Lighter Malts and RO mash pH

[thirdeyeo4]

I use RO water and build my water profiles. I typically only add the light malts to mash in and then sparge with the darker malts. Now I understand that the mash pH is what matters and not the water pH, however I checked my RO water's pH and it's around 5.95. After adding the lighter malts like Pils or Maris Otter my mash pH drops to around 5.3 which is a bit lower than I'd like to hit, which is around 5.5. I typically only add gypsum and calcium chloride to my water when possible, so when mashing in I don't add anything at all because these would pull the mash pH down further, so I add these to the boil. I'm guessing the drop is because the RO has no buffering capacity at all. To counter the drop I've been using some lime which I'd rather not have to do. Is this typical to drop so much using RO water and lighter malts? Also I've calibrated my pH meter just before taking measurements. Thanks for your help/input.

 

[mchrispen]

Using RO, I only need to add alkalinity to the mash when I have used a lot of hardness minerals - usually for a pale ale or IPA - or am brewing a beer with a large portion of roast or crystal malts. I find that pickling lime has very little flavor contribution - and I am not that happy using baking soda because of the sodium contribution.

I am curious about your desire to hit 5.5? Many people target 5.4, which drops you into the middle of the 5.2-5.6 range.

You are dropping your boil pH further by using minerals in the boil - so keep that in mind, it will effect hop utilization. I cannot find any charts to indicate the specific impact.

 

[thirdeyeo4]

Ive heard the difference in room temp pH and mash pH is about .3, so I was shooting for 5.5 to get to 5.2 mash pH. Also in order to keep the boil pH correct it sounds as if I just need to add all salts to the mash and get the correct pH there to carry through to the boil.

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[Yooper]

Ive heard the difference in room temp pH and mash pH is about .3, so I was shooting for 5.5 to get to 5.2 mash pH. Also in order to keep the boil pH correct it sounds as if I just need to add all salts to the mash and get the correct pH there to carry through to the boil.

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but with a pH meter, you have to cool the wort to room temperature to take the reading, so we're always talking about room temperature mash pH and never mash temperature pH. So no reduction is needed.

I usually like the results of having a mash pH of 5.4-5.5 (again, measurement taken at room temperature) for pale ales and lighter beers- the flavor seems "bright" without being tart.

 

[thirdeyeo4]

My room temp pH has been 5.2-5.3 adding only the light malts like Pilsner or Maris Otter to RO without salts being added, is this normal? If not what could be the cause? Thanks again

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[mchrispen]

I don't see how that is possible without acid or a lot of minerals. 20# of Munich 4L in a 10 gallon DI mash should come in between 5.7-5.8 room temp mash pH. I am guessing it would take nearly 7 ml of 88% lactic acid to drive that mash pH so low... or roughly 13 ounces of sauermaltz.

 

[ajdelange]

My room temp pH has been 5.2-5.3 adding only the light malts like Pilsner or Maris Otter to RO without salts being added, is this normal?

No, not normal at all. The Pilsner malt, mashed in RO water, should give a pH, referred to room temperature, of 5.6 - 5.8 depending on the malt. Maris Otter should come in close to 5.6. Something is very wrong if you are seeing 5.2 - 5.3 for these malts. The first suspect is always the pH meter but you say you are calibrating that before readings. How about a post reading cal check? What does the meter read in pH 4 buffer after you have completed your readings on the mash?

If not what could be the cause?

Those malts just don't carry that much acid. Bad pH reading is really the only reasonable explanation as others, such as someone dumped in some lactic acid when you had your back turned, don't seem very likely.

 

[thirdeyeo4]

Thanks for the replies. I suspected my pH meter is on the way out but wanted to see if there could be any other culprits for the mash being so low before making another purchase.