Headspace Temperature and Fermentation

[BolgBeorach]

Does anyone have any data on how the temperature of the headspace affects yeast, particularly if it is soon after pitching? My understanding is that the yeast ferments from the top of the wort, so if they have been only recently pitched, might they still be floating around on top and drawing heat from the headspace? I ask this because I am fermenting 10 litres in a 30 litre vessel (which isn't ideal, I know), and while the therm strip on the side of the vessel reads 18 degrees Celsius, I got a reading of 24 degrees from the surface of the wort using a thermometer gun. I have a heating control system in place, but since it controls the temp according to the body of the wort, and not ambient, it means that the ambient can fluctuate between extremes, because it obviously heats up and cools more quickly than the liquid. However the headspace follows the ambient, and as a result I am curious as to how it might affect the yeast.

 

[day_trippr]

Leaving aside the crux of the concern for the moment, I would not trust an IR gun in that application - even my Fluke - over your "LCD" strip.
I'd find a more reliable way to meter the head space temperature, if only for the science-y aspect

As to the concern - even if there was a 6°C delta extant, that's still well within the comfort zone for pretty much any yeast strain. Note I say "comfort" as opposed to "ideal", because while the yeast may have a righteous party at 24°C they may crank out byproducts one doesn't desire that are greatly attenuated at a cooler running temperature - like 18°C.

Still, air has a lot less thermal mass than wort, most of the yeast will have sunk under the meniscus within 10 minutes of sprinkling (if that's what was being implied), so I expect one would never know there was even a temperature differential, never mind have it affect a pitch...

Cheers!

 

[BolgBeorach]

Leaving aside the crux of the concern for the moment, I would not trust an IR gun in that application - even my Fluke - over your "LCD" strip.
I'd find a more reliable way to meter the head space temperature, if only for the science-y aspect

As to the concern - even if there was a 6°C delta extant, that's still well within the comfort zone for pretty much any yeast strain. Note I say "comfort" as opposed to "ideal", because while the yeast may have a righteous party at 24°C they may crank out byproducts one doesn't desire that are greatly attenuated at a cooler running temperature - like 18°C.

Still, air has a lot less thermal mass than wort, most of the yeast will have sunk under the meniscus within 10 minutes of sprinkling (if that's what was being implied), so I expect one would never know there was even a temperature differential, never mind have it affect a pitch...

Cheers!

Thanks for the info! That pretty much addresses my concerns about it.

 

[Vale71]

My understanding is that the yeast ferments from the top of the wort, so if they have been only recently pitched, might they still be floating around on top and drawing heat from the headspace?

That is a common misconception possibly caused by outdated terms such as bottom-fermenting and top-fermenting which have been replaced by the more correct terms of bottom-cropping and top-cropping. The yeast that does the fermenting is only the yeast that is happily swimming (or raher aimlessly floating) aroung in the wort itself. Being fully immersed in the wort it will have the same temperature as the medium surrounding it and that's the only temperature you need to worry about.