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Classic Lloyd

pH levels during fermentation

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I’m trying to get a sense on how I should be adjusting pH during my rum fermentations.  I currently add acid to a 4.6 pH and this ferments fine, but I’ve read of folks going lower and higher (presumably to encourage or discourage bacterial growth?)

How do you guys adjust your pH in your rum fermentations?

thanks!

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I add citric and calcium carbonate at the beginning to get more buffer, then adjust mid run with cc.  I start about 5.2 and adjust if it drops below 4.0.  

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5.4 and citric to lower to 4.9 here...  which seems counter-intuitive, but works great.  Wheras not 'shocking' the pH downward will result in a stuck fermentation with a pH in the mid 3's in a few days

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I’m also wondering about pH on my 100% mollases wash. My pH came in at 5.74, but would love to be somewhere around 5.2-5.4. I am wanting to make a heavier and estery rum so not necessarily worried about staving off bacterial inoculation. Does anyone have a comparison in flavor profiles from using backset vs. lactic acid to lower their pH? Or is there no flavor difference?

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It seems like I've come across a fair number of anecdotal accounts that suggest that adding lactic acid does affect the end flavors - it being a fatty carboxylic acid and all, but it still seems like some folks are using it. That said, from what I've seen, most folks are using gypsum, citric acid, or sulfuric acid (or some combo of these) along with lime to control pH.

One learning since I posted this. The pH doesn't affect bacterial growth as much as it does yeast growth.  The range you're in encourages a fast, clean fermentation. Lower pH's will ferment slower but seem to produce more flavors (for a number of reasons).

Also, it takes a number of generations for your backset to become very acidic (well, actually just one really acidic batch).  Think about it as a chemical environment that resembles what you're going to ferment in.  Carrying batch to batch helps keep consistency there.  

So, I would definitely think about an acid additive.

Edited by Classic Lloyd
WHOOPS

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Lactic acid is definitely not a fatty acid. That being said it does have a lower sensory threshold so most people don't bother with it. I personally use phosphoric acid for pH adjustments but citric is also common. If you're looking for a heavy, flavorful rum, most people will agree that recycling dunder is the best approach.

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On 2/23/2019 at 8:04 PM, Classic Lloyd said:

It seems like I've come across a fair number of anecdotal accounts that suggest that adding lactic acid does affect the end flavors - it being a fatty carboxylic acid and all, but it still seems like some folks are using it. That said, from what I've seen, most folks are using gypsum, citric acid, or sulfuric acid (or some combo of these) along with lime to control pH.

One learning since I posted this. The pH doesn't affect bacterial growth as much as it does yeast growth.  The range you're in encourages a fast, clean fermentation. Lower pH's will ferment slower but seem to produce more flavors (for a number of reasons).

Also, it takes a number of generations for your backset to become very acidic (well, actually just one really acidic batch).  Think about it as a chemical environment that resembles what you're going to ferment in.  Carrying batch to batch helps keep consistency there.  

So, I would definitely think about an acid additive.

It's a good insight that lactic acid (and other carboxylic acids) are prone to esterification and so will most certainly affect the flavor of distillates. In rum, this is not always a bad thing. In fact, it's one of the reasons dunder and backset are often used - to coax greater esterification of bacterially produced carboxylic acids. 

 

Our experience is that you CAN have too much of a good thing with this. Butyric acid in very small quantities results in a delicious pineapple note. Too much of it and the vomit smell will never dissipate. So the takeaway is to be careful about using carboxylic acids to adjust fermentation pH. 

All that being said, I typically do not adjust the pH of our fermentations. They usually start at around 5.0 and finish at 3.8. If it drops too fast, I will sometimes adjust up with calcium carbonate, but I have never needed to adjust the pH down. 

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I have never had to adjust down as molasses doesn't have any natural buffer and will crash within 2 days if you don't catch it. I usually dose Calcium Carbonate at 12 and 24 hours to hold at 4.0 then it finishes at 3.8 in 72 hours. My school of thought is the lower the pH the more the flavors of the substrate carry through into the distillate and the opposite is true of high 5.0 to 5.5 pH.

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On 2/14/2019 at 10:27 AM, clearwaterbrewer said:

5.4 and citric to lower to 4.9 here...  which seems counter-intuitive, but works great.  Wheras not 'shocking' the pH downward will result in a stuck fermentation with a pH in the mid 3's in a few days

Welp, I wish I knew this before it happened to me.  Did pH adjustment (I assume with Calcium Carbonate) and re-pitching yeast work to get them started again?

First time post for me.  Appreciate all the valuable help by all you out there.

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13 hours ago, 1911 est Distillery said:

Did pH adjustment (I assume with Calcium Carbonate) and re-pitching yeast work to get them started again?

Yes it should start again. As long as the low ph was truly the reason it stalled, not a lack of yeast nutrient or something else, and as long as you haven't produced enough alcohol already that new yeast cells will be shocked when you pitch them. Maybe rehydrate them first if you're over 4% alcohol or so.

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Quote

Does anyone have a comparison in flavor profiles from using backset vs. lactic acid to lower their pH?

Very very very different.

Backset is doing much more than just adding acidity - it's adding nutrients, carboxylic acids, heavy alcohols, buffer capacity, etc etc.  Typically, backset creates a more robust, complex, rich flavor profile in rum compared to simple acid adjustment.

Quote

  I currently add acid to a 4.6 pH and this ferments fine, but I’ve read of folks going lower and higher (presumably to encourage or discourage bacterial growth?)

Adding acid to bring the starting pH to around 5.2 is typically enough to give yeast a head start over bacteria and prevent a pH crash.

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I haven't been using backset, but I think I need to start playing around with it. I distill on the grain, and I've been thinking of simple ways to separate grains from the liquid post distillation, but then I thought what if I just used "backset" from my low wines after the spirit run? It would probably have less nutrients in it from dead yeast cells, but, possibly more of of the other things Silk mentioned.

1 hour ago, Silk City Distillers said:

Backset is doing much more than just adding acidity - it's adding nutrients, carboxylic acids, heavy alcohols, buffer capacity, etc etc

Has anyone tried using backset from a spirit run instead of a stripping run? I'd love to know what you think @Silk City Distillers you seem to be an authority on backset, among other things.

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Nah, you would use the backset/dunder from the strip runs, not the spirit run.

Make sure you run your strip run down low so you aren't leaving a lot of alcohol left in the boiler or you'll be starting your fermentation off with alcohol present which depending on your potential ABV % could be problematic at the upper range.

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I know that is how it is done traditionally, just wondering if it would work the other way, and if not, why. I might try both ways, after checking the ph of each, for kicks. Unfortunately I'm done with whiskey production for another 7 months or so.

I strip pretty low, and keep my SG reasonable, so a little extra alchohol should be ok. Good tip though, thanks.

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Think about it this way.  You do a strip run to pull the alcohol from the mash.  This leaves behind a lot of flavor in the boiler.  Now when you do a spirit run what is left is mostly water.

So besides trying to lower pH you want to try and add some flavor back correct?  That will be in the backset from the strip run, not spirit run which is probably really foul tasting water. :)

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@DrDistillation Makes sense. Guess it is kind of a stupid idea the more I think about it. I think I should be playing around with backset more though.

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When adding backset into a new wash, how much is typical to use?  What percentage volume?

Thanks!

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