I do my own recipe calculations with the formulas in Designing Great Beers by Ray Daniels, but haven’t found any mention of modifying the IBU calculations when adding lactose to a recipe.
Is there a formula for that or is it strictly trial and error?
Thanks in advance for your advice.
I don’t know how much lactose affects IBUs. It isn’t substantially sweet nor does it ferment. I can’t say I’ve ever seen anybody make that adjustment.
Lactose should only affect the mouthfeel. I can’t see why it would affect IBUs.
If he’s planning to add it during the boil it might. But not sure why one would do that.
I think that the theory that boil gravity affects hop utilization has been shown to not be true.
Link?
I’d have to look for it but it was big news a couple years ago.
ETA: here’s the first stuff I Googled…
Denny, I think that link says that the assumed cause of reduced utilization was found to be not true. However, it does go on to say that the net result is still that wort with higher gravity does have reduced bittering utilization from the hopping.
Why wouldn’t a lactose addition into the kettle be treated as any other fairly unfermentable addition (ie crystal malts, dextrin malts, etc)? When in doubt, brew your intended recipe as is, then make adjustments on your next go round based on what your palate is telling you.