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Li Y.C.,Bohai University | Zhang X.,Food Safety Key Laboratory of Liaoning Province
Advanced Materials Research

Polyphenols from Porphyra are important biological active substances. The effects of temperature, times, ethanol concentration and liquid to solid ratio were studied for the extraction yield of polyphenols from Porphyra through a single-factor exploration.Then, through an orthogonal experiment, it was investigated to get the best extraction conditions. The content of polyphenols was determined by Folin-Ciocalteu method. Scavenging ability to oxygen free radicals was also assessed. The results show that extraction temperature is 75° C, the extraction time is 2.5 h, ethanol concentration is 70% and the ratio of liquid to solid is 25:1(mL/g).The proportion of the extraction of the polyphenols from Porphyra under these industrial process conditions is 6.263mg/g. Polyphenols from Porphyra have strong scavenging hydroxyl radical and superoxide anion radical. IC50 of polyphenols from Porphyra on hydroxyl radical and superoxide anion radical is 0.405 mg/mL, 0.539mg/mL, respectively. © (2014) Trans Tech Publications, Switzerland. Source

Di H.-L.,South China University of Technology | Zhang Y.-Q.,South China University of Technology | Shan X.-X.,South China University of Technology | Yan H.,South China University of Technology | And 2 more authors.
Modern Food Science and Technology

In this study, the usefulness of fatty acid typing to identify and evaluate strain similarity among Listeria monocytogenes (LM) strains was evaluated. Ninety LM strains isolated from six types of food in Hebei area from 2005 to 2007 were selected for this study. The fatty acids were extracted, and their components were analyzed using the MIDI Sherlock system. SPSS 19.0 statistical software was used for data and cluster analyses. The fatty acid typing was compared with traditional serotyping and pulsed-field gel electrophoresis (PFGE), which is the gold standard for typing. The results showed that the fatty acid analysis method successfully identified 96.67% of LM strains, 20 fatty acid components were detected from all of the tested strains, and the three main fatty acid components were 15:0 anteiso, 17:0 anteiso, and 15:0 iso. The fatty acid components differed among the different serotypes, and the differences in two main fatty acid components between serotype 1/2c isolates and serotype 1/2a, 1/2b, and 4b isolates were statistically significant (P〈0.01). Compared with PFGE typing, fatty acid typing was a more efficient method for identifying genetic relationships between strains in small samples with simple structures. The combination of fatty acid typing along with serotyping and PFGE typing could better identify correlations among LM strains. ©, 2014, South China University of Technology. All right reserved. Source

Di H.-L.,South China University of Technology | Yan H.,South China University of Technology | Yan H.,Food Safety Key Laboratory of Liaoning Province | Shi L.,South China University of Technology
Modern Food Science and Technology

In order to find out CRISPRs in 18 lineage I (serotype1/2b, 4b) strains of food-borne Listeria monocytogens isolated from 2177 retail food samples in Hebei province, the CRISPR sequences were obtained by PCR amplification, and homology analysis was predicted using bioinformatic methods, then cluster typed by using a CRISPR-based approach. We detected three CRISPR loci in all studied strains. Loucus1 was most popular (13/18); locus2 and locus3, as two activity loci, were only detected at least one in 5 serotype 1/2b strains. Locus1, a putative remnant of a functional CRISPR ancestor, was beared unconserved repeats (DR1) and a few of spacers; locus2 and locus3, relative new functional structures, were beared conserved repeats (DR2, DR3) and fast growing number of spacers. In all, 2 strains containerd all three loci, 3 strains contained the first 2 of the three loci, as well as 8 strains only contained the first one locus, and 5 strains did not find any CRISPR structure. As the diversity of CRISPR arrays, 18 strains typed to 5 clusters (A~F), and 4 subset clusters (A1and A2, B1 and B2). CRISPR typing can be good used in differentiating serotype 1/2b strains. In other hands, the CRISPR structures, especially that beared more spacers, enhance the host's environmental adaptability, enlarged the clear difficulty in food processing, alarm the food safety. The government should reinforce the control of these kinds of L. monocytogenes. Source

Meng H.-C.,South China University of Technology | Bi S.-L.,Guangdong Pharmaceutical University | Yan H.,South China University of Technology | Yan H.,Food Safety Key Laboratory of Liaoning Province | Shi L.,South China University of Technology
Huanan Ligong Daxue Xuebao/Journal of South China University of Technology (Natural Science)

Eight poultry samples including chicken and duck were collected in a certain fresh market and were enriched in Bolton and Preston broths, followed by the inoculation on selective agar media (Skirrow and mCCDA) and by the membrane filtration. Then, the molecular types of the isolated Campylobacter strains were analyzed by means of pulse field gel electrophoresis (PFGE) and denaturing gradient gel electrophoresis (DGGE), and C. jejuni or C. coli were isolated from six samples. The results show that the combination of Preston broth and mCCDA media is the optimal isolation method, that there are four samples contaminated by the same C. coli isolate and two samples contaminated respectively by 2 species of C. jejuni and 3 species of C. coli, and that, though DGGE genotyping is not as sensitive as PFGE genotyping, it is more suitable for the rapid genotyping of Campylobacter in food borne because it is of high speed, low cost as well as stable and accurate operation. Source

Chen J.,Zhejiang Ocean University | Huang Y.T.,Zhejiang Ocean University | Deng S.G.,Zhejiang Ocean University | Li J.R.,Food Safety Key Laboratory of Liaoning Province
Advanced Materials Research

Resting cells of Pseudomonas sp. SY031 were used for the direct transformation of adiponitrile to 5-cyanovaleramide (5-CVAM), which is an important intermediate of azafenidin, a new kind of herbicide with high efficiency, low toxicity and non-pollution. In this study, reaction conditions for this nitrile hydratase mediated conversion were optimized. It was observed that the maximum conversion of adiponitrile to 5-CVAM was in a solution containing 50 mM phosphate buffer (pH 6.4), 10 mM adiponitrile at 35°C. 10 mM adiponitrile was completely converted into 5-CVAM and adipamide in shaking flasks with 5-CVAM as the main product (9.004 mM) and adipamide as a low yield (0.896 mM), indicating high regio-selectivity of the nitrile hydratase in Pseudomonas sp. SY031. © (2013) Trans Tech Publications, Switzerland. Source

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