Yeast recovery and disposal are daily production concerns for beer manufacturers. Understanding the key points for yeast recovery and disposal in beer equipment can help save beer production costs.
1. Yeast recovery and disposal: The timing of yeast recovery is crucial. Previously, we started recovering yeast after diacetyl reduction, but we found that the yeast mortality rate was higher, around 7-8%, which would be detrimental to the next fermentation cycle. Through repeated experiments, controls, and follow-up yeast testing, we discovered that most of the yeast settles at the bottom of the cone after 4-5 days of sealing, with only a small amount suspended in the beer for diacetyl reduction. At this stage, yeast recovery has no effect on diacetyl reduction, and the mortality rate of recovered yeast is reduced to 2-3%. Proper preparation work before recycling is also important. The yeast temporary storage tank must be cleaned with hot water at 80℃, then cooled to 7-8℃, and provided with a certain amount of sterile air to prevent sudden decompression and yeast cell wall rupture. When recovering yeast from the cone tank, it is advisable to take the whiter part in the middle, and after complete recovery, slowly cool it down to about 4℃. The yeast should be used within 36 hours if stored in the yeast tank.
2. When the temperature drops to 0℃, frequent yeast discharge is necessary. Otherwise, due to the high temperature at the bottom of the cone, the self-dissolving yeast will produce its own odor, and the amino acids released during self-dissolution will enter the beer, resulting in a rough bitterness and astringency. Moreover, proteins produced by yeast autolysis are prone to precipitate and form sediments under the beer’s acidic conditions, especially during high-temperature sterilization, which compromises the colloidal stability of beer. Therefore, yeast discharge work in the later stage of beer storage cannot be neglected, especially in summer.
3. Yeast’s impact on beer flavor: Beer with a pure taste should not have a yeast flavor. However, if the fermentation and storage temperature is high, fermentation is not vigorous, a large amount of yeast is added, or the yeast ages, it can lead to yeast cell autolysis, resulting in a varying degree of yeast flavor in the final beer. Therefore, dead yeast and cold protein sediment at the bottom should be promptly discharged within 24 hours after the tank is full. After meeting the process requirements for diacetyl reduction, cooling should be initiated, and the tank of self-brewed beer equipment should be opened and cooled promptly to prevent yeast self-dissolution.
4. In conclusion, yeast plays a crucial role in determining the flavor of beer during the brewing process. Only by utilizing and managing yeast correctly can good beer be produced.