Doubly Modified Carlsberg Test combined with Dynamic Light Scattering allows prediction of the primary gushing potential of harvested barley and malt

Abstract

Despite intensive research on the gushing of carbonated beverages during the last decades, there is no universal method to predict its occurrence and consequently how to avoid the economic losses it induces. Primary gushing can be visualized as the strong overfoaming and/or strong liquid expulsion of liquid when a bottle of carbonated beverage is opened. This process results from the interaction between gaseous CO₂ and class II hydrophobins. Both chemicals are present in the pressurized liquid as CO₂ nanobubbles coated by hydrophobins which explode when at bottle opening the pressure is released, which results in a vigorous expulsing of CO₂. Hydrophobins are produced by filamentous fungi in the field or during storage and processing. To avoid gushing of beers, their early detection in the barley-to-beer chain is of capital importance. To ascertain with more certainty the presence of hydrophobins on barley and malt and their gushing inducing property, the gushing test mostly often used in practice, the doubly Modified Carlsberg Test, was used but it was followed by a new test based on the detection of CO₂-hydrophobin nanoparticles by Dynamic Light Scattering (DLS). This allowed to certify that the potential of provoking gushing by samples of barley and malt is due to the potential of provoking a primary gushing and the presence of fungal products: hydrophobins. The results showed also that only 5% of gushing provoking grains in the grist is sufficient to induce gushing and the detection of the nanoparticles, typical for primary gushing.