Date

2011

Author

Yüce, Özlem

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The aim of current research is to analyze the effect of microfluidization on the stability and some quality characteristics of orange juice with respect to treatment pressure and cycle. Orange juice was microfluidized with four different pressures (34, 69, 103 and 138 MPa) and three different cycles (1, 2 and 3) at 18 ± 2 0C. Physical and chemical properties of microfluidized juices were compared with non-microfluidized freshly squeezed orange juice. Microfluidization made orange juice brighter and decreased redness and yellowness. There was a huge difference between non-microfluidized juice and microfluidized juice in terms of particle size. Microfluidization decreased the volume weighted mean (VWM) of orange juice between 90 % and 97 %. The results of total phenol content and antioxidant activity experiments showed that treatment pressure affected them positively; however cycle had not a significant effect on total phenol content and antioxidant property of orange juice (p<0.05). Our current research also includes effect of microfluidization on stability of orange juice. The broken down of aggregated structure and reduction in particle size due to treatment were observed by the scanning electron and light microscopes. Therefore, it was observed that treated orange juice could be homogeneous and opaque for 14 days at 4 0C. Cloud stability of juice showed that both pressure and cycle had important effect on the cloud stability (p<0.05). Microfluidization made the juice very stable but increase in pressure and cycle resulted in less stable juice. It was also measured that pectin methyl esterase activity was increased due to treatment of microfluidization.

Subject Keywords

Food

URI

http://etd.lib.metu.edu.tr/upload/12613495/index.pdf
https://hdl.handle.net/11511/20733

Collections

Graduate School of Natural and Applied Sciences, Thesis