Guide to the beer fermentation process

Fermentation is the process by which yeast converts the glucose in the wort into ethanol and carbon dioxide gas (CO 2) to give beer alcohol content and carbonation. When the cooled wort is transferred to the fermentation vessel and yeast is added, the fermentation process begins.

How long does my beer ferment?

Many new brewers want to know the best time frame for fermenting beer. The fact is that we have no control over the fermentation time. Once we cast the yeast, they will do all the work!

However, we can change certain conditions to shorten or extend this time frame-such as controlling the fermentation temperature. This will depend on the yeast strain you use and the ingredients you are looking for in beer.

Control the fermentation temperature

Temperature control is a very important part of fermentation and can easily make some of the most significant changes during the fermentation process-whether it is the quality of the finished product or the fermentation time.

Each yeast strain has a temperature range that they are most suitable for. Different temperatures within this range will affect the fermentation capacity of different yeasts. Generally, the lower the temperature, the slower the effect of yeast, and the higher the temperature, the faster the fermentation speed.

The general rule is that the hotter the fermentation—especially outside the temperature range specified by the yeast—the more likely you are to develop off-flavors and unwanted properties in the beer. If lower temperatures are used—especially outside the specified temperature range for yeast—sometimes they encounter the challenge of stagnation, prolonged time, or reaching normal fermentation levels.

The basic rule of thumb for fermentation temperature

Aim at the low and medium temperature of the yeast fermentation range. For example, if the range is 18-22°C, it is better to target 19-20°C.

As mentioned above, this rule may be different for styles such as wheat beer. These usually require more complicated fermentation procedures.

10BBL copper beer brewing equipment

How do I know when my beer has finished fermentation?

A common mistake new brewers make is to use the airlock on the fermentation tank to measure progress. The airlock is exactly what it describes—it is a device that ensures that nothing enters the fermented beer and allows the accumulated CO 2 to escape.

Although many of us are fascinated by the “gloop” airlock that sounds every few seconds, all this tells us that CO 2 is escaping from the fermentation tank. If the fermentation tank is not properly sealed, CO 2 may escape and the air lock will stop bubbling.

After all, there is only one way to know if your beer has finished fermentation-using a hydrometer or refractometer. These devices allow you to check the sugar content of wort/beer.

The general recommendation for knowing when the beer is finished and ready for packaging is to obtain a stable specific gravity (SG) reading within 2-3 days. This is to ensure that the fermentation has indeed been completed.

What should I do when my beer is fermented?

It is recommended to let the beer rest for a few days after fermentation. This will allow the beer to settle and clarify, and the yeast will flocculate at the bottom of the fermenter. If you can lower the temperature slightly, we would recommend you to do so, as it can help clear the beer.

After the fermentation is complete, you can choose to pack immediately, extend the aging time or add other things, such as fruit, oak or in the case of some beer. It all depends on the beer you brew.

For a long time, you should "put" the primary fermentation beer into the secondary fermentation tank to remove it from the yeast cake and put it in a better packaging condition. Today, the risks of potential oxidation and contamination rarely outweigh the benefits of secondary fermentation. Secondary fermentation is usually recommended only when it actually occurs-that is, bottle or barrel carbonation.

Copper fermentation tank

What should my beer look like when it is fermented?

It's a bit like Schrodinger's cat... You can open the top and watch what is happening inside the fermenter, but this may change the result, and in many cases it will get worse. If you want to check the progress of the fermentation without opening the fermentation tank and exposing the beer to the air, then the transparent/transparent fermentation tank is perfect.

What beer looks like during the fermentation process depends on our little partner-yeast. Here is a summary of what they are doing after adding the wort:

Lag phase (0-15 hours) | Who is that? Who is there?

At this stage, the yeast cells are waking up and trying to figure out what is going on.

When they wake up and prepare to start a new day, they will look for morning stimulants such as oxygen, minerals and amino acids. When they did this, they began to realize all the food around them. We like to imagine them thinking "how do I eat all this by myself?"

At this stage, there is no airlock activity, and due to any remaining temperature stratification, there is only a small amount of wort naturally convection in the fermenter.

Growth period (4 hours – 4 days) | Making friends and feeding

"Well, I need some partners to eat these foods!" Yeast began to replicate and began to process the sugar in the wort.

Foam heads of yeast protein and sugar—begin to form and grow. A large amount of CO 2 began to be produced, and the airlock started to go crazy. In addition, since the alcohol-producing yeast generates heat, the thermal convection in the wort starts to increase, and you start to gently roll the wort in the fermenter.

Most alcohol, flavor and aroma compounds are produced at this point.

Quiet period (3-10 days) | Let's clean up this mess

Now that all the easy sugars are eaten, the yeast starts to change from milky white to yellow (from precipitated malt and hop components) and brown (from oxidized hop resin).

Yeast begins to absorb many compounds that we consider to be off-flavors, such as higher alcohols, diacetyl, sulfur compounds and esters, and convert them into more alcohol and other "better" esters.

At this time, the fermented wort is called "green" beer, and does not reach the proper flavor balance. When the yeast enters a long distance and enters a sleep state, the airlock and convection begin to slow down, disappearing from the solution as the remaining small amount of food disappears.

Death stage (several weeks) | I've finished my work here

Airlock activity may stop (or occasionally bubbles appear) and convection ceases. At this time, most of the yeast is in a dormant state, and it hangs on the bottom of the fermentation tank. The beer begins to clarify and the flavor in the beer matures.

Stainless steel fermentation tank

If you are not familiar with brewing and want to increase your knowledge, please check the rest of our article. If you have any questions, please contact us at kate@degonget.com. We are happy to help!