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junglejimmy

Filtered Water for grain mash

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So we recently got a band new reverse osmosis filter system that we use to dilute our vodka. I wanted to try an experiment using the filtered water in the mash, but I have come across a problem that has got me stumped. That is, the pH of the resulting mash is extremely low during fermentation.

We usually use spring water for our mash that is very basic (8.5pH). We add citric acid to our mash to it down to about 6.0pH. The filtered water has a starting pH of 6.6, so very little citric acid is needed to bring it down. However, about 2 days into the fermentation I measured the pH and it was 3.2pH. That seems very low to me. Can anyone please tell me what they think is going on with the chemistry.

Some things to note:

  • Mash consists of half white winter wheat, with half sugar
  • enzymes have been added to the wheat to extract the sugar
  • the temperature here is quite high 33C (91F) in the daytime
  • Im using a pH pen with auto temperature compensation to mesure the pH

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Hey Jimmy,

I think it might have something to do with RO removing salts from the water. So unless you compensated for that, you removed the natural buffer system in average (unfiltered) water. This would allow the acidification of the mash to continue to much lower levels than normally seen because nothing is slowing down the process.

http://byo.com/malt/item/1675-advanced-brewing

More info about buffer systems in the link above.

You would need to re-add salts to the mash or water to prevent this from happening again.

Cheers!

CDE

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CDE is correct, RO is a poor choice for mash, unless your natural salts are bad (iron for example). You need to add back the buffering salts, or the pH will be all over the place. If your local water has a reasonable mineral content, you might just particle and carbon filter it instead.

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Ah ok. That puts an emd to that little experiment. I know the mash environment needs to be acidic for the yeast. Disnt realise it needed a pH buffer.

So then my next question would be, what is the ideal final pH for a wheat based vodka?

I've read that the ideal final pH for wheat beers is in the high 3's or low 4's. Is that what I should be aiming for?

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Hey Jimmy,

A better question is "What is the ideal pH for my initial yeast inoculation/pitch?" And/or "What is the ideal pH for whatever enzymes I am using to ensure I get a good conversion of starch to sugar?"

Yeast (generally) enjoys being in the range of pH = 4-5 at the start, and then the mash acidifies as ethanol is produced and other products that acidify the mash over the course of the fermentation. It is not uncommon for a mash to drop from 4.5 to about 3.5 at the end of fermentation. This doesn't need to be corrected for typically, just start the yeast in the right pH range and they will do the rest (provided temp and nutrients are sufficient).

Enzymes is a whole nother topic and details will vary based on enzyme source, I'll spare the details as there are other threads or websites that have good information about enzymes.

Final pH is good information to have, but it should not be terribly important to your actual procedures. Instead final pH gives you an indication if something has changed. For instance if your mash was infected, your pH would keep dropping due to a sour bacteria or the like.

Cheers!

CDE

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