Mash ph - AMS/CRS addition advice

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M3Brewery
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Mash ph - AMS/CRS addition advice

Post by M3Brewery » Mon Aug 05, 2019 1:04 pm

Hello Everyone,

We're having problems with mash ph when brewing all grain bitters and IPA style beers. The last three brews had a mash ph of 4.2, using ph test strips. The test strips were checked with tap water for reference and came out at 7ph.
We have added AMS/CRS as recommended by the Murphy's water report. We have hard water (South East Water - Blackhill supply zone).
Typically we brew 90 litres in solid steel equipment, HLT, Mash Tun and Boiler.

The HLT will be filled 24 hours before a brew day, and the AMS/CRS will be added on the morning of a brew, jut before we heat the liquor.
We do not use campden tablets or any other treatments in the liqour.

End result is the beers have a slightly acidic tang (this is after a couple of weeks conditioning in Corni kegs).

Is there a recommended process for adding the AMS/CRS, e.g. 1 hour before heating the liqour, 24 hours before heating the liquor?

Thanks

M3

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Re: Mash ph - AMS/CRS addition advice

Post by guypettigrew » Mon Aug 05, 2019 2:25 pm

It might be worth you investing in a pH mater as a first step. One like this, perhaps?

Your paper strips may be telling the truth, or they may not!

Not sure if a low pH mash gives an acidic tang. Others may be able to advise on this.

A low pH mash suggests extremely low alkalinity liquor for the mash. What's your starting alkalinity and how much CRS/AMS do you add to how much water in your HLT?

My method (for what it's worth) is to add the CRS to the water the day before brewing, then have the HLT on a timer so it's at 83°C by the time I get up on brewday.

I run about 60 litres of hard tap water in the HLT, alkalinity 204ppm, to which I add 45ml of CRS to drop the alkalinity. Then it's tested with a Salifert kit and more CRS is added if necessary to get it to where I want it. Which, for the very light hoppy bitter at about 5.5% abv I'll be brewing tomorrow, will be 15-20ppm.

Hope this helps.

Guy

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Eric
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Re: Mash ph - AMS/CRS addition advice

Post by Eric » Mon Aug 05, 2019 3:58 pm

What Guy said.

I can't say how much extra acid would be needed to get a mash pH of 4.2, but without a lot of dark malts it wouldn't be a minor amount.

How does Murphy's analysis compare with the mean values provided by your water supply company?

What value of pH do your strips give for your finished beer? Similarly, what value of pH do they find for your water after it is treated with CRS/AMS as advised by Murphy? Roughly speaking, water treated for beers such as IPA and Bitters should be around pH 5 and a bit with such beers being pH 4.0 plus or minus not a lot.

All such beers should be acidic, but not to the point of tasting tart.

You wouldn't be the first to suffer at the hands of an analysis by Murphy, but what you report is quite extreme.

You need a Salifert Carbonate Hardness (KH) kit that you might measure alkalinity after treatment to see if it is in line with Murphy's advice.
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Re: Mash ph - AMS/CRS addition advice

Post by Robwalkeragain » Mon Aug 05, 2019 5:57 pm

That’s exactly the process i use and no acidic twang here. The best advice i can give you is to measure pH of liquor, mash, pre boil, post boil and post ferment and see if the drop is gradual (which it should be). The obvious easy solution is to dial back your AMS, if it’s over acidifying it’s not doing its job!

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Re: Mash ph - AMS/CRS addition advice

Post by M3Brewery » Mon Aug 05, 2019 8:47 pm

The alkalinity from the water board report was reported as 220ppm. This was from December 2018.
Therefore we added 93ml of AMS/CRS into 100 litres of tap water, then commenced heating to 76'C.

We also tested the tap water using a Salifert kit for cross reference with the water report, this was after the mash had started. Salifert result was 166ppm alkalinity.

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Re: Mash ph - AMS/CRS addition advice

Post by M3Brewery » Mon Aug 05, 2019 8:48 pm

Will measure the ph in the fermentation vessel. What should we expect the ph to be there?

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Re: Mash ph - AMS/CRS addition advice

Post by guypettigrew » Mon Aug 05, 2019 9:09 pm

Thanks for the additional info.

Your CRS addition would seem to be about right. Should have reduced your alkalinity to about 45ppm. Bizarrely, this is higher than you'd want for most bitters and IPA style beers!

So, two thoughts.

Firstly,Your pH papers may be telling porkies. A meter would be really useful. Run some wort from the mash after about 15 minutes, calibrate the meter and test the pH. Bet it's higher than 4.2! But it seems increasingly unlikely your taste issue is due to pH problems in the mash.

Secondly, the taste you describe is possibly due to over sparging, but more likely due to a low level infection. This can be a PITA to sort out. When it happened with my small scale home brew set up I eventually tracked it down to the fermentation not starting quickly enough. This was, annoyingly, after stripping everything down and sanitising it! I used to pitch harvested liquid yeast from the warmed up harvest container. Now I use starters the problem has gone away.

My guess, though, is you'll be using dried yeast.

How long is it between pitching and seeing fermentation start? Despite what I read on here and other places I reckon anything over 12 hours is a cause for concern. I expect to see signs of active fermentation (bubbles through the blow off tube) within 5-7 hours.

Guy

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Re: Mash ph - AMS/CRS addition advice

Post by Eric » Mon Aug 05, 2019 9:43 pm

Still with Guy on this and doubt that the problem you have is due to a mash pH of 4.2. That said we can't discount what you measured until it can be confirmed to be incorrect and if the alkalinity is as you measured, 166ppm but you are treating it as if it was 220, you would get a low mash pH.
Water untreated can be anywhere between pH 6 and pH 8 or beyond and is not important.
Water treated for mashing pale beers will be close to pH 5
Wort in kettle before boil should be pH 5 to pH 5.3, weak beers can be a bit higher. After boiling wort will be 0.2 pH units lower.
Ales after fermentation will be pH 3.7 to 4.2.

I give these figures to compare with your strip measurements.
Without patience, life becomes difficult and the sooner it's finished, the better.

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