The effect of hop beta acids oxidation products on beer bitterness
2013
Krofta, K., Hop Research Inst., Zatec (Czech Republic) | Vrabcova, S., Hop Research Inst., Zatec (Czech Republic) | Mikyska, A., Research Inst. of Brewing and Malting, Prague (Czech Republic) | Jurkova, M., Research Inst. of Brewing and Malting, Prague (Czech Republic)
Instability and tendency to oxidation depending on conditions is a dominant property of hop beta acids. This property has an impact on both the hop storage and the beer brewing process. Approximately one half of the amount decomposes in the air at room temperature in the course of one month. After 6 months the rate of degradation is more than 90%. The dynamics of the decomposition is much slower in leaf hops, primarily during the first 6 months of storage. Changes of beta acids during ageing explain why the bittering potential of old hops does not decline proportionally to the alpha acid loss. A large share of degradation products are formed by cyclization of prenyl side chains of beta acids (tricyclolupulones and hydroxytricyclolupulones). Beers hopped by oxidation products of beta acids at the rate of 20 g/hL showed distinct sensorial bitterness that was not unpleasant and clinging. The bittering potential of oxidation products of beta acids reaches approximately 35-40% of the bitterness of iso-alpha acids.
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