Continuous and Pulsed Ultraviolet Light for Nonthermal Treatment of Liquid Foods. Part 1: Effects on Quality of Fructose Solution, Apple Juice, and Milk

Performance of three innovative high-intensity pulsed (HIP) ultraviolet (UV) sources characterized by different emission spectra, energy per pulse, and frequency (HIP-1: 31 J/pulse, 8 Hz; HIP-2: 344 J/pulse, 0.75 Hz; HIP-3: 644 J/pulse, 0.5 Hz) was evaluated at UV fluence of 5 mJ/cm2 by measuring the effects on quality parameters of 30% (w/v) fructose solution, apple juice and milk. The results were compared with the continuous monochromatic low pressure (LPM) and medium pressure polychromatic (MPM) mercury lamps at the UV fluence of 10 mJ/cm2 that was determined based on 5-log microbial reduction requirement. The effects of HIP-1 and HIP-3 pulsed lamps on color, pH, and vitamin C, were comparable with the LPM lamp. For example, pH of fructose decreased by 1.94% for the LPM lamp and by 0.78% and 4.31% for HIP-1 and HIP-3, respectively. Treatment with the LPM lamp reduced the vitamin C content by 1.30% in apple juice and 35.13% in milk. In the case of pulsed lamps the reduction of vitamin C was 0.85% for HIP-1 and 1.78% for HIP-3 in apple juice, 12.31% (HIP-1) and 21.66% (HIP-3) in milk. HIP-2 and MPM lamps caused the most significant deterioration of the quality parameters in all tested liquids. The HIP-2 lamp decreased vitamin C by 8.52% in apple juice and 35.80% in milk, and also reduced pH of fructose solution by 5.29%. These results indicate that UV treatment with pulsed HIP-1 and HIP-3 sources could represent a promising alternative for the treatment of low UV transparent and opaque liquid foods.