Investigation of sunlight-induced deterioration of aroma of pummelo (Citrus maxima) essential oil.

Deterioration of aromas of pummelo essential oil (EO) induced by sunlight was compared to those induced by heat and oxygen exposure using the techniques of sensory evaluation and GC-MS analysis. The sunlight-exposed EO was found to possess an oily off-flavor odor, which was significantly different from its counterparts induced by oxygen and heat. The strong oily note of the sunlight-exposed EO was attributed to the existence of linalool oxides and limonene oxides, as well as the lack of neral and geranial, for which UV sunlight was revealed to be the critical contributor causing the chemical reactions for the aroma changes. The results demonstrated that UV sunlight could significantly affect the aroma of the pummelo EO, providing valuable information that will benefit the production and storage of EO-based aromatic products.

Development and evaluation of an HPLC method for accurate determinations of enzyme activities of naringinase complex.

An HPLC method that can separate naringin, prunin, and naringenin was used to help accurately measure the activities of naringinase and its subunits (α-L-rhamnosidase and ß-D-glucosidase). The activities of the naringinase and ß-d-glucosidase were determined through an indirect calculation of the naringenin concentration to avoid interference from its poor solubility. The measured enzymatic activities of the naringinase complex, α-L-rhamnosidase, and ß-D-glucosidase were the as same as their theoretical activities when the substrates' (i.e., naringin or prunin) concentrations were 200 µg/mL, and the enzyme concentrations were within the range of 0.06-0.43, 0.067-0.53, and 0.15-1.13 U/mL, respectively. The ß-D-glucosidase had a much higher Vmax than either naringinase or α-L-rhamnosidase, implying the hydrolysis of naringin to prunin was the limiting step of the enzyme reaction. The reliability of the method was finally validated through the repeatability test, indicating its feasibility for the determinations of the naringinase complex.

[Establishment of immunomagnetic capture-fluorescent PCR detection method for Campylobacter jejuni].

In order to develop a rapid method which can check Campylobacter jejuni in animal and poultry foods nicely, an immunomagnetic capture-fluorescent PCR (IMC-FPCR) method was established in this paper. The reported method involves isolation of the target pathogen by immunocapture prior to the fluorescent PCR step, therefore the immunomagnetic-beads for Campylobacter were developed, and two groups of primer/probe, which targeted for the species special sequence of flaA gene and hipO gene for Campylobacter jejuni were designed. The immunomagnetic capture-fluorescent PCR assay amplification of the hipO gene and flaA gene for detection of Campylobacter jejuni was firstly reported in this paper. Result indicated that IMC-FPCR method permits direct detection of the pathogen without an enrichment step and can be performed in approximately 24 h. The assay results are positive for all of the isolates of Campylobacter jejuni (3 isolates, including type strain ATCC 33560 and ATCC8341) with a detection limit of approximately 10 cfu/mL, are negative for Campylobacter coli and several other bacteria. IMC-FPCR assay provide not only a rapid, sensitive method for quantitative detection of Campylobacter jejuni, but also an important method for detecting of Campylobacter jejuni of viable but non-culturerable (VNC) state.