Are magnetic fields a technical opportunity to influence the structure of CO2 nanobubbles responsible for primary gushing in beer?

Gushing is the spontaneous wild and uncontrolled overfoaming phenomenon that occurs in beer and other over-carbonated beverages. This problem represents important commercial damages for the companies since this phenomenon can only be disclosed after the opening of bottled or canned beverages. Only few preventive and no curative techniques are currently available, but some detection methods such as the patented ELISA test exist or are in progress. We demonstrated recently that the key factor for gushing is the carbon dioxide and mainly the bubbles sizes during the carbonation phase. There is a critical diameter for bubbles in a liquid above which they will grow until they explode at the surface and under which they will shrink in size until they have been completely dissolved except in the presence of a contaminant (in the latter case, the bubble becomes unable to solubilize because of the contaminant that adsorbs on the surface of the bubble). In beer, it is well recognized that hydrophobins are responsible for the gushing and they can be defined as the contaminants. Hydrophobins are amphiphilic molecules produced by filamentous fungi and are present when the weather conditions on barley fields are wet. Hydrophobins can adsorb at hydrophilic-hydrophobic interfaces and it is proposed in our model that they coat the CO2 nano-bubbles and thus prevent their complete dissolution. As a consequence, they are a source of primary gushing by decapping of a bottle or opening of a can. The objective of this research is to show if a magnetic field can modify the self-assembly of hydrophobins and prevent them from coating CO2 nano-bubbles. For this, we have used different extracts of gushing and non-gushing malt. The extraction is realized with a Tris/HCl buffer 170 mM (pH 9) containing 1% SDS (Sodium Dodecyl Sulphate). The SDS is then removed by precipitation with KCl (2M). For experiments at the pilot scale several liquids are studied: first, water as the simplest model and then beer without gushing. Gushing malt extracts are added to the liquids to simulate the gushing beers and the buffer is added to the control samples. To study the effect of a magnetic field during carbonation process, CO2 is injected by a Venturi in the liquid coming from a container, and just after the Venturi, the carbonated liquid is submitted to a magnetic field. The objective is to assess the interaction of hydrophobins with CO2 in water and in beer after treatment with magnetic field and to see if the hydrophobins can still stabilize the CO2 bubbles to provoke gushing in the magnetically treated carbonated liquid. This research is conducted under the “Hydrophobin Leerstoel” which is funded by Duvel-Moortgat N.V., Brasserie d’Orval S.A., Bières de Chimay S.A. and Cargill Malt.status: publishe