UV-C-inactivation of microorganisms in naturally cloudy apple juice using novel inactivation equipment based on Dean vortex technology

A novel UV-C irradiation device in laboratory scale was tested for its potential to inactivate bacteria in naturally cloudy apple juice. in this device, liquid flows through a helically wound tubing wrapped around a quartz glass tube containing a 9 W UV lamp with an irradiation intensity of 60 W/m(2) at 254 nm. The equipment was capable of reducing numbers of inoculated Escherichia coli and Lactobacillus brevis from an initial concentration of approximately 10(6) CFU/ml or 10(4) CFU/ml to below detectable limits in commercial naturally cloudy apple juice at a flow rate of 2 l/h, and to well below 1 x 10(2) also at higher flow rates of 4 and 8 1/h. Numbers of Saccharomyces cerevisiae could be reduced from an initial level of ca. 1 x 10(4)-1 X 10(2) CFU/ml or less at flow rates of 2 and 4 l/h. Although E. coli could be effectively inactivated also in self-extracted, as well as industrially processed apple juice, contaminating yeast and lactic acid bacteria were not completely eliminated. (c) 2009 Elsevier Ltd. All rights reserved.