Fermentation temperature

[PeteB]

I am heading into my first southern hemisphere winter of fermentation/distillation. My small distillery is at about 6 C (43 F) and the temperature in my current fermention (1000 liters) has dropped to 10 C (50 F) , it is VERY slow and fermentation has not finished. I warm a sample and it takes off again.

Will the fermentation finish satisfactorily at this temperature ?

(not too concerned about time taken for this batch)

I don't have a jacket on fermenter so next batch I assume an insulated blanket should keep the temperature up.

I think fermentation is exothermic so it should keep itself warm .

[Paul Tomaszewski]

We had a similar situation, in the end we insulated our production area so that the temp inside never goes below 60 F. That being said, you don't want your mash going too far below 55-60 F range. A blanket may work, depending on the ambient temp (how low it goes), as you are correct in that the mash will help maintain a temperature in itself through the heat it puts off. Finally, worst case scenario, you can also use some simple immersion (aquarium) heaters, but go plastic as the glass ones will crack and burst.

[PeteB]

Thanks for the reply Paul. I think 43 F ambient is about as low as it will get.

Since I wrote the post I found a foil blanket that I use to keep pallets of plants cold while shipping. I put that over the fermenter and lit a small propane burner under the tank and it is slowly warming up. Probably not the safest option but I am watching it carefully.

This is a good reason to keep the distillery constantly running for the winter so everything stays warm.

[Beauport Bob]

Our space gets cool to about just below 50 f. We cover open fermenters with food grade plastic wrap. We end up peeling back to vent a little.

[PeteB]

I received the following information from someone who is not a forum member. I am posting it for others to view.

"Regarding your question about fermentation temperatures – the only downside of cold fermentation is the longer time taken. In a beer brewery, where they have no method of removing impurities that are generated in the fermentation process, it is common for them to ferment at very close to 32 F (= 0 C) and the batch time can be 2 or 3 weeks. In a neutral spirit distillery there is the infrastructure in place to remove the unwanted by-products of hot fermentation so we used a temperature of 32 C (= 90 F). When I first worked in such a distillery the fermenter temperature control was manual, and the operators regularly allowed the temperature to go too high during the night. This led to lower yields because of all the side products generated by the wild yeasts and bacteria that thrive under warm conditions.

When we finally added decent external cooling with plate exchangers and automatic temperature controllers we found that the yield jumped up by 1-2%. "

[Rich Morgan]

I am heading into my first southern hemisphere winter of fermentation/distillation. My small distillery is at about 6 C (43 F) and the temperature in my current fermention (1000 liters) has dropped to 10 C (50 F) , it is VERY slow and fermentation has not finished. I warm a sample and it takes off again.

Will the fermentation finish satisfactorily at this temperature ?

(not too concerned about time taken for this batch)

I don't have a jacket on fermenter so next batch I assume an insulated blanket should keep the temperature up.

I think fermentation is exothermic so it should keep itself warm .

Most grain and sugar ferments will stall (stop) at or below 5C, they usually will spark up again if warmed up. But, with any slow or stalled ferment there is a risk of it stopping altogether (aka a stuck ferment), so its best to keep it warm and lively. Insulation may help, but also consider immersion coils with hot water, or maybe an electric band heater (both with thermostats of course). The thing to remember is that although the fermentation may have stopped, other reactions (autolysis) can continue, and reduce your viable cell count. The longer a ferment hangs around with low alcohol levels, there is also a chance of bacterial infections taking hold, which most are more temperature tolerant than the yeast.

The general rule is always, a quick, clean and total ferment.

rich..