Fermenting Store-Bought Beer: Is It Possible?

Fermentation is a process that involves yeast converting glucose in the wort to ethyl alcohol and carbon dioxide gas, giving beer its alcohol content and carbonation. The process begins when cooled wort is transferred to a fermenting vessel and yeast is added. The fermentation process can be influenced by factors such as temperature and yeast type, with different strains of yeast having specific temperature ranges in which they work best. While fermentation typically takes about two weeks for ales and six weeks for lagers, it is not a set it and forget it process. Brewers need to monitor the progress and make adjustments to ensure the desired outcome. Additionally, the duration of fermentation can vary depending on the style of beer being brewed and the specific recipe being followed.

Fermentation process and ingredients

Fermentation is the process by which yeast converts glucose in the wort to ethyl alcohol and carbon dioxide gas (CO2) to give beer its alcohol content and carbonation. The process starts when cooled wort is transferred to a fermenting vessel and yeast is added.

Ingredients

The sugars used in the fermentation process are derived mainly from malted barley, although other cereal sources and plant sugars can also be used. These materials also contribute proteinaceous substances, which, along with the sugars and added flavouring agents, generate the alcohol, flavours, and aromas of beer.

The Fermentation Process

The fermentation process has three phases: the lag phase, the growth phase, and the stationary phase. In the lag phase, the yeast cells are dormant and trying to figure out what's going on. During the growth phase, the yeast starts replicating and getting to work on the sugars in the wort. The Krausen, a foamy head of yeast proteins and sugars, starts to form and grow, and large amounts of CO2 are produced. Most of the alcohol, flavour, and aroma compounds are produced at this point. In the stationary phase, all the easy sugars have been eaten, and the yeast starts to absorb and reform many of the compounds that are considered off-flavours.

Controlling the Fermentation

The length of the fermentation process depends on the yeast strain being used and the desired outcome. Temperature control is a critical part of the process, with different temperatures within the yeast's range affecting the fermentation ability of different yeasts. The cooler the temperature, the slower the yeast will work, and the warmer, the faster. The general rule is that the hotter the fermentation, the more likely you are to get off-flavours and unwanted attributes in the beer.

Fermentation time

The fermentation time for beer depends on the style of beer being brewed. Ale fermentation follows three phases: the lag phase, the exponential growth phase, and the stationary phase of yeast growth. The lag phase takes between three to fifteen hours, the exponential growth phase takes one to four days, and the stationary phase takes three to ten days. The entire fermentation process for ale typically takes two weeks. Lager, on the other hand, requires a more extended period, typically fermenting in the primary fermenter for two to three weeks, followed by several weeks or months of cold conditioning in a secondary vessel. The whole process for lager takes about two to three months.

During the lag phase, yeast begins to adapt to its environment, taking up minerals and amino acids from the wort. This phase is important for building new, healthy yeast cells that can complete fermentation. The exponential growth phase is when yeast starts to consume sugars in the solution, producing carbon dioxide and a layer of foam on the beer. This phase results in an increase in cell count and the production of ethanol and flavour compounds. The airlock bubbles vigorously during this phase. The stationary phase of yeast growth is when yeast growth slows down, and most flavour and aroma compounds have been produced. The beer at this stage is referred to as "green" as it does not yet have the desired balance of flavours.

While the primary fermentation for ale takes about two weeks, it is recommended to wait for at least two weeks before bottling or kegging to ensure optimal results. For lager, the primary fermentation takes two to three weeks, followed by a longer conditioning period. The longer lager process allows the yeast to complete its job and clean up any undesirable by-products produced during primary fermentation.

The duration of the fermentation process can vary depending on factors such as beer style, brewing equipment, and brewing methods. However, the typical timeline for brewing beer, from ingredients to a finished product, is around two and a half to eight weeks, with three to four weeks being the most common.

Fermentation temperature

The optimal fermentation temperature range for ale yeast is between 66-72°F (18.8-22.2°C). At this temperature range, the yeast thrives and works efficiently to convert malt sugars into carbon dioxide and alcohol. However, if the temperature exceeds 80°F (26.6°C), the fermentation process may produce undesirable byproducts, such as excessive fruity-flavoured esters or harsh-flavoured fusel alcohols, resulting in off-flavours in the beer.

On the other hand, fermenting below the normal temperature range can lead to sluggish or incomplete fermentation. This can be an issue for lager production, as it typically requires cooler fermentation temperatures of 45-55°F (7-13°C). Therefore, lager fermentation is often done during winter months when basement temperatures are more suitable.

To maintain the desired fermentation temperature, brewers employ various techniques, from simple methods like using evaporative cooling with a wet t-shirt to more advanced approaches, such as using temperature-controlled refrigerators or freezers.

Additionally, the choice of yeast strain also plays a crucial role in fermentation temperature. For example, Kveik yeast, a "super fermenter," can ferment very quickly at high temperatures (>90°F) without producing undesirable off-flavours.

In summary, controlling fermentation temperature is essential in brewing beer. It ensures that the yeast works optimally, producing the desired flavours and aromas while minimising unwanted byproducts. By understanding the ideal temperature range for different yeast strains and employing temperature control techniques, brewers can consistently produce high-quality beer with the desired characteristics.

Secondary fermentation

The process of secondary fermentation helps to separate the beer from the "trub", which includes yeast sediment, hops sediment, and grain/tannin pieces left over from the mash. This separation reduces contact with bitter tannins, bitter hop debris, and inactive and dead yeast cells. It is believed that this process allows the beer to clear more quickly and reduces off-flavours in the finished product.

The duration of secondary fermentation can vary from as little as a week to over six months, depending on the desired outcome. Brewers use their senses of taste and smell to determine when the beer is ready for bottling.

While secondary fermentation was once considered essential, some modern brewers argue that it is unnecessary. They suggest that an extended primary fermentation of 3-4 weeks can produce similar results, and transferring the beer to a secondary vessel poses risks of oxidation and contamination.

However, secondary fermentation can be beneficial for certain types of beers, such as highly hopped beers that need time to age before reaching their peak flavour and aroma. It is also necessary when adding dry hops or oak chips to the brew.

Fermentation equipment

• Fermenters: These are the containers in which the beer is fermented. They come in various materials, including food-grade plastic, glass, and stainless steel. Common types include buckets, carboys, and conical fermenters.
• Airlocks: Airlocks allow carbon dioxide to escape while preventing outside air from entering the fermenter, which helps to maintain sanitation and reduce the risk of contamination.
• Hydrometers: Hydrometers are used to measure the density of the liquid, which can help determine the sugar content and potential alcohol level of the wort.
• Thermometers: Temperature control is crucial for successful fermentation, as yeast activity is temperature-dependent.
• Siphons: Siphons are used for racking, or transferring the beer between fermenters, without aerating it.
• Carboy handles: Carboys are heavy, especially when full, so a handle can be helpful for moving them around safely.
• Hose clamps: Hose clamps are used to secure tubing and control the flow rate of liquids.
• Stoppers: Stoppers are used to seal carboys and other containers. They come in various sizes and can have holes to accommodate airlocks.
• Spigots: Spigots are attached to fermenters to make bottling or transferring beer easier.
• Conical fermenter accessories: If you have a conical fermenter, you may need additional accessories such as pressure kits, collection containers, or wireless temperature sensors.

This list is by no means exhaustive, and there are many other pieces of equipment that can be used for fermentation. It is important to sanitise all equipment that comes into contact with the beer to prevent contamination and off-flavours.

Frequently asked questions