Impact of different hop compounds on the overfoaming volume of beer caused by primary gushing

Abstract

When weather conditions favour the growth of moulds on barley, beers brewed from the resulting malts often tend to gush. Certain Fusarium species (e.g., F. graminearum and F. culmorum) may cause this problem. Supersaturated with CO2, a primary gushing beer contains an overcritical concentration of microbubbles; these are reputed to be stabilised by Fusariumderived hydrophobins. Research with varying brewhouse parameters has been performed to investigate the factors of primary gushing. As hops are known to contribute to a wide range of both gushing positive and negative substances in beer, the hopping regime has emerged as an important aspect. This paper examines the impact of different hop varieties on gushing. Hop oils and unsaturated fatty acids are reputed to be gushing-suppressors. Compounds such as dehydrated humulinic acid can intensify the effect. Hop pellets, with a prevalent range of conductometric values (5-10% α-acid), commonly employed in breweries to adjust bitterness and aroma were selected. By working with the same "gushing malt", the spectrum of compounds in the finished beer only differed through the hop product used. The overfoaming volumes of different samples were determined according to MEBAK guidelines. Respective hop oil and fatty acid concentrations (by GC) and iso-α-acid contents (by HPLC) were compared and a chronological sequence of the changing percentages of beer loss is shown. © 2010 The Institute of Brewing & Distilling.