"Munchies" set their own ferment temperature.

[Worthog]

I've noticed over many brews now that the yeast sets its own fermentation temperature for the initial couple of days.

 

I have a fridge and use a Willhi (single relay) temp controller for starting/stopping fridge in summer. The ETC controller probe is taped with electrode not touching anything to the inside of the fridge approx level with bottom 1/3rd of the FV. So this controls the fridge temperature.

 

I then have an electronic temperature gauge with the probe taped under a piece of insulation to the side of the plastic FV at approx the same height as the ETC probe. This tells me the fermentation temperature.

 

If the fridge temperature is set to between 18-19.5c (Ales) via the ETC, then this is the fridge temperature I consistently get.

 

Now, when the fermentation of a new batch begins, at say 21c wort temperature which is my usual starting point for ales, it will very slowly drop until the rapid fermentation kicks in. The temperature for the next 2-3 days will rise to 21.5c, and as the fermentation dies down the temperature will reduce to 19c for the duration of the 6-9 days.

 

This tells me the fermentation process generates it's own heat, and if I did want to overpower that higher temp I would need to go drastically down with the ETC for the first 2 days.

 

So the question is; Is this initial 2 day 21.5c fermentation a problem if I'm supposed to ferment at 19c?

 

Cheers,

[Otto Von Blotto]

Yes, it's well known that fermentation generates heat. This is why I don't think there's much use in controlling the temperature of the fridge because you don't necessarily know how much heat the fermentation will generate at any given point in the fermentation, thus pretty much guessing where to set the fridge temp. If your intended ferment temp is 19C and it's fermenting at 21.5C, it's not necessarily a problem, but the flavor profile will probably be a bit different.

 

What you're better off doing is taping the temp probe from the controller to the side of the FV underneath some foam and measuring the temp of the brew. This way the controller switches on and off the fridge to maintain the brew temp; as long as the brew temp stays where you want it, it doesn't matter what temp the air inside the fridge is.

 

 

[Worthog]

..What you're better off doing is taping the temp probe from the controller to the side of the FV underneath some foam and measuring the temp of the brew. This way the controller switches on and off the fridge to maintain the brew temp; as long as the brew temp stays where you want it' date=' it doesn't matter what temp the air inside the fridge is.

[/quote']

 

Yep, thanks Kelsey. Since your post I went out and did exactly that, then wondered why I decided in the first placed not to run the ETC probe directly onto my FV;

 

During the past late winter (NE Victoria) when I had both my Willhi ETC's running, one for cold and one for heat, both probed directly onto the FV under lagging, I was worried that the heat pad might run for a very long time to heat the 23 litres of brew. I was also worried that the heat pad might introduce "hot spots" directed to limited parts of the FV. BTY I have my heat pad vertical near side of FV, not cooking the cake from underneath.

 

(I should say here that I also have a couple of "heat belts" which I don't trust due to their localised heat. Don't ever place them in a fridge if they are not wrapped around a filled FV, ie don't dangle them; they get dangerously hot, I have burned my fingers and wondered about the rubber casing).

 

Because we have freezing temperatures in my shed in winter. I decided then that if I ran the fridge rather than the FV to temp, then the heat pad would switch off earlier. and theoretically the FV should end up the temperature of the fridge.

 

Anyway, it wasn't until this summer when I had the cold ETC only running, that I became aware of the self heating fermentation phenomena of the munchies.

 

I will now "probe under insulation" the FV only, and have another think about my winter process.

 

Cheers and thanks,

 

 

[Greenyinthewestofsydney]

My ferm fridge is in my garage which is connected to my house. Lowest temp in a sydney winter is probably about 6 or 7 in there. Have found in my 3 years brewing in the fridge that I have never needed a heat source. The insulation of the fridge and heat generating properties of the yeast doing its thing will keep the temp high enough that I only need cool. When the fermentation dies down I take it out and wack a heat belt on it for the diacetyl rest or to get it to finish off.

[Worthog]

My ferm fridge is in my garage which is connected to my house. Lowest temp in a sydney winter is probably about 6 or 7 in there. Have found in my 3 years brewing in the fridge that I have never needed a heat source...

 

With subzeros here from close to midnight in winter my shed fridges still go as low as 13-14c if turned off, but that is not FV temp is it, but we don't want temp variation in the FV.

I may still hook up my heat source to my second relay but you are most likely right that it wont operate much.

 

That said, my probes will be directly connected to my FV, not fridge internals.

 

Cheers,

 

 

[ChristinaS1]

Your observations are spot on Worthog. Instead of pitching your yeast at 21C, try pitching it at 18C, so the peak temperature will be that much lower. Pitching temp is one of the main way you can influence fermentation temperature, if you don't have a brew fridge.

 

It is also important to use some form of insulation to protect the fermenter from ambient temperatures, and keep the cold in. My "chamber" consists of a couple of layers of foil faced bubble wrap, with about a 5cm gap around the FV, and three old towels for a lid. You could probably use a cardboard box with a couple of sleeping bags thrown over it instead.

 

Once you see a bit of foam developing on the surface (which coincides with a slight (0.2C) increase in temp) put a blue ice pack in your "chamber" and swap it out every 12 hours, until fermentation starts to slow. Ice packs are usually only required for two or three days. After that it is okay if the temperature rises.

 

It is *very* important to use those proper, blue ice packs from the store, and not frozen bottles of water. Ice will NOT give you good temperature control; in fact, it will bounce around all over the place. So don't cheap out, buy some blue ice packs; they aren't even expensive. The ones I use are "medium" size and measure 20mm x 15mm x 3.5mm. Depending on the ambient temperature outside your insulation, you may need slightly larger or smaller ice packs.

 

Cheers,

 

Christina.

 

PS Ice is okay for an ice water bath, but not for chilling air.

 

[Otto Von Blotto]

Christina, did you miss the part about Worthog having a brew fridge?

 

One solution to that is to take the heat pad off the fermenter altogether and just place it inside the fridge somewhere to heat the air. Or use something that doesn't get ridiculously hot; a lamp underneath a terracotta pot is a common one. Obviously as you've found, it won't be really needed at all during the active fermentation stage, or in summer. In any case, the heat pad won't stay on any longer than it needs to. Once the temp rises to the set point, it will switch off, just the same as the fridge switches off when the temp drops to the set point.

 

I have a similar situation to Greeny, in that I never need heat inside the brew fridge - or at least not often enough to bother with an electrical heat source. On the odd occasions I do require a bit of heat in there, I just grab an Erlenmeyer flask, fill with water and boil it, then stick that inside the fridge. Works well.

 

Cheers

 

Kelsey

 

 

 

 

 

[ChristinaS1]

Christina' date=' did you miss the part about Worthog having a brew fridge? [img']tongue[/img]

 

Doh! That's what I get for just skimming the post. All I got out of it is that he was noticing temperature changes consistent with ambient temp brewing.

 

I guess that is what he had going on. With the temperature probe hanging in mid air like that, the fridge was sort of like a small, air conditioned room.

 

I'll try to pay more attention next time Worthog. Sorry about that!

 

Cheers,

 

Christina.