Lagering Techniques and Two Water Chemistry Questions

Q Reading some forums and brewing websites from the Czech Republic, I understand that one can interrupt the primary fermentation when it reaches 75%, perform a cold crash, dump the yeast in the case you ferment in a unitank — or rack beer to a clean, sanitized and CO2-purged Corny keg/vessel/britetank — install a spunding valve, set this on 15 psi, maintain the temperature at ~2 °C (36 °F), and let nature do the rest for the coming eight weeks or so, resulting in a fully carbonated, clean Bohemian Pilsner ready for bottling.

Are you familiar with this process? I cannot find any literature on this topic. Will it work without adding gyle/kraüsening/priming sugar and yeast, or is the remaining dissolved yeast and sweetness enough to complete the fermentation and carbonation? That would be something.

Nici van Nieuwkasteele
Lommedalen, Norway

A Nice to see another great question coming in from brewers in Norway! The process outlined above may sound a bit extreme to the modern brewer, but the temperature and time progression described essentially follow traditional cold-lager fermentation and a subsequent cold maturation. In Wolfgang Kunze’s textbook Technology, Brewing & Malting, this basic method is covered in Section 4.4.3.2. So, the answer to your basic question is “yes,” this technique is a thing. The only bit of information in your question that looks unusual is the cold crash, or rapid cooling, before fermentation is complete.

Let’s roll back the discussion a bit and review some of the basics. I will use Kunze’s description here as a benchmark. Kunze references pitching yeast into wort chilled to 6–7 °C (43–45 °F), followed by a natural rise to a peak fermentation temperature in the 8–9 °C (46–48 °F) range, tank spunding, a slow cooling period to 3–4 °C (37–39 °F), and finally lagering at -1 °C (30 °F). One thing to note with this description is that the timeline is gradual. Kunze does not suggest lagering longer than about five weeks because yeast autolysis and off-flavor generation is a real risk. If very long aging is desired, a racking step is a good way to protect beer from autolyzing yeast. An alternate to this when using cylindroconical vessels is the periodic removal of yeast from the bottom of the cone. Aside from the details about yeast removal, this process is generally what you have described. I will leave the topics of crash cooling, priming, and kräusening for the moment.

The elephant in the room with this general overview is the relatively fine temperature control and the slow changes made to temperature. When these methods are read with modern eyes, a brewer may wonder how these methods came to be and why they were used. The answer is likely found in the environment surrounding the production of these traditional lagers. The temperature changes were probably not designed into a process, rather the specifics were teased out of established practices.

Wort cooling to 6–7 °C (43–45 °F) likely became the norm because that’s the temperature resulting from cooling methods used in lager brewing centers before closed wort coolers and the ability to control wort temperature to any temperature desired by the brewer. Pitch yeast at this temperature, conduct fermentation in relatively small, open, wooden fermenters, housed in 7–8 °C (45–46 °F) cellars, and the fermentation temperature freely rises to about 8–9 °C (46–48 °F). As fermentation rate slows, it makes sense to move the beer into a closed, lagering vessel where fermentation completes, carbonation increases, and beer aging occurs. This is where a bit of conjecture is required, but if we assume that lagering cellars were located “downhill” from fermentation cellars to facilitate gravity beer transfers, and the cellars were cooled using ice stored in ice rooms, the temperature of lagering cellars would have been colder than the fermentation cellars because cold air is denser than warm air and tends to move downhill. This is true of the labyrinth beneath many old breweries, such as Pilsner Urquell in Pilsen.

Assuming that lagering cellars from the past were in the 2–4 °C (36–39 °F) range, it follows that beer racked from open fermenters at ~8 °C (46 °F) slowly cooled to 2–4 °C (36–39 °F). Bear in mind that cooling rate slows as beer temperature approaches the coolant temperature, in this example air. None of these traditional vessels were equipped with cooling coils and temperature changes occurred slowly as the beer warmed with yeast metabolism and slowly cooled as fermentation subsided. A feature of these slow cooling rates was the absorption and reduction of diacetyl from the aging beer because of viable and metabolically active yeast cells. Today, brewers are careful not to cool beer too cold before diacetyl reduction is complete; “crash cooling” before fermentation and diacetyl reduction is complete is the one step in your question I would reconsider.

The modern brewer may raise a suspicious brow at these low lagering temperatures and question if yeast is actually active at such low temperatures. The world may move at a faster pace today than it did in the past, and waiting weeks for a beer to finish fermenting may seem like an eternity, yet lager yeasts are indeed capable of very slowly fermenting at cold temperatures. The practical brewer can empirically determine the lower limit for their yeast strains and cellar designs as there is no single number for the practical minimum.

Some of the challenges of these slow processes include the risks of incomplete attenuation, incomplete diacetyl reduction, contamination by opportunistic bacteria that may find the residual carbohydrates in green beer appetizing, and the questionable economics of very long aging practices. While kräusening is a very traditional lager brewing method, it was most surely developed as a practical and effective way of speeding up the aging process. Kräusen beer brings fermentable sugars and a fresh charge of viable and vital yeast to the party and helps to speed things up so that the aging beer can perform its real function to the brewer, and that is being converted into revenue by the business end of the brewing operations! Gyle or priming sugar additions can also be used at home if beer is racked to a closed secondary with insufficient fermentable sugars to carbonate the beer.

Here are a few practical considerations for both commercial and homebrewers:

• Temperature stratification (layering) easily develops in beer and water tanks because of the relationship between liquid temperature and density. This is especially a problem when tanks are cooled with cooling jackets or coils. Very slow cooling (and heating) rates are a challenge in unstirred tanks.
• Small vessels cool very quickly, whether air-cooled or equipped with cooling jackets.
• Temperature stratification also develops in closed coolers with little to no air movement.
• Perhaps the easiest way to slowly change temperatures to mimic cold fermentation and maturation is to create air-cooled cellars at home. Chest freezers are relatively inexpensive and can be reliably controlled using external thermostatic controllers to cycle power. Probe placement is important because freezers do not have fans and gradients can easily develop if probes are placed too high or too low in the freezer. Slow cooling rates are easy to achieve by changing the cellar temperature by a degree every couple of days.
• Be careful not to reduce the temperature of your lagering cellar too much lest your yeast will become sleepy and not finish what was begun before cooling things down. My inclination would be to use 4 °C (39 °F) for the final bit of fermentation, natural carbonation, and diacetyl reduction before reducing the temperature to -1 to -2 °C (30 to 28 °F) for extended lagering.
• There are many modern methods aimed at speeding things up while maintaining beer quality. If you want to use the cold fermentation and aging methods that have piqued your interest, ignore much of what you may find written about modern lager fermentations and enjoy the slow life.

Q I’ve been researching water chemistry for brewing and I haven’t found an answer to my question. When you are planning for the chemistry of the water, do you target the ratio of the chemistry pre-boil or post-boil? Do the minerals evaporate out of the water or do they concentrate in it? This question has been bothering me, one of your fervent readers, for a while.

Jimmy Fortin
Montreal, Quebec

A This is a really good question. Water chemistry is discussed in terms of pre-mash concentrations with minimal attention given to the concentration of ions following mashing (and boil). Perhaps the primary reason for this view is that water chemistry’s greatest influence on beer is through its effect on mash and wort pH. Malt enzymes, protein precipitation in the mash and boil, extraction of malt tannins, alpha acid isomerization, and color development during boiling are some of the key brewing variables affected by the wort’s pH. However, just because water chemistry’s effect on mash and wort pH are the hot topics surrounding water does not mean that it’s the only topic.

Calcium, magnesium, manganese, and zinc are constituents found in varying levels in water, and they all have relevance to yeast metabolism. Calcium and zinc also influence yeast flocculation, giving these two compounds high priority to the practical brewer. Iron is found in some waters and can also make its way into wort from brewing equipment and even raw materials depending on growing regions and malthouse specifics (e.g., water used for steeping and iron contamination from some equipment). Iron can also be introduced to beer from filtration materials. Brewers keep a lookout for iron because it is a potent oxidizer of beer flavor.

So, the short answer to your question is that the composition of brewing water and mineral additions is typically confined to pre-mash concentrations of the ions of interest. When wort is boiled, there is definitely a change in the concentration of substances dissolved in wort. Calcium and magnesium from water is partially lost during the boil through pH-reducing reactions with phosphates and proteins/polypeptides from malt. Some brewers add calcium to the kettle before boiling for the purpose of reducing wort pH and checking color formation during boiling. Calcium and magnesium also react with carbonates during boiling. In addition to precipitating as calcium and magnesium salts, carbonates can also decompose into carbon dioxide and water. And anything from water that does not react with wort during boiling will be concentrated by the evaporative process. Other such reactions occur that alter mineral composition during boiling.

The practical, take-home message is that brewing is a continuum from raw material production to finished beer. While the specifics about water chemistry are typically confined to concentrations of minerals in brewing water, the relevance of the topic has a much broader reach.

Q When I began many years ago, I used our own well water. In attempts to improve, I have used bottled spring, distilled, reverse osmosis (RO), etc. I would like to get back to using my own water if possible. I have read all kinds of information regarding water treatment, but I am still not sure of how to attack this. I have attached my complete analysis from Ward Laboratory. Any help I can get is much appreciated!

Rick Pfarr
Marysville, Ohio

A Rick, water chemistry can indeed be confusing. I think one of the reasons that the topic is so frustrating to read about is partly due to the number of different units that are used to express the concentration of ions in water. The analysis you sent from Ward Laboratories is typical of modern water lab reports and provides the concentration of the specific ions of interest, versus “lumpy values” like total alkalinity as CaCO₃.

Another reason that water chemistry is confusing to read about is because folks who write about water want to explain other stuff along with providing practical and easy to use information; the resultant works are often trying to digest. I am guilty of this and want to take another crack at this topic in an attempt to convert the values in your water analysis into something you can use.

To begin with, most of what is provided in a water analysis can be ignored for the first step used to evaluate water for brewing. The critical ions are calcium (Ca⁺²), magnesium (Mg⁺²), bicarbonate (HCO₃^–), and carbonate (CO₃^-2) because these affect mash and wort pH. The practical brewer wants to know some specifics about how different waters will affect pH, not just that some effect is going to occur.

To answer this question, we are going to use a simple calculation table that is loosely patterned on a currency conversion table. Think of this process as converting four different currencies into one so that we know how much beer we can buy at the local pub . . . or something like that!

Step 1 – Fill in the blanks in Table 1 with what is known about your water (the colors in the table are used to categorize the information).
Step 2 – Do the math that the table instructs.
Step 3 – Total up the values to approximate how mash pH will be influenced by the water.

So, what does this table do and what does it tell us about your water? For starters, this is a conversion table that converts the concentrations of the ions in water that go on to influence mash pH directly into a variant known as degrees German Hardness (˚dH) that can be added together to predict how mash pH will be altered using this water instead of distilled water (this is a digested form of residual alkalinity calculations). The nice thing about Table 1 is that the messiness of water chemistry is totally skipped. This table may be helpful if you want to see how your water compares to a few examples.

In the number crunching shown here, the prediction is that your mash pH is going to pushed up by 0.2 pH units compared to brewing the same beer with mineral-free or distilled water. The +0.2 value means that for most beers, your water needs some acid balance, either by directly adding acid, acidulated malt, or acidic specialty malts. Another approach is to remove some of the bicarbonate by boiling. These adjustments are really outside of the scope of your question, so I will leave adjustment for the time being.
OK, we have answered the mash pH question; we know your water has residual alkalinity that is going to push mash pH upwards and you have some remediation options that we will circle back on later. What about flavor ions? The biggies are: Magnesium, sodium, chloride, and sulfate. Brewing waters are really all over the place with these ions and there is no right answer when it comes to flavor ions. Depending on the style of beer you are brewing, chloride and sulfate concentrations, as well as the ratio of the two, are something to consider. Chloride is generally associated with a softer, “sweeter” water and sulfate is considered to be a more aggressive mineral water that accentuates dryness and bitterness. My preference is a combination of the two. I also like some sodium in my water as long as it does not lend salty flavors to beer because sodium rounds out the palate; for whatever reason, much of the information about brewing water tends to gloss over sodium.

Magnesium is the one flavor ion (also a pH ion) that may raise a hairy eyebrow, or two, with your water. Although magnesium pushes mash pH downward, which is generally viewed as positive, it can add bitter and metallic flavors when concentrations exceed about 50 ppm. While magnesium values reported in the literature vary by style, the takeaway is that this is an ion that has the potential to drive beer flavor onto unwanted paths. Your water is high in magnesium, plain and simple, and the flavor of magnesium is unmistakable. In some English ales, it does add a very interesting and enjoyable flavor layer when the levels are not extreme, but in other styles magnesium can simply add a distracting and unpleasant flavor note.

I have never been a huge fan of looking at textbook values for classic brewing waters by style and city because much of this information lacks context. Take Munich for example. The water in Munich is well-suited for brewing dark lagers because its chemistry pushes mash pH up, balancing the malt grist used to brew darker beers. But what about all of the great helles lagers and weizen beers brewed in and around Munich? Well, Paul Kolbach did develop the concept of residual alkalinity to help brewers tailor local brewing waters to beer type in the early 1950s and German brewers certainly have not been blind to water chemistry. In other words, textbook water values of traditional brewing centers may or may not describe the actual water used for brewing.

What are the takeaways from this brief jump into the cloudy pool of water? Here are some bullets that may be helpful:

Start your water review by considering how your water’s composition will affect mash pH because that is really the foundation of this entire topic.
Does your water have anything that may have a detrimental effect on beer flavor?

If you want to use local water and the analysis from the points above don’t suggest alignment of the brewing stars, there are a few things you can do to mitigate the issues. You can dilute your water with RO or distilled water to minimize the concentrations of things that may be problematic, for example magnesium. However, water dilution does not change the alkalinity balance.

Adding more calcium to your water can balance the alkalinity, however, you may be moving into a water profile that is not well-suited for a diverse selection of beers.

Written by Ashton Lewis