The content of hop prenylflavonoids in czech and foreign beers

The content of isoxanthohumol (IX) in most of Czech and foreign beer brands did not exceed the limit of 2000 mu g.l(-1). The concentration of xanthohumol (XN) was up to 100 mu g.l(-1). The largest quantities of prenylflavonoids in all beers investigated were found in Czech dark 12 % lager (2522 mu g.l(-1) IX and 505 mu g.l(-1) XN). On average less prenylflavonoids were found in draught and alcohol-free beer brands due to the lower hopping rate and the higher proportion of CO2-extracts. Choosing a hop variety with a higher XN/alpha-acids ratio can influence the level of IX in the beer. The amount of prenylflavonoids in beers increases if Sladek and Saazer are used for hopping. The monitoring of isoxanthohumol concentrations in intermediate products during the brewing process, in two industrial breweries confirmed that high losses occur in the course of beer production. The critical points are cooling of wort, fermentation and filtration. The total amount of xanthohumol remaining after the beer production in full operating scale is approximately 20-30 %. Tracing of the stability of the IX and XN contents in bottled beers, which was done over a period of 3 months, showed that the concentration of IX was reduced by 10-15 % depending on the storage temperature. Losses of XN were higher and reached about one third of the original content.