pH & Finished Beer

[Mardoo]

Hi folks,

I've started paying attention to the finished pH of my beers, more as a learning exercise than anything else. However, I do understand that it can have a relative effect on flavour and bitterness perception. I'm interested in hearing things folks have learned by paying attention to the final pH of their beers.

I also have a process question which I have yet to find an answer to. Should the beer be carbonated before reading post-ferment pH? It seems like the amount of dissolved carbonic acid would affect final pH, and therefore the final pH should be tested once and while the beer is at its final level of carbonation.

 

[Lyrebird_Cycles]

Whilst laboratory practice is to degas samples*, residual CO2 has very little effect on the pH of finished beer because beer pH is very close to the apparent pKa of dissolved carbonate.

Final pH has an effect on flavour balance: when testing this (over twenty five years ago) I found a difference of 0.05 unit was perceptible and 0.1 was obvious.

If you correct the final pH (as I sometimes do for dry hopped beers where the pH can rise**) the type of acid used also makes a difference: I recently split a batch and did half with lactic and the other half with sulphuric and I strongly prefer the one with added sulphuric.

* Easily achieved by pouring the beer from one beaker to another and back again about 10 times. An ultrasonic bath also works well but the beer can gush and then you have to clean the bath.

** I believe this is likely to be due to potassium in the hops.Most plants preferentially uptake potassium

 

[n87]

Residual CO2 has very little effecton the pH of finished beer. If you want to measure total organic acids you'll need to degas, but generally not for pH.

Final pH has an effect on flavour balance: a difference of 0.05 unit is perceptible, 0.1 is obvious. If you correct the final pH (as I sometimes do for dry hopped beers where the pH can rise*) the type of acid used also makes a difference: I recently split a batch and did half with lactic and the other half with sulphuric and I strongly prefer the one with added sulphuric.

* I believe this is likely to be due to potassium in the hops.Most plants preferentially uptake potassium

I am curious on the differences that... say 0.1 unit can make.
Do different (not infected ) beers favour different acidity?

 

[rude]

Good post I'll be reading with interest Mardoo
I think the Brewdog recipes on some of them had a final PH reading
was around 4.6 I think without checking
With darker beers Brun suggests a higher mash PH so does it finish higher as well ?

 

[Lyrebird_Cycles]

I am curious on the differences that... say 0.1 unit can make.

When I set this up it was with a very large volume selling bog standard Australian beer... think green cans.

One brewery in the group consistently ended up with lower final pH from the use of sugar syrup as an adjunct instead of glucose syrup. The corrective action was to dose potassium carbonate in the filter room.

We set up a tasting trial of different dosing rates (and thus pHs). It was a long time ago but I remember being able to pick up the differences mentioned. Lower pHs tightened up the palate structure and made the beer seem thinner, higher pHs tended towards soapiness. Large additions of carbonate gave a burnt effect on the palate but I believe that is due to the mixing of the carbonate into the beer, not the pH as such.

Do different (not infected ) beers favour different acidity?

I believe so but I don't have the data on beer to back that up.

I know it's the case with wine: of the ones I bottled last week, the whites (a pig, a sab and a fiano) all had pHs around 3.25, the red (a tempranillo / graciano blend) had a pH of 3.55. If you reversed these the red would look thin and harsh and the whites would look flabby and tired.

 

[wide eyed and legless]

Gordon Strong's take on this taken from the American Homebrewers Association site.

I did some research and experimentation with this last summer while working on my book. I think the desired target range is 4.1 to 4.5, with the tradeoff being between flavor and stability. The higher the pH, the better the flavor. The lower the pH, the better the (microbial) stability. Above 4.5, you start to get into food safety issues (i.e., stuff can grow in it). Lowering the pH does make the beer seem thinner, and eventually starts getting tart. I only used phosphoric acid (it's an ingredient in soft drinks as a flavor enhancer).

When the pH of beer is above 4.6 or so, it does have a bland taste, sort of like underseasoned (undersalted) food. Adding phosphoric acid did improve the flavor, to a point. Like salting food, there is an optimal point and it's somewhat subjective. Going too far means you start tasting the flavor enhancer and not the enhanced flavor. The flavor impact was different based on the serving temperature as well. Measuring at room temperature and then tasting at the colder serving temperature can result in over-adjusted beer. The desired final pH is also affected by the flavor profile (beer style) of the subject beer; there isn't one magic pH where all beers taste best.

I did find that finished beer did buffer pH change quite a bit. Certainly more so than RO water. Another way of illustrating that adding acids to adjust pH is not something with an easy linear formula. You have to add and test carefully, at least until you've neutralized the buffer and start moving the pH.

 

[TheWiggman]

Very interesting LC, glad to have your input.

... would look thin and harsh and the whites would look flabby and tired.

I'll add these adjectives to my tasting vocabulary.

 

[MHB]

Mucking about with some Potassium Hydrogen Carbonate (Pot-BiCarb) and Cider.
The Cider was twangy and thin with a very noticeable acidity, as it was adjusted up to around 4.2pH, it totally changed, even the apple flavor came all the way to the front after being almost totally invisible in the start cider.
The difference is very pronounced.
Mark

 

[Mardoo]

Fascinating stuff guys! Totally stoked I asked.

 

[Mardoo]

Here's something I downloaded for free last year from the MBAA website (so I assume it's public domain), a paper by Charlie Bamforth that's an overview of pH in brewing. I had forgotten I had this and started digging around in my computer this afternoon and found it. This specific excerpt is about beer final pH, but there is a lot more to the paper that will be of interest. I'll attach it below:

BEER

As beer pH decreases over the typical range from 4.5 to 3.9 there is:

ï increased resistance to microbial spoilage
ï increased colloidal stability (for reasons not fully understood) ï increased foam stability (for reasons not fully understood, [42]) ï decreased flavor stability
ï (possibly) decreased palate smoothness and drinkability

Brenner et al. [7] say pH affects the quality of bitterness. Rigby [48] claims that bitterness is harsher at higher pH values. However Simpson et al. [52] found no impact of pH on the flavor threshold of isohumulone.

Simpson[50]showed that the antimicrobial activity of hop bitter compounds is much greater when they are in their uncharged forms, at low pH, pKa values for the iso-α-acids are of the order of 3.

Grigsby et al [20,21] demonstrated that the tendency of beer to oxidize is less at higher pHís. Nordlov and Winell [44] suggest that this can be explained in terms of the impact of pH on the dissociation constant for the adducts formed between staling carbonyl compounds and sulfur dioxide, but Kaneda et al. [29] invoke the role of pH in protonating the superoxide radical to form the much more damaging perhydroxyl species. The pKa for this interconversion is 4.88.

Pellaud et al 45] observe that at a given temperature the major parameter influencing the precipitation of oxalate is pH: at pH 4.5 as compared to 4.0 there is a far greater opportunity for cal- cium to precipitate oxalic acid.

Taylor [57] looked at the impact of pH on flavor by altering pH through addition of acids. At low pH (< 4) beers became more sharp, with an increased drying character in the after-taste and an increased perceived bitterness. At pHís < 3.7, there was a metallic after-palate, while especially at pH > 4.4, soapy and caustic notes were reported. Higher pHís were accompanied by comments about mouthcoating, biscuit and toasted.

Siebert [49] highlights that it is not simply a role for organic acids as a supplier of H+ that causes their sourness impact, but that structural features of these molecules also determine their flavor threshold.

 

[Jrrj]

Great thread Mardoo! I've been meaning to raise this topic for months. For me the issue is taste - I find I just love lower-pH balanced foods and drinks.

Ever since I read Gordon Strong's thoughts on the subject in Brewing Better Beer, I've been interested. Testing my beers I've found finished pH (pre-carbonation) consistently higher than the supposed ideal levels - typically around 4.4-4.5 and never below 4.35 (using a just-calibrated Hanna Halo to test each time).

I also tested a degasses sample of S&W Pacific Ale, which is the summer beer I want to get close to. From memory (I've lost my records) it was close to pH 4.0 - so a lot lower than my attempts.

I'm hoping that nailing finished-beer pH adjustment with phosphoric (as suggested by Strong) will finally reproduce that sharpness of a cold S&W PA downed in the heat of summer.

Using 85% phosphoric acid seems to require a fair bit of precision and effort though - repeatedly diluting a solution with a 0.02ml pipette before anything can be added to a small beer sample for taste testing. Once I get around to this I'll post about the experience here.

 

[Mardoo]

This has really got me thinking about the effects of recipe and process on final pH. Hmmmm...

 

[Jrrj]

So I just did some testing on my current batch in the fermenter. It has fully attenuated (1.007 gravity) but the pH has only come down to 4.71, so definitely a candidate to experiment with phosphoric acid pH adjustment.

To your point about process and recipe - for this beer I didn't bother with any acid or salt additions to the hot liquor (Melbourne West tap water), and used only wheat and ale malt. Unsurprisingly the pH was high at every stage of the brewing process (mash pH was 5.7).

When I made a Belgian Witbier with similar grain bill earlier this year I adjusted the hot liquor to 6.2 pH with phosphoric acid, and added some gypsum and calcium chloride, which ended up with 5.4 mash pH and 4.35 finished beer pH.

Based on those two experiences I don't think I'll skip the acid and salts next time!

 

[manticle]

I've never measured finished beer pH but my understanding has always been that getting mash, sparge and boil pH correct should result in expected finished beer pH.

Interesting topic, worth reading more about.

 

[Jrrj]

Yesterday I tested another S&W Pacific Ale bottle and got pH 4.15 +- 0.02 at about 15 degrees (completely degassed). (And 1.009 FG in case anyone ever wondered).

So taking that as my benchmark, the plan is to modify samples of my current brew to a range of different pH levels (say 4.1 to 4.5 in 0.1 increments), chill then taste to see what I notice.

Obviously this is not going to be blind, or in any way scientific, but it should at least give me a subjective guess at how much I need to worry about final pH (since I consume most of my beer myself).

 

[mtb]

This is a VERY useful thread - especially given the ongoing discussion about whether or not water chemistry is worth looking into.
Recently bit the bullet and bought a pH meter, and found that my finished beer is consistently around 4.6; no lower than 4.5, at least.

@Lyrebird_Cycles you mentioned sulfuric was preferred over lactic to reduce pH. Would I find sulfuric locally at all? Can't find much via Google.

 

[rude]

This is a VERY useful thread - especially given the ongoing discussion about whether or not water chemistry is worth looking into.
Recently bit the bullet and bought a pH meter, and found that my finished beer is consistently around 4.6; no lower than 4.5, at least.

@Lyrebird_Cycles you mentioned sulfuric was preferred over lactic to reduce pH. Would I find sulfuric locally at all? Can't find much via Google.

What do you mean whether water chemistry is worth looking into
Mate there is no need to discuss any more
It is worth it 100% dead set cert

 

[fletcher]

This is a VERY useful thread - especially given the ongoing discussion about whether or not water chemistry is worth looking into.
Recently bit the bullet and bought a pH meter, and found that my finished beer is consistently around 4.6; no lower than 4.5, at least.

@Lyrebird_Cycles you mentioned sulfuric was preferred over lactic to reduce pH. Would I find sulfuric locally at all? Can't find much via Google.

there's an ongoing discussion about whether or not it's worth it? i find that hard to believe. i've only been adjusting my water for about a year and have noticed remarkable improvements in my beers. perhaps you're referring to your internal discussion? if so, silence the haters and nay-sayers; it is incredible.

 

[twinathon]

Is there any academic material that links fermentation health to final pH? I test all of my brews for final pH and aside from one imperial stout, they were all within 4.0 - 4.2 pH. The imperial stout was as high, I think something like 4.75. Perhaps relevant is the fusels that were present on the finish of the stout, which is a characteristic of a poor ferment.

 

[mtb]

Yeah alright, point taken, it's certainly worth the effort. In any case I'm keen to get my hands on sulfuric since I definitely can taste lactic acid in higher dosages, or a different acid if anyone has another idea.