Hop beta acids - from cones to beer

K. Krofta, J. Hervert, A. Mikyška, M. Dušek
Hops contain a considerable amount of beta acids, 3-10% w/w depending on cultivar. The most important property of beta acids that determines their behavior in the course of the brewing process is oxidation initiated by airborne oxygen. Oxidation of hop beta acids occurs during natural ageing. Decomposition products, soluble in water, showing distinctive bitterness in beer arise during oxidative decomposition of beta acids. Hulupones, hulupinic acid, minority epoxy-hulupones and some cyclic products were found in beers exclusively hopped by pre-oxidized pure beta acids. Beer bitterness brought about by oxidized beta acids is not unpleasant or clinging. Analytical bitterness of beer hopped with alpha acids showed that bittering intensity beta acids oxidation products achieve approximately 35-40% rel. of iso-alpha acids. Pure beta acids added to the wort show practically no bitterness in beer. Probably due to their low solubility in boiling wort and by minimal formation of bitter decomposition products because of negligible concentration of dissolved oxygen. Presence of oxidation products of beta acids in aged hops contributes to the phenomena of bittering power declining un-proportionally to the reduction of alpha acid content. Beers made of aged hops have comparable sensorial and analytical bitterness in comparison with beers hopped by fresh hops. Bittering potential of beta acids is more distinctive in aroma hops with a high content of beta acids.
Krofta, K., Hervert, J., Mikyška, A. and Dušek, M. (2019). Hop beta acids - from cones to beer. Acta Hortic. 1236, 15-22
DOI: 10.17660/ActaHortic.2019.1236.3
hops, alpha acids, beta acids, hops ageing, decomposition products, brewing test

Acta Horticulturae