Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Uv Disınfection of Some of the Fruit Juices(Izmir Institute of Technology, 2009) Hakgüder, Bengi; Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyAlthough 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.Master Thesis Disinfection of White Grape Juice by Using Continuous Flow Uv Reactor(Izmir Institute of Technology, 2011) Kaya, Zehra; Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyAlthough continuous flow UV irradiation process is applied to several kind of fruit juices as a non-thermal method, it hasnot treated to white grape juice before. The main objective was to study the effect of commercial UV disinfection system on the spoilage microorganisms in white grape juice. Physical, chemical and optical properties were measured after and before irradiation. Biodosimetric studies were performed by using Bench Top UV apparatus and continuous flow commercial UV reactor. Bench top UV study showed that 228.96 mJ/cm2 UV dose provided complete inactivation of S. cerevisiae in the pasteurized juice at 0.91 mW/cm2 UV intensity.. 3.00±0.16 log cfu/ml yeasts and 4.32±0.03 log cfu/ml lactic acid bacteria reduction were detected in naturally fermented juice after 282.24 mJ/cm2 UV dose. D(10) of yeasts (43.86 mJ/cm2) were higher than lactic acid bacteria (33.78 mJ/cm2) because of showing higher resistance to UV light. In the continuous flow UV reactor, the highest reduction of S. cerevisiae was achieved as 3.39±0.044 log cfu/ml at 56.06 mJ/cm2 UV dose and low flow rate (820 ml/min) in pasteurized juice. However, highest reduction was observed in yeast and lactic acid bacteria count as 1.70±0.028 log cfu/ml and 2.49±0.0031 log cfu/ml respectively at 19.96 mJ/cm2 UV dose in medium flow rate (1516 ml/min) of fresh squeezed juice. Absorbance, color, and titratable acidity were changed by irradiation. As a result of 13 days shelf life study, no significant increase was seen in spoilage microorganisms after irradiation.