Metal-Induced Wildness in Beers

143

102

Generally referred to as polyphenols (PPs), beer flavonoids such as the flavan-3-ols and their condensed products, the proanthocyanidins, represent a class of readily oxidizable compounds capable of hindering or preventing the oxidation of other molecules present in beer. Flavan-3-ol and proanthocyanidin capacity to improve oxidative stability has been well established in other food systems, and thus these antioxidants have recently gained significant consideration as potential beer flavour modifiers and/or stabilizers. The duality of their presence in beer is that PPs complex with proteins in the beer matrix to form temporary and permanent hazes. Undesirable physical instability caused by PP-protein interactions can be resolved via use of adsorptive resins such as polyvinylpyrrolidine. While there is no doubt that polyphenol removal increases beer shelf stability in terms of haze formation, the impact of polyphenol removal on beer flavour remains unresolved. This review discusses the sources, content and impact of polyphenol presence and removal on beer physical and flavour stability.

Section: Occurrence and Effect Of Transition Metals In Beermentioning

confidence: 99%

Section: Beer Physical Stability Gushingmentioning

confidence: 99%

A Discussion of Polyphenols in Beer Physical and Flavour Stability

Aron

Shellhammer

2010

143

102

Gushing Promoters and Suppressants in Beer and Hops

Carrington¹,

Collett²,

Dunkin³

et al. 1972

The fatty acids present in beer and hops were found to have pronounced effects on gushing, some at concentrations of I ppm or less. Saturated fatty acids are weak gushing promoters, while unsaturated adds are powerful suppressants. A parallel structure-activity correlation also exists in a series of a-acid derivatives and their analogues. Compounds with the unsaturated side-chains intact showed either weak suppressant activity or none at all. Loss of carbon-carbon unsaturation through hydrogenation or cyclization produced powerful gushing promoters, but reduction of carbonyl unsaturation as in p-isohumulones, or loss of side chains as in humulinic acids had no effect on gushing. Promoter and suppressant effects of the compounds tested were non-specific and mixtures of unsaturated fatty acids suppressed all instances of gushing, whether natural or artificially induced. The results indicate that beer normally contains both gushing promoters and suppressants, and gushing may sometimes be due to an imbalance between them.

Surface Viscosity and Gushing

Gardner¹

1972

Surface viscosity correlates qualitatively with gushing induced by a standard gushing test. Substances which provoke gushing cause a large increase in surface viscosity when they are added to beer. Conversely, the very high surface viscosities induced by gushing agents fall to normal or intermediate values when anti‐gushing agents are added. High surface viscosity does not ‘cause’ gushing, but appears to be a frequent concomitant of the existence of stable nuclei. These observations support a hypothetical mechanism which suggests that anti‐gushing agents should be extremely surface‐active but incapable of forming a solid‐condensed surface film.