Temperature Control

My fermentation has just kicked in an my wort has been running at 24c all day (it stipulates 18-20c) whilst I've been out all day. I put my brew belt on this morning as the wort was below temperature.

How imperative is it in the primary stages of fermentation (particularly during the first 48 hours) that I keep my brew at a steady temperature and how do I achieve this in a cellar with a brew belt without my temps going up and down all the time.

Any ideas?

For starters, if you don't have a cooling source to bring the temp DOWN, I wouldn't use a brewbelt, which is designed to keep temps up.

It's VERY important to keep temps fairly stable and in the yeast's preferred range. At 24C you're too high. If this is the first big day of fermentation, the results are likely irreversible and you're going to get higher alcohols/fusols/jet fuel/hot type esters from the yeast. I'd get the belt off of there. If the temp dipped one degree below the target it won't hurt you. If the belt kicked in and thrust it 4 degrees ABOVE the target, it'll have a negative impact.

Great :/

Well what yeast are you using? 24C might be okay.

24C = 75 F. That's too hot for almost any yeast besides Saison.

It was just a dried yeast that came with the beer kit. It didn't say on it what strain of yeast it was.

The FV was at 24c for around 3 hours, after which I turned the belt off and allowed the wort to cool.

Now it's back to 20c where it should be.

Have I totally ruined my beer on that 3 hour period?

There may be some off flavors, but it will still be beer at the end.

So when people say 'off flavours' what do they mean? Is it something that's going to be terribly noticeable or just kind of like, 'that tastes okay but with a strange twang'?

Off flavors are basically unintended flavors. Yeast can produce different flavors at different temperatures. In particular, yeast tends to produce harsh alcoholic/solvent and fruity/green apple flavors when operating above its preferred temp range. Even within the temp range the flavors can vary. This varies from strain to strain.

http://www.howtobrew.com/section4/chapter21-2.html

Honestly, unless you're a seasoned beer taster, or you had the "correct" beer to directly compare the taste against, you might not even notice unless it's really bad. Either way, you made beer that will be drinkable. If you don't like it then send it to me.

LOL! Thanks.

nicklawmusic said:

So when people say 'off flavours' what do they mean? Is it something that's going to be terribly noticeable or just kind of like, 'that tastes okay but with a strange twang'?

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if you think that "beer is beer" then you may not mind drinking a hot fermented beer. if you've had a hot ferment with an ale yeast you can expect solvent like flavors that will not go away with time. a beer like this i would just dump.

I tend to agree with eastoak. Life's too short to drink bad beer. I would brew another batch and focus on getting your temperatures down. There are many ways of doing this that you can find with a quick search of the forums.

As it's my first batch, I'll ride it out for the sake of going through the process. It's not the end of the world.

I fermented too hot on my first batch and the yeast produced an unintended banana flavor...the smell was almost overpowering and I considered scrapping the batch. Instead I let it sit and age a little while. The resulting beer was actually quite pleasant! i got a few compliments on it too! Moral of the story: Don't assume your batch is ruined unless you get some nasty infection that would make it dangerous to drink. Heck, I think beer/mead/wine were all created originally by mistake right?

I can just hear it now, "Wow, that stuff has been sitting there for a few months...but I am really thirsty...oh what the h***!" LOL

Thanks. I guess what I'm trying to get my head around is whether the quantity of off flavours is directly proportional to the length of time you overheat? Or does it mean that if my fermentation overheats for 30 minutes all the off flavours come out?

nicklawmusic said:

Thanks. I guess what I'm trying to get my head around is whether the quantity of off flavours is directly proportional to the length of time you overheat? Or does it mean that if my fermentation overheats for 30 minutes all the off flavours come out?

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some where between 12-24 hours is the point of no return depending on the yeast and how hot it gets.

It was around 3 hours at 24c (possibly 33c) and 2 at 22c whilst I brought the temperature down.

If you can get your process down to where you are pitching your yeast at your targeted fermentation temperature, and hold it there, you'll get the flavor profiles that you're looking for from your yeast and you'll eliminate almost, if not all, yeast derived off-flavors. It is easily the best improvement that you can make with your brewery.

Darwin18 said:

If you can get your process down to where you are pitching your yeast at your targeted fermentation temperature, and hold it there, you'll get the flavor profiles that you're looking for from your yeast and you'll eliminate almost, if not all, yeast derived off-flavors. It is easily the best improvement that you can make with your brewery.

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Good point! On my 2nd brew I made darn sure the wort was at the desired fermentation temp before pitching. The yeast was about 10F higher. For my next batch, I'm going to pre-cool my top-off water so I don't have to worry about getting my boil down to room temp which takes forever even with a wort cooler.

I agree with Darwin18, temperature control during the first two or three days is paramount. Longer if possible. I would say yes, that higher temps for the first three day can/will produce unwanted results. I personally know from experience the things that can happen early in the fermentation when temps are too high: hot alcohol taste, buttered popcorn flavor,and nail polish remover smell too. I mostly fixed the problem by leaving the beer in the fermenter for months. The nasty taste was almost gone, and then after bottling a couple more months to rest, I could still taste it, but nobody else seemed to notice.

nicklawmusic said:

So when people say 'off flavours' what do they mean? Is it something that's going to be terribly noticeable or just kind of like, 'that tastes okay but with a strange twang'?

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It depends on how warm you pitched, how far above the proper temp range it fermented and whether or not you under-pitched the yeast. It's essentially unwanted flavor(s) in the beer that can be anything from just a slight "twang" to so nasty that it taste like a**.

nicklawmusic said:

It was just a dried yeast that came with the beer kit. It didn't say on it what strain of yeast it was.

The FV was at 24c for around 3 hours, after which I turned the belt off and allowed the wort to cool.

Now it's back to 20c where it should be.

Have I totally ruined my beer on that 3 hour period?

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No. And I certainly didn't mean to say that in the first response to the thread. But your question was how much does it matter, and it DOES matter a lot. It'll still be beer, but I bet it won't be as good as the next one you brew when you don't bother with the belt, or turn the settings WAY down on it.

What happens is that when it turns on, the thermal inertia of the wort takes a while to heat up and then the belt shuts off when it gets to temp. But inertia doesn't stop there, the wort temp continues to rise to several degrees above the set point of the belt, and therefore overheats your wort.

In the future, if the ambient temp in your basement is a few degrees below where you want to ferment at, you can let the yeast's own heat production take care of the difference. I deal in Fahrenheit, but I'd say if you want to ferment at 65 and your ambient temp is 60, you're in a pretty good place. For finishing out really big beers after 3-4 days of fermentation are done you can start using the brewbelt to ratchet temps up gradually to the 70F+ range. The key is that fusol alcohol production generally happens in the first 72 hours of fermentation so turning up the heat for a few days after that won't hurt your beer.

Edit, it sounds like you weren't too hot for too long, so the effects could be mild. It's still beer. I personally dump batches that don't turn out right, but then again, I've brewed almost 70 batches of beer, and I brew 2-3 times a month, so I have that luxury. I wouldn't recommend dumping your first ever batch of beer unless it's completely unpalatable. You'll probably be alright, but what's been shared in this thread will help you make your next batch even better.