Gushing
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Over-foaming can produce on opening packages. This phenomenon called gushing is one of the major source of economical losses for the brewers. Primary gushing is caused by factors from malt or other cereal raw material entering in the brewing process. Secondary gushing is due to the presence of aggregates and particles related to technological impurities or to haze. Primary gushing is closely related to Fusarium contamination of malt and is assumed to be due to surface active proteins that form a highly stable film around gas bubbles. Most studies converge for a role of small proteins of fungi (i.e. hydrophobins). These fungal proteins with four disulfide bonds are highly stable. They can survive to heating on brewing and only small quantities of these proteins can induce gushing. These proteins display an amphiphilic character that allow rapid adsorption at the gas–water interface to form stable and ordered aggregated protein films with unique elasticity. As suggested by Hippeli and Elsner, the modified forms of LTPs (i.e. glycated and acylated proteins) could also be involved in gushing. These proteins share structural characteristics with the gushing factor isolated from wort. Although these proteins are essential to the foaming properties of beer, they could induce gushing above a threshold concentration. Since synthesis of most LTPs is induced on pathogen attack, higher level of LTPs could be produced in response to the fungal infection of barley. The role of LTPs in gushing, alone or in interaction with fungal hydrophobins, has not been highlighted yet, but has to be investigated in the perspective of improving the quality of beer foam by increasing LTP content either through barley breeding or by genetic modifications.[1]
modified LTP1 by fungal proteases together with hydrophobic fungal proteins promotes beer gushing (over foaming at the bottle opening).[2] Malt derived gushing is caused by barley infection either in the field (Fusarium, Alternaria, Stemphylium, Cladosporum) or during storage (Aspergillus, Penicillium, Rhizopus).[3]
It seems that, in the amounts found normally in beers lipids do not influence gushing.[4]
The ratio between unsaturated and saturated fatty acids is associated with the gushing phenomenon, with unsaturated fatty acids acting as gushing-suppressors and saturated fatty acids acting as gushing-promoters [18,23,24,28,37,38].[5]
Humulones and linalool, the two-hop constituents, tend to prevent beer gushing [64] if added during wort boiling [65].[6]
A beer may exhibit gushing, explosive release of carbon dioxide gas, upon opening when the pressure is reduced from approximately 2½ atmospheres to atmospheric pressure. Several factors are known to cause this physical phenomenon: presence of trace metals, oxidation, and prolonged low temperature storage42. Transition metals of the fourth or higher periods are known causative agents of gushing48. While copper may not be as active as iron or other metals tested, copper may accelerate oxidative reactions that cause gushing. The addition of chelating agents such as EDTA can be used to prevent metalinduced gushing. Beer itself possesses endogenous metal chelators that may provide a natural resistance against gushing65,121.[7]
Ca oxalate produced by the reaction of Ca and oxalic acid may be a cause for gushing, which is the spontaneous over-foaming of beer (11,51). At this juncture, other metal ions such as copper, zinc, nickel, cobalt, manganese, and, above all, iron were also claimed to promote gushing reactions (13,15).[8]
References[edit]
- ↑ Didier M, Bénédicte B. Soluble proteins of beer. In: Preedy VR, ed. Beer in Health and Disease Prevention. Academic Press; 2009:265–271.
- ↑ Iimure T, Nankaku N, Kihara M, Yamada S, Sato K. Proteome analysis of the wort boiling process. Food Res Int. 2012;45(1):262–271.
- ↑ Stanislava G. Barley grain non-specific lipid-transfer proteins (ns-LTPs) in beer production and quality. J Inst Brew. 2007;113(3):310–324.
- ↑ Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
- ↑ Gordon R, Power A, Chapman J, Chandra S, Cozzolino D. A review on the source of lipids and their interactions during beer fermentation that affect beer quality. Fermentation. 2018;4(4):89.
- ↑ Habschied K, Košir IJ, Krstanović V, Kumrić G, Mastanjević K. Beer polyphenols—bitterness, astringency, and off-flavors. Beverages. 2021;7(2):38.
- ↑ Aron PM, Shellhammer TH. A discussion of polyphenols in beer physical and flavour stability. J Inst Brew. 2010;116(4):369–380.
- ↑ Wietstock PC, Kunz T, Waterkamp H, Methner FJ. Uptake and release of Ca, Cu, Fe, Mg, and Zn during beer production. J Am Soc Brew Chem. 2015;73(2):179–184.