it turns out, I'm using some fermenting buckets, and my 16 gallon stainless Brew kettle.
That fit more nicely in my fridge. It will still go into carboy's when primary is down to the level we want, then rack to carboys and chill.
The reason we normally reserve some juice, is because we don't want to alter the flavor by using something else to back sweeten.
I think I'll give it a try this year, if it doesn't work out well, then next year we'll go back to the other method.
I'll keep everyone up to date on how it turns out.
I'll have to check on the filter to see if it is absolute or nominal. hopefully even if it's nominal, being 0.1 micron smaller than I need, will be enough. That combined with the sorbate I think should prevent a re fermentation.
 

jgmillr1

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I don't believe wineries use sorbate. Their sweet wines are sterile filtered.
Both sorbate and sterile filtration are used commercially. I've known some that will do one or the other but most I know do both, including me. Not worth the risk otherwise. Sorbate will give a taste if used in excess and has a longevity issue but sweet wines are consumed young anyway.

Then we'd rack it out, and run through a 1 micron, then 0.35 micron filter
Running the wine through a 0.35um house filter is not sterile filtering it. Sterile filtration means using an absolute membrane filter that is precisely manufactured to not permit more than 99.999% of the nominal size particle through. Read here for more info. As the saying goes, it's not the size that matters. It is the number of 9's. You must also bubble point test its integrity to verify it.

It sounds to me that you're getting a protein or pectin haze issue. Bentonite is a good fining agent and pectic enzymes are available. Cold crashing makes an excellent sweet wine but can be difficult to stop the fermentation on a dime. Backsweetening a dry wine works great as well. Good luck.
 

Scooter68

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As an "Outsider" in this discussion, the cold crash and sterile filtering (That we hope will truly work) sounds like a lot of work compared to simply letting the ferment finish. Just make sure the fermenting room is on the warm side and unless you are really pressing for a high ABV, you should be able to ferment dry faster than the time and effort to cold-crash and sterile filter.
The old expression that seems apropos for this - "Just because you can, doesn't mean you should."
 
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Rice_Guy

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You could push the temp to 30. we see slush like crystals at 28 up north.

ought to work.
 

AaronSC

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One thing to consider: I have definitely noticed a difference between wines that were stopped in their fermentation through chilling to be naturally sweet with residual and wine that went to dryness and were back-sweetened. The process of slowing and stopping the fermentation seems to maintain much more of the flavor and aromatics of the grape. It seems to me the the last phase of fermentation to dryness is where a lot of the volatile aromatics of a white wine are lost. I got to see a direct comparison of this with Seyval. Two carboys, same yeast (Epernay 2 or "Cotes des Blancs" or whatever the new name is now, this yeast has had more name changes than Prince) same must, one fermented to dryness and one stuck at around 3-4% residual (not sure why). The dry Seyval was essentially neutral (as dry Seyval often is), the one with arrested fermentation had such wonderful fruit flavor and aromas-it was a very different wine. I did a tight filtering and bottled it with sorbates and it was great.

If one of your goals is maintain a lot of fruitiness in the rosé then halting fermentation, fining, filtering and sorbating seems to me a good idea to me. It what most commercial wineries in the Finger Lakes do for a sweeter wine.
 

robert81650

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I usually save about 4 cups of the dry wine and then use that to make a syrup with sugar to back sweeten with............
 

Scooter68

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.....It seems to me the the last phase of fermentation to dryness is where a lot of the volatile aromatics of a white wine are lost.
It would make sense since fermentation is a process that could 'blow off' or release the volatile elements of the wine. So the shorter the time the juice is fermenting the more of those elements remain. That's one of the reasons it's recommended to ferment whites a the lowest temps possible. As long as you have the ability to stop the fermentation and prevent it's restart later on, then the proposed process is great for preserving those elements that might otherwise be lost.
 

GreenEnvy22

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So far so good. when the wine got down to about 1.024, I moved it into the fridge, knowing it would take a couple of hours to cool down.
It's been in there for about 2 weeks, holding at 1.020.
My 0.35 micron filters are here, so once this all settles out I'll run it through those. I'll still sorbate since the filter is nominal not absolute, but I think we'll be in good shape. I'll watch it for a month or so before bottling to ensure it's not fermenting again.
 

AaronSC

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Are you planning on prefiltering with a coarser filter before the .35µ? Those guys can get gummed up shockingly fast if there's any kind of suspended material in the wine.
 

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