K. INOMOTO (1), N. Doi (1), S. Masuda (1), M. Aizawa (1);
(1) Asahi Breweries, Ltd., Ibaragi, Japan
Hydrophobin, an amphiphilic low-molecular protein produced by filamentous fungi that infect barley and malt, is the direct cause of beer gushing. Hydrophobins produced by Fusarium fungi are especially known for their tendency to induce gushing in beer. It has been reported that, in beer, ~3 µg/L of such hydrophobins can cause gushing (Sarlin, T., et al. J. Inst. Brew., 111:105, 2005). To evaluate the gushing potential more accurately, the hydrophobins need to be quantified with higher specificity. Previously, papers reported measurements performed by the ELISA method using polyclonal antibody (Sarlin, T., et al. J. Inst. Brew., 111:105, 2005). However, since it does not quantify hydrophobin proteins with high specificity, a highly specific quantification method is desired. Thus, in this research, to analyze hydrophobins with higher accuracy and specificity, we established an analytical method that specifically quantifies hydrophobins derived from Fusarium fungi in beer and malt using liquid chromatography/triple quadrupole tandem mass spectrometry. A multiple reaction monitoring method was designed, using the target peptide fragments derived from hydrophobins that were detected after pre-treatment via enzymatic digestion and solid-phase extraction. This allowed for highly sensitive analyses with a detection limit of several µg/L for beer and less than 1 µg/g for malt. Malt samples that exhibited different gushing propensities in the gushing test were analyzed using our method. Results showed that malt samples with high hydrophobin content had a tendency to exhibit gushing. This indicated that our method has the potential to be useful for predicting gushing potential in malt and beer.
Kumiko Inomoto joined Asahi Breweries, Ltd. in 1986. She has been involved in analytical chemistry research for 20 years. She is now in the Department of Flavor and Chemical Analysis Research Laboratories for Alcohol Beverages.