Consequences of temperature fluctuation?

Greetings, I'm a new brewer, currently in the stage of my first brew where I worry about everything!

It was the house-written extract Hefeweizen recipe of my brew shop. I believe my cleaning and sanitation were thorough, and that I did the recipe as directed, with one exception being that I put all of my extract in at the beginning of the boil instead of doing the dry at 60 minutes remaining and the liquid at 30. My brew shop owner advised me to make that change because I let him know I had a 10-gallon pot and could do the full boil.

The boil went as planned but turned out darker than I expected, though the wort still tasted like wheaty wort, so I'm fairly confident that it's still the makings of beer.

Now...what I was not prepared for was the reality that without putting a big bucket in my and my roommates' walking path, I can't really find a sweet spot in my drafty apartment that will consistently stay in the recommended temperature range for my Wyeast 3068 yeast (65-70 degrees). Like many apartments in NYC, the temperature swing between a spot by the window and a spot by a radiator can be drastic.

The smack pack swelled as expected, I pitched it at about 4 pm on a Monday afternoon, and I had vigorous airlock activity by the time I woke up in the morning. :rockin: But I also had the temp in my cabinet drop somehow to high 50s while I was at work. The bubbles were still going, though.

Would it be true to say that more off flavors are caused by too-high temperatures than too low? (I've read an article or two now on what causes off flavors, and there's much more talk about too warm than there is about too cool.) If the weather in my cabinet dips into the high 50's for a few hours a day, what is the worst that can happen? A somewhat-slowed-down fermentation?

Am I totally off base and should move it to a mid-to-high 70's spot? Should I just straight up not mess with it, at least while it's bubbling seemingly happily?

Thanks! Looking forward to getting some of these worries out of my system!

Remember the air temp does not equal liquid temp. Could be as much as 10 degrees higher. Cooler temps will be fine. Higher temps could produce off flavors. 5 gallons of beer take a bit of time to change temps.

The high 50's won't really hurt. The fermenting wort is about 10 to 15 degrees hotter than the ambient temperature. I'd keep it there until active fermentation slows then move it to the area around the 70's to finish.

Higher temps attribute more fusel alcohol type flavors.

Lowers tend to give off somewhat fruitier flavors (i think)

mrrshotshot said:

The high 50's won't really hurt. The fermenting wort is about 10 to 15 degrees hotter than the ambient temperature. I'd keep it there until active fermentation slows then move it to the area around the 70's to finish.

Higher temps attribute more fusel alcohol type flavors.

Lowers tend to give off somewhat fruitier flavors (i think)

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Gotcha. So the fact that it's bubbling away is a clue for me to not mess with it? I hoped that was the case!

IgloosNate said:

Gotcha. So the fact that it's bubbling away is a clue for me to not mess with it? I hoped that was the case!

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The air lock means nothing. Don't rely on it as a sign for fermentation cuz sometimes it wont bubble but things are still happening. Relax and let the yeast do its thing.

I don't know that I agree with the 10-15 degree figure. Empirical evidence sugests that 5-10 degrees is more typical. That being said, yes, you get more off flavors from high temps than from low ones (in most cases).

A rapidly bubbling airlock tells you that you have fermentation, but lack of bubbles does not mean that you DON'T - CO2 may be escaping from a leaky seal (buckets are notorious for this).

homebrewdad said:

I don't know that I agree with the 10-15 degree figure. Empirical evidence sugests that 5-10 degrees is more typical. That being said, yes, you get more off flavors from high temps than from low ones (in most cases).

A rapidly bubbling airlock tells you that you have fermentation, but lack of bubbles does not mean that you DON'T - CO2 may be escaping from a leaky seal (buckets are notorious for this).

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Oh yes, if there's one thing I got from reading the entirety of the "help, I don't think it's fermenting!" thread, it's that it can stll be fermenting even if the airlock is doing nothing.

But the fact that the airlock IS bubbling can only be good, right?

Typically, yes, but it can also just mean temp changed and the pressure in the fermenter went up.

Fair enough. The banana smell I'm perceiving is also desirable, right?

IgloosNate said:

Fair enough. The banana smell I'm perceiving is also desirable, right?

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Hefeweissen are known for having banana esters as part of the flavour/aroma profile so, yes. A lot of the time the smells that escape from the air lock are not necessarily there when the beer finishes fermentation.

Towards the end of the first few days of initial fermentation you might want to look into raising the temp of the fermenter so that you can encourage the production of some desirable estery flavours/aromas that your yeast strain is known for, if you are looking to have them.

Ok, final question...I have been convinced by the talk here to, in general, allow about 3-4 weeks in the initial bucket as a substitute for what people used to do with a secondary fermentation in a carboy.

But I know hefeweizens are meant to be cloudy and yeasty and drunk young compared to many other styles. What's the happy medium here? If I'm at my desired gravity at say, 7 days, does it make sense to bottle at say, the 2-week mark?

Thanks again, everybody. This is a really cool community.

It's really up to you. If you are at a stable gravity in the correct FG range, you can bottle without the risk of bottle bombs. If you want to let your beer sit a while, it will (in general) get better. However, as you said, your beer is meant to be consumed young. So "better" on this case may actually be less "to style" because of the estery flavors that will fade.

Basically, it is totally your call. Personally, I would do exactly what you said and bottle a few days after a stable FG is determined. Others may disagree.