What Is The Process of Beer Fermentation?

Fermentation is the process by which yeast converts the glucose in the wort into ethanol and carbon dioxide gas. To start the fermentation process, the cooled wort is transferred to a fermentation tank where yeast has been added. Without fermentation, there is no alcohol, the sugars are not degraded, and the flavors are not developed.

Beer fermentation requires yeast

Beer fermentation requires yeast. Yeast converts glucose into carbon dioxide and ethanol during the fermentation process. This fermentation does not require any oxygen. Yeast is a living microorganism that must be properly cultured in order to thrive. Yeast requires the right temperature and sufficient food (glucose) to function. Therefore, the first few steps of beer brewing are to create the right environment for the yeast to grow.

How long does beer ferment?

Many brewers wonder what the optimal time is for beer fermentation. We have no control over fermentation time. Once it is in, the yeast does all the work.

Controlling Fermentation Time

Temperature control is a very important part of the fermentation process and can be adjusted during the fermentation process. Each yeast strain has an optimal operating temperature range. Within this range, different temperatures will affect the fermentation ability of different yeasts. Generally, the lower the temperature, the slower the yeast ferments; the higher the temperature, the faster the yeast ferments.

The higher the fermentation temperature, outside the temperature range specified by the yeast, the more likely the beer will develop off-flavors and undesirable characteristics. If lower temperatures are used, stagnation, prolonged fermentation, or difficulty in achieving normal fermentation levels may sometimes occur. Of course, certain types of beer are excluded.

Basic experience of fermentation

The temperature of yeast fermentation should be controlled in the medium-low temperature range. For example, if the fermentation temperature range is 18-22°C, it is better to control it at 19-20°C.

The process of beer fermentation

Once there is enough "nutrition" in the wort and the initial flavor (by adding hops) has been formed, the fermentation process can begin. Yeasts are added to the liquid and they start to consume glucose.

Fermentation does not always start immediately. At the beginning, oxygen is still present, allowing the yeast to breathe instead of fermenting. When breathing, the yeast uses oxygen to break down glucose. Ethanol is not formed at this time, but the glucose is completely broken down into water and carbon dioxide, and all possible energy is obtained from the glucose molecules.

The basic process of beer fermentation is the same as that of common yeast fermentation. Glucose is converted into ethanol (alcohol) and carbon dioxide. However, more than these two molecules are produced during fermentation!

How do you know your beer is done?

A common mistake new brewers make is to use the airlock on their fermentation tank to gauge fermentation progress. An airlock is a device used to ensure nothing gets in during fermentation and to allow built-up CO2 to escape. If the fermentation tank is not sealed, CO2 can escape and cause the airlock to stop bubbling!

There is only one way to know if your beer is done - with a hydrometer or refractometer. These devices allow you to check the sugar content in your wort/beer.

It is generally recommended that you get a stable specific gravity (SG) reading within 2-3 days to tell if your beer is done and ready to be packaged. This is to ensure that fermentation is indeed complete.

What to do after your beer has finished fermenting?

After fermentation, let the beer sit for a few days. This allows the beer to settle and the yeast to collect at the bottom of the fermenter. If you can lower the temperature a bit, we recommend this method as it helps to clarify the beer.

Once fermentation is complete, you can choose to package it immediately. You can age it longer, or add other ingredients such as fruit, oak in certain lagers, or use it as is. It all depends on the beer you are brewing.

What beer looks like after fermentation

• Lag phase

During this stage, yeast cells wake up and begin to look for food like humans, such as oxygen, minerals, and amino acids. At this stage, there is no air lock activity due to temperature stratification, and only a small amount of wort is convecting in the fermenter.

• Fixed period

All sugars are consumed, and the body of the beer begins to change from milky white to yellow and brown. The yeast begins to absorb many off-flavor substances, such as higher alcohols, diacetyl, sulfur compounds, and esters, and converts them into more alcohol and other "better" esters.

At this point, the fermented wort (called "green beer") has not yet reached the best flavor balance. As the yeast gradually settles and enters a dormant state after a long fermentation, the air lock and convection begin to weaken, and as the remaining small amount of nutrients disappear, the yeast also leaves the solution.

• Work completion stage

The air lock activity may stop (or the bubbles stop), and the convection stops. At this time, the yeast is dormant most of the time, hanging at the bottom of the fermenter. The beer begins to clarify and the flavor gradually matures.