Troubleshooting -Resuspending Yeast
If fermentation slows or never takes off, it's possible the yeast has prematurely dropped out of suspension and needs to be resuspended. "I bubbled CO2 from the bottom of the tank" is a common note from brewers. While this can work on occasion, bubbling CO2 does not effectively resuspend yeast compared to other techniques.
Bubbling CO2 from the bottom will push the yeast that's directly above it, but will do very little else to the yeast on the sides of the cone. Also, in the instance of very flocculant yeast, the gas can merely bubble through the large clumps of yeast without truly moving the yeast. We recommend using a pump to resuspend yeast. Connect short brewery hoses from the bottom of your tank, into your pump inlet. From there, connect the outlet of the pump to a hose that's connected to the racking arm. Use sight glasses on both ends to visualize the yeast/beer slurry. You'll then need to pasteurize this loop from either end with 180F water for 15-20 minutes. Purge the lines and set your pump to its lowest setting to begin the circulation. You can adjust the racking arm to point at different locations on the cone as well. 15-20 minutes of recirculation should be sufficient and you will see the yeast mixing in with the wort. This method requires more setup than bubbling CO2, but it works very well. It can be used both at the beginning of a brewed batch, prior to fermentation starting, or used during the ferment to assist the yeast in full attenuation.
Lagers
This method is particularly useful when brewing lagers. If you cast out at 50F or lower, know that there will be a temperature difference from the probe height, down to the bottom of the tank. In some instances, we've seen the bottom of a tank measure 7-8F cooler than the reading at the height of the temp probe. It's always good to remember that cold air and liquids fall, while warm air and liquids rise. Yes, lager yeast will ferment at 50F, but if you cast out into the FV at 60F and the glycol jackets were on for several hours working to lower the temperature, it's very possible your yeast dropped out of suspension and is having a hard time resuspending itself. This can cause an exaggerated lag phase. Raising the temperature and resuspending the yeast is necessary to speed up the start of fermentation.
Using a pump to resuspend yeast can also be helpful if you decide to repitch yeast during fermentation. We'll discuss this method in another post.
Lagers
This method is particularly useful when brewing lagers. If you cast out at 50F or lower, know that there will be a temperature difference from the probe height, down to the bottom of the tank. In some instances, we've seen the bottom of a tank measure 7-8F cooler than the reading at the height of the temp probe. It's always good to remember that cold air and liquids fall, while warm air and liquids rise. Yes, lager yeast will ferment at 50F, but if you cast out into the FV at 60F and the glycol jackets were on for several hours working to lower the temperature, it's very possible your yeast dropped out of suspension and is having a hard time resuspending itself. This can cause an exaggerated lag phase. Raising the temperature and resuspending the yeast is necessary to speed up the start of fermentation.
Using a pump to resuspend yeast can also be helpful if you decide to repitch yeast during fermentation. We'll discuss this method in another post.
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