Temp controller strategies

[heyjaffy]

I just started fermenting a batch o' brew (AHS Milk Chocolate Stout) in my old keezer with dual-stage temp controller. This is my first time fermenting with temp control - in the past the only temp control I've had is via swamp cooler and in moving the fermenter around to different spots in my house. I'm pretty excited to be able to lock in a specific temperature.

I've heard of starting the fermentation on the warm side and then moving to a cooler temp - is there a guideline here? e.g. keep the temp on the warm side of the yeast temp range for x hours or days then move the temp to the cooler side of the yeast temp range until fermentation finishes? What is x in that equation?

 

[Grizzlybrew]

If anything... I would suggest keeping the yeast at the cooler end of their respective fermentation temps at the beginning and then move it to a warmer resting spot.

The majority of esters are formed during the reproduction stage and can be minimized by lowering the temps and relaxing the yeast.

At the end of a fermentation, you don't want the yeast to peter out and raising the temps (within the normal fermentation range for the strain) can promote activity and a strong finish to the fermentation. Any time you decrease the temp of a fermentation, you run the risk of the yeast becoming 'shocked' and becoming dormant and leaving you with an under-attenuated fermentation.

Start cool, finish warm.

 

[william_shakes_beer]

If anything... I would suggest keeping the yeast at the cooler end of their respective fermentation temps at the beginning and then move it to a warmer resting spot.

The majority of esters are formed during the reproduction stage and can be minimized by lowering the temps and relaxing the yeast.

At the end of a fermentation, you don't want the yeast to peter out and raising the temps (within the normal fermentation range for the strain) can promote activity and a strong finish to the fermentation. Any time you decrease the temp of a fermentation, you run the risk of the yeast becoming 'shocked' and becoming dormant and leaving you with an under-attenuated fermentation....

...which will resume when the yeast are stirred during racking and bottling, potentially leading to bottle bombs.

Depending on your temp controller sensor location, you will need to adjust the sensor setpoint to compensate. I just got a digital thermometer last night and dropped it into the wort on my batch. The controlelr sensor is taped to the outside of the bucket in a block of foam insulation. It reads 61-62F. the inside probe reads 67. That's after 2 weeks fermentation, when primary fermentation (and yeast heat generation) has subsided. My next batch I'm going to take daily readings, comparing the 2 over the entire 4 weeks primary to see if the difference is constant.

 

[Snafu]

Thats pretty much what I do as well, the IPA I'm doing right now is in the FC @ 64deg (per white labs web site for optimum range). I dropped the temp last night to cold crash @ 40deg. After I get it kegged I'll let it sit in the house 70 - 72 for maybe 2 weeks to let the yeast clean it up and finally move it to the keezer.

 

[DSmith]

...which will resume when the yeast are stirred during racking and bottling, potentially leading to bottle bombs.

Depending on your temp controller sensor location, you will need to adjust the sensor setpoint to compensate. I just got a digital thermometer last night and dropped it into the wort on my batch. The controlelr sensor is taped to the outside of the bucket in a block of foam insulation. It reads 61-62F. the inside probe reads 67. That's after 2 weeks fermentation, when primary fermentation (and yeast heat generation) has subsided. My next batch I'm going to take daily readings, comparing the 2 over the entire 4 weeks primary to see if the difference is constant.

Did you test that the digital thermometer and the controller sensor read the same before putting them in different locations to collect data and compare? Is the controller sensor "in" foam insulation? That sensor needs to be between the side-wall of your fermenter and insulation (preferably touching the fermenter). Your experiment sounds very interesting and I'd expect no significant temperature difference between the one in the wort and the one under insulation outside the fermemter with calibrated equipment.

 

[heyjaffy]

My comment about starting warm then dropping temp a bit I believe was based on the advice to start warm to ensure that fermentation takes off quickly. At this point I've just started and held temp at 68 degrees. The yeast is WLP013 which has a fermentation temp range of 66 - 71 degress, so 68 seemed like a good midpoint. I have my temp probe in a thermowell that is set right down in the middle of the brew. Visible fermentation activity started within approx. 6 hours and went strong for about 36 hours then slowed significantly. I guess this is something I'll have to test with the different yeasts I use. This is my first try with WLP013.

 

[diS]

Starting warm is good when we have to cope with smaller pitch size because it will ensure high cells growth during lag phase. Negative consequences of rapidly growth in earlier phase is that it will affect flavors more than if we keep temperatures low at this stage of fermentation. Also, too much growth in lag phase creates cells with low condition.

If I have right amount of yeast, I try to pitch little bellow fermentation temperature, and then allow temp. to rise in the next 12-36 hours. This way yeast growth is controlled, which results in better yeast health and less leakage trough cell membrane (which forms diacetyl).
When fermentation temperature is reached, I keep it until last 1/3-1/4 of fermentation, then raise it several degrees for next 1-2 days so the yeasts can attenuate fully and reduce compounds produced earlier in fermentation.

 

[vera]

Starting warm is good when we have to cope with smaller pitch size because it will ensure high cells growth during lag phase. Negative consequences of rapidly growth in earlier phase is that it will affect flavors more than if we keep temperatures low at this stage of fermentation. Also, too much growth in lag phase creates cells with low condition.

If I have right amount of yeast, I try to pitch little bellow fermentation temperature, and then allow temp. to rise in the next 12-36 hours. This way yeast growth is controlled, which results in better yeast health and less leakage trough cell membrane (which forms diacetyl).
When fermentation temperature is reached, I keep it until last 1/3-1/4 of fermentation, then raise it several degrees for next 1-2 days so the yeasts can attenuate fully and reduce compounds produced earlier in fermentation.

Great explanation! How do you know when you've reached the last 1/4 of fermentation. I ferment in soda legs, which means I can't observe the krausen.

 

[pm5k00]

I have my temp probe between the carboy/bucket and a piece of styrafoam or cardboard depending on the vessel. I have taken many readings and have found the temp inside is 2-3*F higher than the probe on the outside and adjust the thermostat accordingly.

 

[william_shakes_beer]

Did you test that the digital thermometer and the controller sensor read the same before putting them in different locations to collect data and compare? Is the controller sensor "in" foam insulation? That sensor needs to be between the side-wall of your fermenter and insulation (preferably touching the fermenter). Your experiment sounds very interesting and I'd expect no significant temperature difference between the one in the wort and the one under insulation outside the fermemter with calibrated equipment.

The TC sensor is between the insulation and the bucket, with the sensor touching the bucket. To get it as far from the brew belt as possible it is near the bottom of the bucket, which is where the coldest part of the ferm chamber (a chest freezer) is located. The top and bottom of the sensor are, however, open to ambient temps. Every time I look at the temp controller curent reading it is consistently 61-62F. No, I did not calibrate the immersion sensor against the TC sensor, something I should definintely do before beginning the experiment. If anyone is interested, I can write up the process in a more formal manner and publish iniital and final results so others can repeat. Any interest? I was initially going to do it for my own purposes only.

 

[diS]

Great explanation! How do you know when you've reached the last 1/4 of fermentation. I ferment in soda legs, which means I can't observe the krausen.

Take a gravity reading, refractometer is great tool for this, just few drops and you know where are you standing.

 

[william_shakes_beer]

Take a gravity reading, refractometer is great tool for this, just few drops and you know where are you standing.

I have never used a refractometer. Does it automatically compensate for temperature or does that need to be done manually like a floating hydrometer?

 

[vera]

Take a gravity reading, refractometer is great tool for this, just few drops and you know where are you standing.

I thought one can only take a gravity reading if there is no alcohol.

 

[diS]

I have never used a refractometer. Does it automatically compensate for temperature or does that need to be done manually like a floating hydrometer?

If refractometer is ATC (Built-in Automatic Temperature Compensation System) it will compensate in range 10-30°C, but even if you take reading from boiling wort it will cool very fast (you need only few drops).

I thought one can only take a gravity reading if there is no alcohol.

Yes, w/no alcohol you can measure gravity instantly, but there are calculations for gravity correction.

I made a chart to calculate it easily:
https://www.homebrewtalk.com/f163/brix-sg-conversion-chart-og-fg-attenuation-302327/