Ultraviolet light as an alternative to thermal treatment in fruit juices

In this study, pomegranate juice (PJ) and orange juice (OJ) were subjected to UV-C lights for extension of their shelf lives and effects of UV-C on quality characteristics (microbiological, chemical and sensorial) and storage stability of juices were investigated. The results were compared with control (untreated) and heat treated (at 90°C, 2 min) juice samples. 3 passes UV-C treatment of PJ and OJ resulted in 1.53 log and 2.8 log reductions in aerobic plate count and, 1.30 log and 0.34 log reductions in yeast and mould count, respectively. After 3 passes of UV-C treatment, 6.15 log reduction in PJ and 5.72 log reduction in OJ were achieved for E.coli ATTC 25922 inoculated juices which indicates an acceptable reduction of potential pathogen in juices with the current UV-C reactor. While, major quality parameters of UV-C treated PJ and OJ, which were anthocyanin pigments and polimeric color for PJ and ascorbic acid for OJ, did not change significantly (P>0.05), these quality parameters were affected significantly by heat treatment (P<0.05). There were no significant changes in antioxidant capacity, total phenolics, organic acid profile, pH, brix and titration acidity values of PJ after UV-C and heat treatments (P>0.05). Consumer tests showed that UV-C treated juices were more preferred than heat treated juices with regard to flavor and aroma characteristics. According to triangle test results, no significant difference was found between fresh and UV treated juices. After storage in refrigerated conditions (4 and 10°C), UV-C treatment notably extended the shelf life of fresh juices and maintained the major quality parameters of juices (anthocyanin and ascorbic acid) compared with heat treatment.Keywords: Ultraviolet light, pomegranate juice, orange juice, quality, storage