Distilling cider with high VA (volatile acidity)

[PeteB]

A nearby cidery rang me today and asked if I would be able to distill some cider and perry that has too much VA

Has anyone had any experience with doing this?

I recently had a batch of rye ferment that smelt like vinegar. I distilled it but the spirit was still vinegar like. I have put it aside for the moment, so I suspect the cider will be the same.

Very basic chemistry suggests to me that if I add an alkaline compound such as calcium carbonate, this will react with the acid and knock out the smell. I have no idea if this is done in real life.

Does anyone wish to put in their 2 cents worth, especially if you have been there / done that.

Pete

[Charles@AEppelTreow]

Most of the aroma of VA is from ethyl acetate rather than acetic acid. So you could shove the pH around with caustic, or carbonate, but you won't clear the aroma. For that matter, I'm not sure that CaAc (for short) would stay put when you heated it. It is highly soluble in water, but wouldn't be surprised if it's equilibrium level of Ac(-) would mean you end up boiling off the acetate and leaving the Ca (or Na, or K) behind.

Cider with too much VA will turn out more like calvados than an American apple jack. I think it takes quite a bit of rectification to get a clean (ish) seperation. My little Col. Wilson still doesn't manage it.

It's supposedly possible to backblend with juice and re-ferment VA away. But I haven't had much luck. I think the batch that I tried had developed enough 'killer factors' that the new yeast pitch never took off. Cider tends to be perverse - it ferments when you don't want it, and sticks when you do.

[Charles@AEppelTreow]

Oh, and perry always has _some_ VA. It's in the fruit, so you can't avoid it. But trace VA is usually an enhancer, not a fault. Pears tend to high pH, and some yeast strains will MAKE VA, trying to get back to a pH they prefer. (Had this happen with cider once, too.)

[Sorghumrunner]

I'm working on my third batch of wines from our partner winery. I keep getting a strong vinegar/ammonia odor/vapor for much of the run. We've been testing acidity, and it seems to be alright. Right now we are making high proof brandy to blend for fortified wines, for this we're using a scuppernong wine. I've done a full set of stripping and then a spirits run, but even my hearts cut had some hint of this odor.

Here is the #'s from the most recent batch:

TA (Total Titratable Acidity) is 0.750 gm/100cc. minus Volatile Acidity of .015, leaves 0.735 gm/100cc.

It's too late to do much about the wines from last year's harvest, but we're working to identify the issue and correct for next season. Frustrating.

[Natrat]

This is interesting chemistry. As I recall, acetic acid can be reduced to ethanol using Lithium Aluminum Hydride LiAlH4 going, coverting to ethanal and then ethanol. Commercially, they use indium-doped cupric catalysts to speed this up.

That's a little outside our industry, though. Excess acetic acid and ammonia smells suggests to me that the must was fermented at too high a temperature. Acetaldehyde will form acetic acid readily, as well. The other possibility is a Clostridium a. infection in your must, which can convert sugar directly to vinegar with no ethanol phase. Clostridum will also make ammonium sulfate and glycerin, which can cause some of your weird smells. I've had good luck using a strong re-fermentation to reduce the level of undesirables...what I did was add the tainted wine to a strong sugar/water/nutrient fermentation...not all at once, but over the course of a few days. My resulting wine had very little detectable odor, and came out of the still sweet tasting. Yeasties are amazing little organisms!

I discussed this with my old mentor, as well...he suggested that re-fermenting the wines would work even better if you stressed the yeast with very low temperatures, as they will try to eat almost anything as they enter dormancy. They tend to produce some weird esters, too. I'd be curious at the outcome of such an experiment.

Sorghumrunner, when I ran scuppernong pomace for a grappa, I noticed some funky smells off the still, too. And fermenting the pomace produced very strong acetic smells, but none of that transferred to the finished spirit. However, when I got acetobacter in a whisky batch, no amount of fixing ever fixed the fix. I ended up dumping the batch :-(

One other thing, when I was fermenting in NC, I noticed that malic acid bacteria hit up my open fermentations soon after they finished unless I crashed them.

Ok, done rambling...

[Charles@AEppelTreow]

Runner, how are you measuring VA?

.15 g/L is moderate. Above the detectable in water, but threshold in wine. Acetic acid isn't supposed to be detectable until .7g/L.

Your association of the smell with ammonia confuses me a bit.

What's the sulfite level, and do you know free and total?

[Sorghumrunner]

Runner, how are you measuring VA?

.15 g/L is moderate. Above the detectable in water, but threshold in wine. Acetic acid isn't supposed to be detectable until .7g/L.

Your association of the smell with ammonia confuses me a bit.

What's the sulfite level, and do you know free and total?

I believe that he is doing an acid titration for total acid, and then heating the wine to dispel volatile acids, and doing a second titration. The smell is more of a vinegar smell, but it's so strong at the outset that it reminds me of ammonia. The wines have been sulfated to 100ppm at fermentation, I believe. I do not have numbers on free and total sulfite.

[Milan]

Pete,

You may seek out a VA filtration system to reduce it or have the cidery do it. VA will carry over into the distillate so the wine (in this case cider) should be treated prior to distillation. I would also try potassium carbonate instead of calcium carbonate as an instant, cheaper option.

Sorghumrunner, I know that small VA filtration units are available for rent in North Carolina. You can fix just about any problem in any wine with it. Elevated VA is most often the result of poor sanitation in the cellar and/or mismanaged fermentation. Also, the condition of the grapes or fruit prior to fermentation is a big factor.