An Investigation of the Relationships between Hopping Rate, Time of Boil, and Individual Alpha-Acid Utilization

Abstract

High-performance liquid chromatography methods were developed for quantitative analyses of α- and β-acids in hop products, α-acids and tso-α-acids in wort, and iso-α-acids in beer. A pilot brewing study then established that cohumulone is utilized much more efficiently than humulone plus adhumulone. The utilization of cohumulone is about 70% higher at equivalent addition levels of 60 mg/L. The difference in utilization decreases as the hopping level decreases. The higher utilization of cohumulone results from proportionately higher losses of humulone plus adhumulone in the kettle and of isohumulone plus isoadhumulone during fermentation. A hop boil time of 90 min exists at the bottom of a shallow cost curve relating hop cost, energy cost, and time of hop boil. A slightly shorter boil time with correspondingly higher hop rate (or vice versa) does not incur a great cost penalty. However, hop boil times of less than 60 min incur substantial cost penalties.