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Zhu P.,China National Center for Food Safety Risk Assessment | Zhu P.,U.S. Center for Disease Control and Prevention | Zhu P.,Nanchang University | Miao H.,China National Center for Food Safety Risk Assessment | And 6 more authors.
Journal of Agricultural and Food Chemistry | Year: 2014

One hundred and one tea samples including green tea, dark tea, scented tea, black tea, and oolong tea were screened and confirmed for the contamination of 31 organochlorine pesticides (OCPs) and 19 pyrethroids (PYs) by gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS). 50 pesticides, 3 deuterium-labeled PYs, and 24 13C-labeled OCPs were separated well with the limits of detection (LODs) ranging from 0.02 to 4.5 μg/kg for GC-NCI-MS, and the positive samples were verified by GC-MS/MS with LODs of 0.1-5.0 μg/kg. High detection rates for some PYs, such as 63.4% for bifenthrin (not detected (ND)-3.848 mg/kg), 55.4% for λ-cyhalothrin (ND-3.244 mg/kg), 46.5% for cypermethrin (ND-0.499 mg/kg), and 24.8% for fenvalerate (ND-0.217 mg/kg), were found in the 101 tea samples. Endosulfan, DDTs, HCHs, and heptachlor, the persistent OCPs, were frequently detected with rates of 63.4% (ND-1.802 mg/kg), 56.4% (ND-0.411 mg/kg), 24.8% (ND-0.377 mg/kg), and 15.8% (ND-0.100 mg/kg), respectively. © 2014 American Chemical Society. Source


Yu C.,Beijing Institute of Technology | Weiping L.,Beijing Institute of Technology | Yanchun Y.,Beijing Institute of Technology | JianQiang G.,China National Food Quality and Safety Supervision and Inspection Center | And 4 more authors.
Journal of Applied Polymer Science | Year: 2015

Biosensor detecting techniques have attracted much attention in the content determination of H2O2, which has been used illegally as a food additive. An electrochemical biosensing membrane for the detection of H2O2 was developed with C6-OH of chitosan immobilized cyclodextrin derivates (6-CD-CTS), which possessed a high cyclodextrin loading capacity (2.12 × 10-4 mol/g), as the carrier. The biosensor was prepared through the inclusion of ferrocene as the electron mediator in a hydrophobic cavity of cyclodextrin and crosslinking catalase (CAT) to 2-NH2 of 6-CD-CTS. The ferrocene-included complex was evaluated by ultraviolet-visible spectrophotometry and thermogravimetric analysis. Its electrochemical behavior was also studied. The impact of the reaction conditions on the CAT immobilization capacity was evaluated. When previous membrane was used to detect the concentration of H2O2 (CH2O2), we found that the catalysis of CAT and the signal amplification of ferrocene had a major impact on the cyclic voltammograms. The optimal working pH of the modified electrode was 7.0. The peak current (I) had a linear relationship with the H2O2 concentration (CH2O2) in the range 1.0 × 10-4 to 1.0 × 10-3 mol/L. The linear regression equation was I = 0.00475CH2O2 - 0.03025. The detection limit was 10-6 mol/L. © 2014 Wiley Periodicals, Inc. Source


Gao X.,Beijing Center for Physical and Chemical Analysis | Gao X.,China National Food Quality and Safety Supervision and Inspection Center | Mi Q.,CAS Institute of Chemistry | Zhang W.,Beijing Center for Physical and Chemical Analysis | And 8 more authors.
Advanced Materials Research | Year: 2011

Bisphenol A poly(carbonate) (PC) pellets used for production of 5 gallon drink water bottles were reprocessed in a twin-screw extruder for three processing cycles which simulated to those of PC bottle processing conditions. The reprocessed PC pellets were characterized by its mechanical, rheological, thermal, and optical properties. It was found that the mechanical properties of the reprocessed PC samples are slightly decreased after reprocessed. Whereas no further change was observed for the rheological and thermal properties and molecule weight of the PC samples after the second reprocessing cycles. Moreover, the melt flow index, color, and optical properties changed obviously after two reprocessing cycles. Source


Wang L.-P.,China National Food Quality and Safety Supervision and Inspection Center | Liu X.-L.,China National Food Quality and Safety Supervision and Inspection Center | Cai X.-F.,China National Food Quality and Safety Supervision and Inspection Center | Cao Y.,China National Food Quality and Safety Supervision and Inspection Center | Zhang F.,China National Food Quality and Safety Supervision and Inspection Center
Modern Food Science and Technology | Year: 2013

In this article, a rapid identification and numberation method for bifidobacterium in fermented milk products was established. Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) technique was used to identify Bifidobacterium present in commercial probiotic yoghurts. Real-Time Polymerase Chain Reaction (Real-Time PCR) technique was used to detect Bifidobacteria. The results showed that PCR-DGGE assays enabled identification of the species of bifidobacterium initially present in commercial fermented milk products with a detection threshold of 105 cells per gram. Real-Time PCR assays enabled numbering Bifidobacterium with a detection threshold of 104 cells per gram of product. Established PCR-DGGE analysis method was suitable for identification and detection of Bifidobacterium in commercial probiotic yoghurts. Source


Wang S.,China National Food Quality and Safety Supervision and Inspection Center | Guo Q.,China National Food Quality and Safety Supervision and Inspection Center | Wang L.,China National Food Quality and Safety Supervision and Inspection Center | Lin L.,China National Food Quality and Safety Supervision and Inspection Center | And 3 more authors.
Food Chemistry | Year: 2014

According to saccharide profile comparison between starch syrups and pure honeys analysed through high performance liquid chromatography (HPLC), a characteristic peak was found at 15.25 min retention time in HPLC chromatogram of syrup, but no peak was observed at the same retention time in chromatogram of pure honeys. This characteristic peak for syrup was identified as an overlapping peak of oligosaccharides with more than 5 degree of polymerisation (DP) based on HPLC chromatogram comparison between starch syrup and a series of standard mono-, di- and oligosaccharides of 3-7 DP. Additionally syrup content correlated linearly with the height of the characteristic peak of syrup under different slope in two ranges 2.5-7.5% and 10-100%, respectively. Therefore, the characteristic peak at 15.25 min retention time can serve as a syrup indicator in HPLC analysis of the adulterated honeys. This new HPLC method for honey adulteration detection was further applied in an authenticity inspection on more than 100 commercial honeys. In addition to the improved accuracy of honey adulteration detection, the proposed HPLC method was simple, low cost and easy practice for honey product quality control by government department considering the popularity of HPLC device and technology. © 2014 Elsevier Ltd. All rights reserved. Source

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