Characterizing the Performance of a Continuous-Flow UV-LED System for Treatment of Juices and Beverages Using Multiple Wavelengths

Recent advancements in ultraviolet light-emitting diodes (UV-LEDs) have allowed for their successful integration into continuous disinfection reactors including small-scale systems designed for low UV transmission (UVT) applications. This study characterized the performance of the first commercially available benchtop continuous-flow multiple-wavelength UV-LED system used for the treatment of juices and beverages in thin film. Three beverages (coconut water, blue lemonade, and pink lemonade), two juices (green juice blend and beet juice blend), and saline solution were inoculated with a non-pathogenic Escherichia coli indicator organism and treated at 281 nm. The volume averaged fluence delivered to the samples per pass ranged between 1.6 and 11.6 mJ cm(-2) and was dependent on their absorption coefficients which ranged from 0.67 to 26.9 cm(-1). Microbial inactivation ranging from 4.2 to 7.2 log(10) was achieved within a reasonable number of passes or treatment time in pink and blue lemonade, coconut water, and saline solution which corresponded to an absorption coefficient below 6 cm(-1) (UVT = 0.3%). Other than in beet juice blend, which had the highest absorption coefficient, a 1-log(10) reduction fluence value in the range of other E. coli strains (previously reported in water) was reported (1.9-5.8 mJ cm(-2)). These results also suggest that the continuous-flow UV-LED system can be used to investigate inactivation kinetics and effects on nutritional and quality parameters at multiple wavelengths following treatment of low UVT water samples and high UVT juices and beverages with absorption coefficients up to 10-12 cm(-1) (4.6e-3 to 6.3e-6% UVT).