Effect of drying temperature on the content and composition of hop oils

https://doi.org/10.17221/482/2018-PSECitation:Rybka A., Krofta K., Heřmánek P., Honzík I., Pokorný J. (2018): Effect of drying temperature on the content and composition of hop oils. Plant Soil Environ., 64: 512-516.
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In terms of content, the paper is aimed at analysing and comparing the quality of fresh green hops and hops dried at two drying temperatures – 55°C (in the traditional manner) and 40°C (using the so-called gentle drying), regarding the maximum preservation of hop essential oils. Comparative experiments were carried out in an experimental chamber dryer with two Czech hop cultivars Saaz and Harmonie. The moisture content of hops at the beginning of drying was 75% and at the end of drying it was 9–10%. By lowering the drying temperature from 55°C to 40°C, the drying time in cv. Saaz prolonged from 8 to 10 h and for the cv. Harmonie from 9 h to 12 h. Compared to fresh hops, the amount of hop oils decreased by 10% when dried at 40°C and by 36% (cv. Saaz) and 43% (cv. Harmonie) when dried at 55°C. These losses can be considered significant, especially for hops intended for late and dry beer hopping. However, by drying the hops at different temperatures, the ratios between various components of the essential oils and thus also their sensory character remained approximately unchanged. Due to the reduced amount of essential oils, the drying effect reduces the intensity of hop aroma depending on the drying temperature.

References:
Forster A., Gahr A. (2013): On the fate of certain hop substances during dry hopping. Brewing Science, 66: 93–103.
 
Henderson S.M. (1973): Equilibrium moisture content of hops. Journal of Agricultural Engineering Research, 18, 55-58  https://doi.org/10.1016/0021-8634(73)90032-2
 
Heřmánek P., Rybka A., Honzík I. (2017): Experimental chamber dryer for drying hops at low temperatures. Agronomy Research, 15: 713–719.
 
Hofmann R., Weber S., Rettberg N., Thörner S., Garbe L., Folz R. (2013): Optimization of the hop kilning process to improve energy efficiency and recover hop oils. Brewing Science, 66: 23–30.
 
Kralj D., Zupanec J., Vasilj D., Kralj S., Pšeničnik J. (1991): VARIABILITY OF ESSENTIAL OILS OF HOPS, HUMULUS LUPULUS L.. Journal of the Institute of Brewing, 97, 197-206  https://doi.org/10.1002/j.2050-0416.1991.tb01066.x
 
(2016): Hop-Picking Machine Control Based on Capacitance Throughput Sensor. Applied Engineering in Agriculture, 32, 19-26  https://doi.org/10.13031/aea.32.11234
 
Mitter W., Cocuzza S. (2013): Dry hopping – A study of various parameters. Brewing and Beverage Industry International, 4: 70–74.
 
Münsterer J. (2017): Flavor-Hopfen optimal trocken. Brauwelt, 33: 958–960.
 
Münsterer J., Kammhuber K. (2015): Erntezeitpunkt, Trocknungs-temperatur – Was beeiflust das Hopfenaroma. Brauwelt, 36: 1063–1066.
 
Narziss L., Forster A. (1972): Gaschromatographische Untersuchungen zur Bestimmung der Aromastoffe in Hopfen nud Hopfenverarbeitungs-produkten (5. Mitteilung). Brauwiss, 25: 239–244.
 
Rybáček V., Fric V., Havel J., Libich V., Kříž J., Makovec K., Petrlík Z., Sachl J., Srp A., Šnobl J., Vančura M. (1980): Hop Production. Prague, Státní zemědělské nakladatelství. (In Czech)
 
Rybka A., Heřmánek P., Honzík I. (2018): Analysis of hop drying in chamber dryer. Agronomy Research, 16: 221–229.
 
Vitázek I., Havelka J. (2014): Sorption isotherms of agricultural products. Research in Agricultural Engineering, 60, S52-S56  https://doi.org/10.17221/35/2013-RAE
 
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