Rye and wheat malt effect on pH?

I rarely (read, almost never!) make rye or wheat beers. But when I do, especially with rye malt, what can I expect to happen to the pH, assuming the rest of the grist is the same? Say, using 20% rye malt in a pale ale (by lowering the US two-row)?

Some sources have said there is no effect, while some other sources I've read say it can definitely raise the pH. I'm wondering what to expect when making my next beer, which I think will include +/- 20% rye malt.

AFAIK it is the level of kilning or roasting that mainly determines a grain's contribution to mash pH and by inference which brewing water profile is desired. As long as your water has a decent Calcium, Ca+, content I don't thing it is anything to worry about. If you normally add brewing salts, Calcium chloride or Calcium sulphate could be used depending on the style and hop profile of the beer.

BigEd said:

AFAIK it is the level of kilning or roasting that mainly determines a grain's contribution to mash pH and be inference which brewing water profile is desired.

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That was my understanding as well. It seems like Weyermann's rye malt has a slightly higher lovibond than Briess 2-row, but I was just unsure if it really is simply kilning that impacts the pH.

Lorena,

You have the pH meter. Let us know what you find. I'd like more definitive information that suggests that those malts act differently from a barley malt of similar color.

mabrungard said:

Lorena,

You have the pH meter. Let us know what you find. I'd like more definitive information that suggests that those malts act differently from a barley malt of similar color.

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Will do! I think I'm going to brew on Tuesday or Wednesday and I'll post the grist, the water, and the resulting pH. The thing is, this one is a kitchen sink beer so I doubt I'd be able to recreate it again. So I may simply do a couple of tests mashes, one with the rye and one without, to see the actual pH readings.

I just brewed an american rye with 20% rye. I put the rye in the EZ-water spreadsheet as regular base 2 row. My estimated ph was 5.53 and my actual ph was 5.51. So my conclusion was that the rye acts almost the same as the base 2 row. Hopes this helps.

I apparently measured a wheat malt some years back and found it to have a DI water pH of 5.67 and a buffering capacity of 14.4 mEq/pH-kg. We all know what the variance associated with a sample size of 1 is but this single data point suggest wheat is slightly acidic but with low buffering capacity (relative to other malts). No idea whether that would be the case with rye or not.

ajdelange said:

I apparently measured a wheat malt some years back and found it to have a DI water pH of 5.67 and a buffering capacity of 14.4 mEq/pH-kg. We all know what the variance associated with a sample size of 1 is but this single data point suggest wheat is slightly acidic but with low buffering capacity (relative to other malts). No idea whether that would be the case with rye or not.

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If you don't mind, what are the buffering capacities of, for example, American 2-row (pale malt) and Weyermann Pilsner? I've only seen data about DI water pH's.

I'm afraid I don't know. I expect they are somewhat higher (around 25 mEq/kg-pH which is what I measured on DWC Pils at the same time I did the wheat measurement) but accurately measuring this is an arduous task requiring a good buret, standardized acids/bases, an accurate scale and pH meter, water bath and lots and lots of time. The reason for this is that the reactions are slow so that one cannot do a titration in the usual way (add acid, measure pH, repeat) but must, rather take a fresh sample for each pH measurement. After all that work one has numbers for a single sample of a single type of malt from a single lot from a single crop from one maltster. Stepping back from the trees far enough to see the forest I conclude that if it were possible to obtain this data with a reasonable amount of effort the maltsters would do the measurements and give them to us as it is clearly useful data.

A few years back I wrote a Zymurgy article for which I did additional testing of base malt DI pH and base malt buffer capacity. A.J. has a point in that the malt’s buffer capacity is also affected by the pH of the mash. However, I simplified things and mashed the malt with DI water, cooled the mashes to 25 C and then titrated them with HCl and NaOH. I still think that the results are valid enough, especially since our biggest error is not coming from measurement errors but from batch to batch variability of the malt. I found only a loose correlation between base malt color and DI pH. This makes it inherently difficult to predict mash pH based on the color, though I did my best developing such a formula.

There was an interesting and fairly strong correlation between base malt DI pH and its buffer capacity. The higher the DI pH, the lower its buffer capacity. The change in buffer capacity was not large enough that I think it needs to be considered in the mash pH estimation, though.

I don’t have the data with me, but try to remember to dig this out tonight.

Kai

Kaiser said:

A.J. has a point in that the malt’s buffer capacity is also affected by the pH of the mash.

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I wasn't particularly trying to make that point. Buffer capacity and pH are intimately related but it also depends on how much of which buffers are present. Malt contains I'd guess dozens of acid/base pairs with phosphoric/mononbasic phosphate and monobasic phosphate/dibasic phosphate most likely the predominant ones but as at mash pH one is about halfway between the pK's of those two their buffering is minimal so it may well be some other pair or the combined effect of several pairs that are responsible for observed DI pH.

Kaiser said:

There was an interesting and fairly strong correlation between base malt DI pH and its buffer capacity. The higher the DI pH, the lower its buffer capacity.

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That's interesting because it implies that one is moving away from a pK at higher DI mash pH when one is in fact moving closer to the 7.2 pK of the phosphate system thus implying that it is other systems that are mostly responsible.[/QUOTE]

Kaiser said:

The change in buffer capacity was not large enough that I think it needs to be considered in the mash pH estimation, though.

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In my limited experiments I found values from 14 - 35 mEq/kg-pH but as noted earlier don't place a lot of confidence in those measurements. Also I noted that some malts had buffering linear over pH and some didn't but I'm not sure the observed non linearity was real i.e. it might have been drift in pH caused by slow reaction times.

Yooper said:

Will do! I think I'm going to brew on Tuesday or Wednesday and I'll post the grist, the water, and the resulting pH. The thing is, this one is a kitchen sink beer so I doubt I'd be able to recreate it again. So I may simply do a couple of tests mashes, one with the rye and one without, to see the actual pH readings.

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Did you ever do this? I'm also wanting to know if rye is much different to 2-row!