10-Hydroxy-2-decenoic Acid as an Antimicrobial Agent in Draft Keg-conditioned Wheat Beer

In nature, 10-hydroxy-2-decenoic acid (10-HDA), an important unsaturated fatty acid, is only available in royal jelly. Natural 10-HDA exhibits several biological activities, including anticancer activity, and provides protection against acute radiation injury. In this study, we identified a method for extraction of 10-HDA from royal jelly. The antimicrobial effect of 10-HDA on beer-spoilage bacteria and yeast was investigated by flow cytometry and bacteriostatic circle (paper assay) experiments. We also determined the minimum inhibitory concentration of 10-HDA using the double-dilution method. Our results showed that 10-HDA could significantly inhibit common microorganisms, such as Lactobacillus brevis and Pediococcus damnosus, found in beer but had no inhibitory effect on yeast. A novel approach for preparing draft keg-conditioned wheat beer was developed using top-fermenting yeast strain 303 and bottom-fermenting yeast strain 308. The beer was then kegged for secondary fermentation. Because living yeasts were still in the beer, pasteurization could not be used, and it was difficult to keep everything clean and sanitary during brewing and kegging processes. In this study, 10-HDA was added to the green beer during kegging. We confirmed that 10-HDA, acting as an antimicrobial agent, increased the sanitary aspects of the kegged beer and improved the microbiological stability and shelf life of the beer.