UV inactivation of microorganisms in beer by a novel thin-film apparatus

A novel thin-film apparatus with quartz optical fibers for UV-light delivery was tested for its potential to inactivate bacteria in beer. Its suitability for application could be shown in experiments with Escherichia coli, Lactobacillus brevis, Saccharomyces cerevisiae and naturally contaminating microorganisms as test microorganisms. We have optimized the optical-fiber distribution density (ODD) and thin-film thickness for treating beer. The apparatus could reduce counts of inoculated E. coli and L. brevis in beer from approximately 106 CFU/ml to below 1 × 101 CFU/ml and from approximately 104 CFU/ml to non-detectable limits at UV doses of 16.1 and 9.7 mJ/cm2 by the thin-film apparatus respectively. The reduction of S. cerevisiae was not so efficient. Naturally contaminating lactic acid bacteria and Enterobacteriaceae in draft beer could be effectively inactivated. Furthermore, the beneficial yeasts in the draft beer were scarcely inactivated. These results implicate that application of this novel apparatus provides a promising approach to improving microbial safety and extending shelf-life of draft beer.