Reduced fouling and enhanced microbial inactivation during online sterilization of cheese whey using UV coil reactors in series

The effectiveness of coil UV reactor series for the online sterilization of cheese whey was compared to those of the single conventional and coil reactors at various flow rates (5-70 mL/min). The residence time varied from 168 to 12 min and from 48 to 24 min for the single and the series reactors, respectively. Hundred percent destruction efficiency could not be achieved in the single reactors whereas in the coil reactor series the destruction efficiency reached 100% at the flow rates of 35 and 40 mL/min. The rate of microbial destruction was described by polynomial equation for the single coil reactor and by exponential equations for the single conventional reactor and the coil reactor series. The temperature of the effluent decreased with the increase in flow rate in all the reactors. The maximum effluent temperatures in the single conventional reactor, single coil reactor and coil reactor series were 45.8, 46.1, and 36.4 degrees C (Deltat = 20.8, 21.1, 11.4 degrees C), respectively. The flow in all the reactors was laminar (R ( e ) = 1.39-20.10) and the Dean number was in the range of 1.09-15.41 in the coil reactors. Visual observation revealed less fouling on the UV lamps of coil reactors than on that of the conventional reactor due to the impact of Dean flow. The total operating time during which 100% destruction efficiency is achieved prior to the advent of fouling was 240 min in the coil reactor series compared to only 45 min in the conventional reactor.