[Show abstract][Hide abstract] ABSTRACT: The chemical composition, antioxidant and antimicrobial activity of Pericarpium Citri Reticulatae (PCR) essential oil obtained using an improved Clevenger type apparatus were studied. Among the five different PCRs examined the highest yield of essential oil was found in Chachi 2004 (harvested and stored in 2004) and the lowest in Chachi 2008 (harvested and stored in 2008). Fifty three different volatile compounds were determined, including terpenic hydrocarbons, alcohols, aldehydes, ketones and esters. D-limonene, one of terpenes, was the major constituent in PCR. The antioxidant capacity of PCR essential oil varied considerably with the duration of storage time, and the oil from Chachi 1994 has the strongest ferric-reducing antioxidant power. In addition, the essential oil possessed varying degrees of antimicrobial activity against Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, Bacillus cereus), except Streptococcus faecalis, while had no effect on Gram-negative bacteria (Escherichia coli, Enterobacter cloacae).
[Show abstract][Hide abstract] 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.
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.
No preview · Article · Aug 2010 · Journal of Food Processing and Preservation
[Show abstract][Hide abstract] ABSTRACT: Headspace solid-phase microextraction has been applied to the analysis of volatile components in longan (Dimocarpus longan Lour.). Silica fiber coated with divinylbenzene–carboxen–polydimethylsiloxane (DVB–CAR–PDMS) was found to be more efficient
for extracting volatile compounds than other fibers such as those coated with polydimethylsiloxane, polyacrylate, and carboxen–polydimethylsiloxane.
The SPME headspace volatiles were collected using a DVB–CAR–PDMS fiber. The extraction conditions were optimized using a response
surface experimental design to analyze the effect of three factors: extraction temperature, equilibrium time and extraction
time. The best response was obtained when the extraction temperature was around 50°C, equilibrium time near 15min and extraction
time close to 25min. The volatile extracts were analyzed using gas chromatograph/mass spectrometry system. Sixty-two different
volatile compounds from the headspace of longan were identified. The linearity was good in the considered concentration ranges
2≥0.965). Average recoveries ranged from 78.6 to 108.3% and showed good accuracy. The precision of the present method was
found to be good (RSD<13.59%). Therefore, this method can be applied to determine the quality of the longan or other volatile
components as an alternative to full-scale headspace analysis.
No preview · Article · Jul 2009 · European Food Research and Technology