UV Inactivation of Bacteria in Apple Cider†

Abstract

Apple cider, inoculated with Escherichia coli and Listeria innocua, was processed using a simple UV apparatus. The apparatus consisted of a low-pressure mercury lamp surrounded by a coil of UV transparent tubing. Cider was pumped through the tubing at flow rates of 27 to 83 ml/min. The population of E. coli K-12 was reduced by 3.4 ± 0.3 log after being exposed for 19 s at a treatment temperature of 25°C. The population of L. innocua, which was more resistant to UV, was reduced by 2.5 ± 0.1 log after being exposed for 58 s. The electrical energy for the process was 34 J/ml and is similar to that for conventional thermal processing. UV processing has the potential to improve the safety and extend the shelf life of apple cider.