The relation between the molecular structure and gushing potential of dehydrated humulinic acid

Abstract

Dehydrated humulinic acid, 2-isovaleroyl-4-(3-methylbut-2-enyliden)-cyclopentane-1.3-dione (DHA) sometimes occurs in isomerised hop extract. The use of any such extract can cause beer gushing. It was attempted to establish whether this gushing-releasing characteristic is related to specific functional groups of the molecule. Two hydrogenated derivatives of DHA, 2-isovaleroyl-4-(3-methylbutyl)-cyclopentane-l.3-dione (IMCD) and 2.4-di-(3-methylbutyl)-cyclopentane-1.3-dione (DMCD) were prepared and their gushing-releasing potential was compared with that of DHA in various types of beer. These three components released gushing but DMCD, probably on account of elimination of a carbonyl group, reacted differently from DHA and from IMCD. The gushing potential of IMCD was lower than that of DHA.Since both the DHA and the IMCD molecules contain the ~,-tricarbonyl system of isohumulone but lack a hydrophilic hydroxyl group on the cyclopentane ring, it was suggested that the gushing potential of DHA was due to the [~-tricarbonyl system and to the absence of the hydrophilic hydroxyl group. The results also indicate that gushing caused by DHA occurs if concentrations of certain DHA protein complexes are sufficiently high in the beer.It was shown that DMCD-induced gushing is released by DMCD crystals and consequently is different in nature from that of DHA-induced gushing.

Hydrophobins, beer foaming and gushing

“…tetrahydro and hexahydro iso-alpha acids) are weak promotors. Polyunsaturated fatty acids present in hop oil show inhibitory effects on gushing (Carrington et al, 1972;Laws and McGuinness, 1972;Outtrup, 1980). Crown corks cause gushing by the release of remaining detergents in beer, or by releasing iron ions from the scratch parts to the beer (Garbe et al, 2009).…”

A Curative Method for Primary Gushing of Beer and Carbonated Beverages: Characterization and Application of Antifoam Based on Hop Oils

“…In early studies, primary gushing was recognized to be associated with mycoflora from the grain (22). called hydrophobins (4,40) whereas secondary gushing is due to residues of calcium oxalate, metal ions, isomerized hop extracts, the crown cork, filter aids, and cleaning agents of bottles, as well as uneven carbonation (3,7,17,20,28,37). called hydrophobins (4,40) whereas secondary gushing is due to residues of calcium oxalate, metal ions, isomerized hop extracts, the crown cork, filter aids, and cleaning agents of bottles, as well as uneven carbonation (3,7,17,20,28,37).…”

Novel Perspectives in Gushing Analysis: A Review

“…In contrast to the described gushing suppressing effect of hops 6,8,15,16,25,26,42,43,49,62,73,78 , gushing supporting hop components are known, such as polyphenols 46,55,62 . The gushing inducing capability of iso-extract 22 can be ascribed to certain reactions in its production process, e.g., the isomerisation of humulones to iso-humulones 8 or the formation of humulinic acid, especially dehydrated humulinic acid (DHA) formed under extreme alkaline conditions, which is known for its distinct gushing inducing characteristic 25,26,46,55,67 . Furthermore, several reaction products resulting from the oxidation of αand iso-α-acid can be responsible for gushing 26,55 .…”