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Distillate Off-Flavor

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So this has been plaguing me for the past month or two. Our 100% corn mashes have been producing an abnormal distillate. It's hard to describe but it brings to mind images of camphor, chloraseptic, vegetal-sulfur, plastic-y and metallic. It's very volatile and astringent on the tongue but usually fades and is replaced by how the distillate should taste. At high proofs it lacks any displeasing aroma but when proofed down (Distilled, RO, you name it) the aroma begins to match its flavor.

This was my latest batch:

1. Sanitize mash tun then fill with 80 gallons of water (goes through a activated carbon filter) at ~110F. Add 4 tablets of potassium metabisulfite to treat any left over chlorine/chloramine.

2. Add 200 pounds finely milled corn as water is filling. pH at this stage is around 6.2. Add 25ml Hitempase 2XL to help thin the mash and begin heating. Heat to 185F and add another 50 ml of HT2XL and hold for 30 minutes. Let it passively cool, adding 75 ml HT2XL when it gets below 170F (this specific occurrence it was 166F). Continue to passively cool to 145F, altogether this takes around 1 to 1.5 hours.

3. Adjust pH to 5.4 using phosphoric acid (150 ml to be exact). Add 100 ml Amylo300 and let rest for 1.5 hours. After the second rest, add 40 gal of water (and 2 more Campden tablets) to assist in cooling. Use cooling jackets to bring down 80F. Readjust pH to 5.4-5.5. 

4. While all that is happening, rehydrate half a pound of Red Star DADY using 150 g of StartUp (no DAP) nutrient in 1 gal of 100F treated water (50g/L dosage suggestion). Add 100 g SuperFood nutrient (DAP). After awhile a slurry is formed but the yeast don't look super active (no foamy head or anything). 

5. Once the mash reaches 80F, pitch yeast and let ferment in the mash tun (ruling out any dead legs or improperly sanitized hoses). Final OG is 1.054, pH is 5.4-5.5. It ferments mostly dry in 3 days (around 1.000) with a final pH between 3.9-4.0. The flavor and aroma seem typical; dry, slightly tart, slightly bitter, perhaps a little sulfurous. No signs of infection.

I then transfer to the still and immediately strip it. It is a 240 gallon, all copper, steam jacketed, alembic still. The off-flavor is most prevalent in the heads but stretches throughout a good portion of the hearts. Usually not noticeable in the tails. I dump the first half gallon or so then collect everything in a receiving tank. I run it down to about 35 proof leaving me with around 15 gallons of 70 proof low wines. 

Running it that deep into the tails does cause some copper salts to come out in the distillate and they seem to mix nicely with the fatty acids (film of oil on top) to my displeasure.

Normally I would run a few strips then do a second finishing run through the alembic. However, while I've been fiddling with these half batches I've been running them through a 50 gallon direct heat (immersed heating coils) still with two plates and very minor reflux. Seems to only get concentrated while still bleeding throughout the hearts. If I'm lucky I get a few gallons of usable product. 

In the beginning I thought it was a problem with water or fermentation (wild yeast/bacteria infection) but I'm beginning to suspect something with the stills. I clean them between each run with a caustic, citric, rinse routine using CIP. The lyne arm I have to remove and let it soak with each (only able to do ~110F). I also have to manually soak the condenser (again only ~110F). Today I took apart and hand cleaned everything that I could. I noticed a dog-legged piece that connects the condenser to the parrot. Several large chunks of copper salts came out as I rinsed it and it smelled horrible. Even after soaking and rinsing it still smells slightly. 

I also run a very flavorful, macerated redistilled gin through the alembic. It doesn't have any noticeable off-flavors, but I'm not 100% positive it isn't covered up by the botanicals. 

Could my problem be in the copper salts? Or is it possible that the gin is causing it? Any advice, ideas, or consolations are appreciated!

 

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Just an idea; I know people use metabisulfite tablets to treat water, but I also know that if you distill wine which has added so2 the heads and early hearts will have plasticy, metallic, harsh, chemical sulfur taint to it. Depending on the tablets and chlorine levels, 4 tablets in 80 gal is something like 70 ppm so2 which is a noticeable amount when distilling wine. 

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I am by no means claiming to be a master or even close in the distilling world so take what I say with a grain of salt..... but I do it a bit different than you.

I start the same - mixing hot water (just use city water but its real good city water) with corn flour with some high temp enzyme. Bring it up to 190 and cook for several hours (adjust PH to 5.5-6).

Then drop temp below 150. Adjust PH (using citric acid) to 4.5-5 and add second enzyme (no rest here).

Continue to crash cool to pitching temp. When I get close I grab a gallon of mash and combine with a few gallons of water (at the right temp -just barely warm)  to re-hydrate my yeast (the bit of mash adds a bit of sugar but not so much as to explode the yeast).

When the yeast bucket forms a good head I knock it back and add it back to my now cooled mash. Goes to zero in three days or so.

I then strip (grain in wash)  in a pot still cleaned the same as you (hot PBW water, Hot water rinse, hot citric acid water, hot water rinse). I strip down to 10% or less at the parrot (with the heads and tails from last likker run). I get a 55+/- gallon drum of 30-35% low wines from 275ish gallons of distillers beer.

Several strip runs later I likker run it.

I do get copper crap and crud if I don't clean the still well enough (I usually rinse while hot with hot water between stripping runs and then clean real thorough before a spirit run)

Good luck

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And stop using sulfur tablets for Christ sake! You need to be clean but can be pretty far from sterile in the distilling world. Ha!

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Like Kelbor says dump the Campden tablets. The sulfur is causing the off flavors. It's also harmful to your yeast. Sanitation isn't as important in the distilling world as you're running it before an infection can cause much trouble. If you keep stuff clean that's all that is needed. This is the hardest point that ex-brewers/vintners have trouble wrapping their heads around. 

If you're only worried about chlorine/chloramine read this: https://homedistiller.org/wiki/index.php/Water_Conditioning

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17 hours ago, JustAndy said:

Just an idea; I know people use metabisulfite tablets to treat water, but I also know that if you distill wine which has added so2 the heads and early hearts will have plasticy, metallic, harsh, chemical sulfur taint to it. Depending on the tablets and chlorine levels, 4 tablets in 80 gal is something like 70 ppm so2 which is a noticeable amount when distilling wine. 

Can you show me how you are getting these numbers? I'm getting something much, much lower (around 3-4 ppm  if none of the metabisulfite is reacted out with any present chloramine). The metabisulfite is also a new addition (read: problem was present before) because I feared chlorophenols but the consensus says to ditch it so I will! I was just going off of Bru'n Water which shows that the small addition of metabisulfite when reacted with chloramine (depending on the level) should leave minute traces of sulfate (8 ppm) which shouldn't affect the flavor.

Thanks everyone for the input! I'll ditch the tablets. The description of SO2 sounds spot on. Is there any way of removing it from a distillate? 

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-Get rid of the meta tabs they're fuckin your mojo and they're cranking up the still. IMO/E thats the core issue with your fault.

 

-I would recommend not cleaning a copper still with true caustic

 

-Flush out all that copper sulphate and keep it out of there. This is going to jeep keep you fault free in the future.

 

-We like to allow our fermentations to start low in temperature (sixties) and naturally regulate themselves (if possible) to complete fermentation.

 

-We've found that allowing ferments to sit a little after fermentation usually makes for a better distillate

 

-We've found specific acidic adjustments can have consequences (sometimes good sometimes bad) in final distillate, so we try to use buffers that all us the least volume addition without negative ester formulation/transformation. 

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Sorry to piggy back on this conversation but can someone shed some light on the pH as you mash and ferment.  We have a similar profile:

Carbon filtered water, heat to 90F, add wheat (90% of mash bill), heat to 165F, drop pH to about 5.8 with citric acid, add HTAlpha rest 90 min

As it cools add barley (10% of mash bill) at about 152F, add a bit more citric to get pH to 5.5, at 140F add Glucoamlyase - let sit for 45 min.

Begin cooling to 80F, transfer to fermenter add yeast (hydrated).

pH drops to 4.5 day 1 and then to 3.5 on day 2.  I don't get great attenuation and my striped distillate has a bitter taste.

Is my carbon filtered water missing something to buffer the pH?

Any help is appreciated.

 

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PH drops through fermentation as a result of acidic by products of fermentation...... this is standard...... what are you actually asking for light to be shed upon because based off your process listed above nothing irregular is happening or at least you haven't pointed it out.....

 

 

REPHRASE

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Is your wheat malted? If not are you using nutrients? That could have something to do with with the low attenuation, but I'm not sure why your Ph would finish so low. Most grains work pretty well as buffers just by themselves. 4.5 after day 1 seems right to me. Does the fermented mash have any lactic acid sourness to it? How long is the ferment active? Where does it finish?

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Sorry - I should have been more clear.  Non malted wheat, no nutrients.

Day 0 pH 5.7 SG 1.070

Day 1 pH 4.5 SG 1.050

Day 2 pH 3.5 SG 1.042

Day 3 pH 3.4 SG 1.038

Day 4 pH 3.5 SG 1.030

I will get down to about 1.010 in another 3 days with pH staying about 3.5 or 3.6

Seems to me at 1.01 I am leaving a fair bit of potential alcohol in the fermenter.  And yes it has very sour flavor by day 3.

I suspect part of the problem is the soft water that does not have sufficient alkalinity (buffer capabilities).  There are a number of websites with data for water profile depending on the type of beer you want to make but I can't find anything in terms of water profiles for distilling vodka.

Thanks again for any help

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On 2/7/2019 at 4:00 PM, bcoutts said:

Begin cooling to 80F, transfer to fermenter add yeast (hydrated).

Do you control temp during fermentation? 

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Id try to pitch nutrient (FAN) in the next batch. I don't think unmalted wheat has enough for a healthy ferment. I would guess the high acidity is coming from the acid being produced by the lacto or whatever infection that is souring your mash. Your yeast still seems to be active at 3.5 though.

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pH is usually never the problem.  It can be a symptom,  but seldom the cause.

I agree with nutrient additions for an entirely raw (non-malt) batch, especially if you aren't using backset.

If your end result is neutral, you might opt to go the route of a small addition of DAP vs. using a fancy organic/amino acid-based nutrient.

Try something like 470g of DAP per 1000l of mash - that will add 100mg/l FAN.  You might be able to pull that back to 235g/1000l.  Hard to estimate since you don't know the starting FAN of the mash.

In addition, if neutral is your goal,  you might want to consider dialing back that starting gravity to 1.055-1.06 and trading a faster fermentation for a higher yield, especially if you are just stripping anyway.  Duration of fermentation isn't linear, once you start pushing near 10%, you risk protracted/long fermentation times.  Protracted/long fermentations emphasize bacterial flavor contributions (positive or negative).  The pH dropping is a sign of this, and means hitting terminal gravity is going to draw out as the lower pH starts to stress yeast.

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Thanks for the advice much appreciated - I've lowered the starting gravity  (1.06)  and will add 470g of DAP - I will let you know how it works.

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