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At the moment it's bloody cold (by our standards) in the U.K. 0 degrees C tonight. I keep the fermenters inside but my house is pretty cold as well (I wear a coat until I get into bed). The temperature is fine for fermentation because I can see the air locks going but the normal washes (UJSM and a black treacle thing) are taking and extra week or so to finish. I can't afford to heat the vats so I guess I'm stuck with these slow ferments.

I'm going to put on another batch so the rate of production doesn't slow but I was wondering what effect these slow fermentations will have on the flavour. I think I'm right in saying they ferment lager at lowish temperatures and I read somewhere that a low temperature fermentation produces a "cleaner" flavour (this was in wine making circles).

Is there going to be any difference at all? Could I use these conditions to my advantage or does it just slow the whole process down?

there is a slight advantage but distilling you mite not notice.

You mentioned treacle so I will jump in. My still room sits at 5 deg C so I have my fermenters heated with 75w soil heating cables that you normally use for seed germination. Wrapped in blankets they just tick over slowly. My last batch of rum has been going for over 6 weeks but it has been f*king cold.

I have fermented mead, wine and cider through the winter months and am sure it does not matter, slow and steady. My opinion is that there is more of an issue with the really fast turbo fermentations. All sorts of bad flavours. I had a batch of mead that hibernated for 4 months last year!! It carried on just fine when it warmed up.

Traditionally they ferment after harvest and still in the cold months. With our electric heaters etc we spread out the season. Keep going it will be fine in the end.

I have always fermented at lower the optimal temps and I don't have a problem, it just takes longer.

Well I checked the current fermentation as it has been really cold here for some time.

1 gallon (7.25kg) catering grade treacle
20kg raw cane sugar
8oz tomato paste ( haven't got any DAP at the moment)
5 vitamin B tablets
20gm citric acid
10oz fresh bakers yeast boiled for 15 minutes
4oz fresh bakers yeast (in starter jar for 24 hrs)

All topped up to 25 gallons.

This was started off in the last week of Nov. Heated with a 75 watt soil warming cable, it hibernated for a week or two after the power tripped out and I had not realised the heater was off. I actually had ice in the fermentation drum at one point, but it recovered. It is currently at SG 1.03 @ 16 deg C, and still very slowly fermenting. Smells just great, no contamination, just slowly fizzing away. Its just my opinion, but I think it is simmilar to mead, you get good flavours with LONG cool fermentations.

Have not tried it with grain yet, but I am willing to gamble that you get a different product with the long cool winter fermentation in contrast to the fast summer one. Has anyone got results of a comparison with the same grain bill, summer vs winter fermentation. Or for the rum?

I look out my window today and what do I see? More f**king snow. I look in my fermenters and find the treacle wash is STILL fermenting; that's its forth week and the total volume is only 20L. I type this wearing a coat and hat in a room so cold I can see my own breath. Bring on the spring, please. I'm growing to hate this winter.

I hope there is some pay-off with the flavour of the shine, if it ever actually finishes fermenting.

I think a long cold ferment make for a slightly better end product. It could just be the lager yeast I use but I think it's the combination of cold and yeast.

I don't really think it's worth waiting around for 6 to 8 weeks, but if you have the room and a lot of fermentors I guess why not.

rubber duck wrote:I think a long cold ferment make for a slightly better end product. It could just be the lager yeast I use but I think it's the combination of cold and yeast.

I don't really think it's worth waiting around for 6 to 8 weeks, but if you have the room and a lot of fermentors I guess why not.

I agree. Trying to ferment in the winter with no / minimal additional heating is always going to be a slow job. I recently insulated a 160 litre HDPE drum for a cold weather fermenter, but have not used it yet. I completely wrapped it in loft insulation (fibre in a bag type) and wrapped it in brown paper. I suppose there is a good 2" to 3" thickness of squidgy duvet type insulation all around it. Planing on covering the whole thing in duct tape to try and give it some degree of waterproofing in case of splashes etc.

Even so you need to get your fermentation really rolling to generate enough heat to keep it going. Perhaps this is a situation where it is worth adding in your sugar or molasses etc in small doses instead of just chucking it all in at the start. I normally just chuck it all in and leave it to sort itself out.

Just for your info I had a second fermentation going to the same mix as above. 20kg cane sugar and 7.25kg treacle in 25 gallons. Left this to ferment unheated over the winter, most of the time it was between 5 and 8 degC. It did ferment out fully but took the best part of 3 months.
No problem as it was out of the way and it was a test to see what would happen. Nice clean fermentation with no contamination using a mix of bakers yeast and wine yeast.
Will keep some of whichever viable yeast it was that survived the conditions, to add in to fresh bakers yeast on the next fermentation. It seems that it will ferment out eventually if you just leave it and keep it covered. It even had ice in it at some points but it came through in the end.

Been staring at a container of recovered trub in my extra fridge for almost 2 weeks now.

Gas bubbles still burping on the surface.

Hearty little buggers.

There is a measure of smoothness from a cold ferment. I've been experimenting with cold fermented rum and different strains of lager yeast. The jury is still out but I'm beginning to think this is the way to go if one has the facilities to do so. At least as far as rum goes.

myles wrote: ... I had a batch of mead that hibernated for 4 months last year!! It carried on just fine when it warmed up. ...

Yup, that's happened to me several time with honey mead. Interesting thing is the they were the meads that I always won first prize with. Mead is funnt stuff.

blanik