Theory 135/Beer foam/Ratio lens
Bitterness Is Iso-Alpha Against Sugar
The claim
Perceived bitterness is set by the ratio of iso-alpha acids to residual sugar, so the same IBU tastes different across styles.
01Mechanism
Bitterness and sweetness suppress each other; the ratio determines the balance.
02Prediction
Perceived bitterness should track the ratio.
03Refutation
Bitterness tracking IBU alone would remove sugar.