Ask The Brewmasters

Im new to this forum, hello all!

     I am looking more closely at our process of mash acidification and was curious about what method we should be using to dose our phosphoric acid. Here's some background. I work on a 30bbl brewhouse and typically we do a single infusion mash at a roughly 2.5 l/kg water/grist ratio. Mash in takes about 20 min and then theres a 40 minute rest before its moved to another vessel for vorlauf/lauter.
     We treat our incoming brewing liquor with phosphoric acid in the cold liquor tank, though the ph of the incoming water from the city is often quite variable, so post treatment it ranges from 5.6-6.6 ph. To compensate for the variability we will an add additional 200-600ml phosphoric acid at the mash stage to target a mash ph in the 5.2-5.4 range.
     My question, is what sort of method seems best for adding this additional acid to the mash process. Should we add it all to the foundation water before mash in? Should we add it at the halfway mark? or should we be staggering the acid addition? There seems to be multiple schools of thought on this among my coworkers. Curious to know your thoughts on this, thanks!

------------------------------
Austin Clem
Duluth MN
------------------------------

-Note: I should also add that Calcium Sulfate and calcium chloride are being added about one third of the way into the mash.

------------------------------
Austin Clem
Castle Danger Brewery
Duluth MN
------------------------------

Hello Austin,

This is a topic we have given considerable thought to at our brewery as well. I am working on a 7bbl brewhouse, single infusion mashing. I also do not have rakes, nor do I stir with a paddle to avoid disturbing the grain bed. 

We use 88% lactic acid and begin by determining the mash acid we require, then blend with water from our CLT in a 1 gallon pitcher (add acid to water). After the foundation water is in the mash tun, I pour in about half of that gallon of that acid/water mixture into the foundation water. Then, as the dough in continues, I continuously add acid to the area of the grain bed directly beneath the water blending assembly where the crushed grain and strike water is falling into the mash tun. I add the acid/water mixture with a large dropper throughout the dough in process. This approach is largely unique to my system and the fact that it is a highly manual operation. This typically results in a mash pH within 0.05 of the calculated value, or otherwise "good enough for government work" as far as we are concerned.

Another important mention is that I time all of this so that all of the grain is in the mash tun with about 20-30 gallons of additional strike water to spare. Our target liquor to grist ratio is in the 3.5:1 range (fairly thin). The majority of that remaining strike water is added via underletting or directly from the bottom of the mash tun. This is highly individual, and is what I have found that works on my system.

This being said, I have also brewed with a brewery that measures their acid in a flask and dumps all of it into the foundation water and never thinks twice about it. That brewery has mash rakes, FWIW. I do still prefer my approach, as it gives me a little better control in my situation.

Whatever approach you take, do your best to ensure consistency and homogenization to the greatest extent possible, while also ensuring you are forming a uniform and stable grain bed that will filter wort well during lauter.

Hope that helps!

------------------------------
Travis Kocurek
Brewer/Owner
Hound Song Brewing Co.
Columbus, TX
979-942-7199
------------------------------

Original Message:
Sent: 06-26-2024 04:29
From: Austin Clem
Subject: Mash Acidification

-Note: I should also add that Calcium Sulfate and calcium chloride are being added about one third of the way into the mash.

------------------------------
Austin Clem
Castle Danger Brewery
Duluth MN
------------------------------

Strike water pH is not important. What is important is its alkalinity. Your total acid addition should be enough to neutralize the alkalinity. The ideal procedure would be to add all of the required acid to the CWT (or HLT), heat it up and mash in with it. Adding acid after the grain mases for a while is not optimal. You did not mention how much PA you add to the CLT, nor do you mention your mash-in volume. For 85% PA, the density is 1.71 g/cm%. 800 mL comes to 1163 g PA = 12 mol. If each mole of PA can neutralize 0.5 mole of CaCO3, (50 g) the 800 mL addition is enough to neutralize 600 g of CaCO3 worth of alkalinity. If your strike water volume is 30 bbl = 3520 L, If the 600g x 1000 mg/g = 6 x 10^5 mg of alkalinity (as CaCO3) is distributed in 3520 L, you have enough to neutralize 170 mg/L alkalinity as CaCO3.
I suggest that you ignore strike water pH and concentrate on alkalinity. If the alkalinity of the incoming water is varying by a lot, you will need to test it for each batch. You can have low alkalinity water with high pH. The key thing to watch for is pH right after mash-in. Set your water alkalinity target to give you the desired pH after mash-in.

Roger Barth, PhD
Professor Emeritus of Chemistry
West Chester University
rbarth@wcupa.edu

Author of
The Chemistry of Beer, The Science in the Suds, Second Edition. ISBN 978-1-119-78333-0
Mastering Brewing Science: Quality and Production. ISBN 978-1-119-45605-6.

________________________________

This e-mail message was sent from a retired or emeritus status employee of West Chester University.

Austin, I would suggest getting some chemistry reporting on your water. There are some labs out there that you can send samples to for a low investment and you could do this over a period of time to develop enough data to create a more consistent approach.  If your water is this variable you may want to get some in house test kits or benchtop instruments to be able to test your water's alkalinity before you acidify so that you don't have to top up with acid.  We use an inline dosing pump to add our acid additions which makes sure that we can have pretty consistent pH throughout our strike and Sparge water additions.  

------------------------------
Landon Swanson
Head Brewer
Pueblo Vida Brewing
Tucson AZ
------------------------------