Ultraviolet disinfection of juice products in laminar and turbulent flow reactors

Individual physical and chemical factors were examined in a model fluid for their effects on the efficacy of UV light on the destruction of Escherichia coli K-12 bacteria using laminar and turbulent flow treatment systems. Factors unique to juice, such as Brix and pH, did not exhibit a large effect over the range tested when examined individually. The single factor found to consistently affect the efficacy of UV light inactivation in juice was absorbance. Particulate material resulted in apparent increased rates of UV killing when solutions of equal absorption coefficients were compared. The flow rates and mixing in the turbulent flow also affected microbial inactivation: the higher the flow rates the higher inactivation rates in turbulent flow UV reactor. Regression equations were developed to describe the relationship between the rate of reduction of E. coli K-12 and absorption coefficient in a thin film reactor and for turbulent flow UV reactor. Running biodosimetry test with minimum and maximum flow rates is recommended to ascertain safe UV disinfection.