How Important is Kettle pH?

Mash pH gets most of the attention when it comes to pH measurement, but there are ideal pH levels at every step of the brewing process and they may get out of line after the mash. The boil pH affects protein coagulation, hot break, and hop isomerization (a higher pH results in a higher hop utilization, although also a harsher bitterness), among other things. So, how important is it to measure pH during or after the boil? We checked in with two pro brewers who know their way around lab equipment to get their opinions on whether homebrewers should sweat over the kettle pH.

Cole Hackbarth is the Director of Brewing Operations at Rhinegeist Brewery in Cincinnati, Ohio.

We look at mash pH more closely than kettle pH as it has a big impact on enzyme activity and conversion. But also because mash pH translates to kettle pH consistently with a 0.2–0.3 pH drop. In fact, we don’t generally measure kettle pH unless it’s needed for the style (such as when we brew a Gose or a Berliner weisse). When we do track kettle pH it’s measured at the end of boil (which is after a 5% boil-off rate on a 60-minute boil).

Brewing literature (including Kunze and Briggs) states that, when measured at room temperature, mash pH should be between 5.2–5.6 depending on style. When you hit that, the kettle pH will be appropriate. We try to keep all kettle pH around 5.0–5.2. This promotes protein coagulation and lends a crisp, clean flavor and mouthfeel to the beers. There is some evidence that higher pH will enhance bitterness and hop utilization, but we find it’s not significant enough to outweigh the benefits of boiling at 5.2 pH.

We rarely acidify or deacidify in the kettle unless we are doing a historic style that used a non-traditional malt bill or intentionally soured wort pre-fermentation. Some lactic acid bacteria used in “quick” or “kettle” sours perform better if the wort is acidified before pitching bacteria. Usually around 4.9 pH; any lower and you start promoting diacetyl formation and creating stability issues.

In addition to calcium sulfate/ calcium chloride or calcium carbonate, we use food-grade phosphoric acid to adjust pH. It has a good balance of acidification without being too dangerous. Sulfuric acid is stronger but also more hazardous. Lactic acid is also often used because of its availability and ease of use. One thing to note with phosphoric acid — it does release phosphates that will bind with and precipitate calcium. So, if you are battling low calcium concentrations in your water and see poor attenuation, flocculation, or trub formation, then lactic acid may be the better choice. 

When it comes to the importance of monitoring kettle pH, what I would say is that I think it’s important for each brewer to understand the composition of the water they are working with, and how it impacts the beer. No need to obsess over, but it is good to check from time to time or if you see haze or yeast performance issues. 

Brewing water chemistry is one of the more complicated parts of recipe formulation and brewing. It’s so much more than just pH. You have to look at hardness, residual alkalinity, calcium content, and how these interact with the other brewing ingredients. You can go crazy trying to create the perfect brewing water. But just like there is no single malt, hop, or yeast variety that should be used in all beers, neither does perfect water exist. It is essential to understand your water and adjust it, as a tool to create exciting flavorful beers.

Cole Corbin is the Director of Brewing Operations at Maine Beer Company, in Freeport, Maine.

I think mash pH, pH during lautering, and pH during fermentation is
more important to monitor than kettle pH. That said, kettle pH is good to check to make sure things are in line before and after the boil. We do measure pH pre-boil and post-boil (with an evaporation rate of about 5% for a 60-minute boil). We’re in the habit of spot checking pH through-
out our processes; we grab a sample post-boil to record gravity, and while we have the sample we check pH. It’s a quick check and another data point to verify everything is going as it should. While we do monitor the kettle pH, we never have needed to make adjustments based on the results of these samples.

Our ideal kettle pH depends on the brand being brewed, but we typically shoot for a pH of 5.2 post-boil when measured at room temperature for beers that are lighter in color. Just by the nature of the ingredients used, the darker beers (stouts and porters) naturally have lower pH because of the higher amount of roasted grains. They’re typically below 5.0, in the 4.7–4.9 range. We monitor this and look for consistency between batches. We never acidify or deacidify in the kettle, nor do we use acid/base to alter pH. When pH adjustments are necessary in the mash and sparge phase we’ll make those using brewing salts. Our water is fairly soft with a total hardness of 85 mg/L CaCO3. This means pH buffering is fairly low and is not hard to adjust with just some salt additions.

My recommendation is to focus on using good-quality water first, then start making adjustments if needed. Monitor pH and don’t over-sparge the grains during the lautering process. If you are using water from your tap, make sure you know your water profile and treat for any chlorines found in there. Reverse osmosis (RO) water is a great canvas to build a water profile if you are dealing with water high in TDS (total dissolved solids) or that displays other problems. 

Issue: March-April 2021