Quality Control: No Cell Counter? No pHroblem.

Craft brewers tend to cycle through a wide range of ingredients and adjuncts, depending on what they’re making, but there is one constant: yeast health.

Even beyond the basic functions of converting sugar to alcohol and carbon dioxide, yeast have many other impacts on beer. Yeast health directly affects aroma and flavor as well as fermentation times. And while brewers may have full control over recipe development and ingredient selection, yeast can be unpredictable and difficult to decipher.

Luckily, if you know what to look for, yeast also can provide clear signs of when they’re happy and when they’re struggling.

To be clear: I’m not saying to not perform cell counts in your brewery. Ideally, the information I’ll share here about pH and yeast health should be used in conjunction with consistent cell counting. However, if your brewery is unable to invest in cell counting right away—because of financial or staff limitations—these guidelines can be useful in assuring a healthy fermentation.

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Why You Should Ask Your Yeast if They’re Okay

Obviously, yeast health is critical for beer quality. But what, exactly, are the implications of pitching unhappy or unhealthy yeast?

One issue that almost every brewer has experienced at some point is a stalled fermentation, which can negatively affect flavor as well as the timing and logistics of a release, potentially tying up tanks in the meantime. If you can’t release a beer on schedule, that may affect employee hours as well as placement in accounts.

Plus, if you crash a beer before fermentation is fully complete, the beer may decide to finish fermenting in the package, leading to foamy kegs, gushers, or exploding cans in the market. While it may be a worst-case scenario, nobody wants to think of the impact that a recall could have on the brewery’s reputation.

However, do you need an expensive cell counter or external lab services to ensure yeast health? Not necessarily.

Speaking the Language of pH

Performing regular cell counts means investing in equipment such as a microscope and a hemocytometer. You’d also need a supply of pipettes and tubes to ensure that your measurements are accurate. Also important is having staff—more than one person—fully trained on the cell-counting method, which can be subjective and prone to human error. Having multiple trained employees is critical for obtaining usable data.

So, while I’m all for breweries performing cell counts as soon as they’re capable, knowing how pH is related to yeast health can be helpful in the meantime. Every brewery should have a pH meter, which can be used for many other measurement points. If your brewery takes care of its pH meter and calibrates it regularly, it should last for many years. Otherwise, the investment involves buffers, cleaning solution, and a new probe every one to two years.

Best of all, taking pH measurements is quick and easy, and any brewery employee can do it with minimal training.

Now let’s get into some more detail about yeast and their corresponding pH values.

The pH of a beer or yeast slurry is very telling during all steps of the yeast life cycle. As yeast grow during propagation, the pH of their medium becomes more acidic—a sign that the yeast are healthy and growing well. By the end of a propagation, some yeast strains can get as low as 3.6. That might seem concerning because that’s a value that a brewer would normally see in a sour beer. However, during propagation, it just means the yeast are doing their job.

When it comes to fermentation, yeast pH will follow a similar trend at the start. As soon as the yeast inoculate wort, the pH begins to drop. Even if you aren’t seeing a change in your gravity or activity in the blow-off bucket, as long as you see a drop in the beer’s pH in the first 24 hours, that’s an indication that the yeast are healthy and getting to work on converting sugars.

After early fermentation is complete and the yeast activity begins to slow down, the pH will begin to rise again and become less acidic—a sign that the yeast are done fermenting and beginning to reach their death phase. This phase is known as autolysis, or automated cell death. During this event, yeast cells rupture and release their proteins and organelles. Letting the yeast sit for too long at the bottom of the cone is a way to produce off-flavors, but it also impacts the final pH of the beer. All these factors play into the final goal of obtaining consistency among batches.

When and How to Test

This method begins with testing the initial pH of the knockout wort. Adjusting that pH—with lactic or citric acid, typically—will help the yeast to begin their growth quicker, kick-starting fermentation. Somewhere around 5.2 pH is a good target.

Once you’ve pitched the yeast, taking a pH measurement is the next step. This is called the pitch-rate pH. Ideally, you would also do a cell count at this point, but the pH will be a quick and easy indication of how the yeast should handle the upcoming fermentation.

Appropriate pitch-rate pH values can range from 5.0 to 4.7, depending on the beer and yeast strain. Be sure to track this data, getting some averages based on yeast strain and beer brand or type. Once you have that data, you’ll be able to predict when a beer will finish and crash—based only on past batches with similar starting pH values.

If the pH value is too high, or too far off the average, you’ll know that your fermentation will be slower than usual and that you could even expect some stalling issues. Catch that soon enough, and a pitch of fresh, healthy yeast before fermentation kicks off could save the batch from stalling out.

Predictability Is Gold

Better, more consistent fermentation means greater brand consistency. Meanwhile, greater predictability will help you plan future batches, getting beer in and out of the fermentors more efficiently—incredibly valuable to breweries with limited cellar capacity.

Plus, tracking these pH values can help you determine when a generation of yeast is reaching the end of its life span, and thus when it’s time to pitch a new crop.

Counting cells is still the gold standard for determining yeast health—but if your brewery isn’t ready to invest in that, or you just want more data, then checking yeast pH is a simple way to track its health.

It’s a good habit to have. All that data will help you better understand your beers and your chosen yeast strains, prevent losses from stalled fermentations that can tie up tanks or, even worse, turn into dumped batches.

Tracking yeast pH for each brand can help you make the best decisions, so you can release the best versions of your beers—on schedule—to your customers.