EnglishViews: 17 Author: Site Editor Publish Time: 2025-06-24 Origin: Site
Once yeast is added to the wort, it enters what we call the lag phase. Although there are no obvious signs of fermentation during this phase, there is still something going on. The yeast is absorbing oxygen from the wort and producing sterols, which are essential for the reproduction and healthy growth of the yeast. So, what is yeast?
Yeast is a single-celled eukaryotic microorganism classified as a member of the kingdom Fungi. The first yeast cell originated hundreds of millions of years ago. At present, humans have discovered at least 1,500 yeast cells. The yeast cell is a living organism, so it needs oxygen to maintain vital signs. This is why aeration of the wort is very important in commercial brewing. Yeast cells need oxygen to grow and produce important cell wall components. In addition, yeast cells need to absorb oxygen and also some vitamins and minerals required for growth.
In modern brewing, all the vitamins necessary for yeast growth can be found in high-quality malt. If your brewing recipe contains a lot of additives, you may need to add some yeast nutrients during the boil to help the yeast do its job. A simple brewing trick is to add some inactive yeast from a cooled conical beer fermenter during the boil 10 minutes before fermentation begins. This will provide the yeast with the minerals and vitamins needed for a healthy fermentation if the nutrients in the wort are insufficient.
In the later stages of the fermentation process, it is a good thing that you don't know about any active substances. The yeast cells are gradually adapting to the environment and establishing the growth required for healthy fermentation. You can shorten the lag phase by increasing the yeast feed rate, but each yeast cell may not be very healthy at the end of the fermentation. Over time, each re-feed will affect the fermentation process. Therefore, don't exaggerate the impact of the feed rate on fermentation.
Depending on the style of beer, you can see noticeable fermentation (a layer of foam) within 24-48 hours after hopping. At this point, the yeast enters the anaerobic phase from the lag phase.
During the active phase, the yeast cell count increases rapidly and the yeast begins to consume the sugars in the wort. As the yeast cell count increases, ethanol and flavor compounds are produced. Once the fermentation drops a few points (2 Plato or 0.07 SG), you can start brewing most styles of beer. If the beer is not dehydrated (for example, you plan to dry-hop your beer), you will see a lot of gas production and escaping the fermenter (FV). This is the carbon dioxide produced by the yeast cells breaking down the sugars. In addition, a thick layer of foam will form on the surface of the wort, called Krausen.
The active phase of fermentation usually lasts 4 to 8 days, depending on:
Beer style
Yeast used
Amount of fermentation
Fermentation temperature
After the active phase, the yeast slows down and enters a dormant phase. Note that most flavor and aroma compounds are already produced during this phase, including fusel alcohols, esters, and sulfur compounds. Early in the stabilization phase, the beer is still considered "green" because the flavors have not yet reached equilibrium.
During the stabilization phase, the beer is conditioned. During this phase, the yeast reabsorbs the diacetyl produced during fermentation, hydrogen sulfide also escapes from the fermenter as a gas, the Clausen decreases, and the yeast begins to settle or flocculate. You will see little change during this phase, and you must measure the specific gravity of the wort to determine how much it has decayed. You know fermentation is complete when the specific gravity readings stabilize at the same level for several days.
Please note: some yeast strains will flocculate before reaching their final specific gravity. If this happens, you will need to "wake" the yeast back into solution. This is done by rapidly sparging the beer with carbon dioxide through the vent at the bottom of the tank. Never use oxygen.
During the conditioning stage, the lager can be transferred to the brite tank (optional), and special care must be taken to prevent the ingress of oxygen. When the beer temperature drops to 0-3°C, the yeast will continue to flocculate and precipitate. At the same time, the beer will usually "mature" slowly due to the reduction of various undesirable flavor substances in the beer. However, ale beer does not benefit from long-term conditioning like lager beer.
The flavor and aroma required for ale beer may weaken over time. For example, for IPA beer, which requires a good hop aroma, aging will reduce the taste of hops. In addition, any oxygen entering during this stage will damage the overall quality of the beer and shorten its shelf life.
During this conditioning phase, we will see:
Most of the yeast is precipitated from the beer (and can be discarded), making the beer clearer.
Proteins that create haze form and precipitate.
The beer becomes "smoother" as the harsh flavors mellow or decrease.
Sulfur compounds, diacetyl, and acetaldehyde decrease.
The overall flavor stabilizes.
For optimal beer fermentation results, we recommend following these steps.
Before adding yeast, record an initial specific gravity sample.
Pitch yeast and set the specified fermentation temperature.
Maintain good hygiene and record specific gravity daily.
If you can control the temperature…When your gravity is 2-3 points away from your desired final gravity, increase the fermentation temperature by 3-4 degrees Celsius. This is critical to the quality of your beer as it ensures that the yeast remains healthy and any undesirable byproducts produced during the fermentation process are removed.
Keep a record of the gravity daily. If the gravity remains the same for 3 consecutive days, you can be sure that the fermentation is complete.
The stages of beer fermentation are indeed a topic worth discussing. Understanding everything that happens during the fermentation process can help improve the quality of your beer. Beer brewing is a very advanced discipline. New technologies and processes are constantly emerging or developing over time, so you need to continue to learn and improve.
