5 CELLAR OPERATIONS

The beautiful properties of Gose

Made it beloved in Leipzig,

When drank as clear and pure as gold

It tastes like mild wine, so know,

For old and young, and thin and thick

Gose always is pure happiness.

(Der Gose schöne Eigenschaften

Sie sehr beliebt in Leipzig machten,

Als trank so klar und rein wie Gold

Schmeckt sie wie milder Wein, so hold,

Für alt und jung, und Schank und dick

Ist Gose stets das reine Glück.)

—From a Leipzig postcard circa 1930, translation courtesy of Randy Mosher

YEAST PITCHING

Once the wort goes through the heat exchanger, it passes over to cellar operations. While the wort was boiling in the kettle, you or one of your fellow brewers should have been preparing a fermentor and the yeast or mixed culture for pitching or adding to the cooled wort.

Whether you plan on using a single yeast strain, multiple yeast strains, or a mixed culture with yeast and bacteria, you will need an ample amount of healthy and viable microbes to ferment the beer. Preferably this will be from a recent, successful fermentation or from a culture that has been adequately propagated to a sufficient quantity ahead of time. It has been my experience over the last 30 years of brewing that no matter what a yeast supplier may tell you is in the package, pouch, or vial, it is always best to get the culture started yourself and grow up an adequate amount of microbes to pitch to get the job done right.

The proper pitching rate of yeast, for any beer, is one million cells per degree Plato per milliliter. So, for a 12°P (1.048) beer you will need 12 million healthy, viable yeast cells per milliliter of beer throughout the entire volume of liquid. This number increases slightly as gravities ascend past 13°P (1.053). The importance of having enough healthy, viable yeast pitched into your wort cannot be overemphasized. It may be even more important with a brewhouse-soured beer, as some yeast strains will not perform as well in a solution that acidic.

If you do not have a method for determining cell counts, I highly recommend you purchase a microscope, a hemocytometer, and some methylene blue dye. All these can be found easily online for less than US$300 total. This equipment will allow you to see your yeast, count the number of cells in solution, and ascertain if they are healthy enough to carry out a proper fermentation. There are some fairly decent articles archived online that explain all the basics of cell counting and yeast management (Allen 1994a; 1994b).1

If you are doing a post-brewhouse souring and will be pitching yeast and bacteria together, you should have similar amounts of bacteria as you do yeast in your mixed culture. That is approximately one million cells per milliliter of wort. There is a more in-depth discussion of bacteria pitching rates in the sections “Bacterial Souring Agents” (chapter 3) and “Souring the Beer” (chapter 4).

At the time of pitching, the temperature of both the yeast culture and the wort to be inoculated is important. If the wort is too cool, the yeast may stall and not completely attenuate during fermentation. If the wort is too hot, the yeast may experience thermal shock or even be killed. It is best if there is less than 20°F (11°C) difference between the temperature of the yeast culture being pitched and the temperature of the wort it is inoculating. A good temperature range for ale yeast is 66–76°F (19–24.5°C). Yeast also need oxygen to get their life cycle started off. It is very important that you get enough oxygen into the wort so that the yeast get a good start on fermentation. If you are using bottled oxygen, it should be medical grade or aviator grade. If you are using air it should be sterile filtered. You want to achieve an absorbed oxygen level of about 8–10 ppm and no greater than 20 ppm for a wort of Gose strength. It is possible to over-oxygenate with bottled oxygen, which is 4.75 times more soluble in wort than air, since air is only 21 percent oxygen; but it would be near impossible to over-aerate, as wort will not hold that much gas at ale fermentation temperatures (Okert 2006). For homebrewers, one of the best methods for dissolving the proper amount of oxygen into wort is to use an aquarium aerator pump with the air pushed through a sterile in-line filter and into a sanitized defusing stone submersed in the cooled wort. Do this for about two minutes in your five-gallon (19 L) batch. For professional brewers it is best to add air (or oxygen) inline on the way to the fermentor, post heat exchange. Optimally, this will give the wort a chance to absorb the gas on the way to the fermentor. What you do not want is to create too many bubbles in the fermentor, as the bubbles will agitate the wort as they rise to the surface, and in doing so drive off volatile aroma components. This is why homebrewers should only inject air for no longer than about 2 minutes.

If you are spontaneously fermenting your beer, as it has been suggested Gose-style beers were during the Middle Ages and possibly beyond, then you may dispense with the above information regarding oxygenation and pitching rates—it will not apply to you. You have thrown caution to the wind, and you are depending on the wind to supply you with what you need. Of course, you should be starting this spontaneous fermenting thing in a shallow, open vessel—a coolship or the equivalent—and then transferring it to a different vessel for fermentation. Some research indicates that many of the microbes participating in most professional spontaneous fermentations reside not on the wind, but in cracks and crevices of wooden structures in a coolship room. This research suggests that the best way to achieve a good, repeatable spontaneous fermentation is to spray down the walls, ceiling, and beams of the coolship room with a lambic beer of your choice.2 A good temperature range for spontaneous fermentations is 66–78°F (19–26°C), depending on ambient temperature.

FERMENTATION

Once you have gotten the cooled and oxygenated wort into the fermentor and pitched healthy, viable yeast, there will be a brief lag period while the yeast take up oxygen, minerals, and amino acids from the wort and get ready to do their work. This lag phase should not last more than about 12 hours and may be as short as one. If the lag phase exceeds 12 hours, rouse the yeast by adding more sterile air or oxygen to the bottom of the fermentor. Once the lag phase has ended and the yeast has taken up most of the oxygen, fermentation will enter the exponential growth phase. During this phase, the yeast consume sugar from the wort and begin to produce alcohol, carbon dioxide, flavor components, and more yeast. This portion of the fermentation is exothermic and the temperature will begin to rise quickly. The generation of heat during this phase of fermentation is of particular concern with larger tanks, as they hold their thermal mass better; insulated tanks, for the same reason; and on days when the ambient temperature is over 80°F (27°C). Once this phase of fermentation starts, the beer will need to be temperature controlled and kept at 66–76°F (19–24.5°C). If the fermentation temperature is allowed to free rise, it could reach as high as 95°F (35°C) or more depending on the batch size and ambient temperature. Almost any fermentation that rises over about 76°F (24.5°C) begins to produce large amounts of fusel alcohols and esters, which are often harsh and solvent-like. The esters can vary from ripe fruit to banana to a heavy dose of butterscotch or butter (diacetyl). If wort is pitched at too high of a temperature and then allowed to cool down, it may also produce excessive diacetyl, so much so that the yeast may not be able to reduce it all later in the process. Excessive fruitiness, strong esters, fusel alcohols, and diacetyl are all considered defects in a Gose.

Level of pH During Fermentation

As the fermentation progresses, the pH will drop rapidly as yeast take up amino acids and create acidic components. For beers soured in the brewhouse, this drop will not appear to be as dramatic because pH is already low. Another potential concern for brewhouse-soured beers is that lower pH levels (below 3.9) can favor diacetyl and sulfur production with some yeast strains. If your yeast produces excessive diacetyl, be sure to address that in the secondary fermentation phase.

End of Fermentation pH

Optimum beer pH (unsoured): 3.9–4.6
Optimum beer pH (soured): 3.2–3.8

Secondary Fermentation

Once active primary fermentation has finished, marked by the end of rapid carbon dioxide evolution, the yeast still needs time to complete its processes. The warm secondary fermentation period should last two to four days. The temperature may drop on its own during this phase, but the beer should not be cooled. This time will allow the yeast to completely attenuate the beer, and reduce diacetyl and some other negative flavor components. At the end of fermentation, finishing gravities should be 1.2–3°P (1.005–1.012 FG). Take pH readings during this warm aging period. If the pH begins to rise, cool the beer. This slight rise in pH is due to the yeast cells autolyzing and releasing their slightly alkaline cytoplasm into the beer. Too much autolysis can have a negative flavor impact.

Additions

Additions of fruits and spices to the cold side are covered in their respective sections in chapter 3.

AGING AND CONDITIONING

The amount and nature of the aging you give your Gose will depend on a great many things, but mostly upon what characters you want for your beer. As discussed in other parts of this book, Gose was often served fresh from the barrel, and there are even some who insist that Gose (at least in Goslar) was never sour due to its freshness and rapid consumption. But, unless you are trying to recreate those fresh-served Gose beers of yore, you will want to give your beer a little time to mature.

Carbonation

Carbon dioxide (CO₂) is what gives beer its sparkle. It is an important part in the overall taste profile of a Gose. It influences mouthfeel, body, and flavor perception. You want your Gose to have enough carbonation to make it lively and effervescent. Without the proper amount of carbonation, your Gose will be lifeless and dull. Most brewers carbonate their beer in the tanks prior to packaging; a few others bottle- or keg-condition. Either way, you will need to understand the relationship between liquid and gas. Gas (in our case CO₂) saturation in a liquid (beer) is related to pressure and temperature. Your beer will need to be cold in order to hold enough carbonation. The proper amount of carbonation for a Gose is about 2.5–3.0 volumes (5–6 g/L) CO₂. To determine the amount of carbonation in beer, you will need to know the temperature of the beer and the amount of pressure in the tank or keg holding it. Then sufficient time must pass for the gas to stabilize and be fully absorbed by the liquid. Figure 5.2 is a chart for CO₂ in volumes as a function of temperature and pressure.

Once your beer has the desired amount of carbonation, it may be packaged in kegs, bottles, or cans (discussed in chapter 6, Packaging and Service). Be aware that packaging can cause carbonation to rise or fall depending on your process. An increase can result from overpressurizing the package. To avoid a loss of carbonation, make sure that the beer is cold enough to hold CO₂, and that the package is purged and pressurized properly.

1 Fal Allen, “The Microbrewery Laboratory Manual–A Practical Guide to Laboratory Techniques and Quality Control Procedures for Small-Scale Brewers, Part 1: Yeast Management,” Brewing Techniques, July/August 1994, reproduced online, https://www.morebeer.com/brewingtechniques/library/backissues/issue2.4/allen.html.

2 Personal communication with Roger Mussche.