pH – pHantastic or pHooey?

By Greig McGill

You’ve all probably heard about pH. You probably know what it measures, in practical terms anyway. The exact nature of pH is about as chemistry nerdy as it gets. The good news is that you don’t really need to understand pH in order to harness it and use it to make your beer much better.

The simple definition of pH is that it measures the concentration of hydrogen ions. Hydrogen is (probably, it’s complicated) what the H stands for. The term comes from the German phrase for the “potential” (potenz) or power of hydrogen. The higher the concentration of hydrogen ions, the more acidic the substance is. Conversely, the lower the hydrogen ion concentration, the more alkaline/basic the substance is. Depending on your level of nerdyness, you might be thinking, “Greig’s got that backwards! Everyone knows acids are a lower pH than bases!” Well, you’re right, but that’s because the pH is expressed as a negative logarithm of the ion concentration in moles (sorry – beer stuff ahead, promise) and so as the concentration goes up, the number goes down and vice versa.

Still awake? I hope so, because here comes the useful stuff. What does pH have to do with making better beer? LOTS!

For a start, the enzymes that convert your malt starches to fermentable sugars really care about pH. Alpha Amylase, the “big starch chain chomper”, in addition to preferring warmer temperatures, also prefers higher pH – 5.3-5.7 is the optimal range. Beta Amylase, “the nibbler”, prefers cooler temperatures and lower pH – optimal range 5.1-5.3. Optimising the pH for the type of beer being produced (more on this later) will help extend the temperature window of both enzymes, allowing them to continue working well when slightly over or under their optimum temperature.

It is often stated that the optimal pH range for mashing in is between 5.2 and 5.5, but one size does not fit all. For beers featuring darker malts, where those malts also add acidity, it is common to target the higher end of the range. A more alkaline mash for these beers will help reduce harsh and acrid flavours which can go along with the more desirable flavours of dark malts. Many brewers go as high as pH 5.6. Of course, some people actually enjoy those harsher flavours too. That’s just fine! The goal is to give you the information to adjust things to the way you want, not to say you must do things a certain way. You do you.  

So that’s mash pH. What about other stages of beer production? pH plays a significant part in the boil also. The clarity of the wort and the type and amount of break formation are directly determined by pH during the boil. Proteins coagulate best in wort of 4.9-5.2. I target 5.0 personally, and find it gives a strong hot break, and very clear wort during boil. If the pH gets above 5.3, the wort can darken and become hazy.

For the hopheads, it’s useful to know that hop utilization during the boil is also altered depending on pH. A higher pH will increase hop utilization, but will also extract tannins from the hops, leading to possible harshness and permanent haze forming compounds. I know, I know, haze is cool now, but this haze will taste harsh and astringent. Not even a little bit cool!

In the finished beer, pH is really just about flavor. Sour beers, for example, are famously acidic. I’ve overheard more than one conversation in bars where the punter was asking for the specific pH of a sour beer… and the bartender has actually been able to tell them! Of course, this is a bit of a silly thing. Much like IBUs, pH is “just a number” when it comes to determining flavor. Generally though, non-sour beer tends to be between pH 3.8 and 4.5. More acidic beers are often a little brighter, with flavours seeming more separate and leaving an overall impression of crispness or even a fruit juice like impression. Again, for the hopheads, in hoppy pale ales a pH of 4-4.2 will often make the hop bitterness seem very bright and clean. Above 4.3, hop flavor and bitterness can become muddled and heavy. A pH of above 4.5 will render the beer far less microbiologically stable, and at that point, harmful bacteria could survive.

Achieving your target pH at various stages of production is a challenge, as doing it perfectly involves a fairly deep knowledge of water chemistry. If you are interested in not only achieving perfection, but also understanding the “why” behind the “how”, I highly recommend the Brewer’s Publications book on Water by John Palmer and Colin Kaminski. If anything in there conflicts with anything I’ve written here… guess which is correct!

The cliff notes are that the mineral composition of your water and your malt bill will determine the natural pH of your mash, as well as the buffering ability of the mash against changes in pH. You can adjust these factors with mineral and acid editions, and you can calculate what you need using one of several pieces of software available. No matter which you use, you will need a water report for the water you are using. Be aware that your water report is only good for the water you have actually tested. It changes regularly due to many conditions. I test my source water quarterly using Hill Laboratories. Many people, myself included, use BeerSmith to formulate their recipes. BeerSmith also includes a useful water-profiling tool. There are several good tutorials on using BeerSmith, Bru’n Water, and EZ Water Calculator to be found on YouTube.

If you just wish to lower your pH in the boil or in your finished beer, you can simply add any food grade acid. Holy wars rage over which is the best to use. I’m a lactic acid guy myself, but many use phosphoric, or even citric acid though the latter certainly has an impact on flavour. I will make no recommendation, but whichever you use, ensure your additions are correct against your calculations by using a pH meter to measure. You can use pH strips if you prefer, though I always struggle to perceive the exact colours and thus achieve the precision I want. Those with a chemistry background might have more luck than me!

Good luck, and may your knowledge of managing pH push your brewing to the next level. Just remember to always use your most valuable measuring tool to test the results – your senses!