We looked at high gravity brewing and blending in Calculations class. There are some very real benefits to brewing a high gravity beer and blending/diluting; one “mother” beer can spawn more than one product downstream, and there are some definite financial benefits. But I can’t help feeling like it’s cheating in a way I can’t quite put my finger on.*
Ray led us through some of the things to watch for should we ever be in a position to do HG brewing:
- weight of the extra grain needs to be under 240kg/m2,
- higher grain bed will affect the efficiency
- treatment of hops needs to be different to account for increased DMS and reduced extraction
- yeast will be under increased stress and should be used for fewer generations
Correction: the right term for the dilution is debrewing. Sounds a bit less…I dunno, cheat-y*, doesn’t it?
So when one is debrewing in Canada, one needs to calculate the water to add using alcohol as the determining factor as ABV is the regulatory necessity on product labelling.
We spent the rest of the class playing with this formula:
Aa + Bb = Cc
It looks simple enough doesn’t it? But each one of those things is something different.
A is volume of concentrate
a is alcohol of concentrate
B is volume of water added
b is alcohol of water added
C is total volume produced
c is alcohol of blended product
With this we can solve the following: 75hL of concentrate in aging has an alcohol of 7.4% vol. How much bright beer can be produced at 4.5% abv.
It sounds a bit like one of those “A train leaves Pittsburgh going 125km/h” word problems I hated so much in high school.
Oh wait. It’s exactly like one of those word problems I hated so much in high school!
In order to solve for B, you have to rearrange the equation. Bb pretty much cancels itself out as the abv of water is 0, and 0 times anything is 0, so you need to change C into A + B and expand it so the whole thing looks like
Aa = Ac + Bc
Plug in the numbers and you should get B = 48.3 hL, making the total amount of beer you can package is 123. hL.
And that’s the easy question.
* I know it’s not cheating. It’s actually a pretty good business practice, especially when you are dealing with high volume and slim margins like the big guys. It’s also something that a small brewpub or microbrewery won’t need to worry about it.