UV-C Treatment of Apple and Grape Juices by Modified UV-C Reactor Based on Dean Vortex Technology: Microbial, Physicochemical and Sensorial Parameters Evaluation

Abstract

A laboratory-scale ultraviolet (UV-C) reactor based on Dean vortex technology was designed and tested for its capability to inactivate microorganisms in apple and red grape juices in relatively low doses of UV-C. Experiments were carried out with freshly squeezed apple juice (AJ) and freshly squeezed grape juice (GJ) inoculated with Lactobacillus plantarum NRIC1749 and Saccharomyces cerevisiae NCIB4932. Furthermore, physicochemical properties, antioxidant activity, total phenolic content, 5-HMF and colour analysis were performed in freshly squeezed apple (AJ) and grape juices (GJ). A UV-C treatment with 1668 mJ cm−2 led to an approximately 4.07-log inactivation of Lactobacillus plantarum NRIC1749 and 1.79-log inactivation of Saccharomyces cerevisiae NCIB4932 in AJ. A 0.69-log and 0.46-log reduction could be achieved for the inactivation of L. plantarum and S. cerevisiae in GJ at 1232 mJ cm−2, respectively. DPPH radical scavenging activity and total phenolic content of UV-C treated apple juice significantly increased, whereas total phenolic content remained constant in GJ. However, UV-C treatment had no significant effect on 5-HMF content of both juices. An effect of the treatment on the colour of both juices was observed. No significant change in the quality attributes (appearance, colour, odour, taste) was determined in the both UV-C treated juices.