Recipe Plan

Recipe Plan

Take a simple recipe:

Boil Volume 3 gallons
Batch Size 3 gallons
2.2lbs DME
1oz Goldings AA5% at 60m

Result from the Tasty Brew calculator:
OG 1.033, FG 1.008, IBU 34

Boil Volume 3G, Batch Size 3G

Now take the same recipe but change the batch size to 3.01 gallons:

Boil Volume 3 gallons
Batch Size 3.01 gallons
2.2lbs DME
1oz Goldings at 60m

Result from the Tasty Brew calculator: OG 1.033, FG 1.008, IBU 140

Boil Volume 3G; Batch size 3.01G

A difference of 0.01gallons results in IBU jumping from 34 to 140. Crazy!

Similarly if I use a Boil Volume of 2.5 gallons and a Batch Size of 3 gallons:

Boil Volume 2.5G; Batch Size 3G

It appears that when the batch size is greater than the boil volume, Tasty Brew uses a different formula that gives wildly different values.

I’ve often used Tasty Brew, adjusting hop quantities based on IBUs. Now I find out the IBU values can’t be trusted. No wonder my All Amarillo IPA tasted weird – and gawd knows what this has done to my other beers, the ones that are still fermenting away.

Damn you, Tasty Brew!

As a check, I ran the same recipes though Beer Recipator (making sure the Alpha for Goldings was 5%). OG was 1.033 in all cases.

Utilisation method: Tinseth
Boil Volume 3G, Batch Size 3G: IBU 33.5
Boil Volume 3G, Batch Size 3.01G: IBU 33.4
Boil Volume 2.5G, Batch Size 3G: IBU 31.6

Utilisation method: Rager
Boil Volume 3G, Batch Size 3G: IBU 38.3
Boil Volume 3G, Batch Size 3.01G: IBU 38.2
Boil Volume 2.5G, Batch Size 3G: IBU 38.3

There’s a description of the methods here. Personally I prefer Tinseth since Rager doesn’t account for differences in boil volume, as can be seen clearly above.

At least one good thing has come of this – I now understand why different hop utilisation methods give different results.

I wont be using Tasty Brew again – I’ll be using Beer Recipator and calculating using the Tinseth method.

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