Does ale fermented cold require a Diacetyl rest?

[Jim Brewster]

I recently brewed my winter ale, which has been fermenting for a week in the kitchen at ambient. Just noticed the thermometer in the cupboard is reading a chilly 12C, and assuming the weather stays cold I am wondering if I need to do a Diacetyl rest before I bottle it in another week's time?

Yeast is US-05

 

[dmtaylor]

In my experience, US-05 doesn't make diacetyl, but when fermented cold it sometimes does produce more peach esters. If your winter ale turns out unusually peachy (maybe a 50/50 chance?), you'll know why.

 

[MashBag]

Just noticed the thermometer in the cupboard is reading a chilly 12C

Are you sure that is ambient room temp, and not cupboard temp.

 

[RichardM]

Isn't 12c a bit cool for US-05? The Fermentis website recommends 18-26°C
I would expect it to take more than two weeks to be ready for bottling at that temperature.
I would perform a diacetyl rest to be on the safe side

 

[The Baron]

A rise in temp will also aid the yeast to clean up too, I would do it

 

[Twostage]

Test it. Stick a small sample in a microwave for 30 seconds and smell it. If it smells of butterscotch it needs a D rest.

 

[Jim Brewster]

Are you sure that is ambient room temp, and not cupboard temp.

Well yes, it's the temperature in the cupboard where the DJ is kept, up against the wall so it's got quite cold in there.

Isn't 12c a bit cool for US-05? The Fermentis website recommends 18-26°C
I would expect it to take more than two weeks to be ready for bottling at that temperature.
I would perform a diacetyl rest to be on the safe side

Yes, not ideal. I've never used temp. control, just hadn't anticipated this cold spell so early in December. It'll be an interesting experiment anyway to see how it turns out, what different flavours might come out.

 

[Jim Brewster]

After a week now, it has sort of cold-crashed, and there is very little activity. Decided to take the air lock off and get the aroma - and even at this temperature which is still showing at 12 I am pretty sure I can smell butter, at least now I have a reference to check against. I'm definitely leaning towards doing a d-rest now, and probably leaving it a lot longer than usual, it won't be ready for Christmas but something for the new year instead. If it's a failed brew so be it, there's only a gallon after all

 

[dmtaylor]

Oh bummer. Yeah I guess it was too cold. Might take several weeks for the diacetyl to get eaten by the yeast, now that fermentation is complete and the yeast mostly inactive.

 

[foxy]

I recently brewed my winter ale, which has been fermenting for a week in the kitchen at ambient. Just noticed the thermometer in the cupboard is reading a chilly 12C, and assuming the weather stays cold I am wondering if I need to do a Diacetyl rest before I bottle it in another week's time?

Yeast is US-05

US-05 is OK at 12C but that is the fermentation temperature, not the thermometer in the cupboard temperature. So the exothermic-driven temperature of the yeast actively devouring sugar and making CO2 will be higher than the cupboard temperature. You can rest it for a couple of days at the same temperature when it's finished.

 

[MashBag]

You could always tip a spoon of sugar in it and warm it up, for a couple of days?

 

[Jim Brewster]

I brought it up to around 18C for a few days and bottled, it still smelled a little weird but being an experimental winter ale of pine and rosemary I wasn't completely sure what the aroma was.

If there is diacetyl will it condition away in the bottles?

 

[Twostage]

As you will be putting sugar in, the yeast will burst back into life as @MashBag mentioned above. It will definitely help.

 

[Jim Brewster]

Opened the first one yesterday and it turned out quite nice, no hint of butter in the aroma or taste, the bottle conditioning phase must have cleaned it up