PULSED ELECTRIC FIELD PROCESSING EFFECTS ON PHYSICOCHEMICAL PROPERTIES, FLAVOR COMPOUNDS AND MICROORGANISMS OF LONGAN JUICE

Abstract

Longan juice was processed using a pulsed electric field (PEF) treatment and compared with a conventional thermal pasteurization method. The PEF treatment was carried out using a laboratory unit, set with a bipolar pulse (3 µs wide), an intensity of 32 kV/cm. PEF-treated longan juice showed no noticeable difference compared with the untreated sample, although well-visible differences were found between untreated and thermal-treated juice. An analysis of variance for pH, titratable acidity and total soluble solids determinations showed no statistically significant difference between the untreated and both thermally pasteurized and PEF-treated samples. The effect of PEF on nonenzymatic browning index and hydroxymethylfurfurol is not significantly different, although thermal treatment show significant difference in comparison with untreated juice. Contents of total phenol compounds presented significant variability for the two compared pasteurization methods. The PEF-treated longan juice retained greater amounts of vitamin C and top five flavor compounds than thermally treated longan juice. PRACTICAL APPLICATIONS: As a new nonthermal sterilization method, pulsed electric field (PEF) treatment is a useful tool in fruit processing. It has been used in some other fruit juice processing, and no apparent changes in physicochemical properties and flavor were directly caused by PEF treatment. We tried it on longan juice and obtained some data for longan juice processing. PEF treatment is a new processing technology that improves longan juice quality and enhances its value.