Mash pH Importance

Mash pH is extremely important. Enzyme activity is a function of pH and all enzymes are only active in a relatively narrow range around their optimum pH. In the case of mashing, there are two enzymes of particular importance; alpha and beta amylase. The optimal range for alpha amylase is pH 5.6–5.8 and the optimal range for beta amylase is pH 5.4–5.6. If mash pH is much higher than 5.6 beta amylase activity begins to drops off and, more importantly, the pH is approaching pH 5.8, or the point where tannins really start to be extracted from malt husks. If the pH is much lower than 5.6 alpha amylase activity drops off. Lower pH levels are favored to these higher levels and most brewers like to see the mash pH in the 5.2–5.4 range. This provides good enzyme activity and does not flirt with tannin extraction.

Mash pH is principally affected by the mineral content of the brewing water and by the grains used in mashing. In general terms, dark and roasted malts tend to lower mash pH. So it is possible that mash pH can be too low when brewing dark beers like stouts, porters, dark lagers, etc. Historically, dark beers were brewed in regions where the water contained significant levels of carbonate, and it is the carbonate in the water that balances the acidity of the roasted grains. If pale beer is brewed with carbonate water, the pH can be too high. In these cases, breweries use a variety of methods to either remove carbonate from water or add acid to the mash.

Mash can be acidified by using acidulated malt, adding soured mash as a natural source of lactic acid, or by simply adding commercially available food-grade acids like lactic or phosphoric. Adding calcium, either in the form of calcium sulfate (gypsum) or calcium chloride is another way to reduce mash pH. Calcium reacts with phosphates from malt and the result of this reaction is the release of hydrogen ions and a reduction in pH. The classic pale lagers and pale ales of the world were brewed in areas that either had extremely soft water, like Pilsen in today’s Czech Republic, or areas that had water rich in minerals and dominated by calcium, like Burton, England.

Mash pH and water chemistry can quickly become very confusing without a strong understanding of chemistry, especially the concept of buffering. Buffers are weak acids that resist pH changes in the region around the buffer’s pKa. (pKa is a quantitative measure of the strength of an acid in solution). As it happens, the brewer’s mash is rich in buffering acids, primarily from malt proteins, and these buffering compounds make the system much more complex than water. And to really make any sense of this a method of pH measurement better than litmus paper is required. For these reasons there are many brewers like you who don’t measure mash pH or do anything to really control it other than adding water salts in approximate quantities specified by recipes.

So the question you pose is relevant to a lot of homebrewers. Here is the simple version of mash pH. When malt is mixed with water the mash pH is normally right around pH 5.6, which just so happens to be right where we as brewers like it. Is this a coincidence? I have always supposed that since the enzymes being used in the mash are also active in the growing barley seed when the seed is hydrated, that the pH of the natural environment of hydrated barley and the pH of the mash should be pretty similar. Whether or not this explanation is correct is really not relevant; the bottom line is that the mash pH normally falls right in the optimum zone.

Rarely is the pH so far outside of this zone to cause real problems. This is why there are many brewers like you who have brewed great beers with good extract yield for many years without ever measuring pH. But fine-tuning pH does have real benefits. Improved extract yield and beer flavor are the two most common reasons for adjusting mash pH. If you are interested in adjusting mash pH I suggest buying a temperature compensated, hand-held pH meter and using diluted lactic acid or acidulated malt to lower pH and baking soda, or sodium bicarbonate, to raise pH. The million-dollar question is what works best, and this, like so many other things related to brewing, depends on what you are doing. If you are in search of some fun experiments, you have arrived at the right location.

Response by Ashton Lewis.