Primary gushing: The explosive love story between CO2 and hydrophobin

Technical Session 06: Quality Considerations Session
Christina Schönberger, Barth-Haas Group, Barth Innovations, Joh. Barth und Sohn
Co-author(s): Sylvie Deckers, KU Leuven, Department M2S, Malt & Beer Sciences and LFoRCe, Belgium; Jean Titze, National University of Ireland, University College Cork, School of Food and Nutritional Sciences, Ireland; Vladimir Ilberg, Hochschule Weihenstephan-Triesdorf, Fakultät Gartenbau und Lebensmitteltechnologie, Germany; Guy Derdelinckx, KU Leuven, Department M2S, Malt & Beer Sciences and LFoRCe, Belgium

ABSTRACT: During the last decade a lot of research was performed on an undesirable and unexplainable phenomenon called gushing, which is characterized by a spontaneous and wild liquid expulsion of carbonated beverages that occurs immediately after opening the bottle without any shaking. Gushing is a tremendous problem for breweries as it is unpredictable and can cause severe delivery and image problems. This work reviews all relevant findings in brewing science throughout the last 20 years and explains the gushing phenomenon based on the facts that are known today. While secondary gushing is due to technical and technological problems, primary gushing is related to the use of raw materials contaminated by a filamentous fungi, a producer of a human safe and amphiphilic protein called hydrophobin. By forming a solid condensed pellicle (i.e., crystalline layer) around gaseous CO2 Class II hydrophobins are responsible for the presence of gaseous nanobubbles insulated from the liquid and pressurized at 4 bars in a bottled beverage. These nanobubbles explode upon opening due to the drop in pressure. This explosion provides the energy required for nucleation, which results in the fast escape of dissolved CO2 and gushing. Knowing the interaction of hydrophobins and CO2, possible solutions for gushing have to be looked for in any material that may interfere with the formation of stabilized nanobubbles. In this regard various hop components seem to be of interest. As gushing is a worldwide problem, it seems important to make a review of this phenomenon and which possible hop characteristics, as a typical ingredient in beer, could offer a solution.

Christina Schönberger studied brewing and beverage technology at the Technische Universität München-Weihenstephan, Germany (1995–1999), graduating as an engineer in 1999. After working as a brewing intern in 2000 at Suntory, Japan, she pursued doctoral thesis work at the Chair of Brewing Technology I on “Sensory and Analytical Characterisation of Non-volatile Taste Compounds in Bottom Fermented Beers,” with which she graduated summa cum laude in December 2003. For her doctoral thesis she received the Dr. Nienaber Award in 2005. After working for the German Brewers Association for one year as a consultant for technical and governmental issues, she joined the Barth Haas Group in 2005 as manager of technical sales. Within this role she is also responsible for the guidance of research projects and authors hop related professional articles. Christina currently holds the role of International Director on the ASBC Board of Directors.