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Yeast attenuation values to plug into BrewMate

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Bribie G

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I'm sharpening up my brewing a bit this year by fine tuning BrewMate - for a lot of items the default values built into the system work quite well and get me within the ballpark. However one priority is to get the yeast attenuation numbers as accurate as possible for the yeasts I currently use. Currently BrewMate sets all the yeasts at 75%

For example a difference of a few percent can make the difference between a beer calculated to attenuate to 1.011 and 1.009 - which can translate to a difference in ABV predicted.

I note that for most of the yeasts I normally use, on the CraftBrewer site I see figures such as "73 - 77 %" for a strain of yeast.

Why would there be a range and not a more precise value? Does it depend on the fermentability of the wort, if so what wort did they use to claim an attenuation of 75% for the above yeast - the midpoint between the 73 and 77?

I'm wondering if it's an idea to put that mid value in for each of the yeasts in BrewMate's table.

Another thing, does anyone know what the attenuation is for Coopers Bottle yeast? Maybe do a mini test-brew with a plain base malt or something?

edit: tidied up post somewhat
 

Bribie G

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Answering some of my own questions here but I'll have a wade through the calculations on the Pint.com site here man I'll need to lock the study door and brew up a few double shots on the Expressi first. :blink:

Edit: so is the figure for each yeast apparent or actual attenuation? I'd guess "actual".
 

Lord Raja Goomba I

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So that would be telling you what had happened.

But predictive attenuation prior to brewing? That would be the bomb.

Unless the idea is that you keep calcs each time you use a particular yeast and there should be an average that pips out?
 

Bribie G

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Brewmate does predict the FG, for example if I edit Irish Ale Yeast in the table and give it a ridiculous 80% it predicts a FG of 1009 as opposed to 1011. What I'm interested in is how this is predicted if they don't know what wort I'm doing. For example it could have a heap of dextrins in it. If indeed that's why there's a range to cover various worts then I'd be happy with that concept and work around it.

I'm particularly interested because I'll be doing comp brewing again this year using a range of widely differing yeasts. Apart from trying to brew dead to style I don't want to present too many gushers to the poor stewards. :p
 

Nick JD

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BrewMate has no correlation between mash temp and yeast attenuation. Would be nice, but you'd really have to factor in ferment temp and pitch rate and oxygen content, get them all accurate and then hope.

Probably a little bit of an ask for some free software.

My FGs are always way under BrewMate's default.
 

Bribie G

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I made some enquiries about mash temp vs FG, when I was doing high temperature mashes for my low-alc class in some Competitions a couple of years ago. A lot more difficult than you might think, if you do a search on the subject it's mind boggling how many variables there are so I can understand why Rob wouldn't want to go there.
 

black_labb

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I think experience is probably the best way to get what you are after. Mainly your experience with your system but also experience with the different ingredients. For example wyeast 1469 is rated for about 73% fermentability off the top of my head but I find I get higher attenuation with it. I'm closer to the expected attenuation with most other yeasts. I'm not sure if it is because of the way I use the yeast (possibly because I'll often top crop it?) or if it is just that it is different from the posted attenuation.

There is too many variables to really get a good number for yeast attenuation. Yeast attenuation is dependent on many things including yeast health, pitching rate, wort fermentability etc. To make things more complicated the yeast cells can apparently lose the function to ferment certain sugars depending on what you feed it. Too many simple sugars apparently leads to them not going through the complex sugars.

Wort Fermentability is the obvious difference but that depends on your mashing temps, your ingredients (not just spec malts, the choice of base malts and the amount of enzymes present), your liquid to grist ratio, the mashing time, your water chemistry and how it works with the grain bill etc.
 

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