Here’s a quote that indicates what I am feebly trying to articulate. “One obvious result from this experiment is that IBU values can not be directly substituted for isomerized α-acid values, especially at short steep times, high hopping rates, and sub-boiling temperatures. This is because IBU values reflect not only isomerized α-acid values, but also contributions from oxidized α and βacids and polyphenols.”
Um, soooo lab measured IBUs contain more than just isolmerized alpha acids. Like I said, whirlpool hops do bring bitterness to the beer. More than an isolmerization chart will predict.
Saying that IBUs only come from isolmerized alpha acids is like saying high alpha hops are for 60 min additions and low alpha are for dry hopping. Ya, maybe a good starting point but keep experiencing and adapting to your experience
That’s what Jeff was getting at with his remark about 60s light lager. BU was developed at a time when they assumed degraded hops, with lots of beta acids oxidized to solubility, and brewhouse procedures that extracted more of other bitter substances from grain and hops. The relation to iso-alpha is tenuous.
EDIT _The Practical Brewer _ (MBAA, 1977) indicates in exemplary analyses that BU is about 1.15x iso-alpha acids.
IBUs by way of calculation are a sensory guidepost. I’m less concerned with absolute values and more concerned with how I can use the calculations to predict what tastes good to me.
Hops are also utilized differently now, so there’s equal but different opportunity to extract bitter substances other than iso-alpha. In the day, increased solubility of beta offset decreases in alpha, then all the other stuff. The whole BU concept needs reevaluation, which I presume they are working towards.
What was your level of Magnesium? I found that was the difference when I was encountering low perceived bitterness. I would regularly have calculated IBU’s of over 100 but the IPA would have the bitterness of a Pale Ale, until I upped the Magnesium… boom! Perceived bitterness.
Thanks everyone for sharing your suggestions! I am not currently adding any magnesium to my water adjustments. Just calcium chloride and gypsum and lactic acid to adjust mash PH. I would guess the magnesium ppm would be pretty close to 0. Would you suggest adding some epsom salt maybe?
It’s a tool. Just like any tool, it can be manipulated to give results that correspond with sensory analysis. IBU calculations are a guidepost. You use values from commercial examples and examples of beers you’ve brewed and you use the equations to make the sensory analysis of those beers line up.