Evaluation of a Methanol-Based UV Spectrophotometric Procedure Against the EBC HPLC Method for Bitter-Acid Determination in Subtropical-Grown Hops

Abstract The determination of hop bitter acids is essential for raw-material characterization and brewing quality control. This study evaluated a simplified methanol-based UV spectrophotometric procedure and compared its results with those obtained using the official EBC HPLC method for the determination of α- and β-acids in Cascade, Chinook, Comet, and Saaz hops cultivated under subtropical conditions. The UV procedure used absorbance measurements at 275, 325, and 355 nm, whereas HPLC-PDA provided selective quantification of the bitter-acid groups represented in the ICE-4 calibration material. The methanol-based UV workflow yielded significantly higher α- and β-acid values than HPLC for all evaluated samples ( $$p<0.05$$ p < 0.05 ). The magnitude of the disagreement varied among samples, with larger absolute differences observed for Chinook and Comet and smaller differences for Saaz. Because the two procedures differed in extraction conditions as well as detection selectivity, the observed bias cannot be attributed exclusively to spectrophotometric interference. Co-extracted UV-absorbing constituents, matrix composition, and differences in extraction recovery may all have contributed. The available $${A}_{275}/{A}_{325}$$ A 275 / A 325 ratios did not show a direct relationship with the UV–HPLC differences, indicating that oxidation alone was insufficient to explain the analytical disagreement. The simplified methanol-based UV procedure may be useful for rapid screening when consistently applied, but its results should not be considered interchangeable with those obtained by the EBC HPLC method or generalized to the official ASBC Hops-6 procedure.