The Time And Principle Of Recycling Yeast

1.The time of yeast recovery
A. Middle of primary fermentation, 10 or 12℃; B. Diacetyl reduction finished; C. Diacetyl reduction finished; D. Diacetyl fermentation finished.
B. Diacetyl reduction complete.
C. Cooling to 5°C;.
D.Cooling to 0-1°C.
Yeast should not be recovered after 7 days, because too long storage in the beer will affect the yeast activity.

2. Principle of yeast recovery
   After settling at the bottom of the fermenter, the yeast is usually under a pressure of 0.19-0.24Mpa. Therefore, the yeast must be recovered under pressure. If it is emptied with atmospheric pressure, the yeast will be harmed or even broken due to the sudden decrease of pressure. In this case, the mortality rate of the yeast will undoubtedly rise. In addition, carbon dioxide will be blown away, producing a large amount of foam, which will turn the white yeast brown.

The yeast will be at its best when the residual sugar drops to 3.6-3.8°P or before the second cooling. Recovered yeast should be clean, pure, free of bad bacteria, neatly arranged cells, and methylene blue staining should be less than 5%.