Kvasny Prum. 2003; 49(11-12): 326-335 | DOI: 10.18832/kp2003020

Qualitative and Economic Aspects of Ageing of Czech Hop Varieties.Peer-reviewed article

Karel KROFTA, Vladimír NESVADBA, Jana TICHÁ, Urban JAROSLAV, Jaroslav ČEPIČKA
1 Chmelařský institut s. r. o., Kadaňská 2525, 438 46 Žatec
2 Chmelařství, družstvo Žatec, Mostecká 2580, 438 19 Žatec
3 Český svaz pivovarů a sladoven, Lípová 15, 120 00 Praha

The dynamics of ageing processes in Czech hop varieties (Saazer, Sládek, Premiant, Agnus) was followed by long-term storage tests in the period since 2000 till 2002. Raw hops and pellets G 90 were storaged for 12 months in an air-conditioned and non-conditioned warehouse. Rate of ageing was analyticaly evaluated by a decline of bitter acid and hop oil contents, further by determination of hop storage index (HSI) and oxydative hop oils index (OIS). In the course of storage gradual decline of bitter acid contents was recorded in complience with expectations. The highest declines of alpha-bitter acids in raw hops were found in Agnus variety (80 %), the lowest ones in Premiant (31 %). Storage of hops in air-conditioned warehouse and pelletizing combined with keeping product under inert atmosphere resulted in a substantial reduction of alpha-bitter acids losses to 5-27 %. Dimensionless indices HSI and OIS showed to be objective parameters for age hops assessement. In comparison with HSI values, OIS is aproximately by one order more sensitive. Relatively significant varietal differences were found in dynamics of hop ageing. The most stable showed to be Premiant variety. The most susceptible is Agnus in the form of raw hops. The brewing tests of older hops performed in pilot scale proved that bittering ampleness of hops changes during ageing to much less extent than it would correspond to alpha-bitter acid contents decline.The dynamics of ageing processes in Czech hop varieties (Saazer, Sládek, Premiant, Agnus) was followed by long-term storage tests in the period since 2000 till 2002. Raw hops and pellets G 90 were storaged for 12 months in an air-conditioned and non-conditioned warehouse. Rate of ageing was analyticaly evaluated by a decline of bitter acid and hop oil contents, further by determination of hop storage index (HSI) and oxydative hop oils index (OIS). In the course of storage gradual decline of bitter acid contents was recorded in complience with expectations. The highest declines of alpha-bitter acids in raw hops were found in Agnus variety (80 %), the lowest ones in Premiant (31 %). Storage of hops in air-conditioned warehouse and pelletizing combined with keeping product under inert atmosphere resulted in a substantial reduction of alpha-bitter acids losses to 5-27 %. Dimensionless indices HSI and OIS showed to be objective parameters for age hops assessement. In comparison with HSI values, OIS is aproximately by one order more sensitive. Relatively significant varietal differences were found in dynamics of hop ageing. The most stable showed to be Premiant variety. The most susceptible is Agnus in the form of raw hops. The brewing tests of older hops performed in pilot scale proved that bittering ampleness of hops changes during ageing to much less extent than it would correspond to alpha-bitter acid contents decline.

Keywords: hops, hops ageing, alpha-bitter acids, hop oils, hop storage index, oxidative hop oils index, beer bitterness

Published: November 1, 2003 

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