Mash Temperature Effect On Final Gravity - Formula?

[Bribie G]

I'm starting to do some digging around to help Rob@BrewMate to refine a feature (can't expect him to do all the work)

Most people mash at mid 60s to try and get a 'sweet spot' between Alpha and Beta amylase activity, so most beers you would expect to attenuate out at say 1010 depending on yeast.
However some recipes call for a mash at, say 70 for a low alcohol beer with body and flavour as this could attenuate to a FG of typically 1022 ... ish

Yet again, when looking for a drier beer some will go for a low mash temp such as 62-64 - typically Aussie Sparklings, some German Alt styles and so on that could end up maybe 1004. Thus the mash temperature can have a massive effect on the final ABV%. Example: my comp mild is in the low alc class but starts at around 1043, mashed at 70. If I mashed lower it would end up as a best bitter strength instead.

So there is obviously a sliding scale relationship, and where it would come in handy for BrewMate is that if you change the mash temp then the ABV% would also change.

OK I realise that the attenuation of yeast strains differs, and recipes can have a lot of stuff like Carapils etc that doesn't ferment much. However ignoring that does anyone know of a formula for mash temp vs final gravity, all else being equal?

 

[Mayor of Mildura]

Hi Bribie

The dude at braukaiser.com did a experiment and has an interesting article on temp and attenuation. here is the article. There is also an overall page on attenuation here .

Hope that helps.

Cheers

 

[goatherder]

I suspect that you may get a "all else being equal" relationship but how useful would it be when FG is so dependent on yeast characteristics, grist composition, fermentation conditions etc?

 

[felten]

Maybe send an email to wyeast/whitelabs and ask them how they work out their range of attenuation %, what kind of wort they're using and how that relates to homebrewer worts.

I'm sure they use a standard mid range mash temp or something to work it out, maybe they have an idea of what to expect, in general, when the mash varies from their set temp.

 

[Nick JD]

Table 4.6 on page 124 of Brewing Science and Practice has the ratio of fermentable-extract : extract at verious mash lengths and temperatures that would allow a general formula to be written off known attenuations with a control yeast at each end of the temperature range.

EDIT: you'd have to incorporate mash length in there for it to have any accuracy.

As an example, at 60C, a 180 minute mash extracts 62.2% and 50.2% is fermentable.

At 70C a 15 minute mash extracts 61.2% but only 40.9% of it is fermentable.