Evaluating the Impact of High and Low Kilning Temperatures on Popular American Aroma Hops

Abstract

Hop drying is an important step during the hop harvest, where hops must be quickly dried from 70–80% to 8–12% moisture to prevent deterioration of hop cones. Collaborating with hop growers in Oregon and Washington, U.S.A., the study employed commercial-scale drying experiments to investigate the impact of drying hops using static 130 °F (54 °C) and 150 °F (65 °C) air-on temperatures with six popular American aroma hop varieties (Amarillo®, Cascade, Centennial, Citra®, Mosaic®, and Simcoe®) over two harvest years, 2020 and 2021. Hop kilning temperature did not significantly impact the chemical and sensory properties of the hops. However, hop dextrin-reducing enzymes responsible for hop creep were reduced with higher kiln temperatures for all varieties over both harvest years. Drying times were significantly reduced by an average of 20-42% (2–4 h) when drying at 150 °F (65 °C) versus 130 °F (54 °C), depending on the variety. These results could benefit the hop industry by allowing hop growers greater flexibility during hop harvest and offer potential energy savings via reduced drying times.

Keywords:

• hops
• hop quality
• kilning

Acknowledgements

The authors would like to acknowledge the Hop Research Council for funding this research and the participating hop growers for helping guide the design of this study, for carrying out commercial scale kilning trials, and for donating their hops. We wish to express our sincere gratitude to Perrault Hop Farms, Loftus Ranches, Coleman Ag, Crosby Hop Farm, and Sauve and Sons, for their participation. Without their involvement, this work would not have been possible. The authors would also like to thank Hopsteiner for their in-kind support by providing thiol analysis of the 2020 samples through Nyséos. We thank the commercial brewer and hop dealer sensory panels who participated in the hop grind sensory evaluations and brewed single hop IPAs with the samples from harvest year 2020. Finally, we wish to recognize the Oregon State University hop analysis lab graduate students (Ricky Molitor, Ronald Samia, and Cade Jobe) and undergraduate students (Charlie Johnson, Ian Savage, Dillon Randall, Drake Graham, and Jordan Chulyak) for their help with the chemical analyses of the hop samples.

Disclosure statement

No potential conflict of interest was reported by the authors.