GigaFemto
Grandmaster Brewer
I have been confused by the gravity calculations for extract in BS 2.3.7. It seems that the points per pound per gallon changes depending on trub losses, which doesn't make sense to me. I made 2 simple example recipes to demonstrate, which I have exported and attached. They both use 4 lbs of base malt and 4 lbs of DME which is listed as having a potential of 1.045 (i.e. 45 ppg).
Recipe 1:
No trub loss, no kettle top-up. BH efficiency = Mash efficiency = 77%
Post-mash gravity = 1.036, Pre-Boil volume = 3.14 gallons, Pre-Boil Gravity = 1.093
The diiference between post-mash and pre-boil gravities is from the DME
The contribution from the DME is (93-36)*3.14/4 = 44.7 ppg, close enough to 45
Recipe 2:
1 gallon trub loss, no kettle top-up. BH efficiency lowered to 64.2% to give mash efficiency of 77% again
Post-mash gravity = 1.026, Pre-Boil volume = 4.4 gallons, Pre-Boil Gravity = 1.075
The contribution from the DME is (75-26)*4.4/4 = 53.9, much higher than before
I understand that the volumes will change and the boil-off amount need to be adjusted, etc. but this is all pre-boil and the ppg shouldn't change.
What am I missing here?
???
Recipe 1:
No trub loss, no kettle top-up. BH efficiency = Mash efficiency = 77%
Post-mash gravity = 1.036, Pre-Boil volume = 3.14 gallons, Pre-Boil Gravity = 1.093
The diiference between post-mash and pre-boil gravities is from the DME
The contribution from the DME is (93-36)*3.14/4 = 44.7 ppg, close enough to 45
Recipe 2:
1 gallon trub loss, no kettle top-up. BH efficiency lowered to 64.2% to give mash efficiency of 77% again
Post-mash gravity = 1.026, Pre-Boil volume = 4.4 gallons, Pre-Boil Gravity = 1.075
The contribution from the DME is (75-26)*4.4/4 = 53.9, much higher than before
I understand that the volumes will change and the boil-off amount need to be adjusted, etc. but this is all pre-boil and the ppg shouldn't change.
What am I missing here?
???