Dynamic Light Scattering (DLS) as a Tool to Detect CO2-Hydrophobin Structures and Study the Primary Gushing Potential of Beer

When weather conditions are damp, barley crops can be infected by fungi that produce amphiphilic proteins called hydrophobins. We postulated that these hydrophobins contaminate CO2 bubbles during beer carbonation or shaking. These molecules prevent the dissolution or redissolution of CO2 and, thus, stabilize CO2 bubbles. These bubbles contain energy (overpressure) that is released when the beverage container is opened, causing the simultaneous nucleation of many bubbles, which leads to primary gushing. In this paper, we present validation of our hypothesis and show that dynamic light scattering (DLS) can be used as a tool to study the primary gushing phenomenon. The results indicate that both hydrophobins and CO2 are necessary to induce gushing. Indeed, addition of a crude mycelium extract containing hydrophobin HFBI to different beverages such as beer, soda, and sparkling water led to gushing, whereas addition to still mineral water did not. Comparison of a commercial gushing and nongushing beer using DLS revealed the presence of particles with a diameter of approx. 100 nm in the gushing beer. According to our hypothesis, these 100-nm particles should be nanobubbles stabilized by hydrophobin assemblages. The presence of these particles was also observed in all gushing beverages obtained after addition of the hydrophobin-containing mycelium extract.