Uv disınfection of some of the fruit juices

Thesis (Master)--Izmir Institute of Technology, Food Engineering, Izmir, 2009Includes bibliographical references (leaves: 101-108)Text in English; Abstract: Turkish and Englishxii, 83 leavesAlthough UV-C irradiation is used in the pasteurization of certain liquids, the application to white grape juice is not sited in the literature. Besides there are a few studies about the inactivation of naturally grown microorganisms by using UV-C treatment. The objective of this study was to determine the effect of UV-C treatment on the inactivation of Escherichia coli K12 inoculated into white grape juice and naturally grown microorganisms in the fresh squeezed orange juice. Also, the effect of UV light on the colors of the products was determined. The data were evaluated considering the properties of the juices. Results of microbiological analysis of white grape juice showed that, maximum log reduction was more than 5-log CFU/mL at a UV dose of 75.04 mJ/cm2 when the inoculation rate was 5.73 (l20.114) log CFU/mL. Although a 5-log reduction requirement of FDA was satisfied with white grape juice, maximum log reduction for the naturally grown microorganisms in orange juice was only 1.76-log CFU/mL even if the sample was subjected to UV dose of 144.36 mJ/cm2. Color analysis demonstrated that orange juice color was not affected from the treatment. For white grape juice, increased UV dose caused a decrease in a* value indicating slightly more green region.Also, increased intensity and sample depth had a pronounced effect on b* value of the juice showing yellow region. As a conclusion, UV-C light can be used as an alternative technique in processing of white grape juice. Combination of UV-C with other techniques is suggested to increase the microbiocidal efficiency in orange juices