End of Fermentation : crash cool or slow cool ?

[AndyBWood]

Evening All,

My first fridge fermentation is over and I have to say that this is already the best AG I've made; almost drinkable now !

Brew has been in the fermentor 10 days, hydrometer stuck at 1.010 for about 4 days, left it to clean up a bit.

Now, as I have a fridge I'm considering cooling before bottling & kegging to really pack the yeast down but..... what temp do I go for and for how long ?

Would you 'crash' cool or 'slowly - slowly' ?

If it makes a difference, I also want to harvest the yeast from the bottom of the fermentor one the beer is transferred.

So, is it cool to crash or will I crash by cooling......

Cheers

A

 

[Dave1970]

I crash down to about 2 degrees (which is as cold as my fridge goes) for 3-4 days.

I don't think it'll have any negative effect on yeast harvesting although for future reference I believe it's better to harvest from the krausen during the ferment than from the bottom of the fermenter. You should get more healthy viable yeast this way whereas from the bottom of the FV there will be dead yeast and proteins mixed in with the good stuff

 

[graysalchemy]

I agree with the above crash cool it and in future harvest off the Krausan. :thumb:

 

[pittsy]

i have info suggesting 10c for 5 days

 

[fuzzy]

I crash to 0.5c / 1c for a minimum 5 to 7 but if I am not in a hurry I will cool for longer sometimes 2 weeks+, but it depends on the colour of the beer, the lighter the colour the longer I try to chill it for, basically the longer the better to allow the proteins and yeast to drop out.

I cool slowly rather than quickly for 2 reasons.

Firstly, on my fermenting fridges I have bypassed their thermostats so they are controlled from digital thermostats. If I was to sudden drop the temperature say from 20c to 0.5c I don’t want to cause any extra strain on the compressor by making it work extra hard for a long time trying to cool to 0.5c in one go.

Secondly in the book Yeast, the practical guide to beer fermentation by Chris White from Whitelabs (page 114), he writes

“Very rapid reduction in temperatures (less than 6 hours) at the end of the fermentation can cause the yeast to excrete more ester compounds instead of retaining them. In addition, if you plan to use the yeast for repitching, you should avoid very rapid temperature changes (up or down), as they can cause the yeast to express heat shock proteins.”

In most of my beer styles I don’t want the fruity taste from the esters so I drop the thermostat in stages usually by a few degrees (2c or 3c) every few hours. The most I would drop the temperature by is usually only a max of 5c at a time, and only if I am in a hurry to get the fermenting fridge back for another brew to go in it would I do that much.

 

[AndyBWood]

All,

Thanks for the prompt replies; appreciated :thumb:

I'll certainly have a go with the krausen next time; never liked the thought of 'interfearing' with the yeast but appreciate its what breweries have done for always traditionally done in one way or another.

Just had a read of Yeast and I'll take on board this advice too and cool in stages; makes sense to look after yeast and put them to sleep gently. To be honest, I wouldn't like to be kicked out of a toasty 20 degree bed into the cold either.....

Thanks again

A

 

[winelight]

Depends what you mean by "crash cool", and depends where the temp sensor in your fridge is.

If the sensor is in the air, then it's going to take a long time, maybe 24 hours, to drop the temp of 23l of wort anyway. Is that "crash"? I don't know. This avoids the problem of overloading the compressor, since what happens is it cools the air temp down to your target temperature relatively quickly, but of course as soon as the compressor switches off, the bulk of that huge amount of warm liquid quickly warms up the fridge air and the compressor comes back on after whatever delay you have set (which is why I have mine set to 10 minutes). I would say that's a pretty gentle cooling.

If you have the sensor in the wort, then the compressor will run flat out until the wort reaches the target temp. If the sensor is in the middle, then you will get a temperature gradient across the wort and the outside will be cooled a degree or even 2 cooler than the STC is set to. But even so, it's going to surely take many hours to cool the whole lot down, much more (I would think) than the 6 hours quoted in that extract.

To me, the only way you can "crash cool" is a coil with cold water or other coolant running through it immersed in the wort. But I've never seen a definition of "crash" so I could be talking rubbish.

 

[Dave1970]

My 'crash cool' takes about 12-14 hours so I'm not too worried about the 6 hours mentioned (That's with the probe in a bubble wrap pocket on the outside of the FV).
My fridge is plugged into the controller so it's own thermostat will still kick in from time to time protecting the compressor and as discussed earlier I will have already harvested yeast from the krausen so not worried about any detrimental effects on the health of the yeast

 

[Fil]

Its a damn good fridge that can chill down 20+L to 0-2C in less than 24 hours (probe external to beer).

So dont fret about damaging the yeasts activity and off flavours, chill to the lowest temp u can imho

When kegging into a corny the cold beer is a filling aid as u can check the fill level easily by how high up the condensation on the keg is

When changing temp in my fridge i set the temp difference that triggers input to a 3 degree window, so as it cools the fridge interior to target and shuts off any nominal over-chill that takes place doesn't trigger heating..

 

[AndyBWood]

Evening All,

Thanks again for all the replies.

Unfortuately, the old fridge I bought has decided to throw in the towel anyway so back to square one again.

Everything was going well up until now with this brew; I will get it right one day.........

Cheers

A