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Wu J.,Ocean University of China | Cao B.,Ocean University of China | Li D.,Laboratory of Food Microbiology and Food Preservation | Zhang Q.,Ocean University of China | And 5 more authors.
Journal of Chinese Institute of Food Science and Technology | Year: 2016

Real-time quantitative PCR is a useful tool for foodborne virus detection, although false-positive results can be generated due to the high sensitivity of this method. In this study, a genetic sequence alignment method was adopted to verify the authenticity of qPCR positive results of Norovirus (NoV) GII.4 detected from shellfish samples., As a result, within the eight shellfish samples with high NoV contamination detected by RT-qPCR, two were confirmed as genuine positive, two might be NoV GII.4 variant strains, one was false positive contaminated by NoV GII.4 plasmids used as standard positive control in this study, and the other three were false positives caused by primer dimmers. This study suggests that genetic sequence alignment as an effective and feasible method of verifying the authenticity of qPCR positive results, will be worthy of further promotion. © 2016, Chinese Institute of Food Science and Technology. All right reserved.


Noseda B.,Laboratory of Food Microbiology and Food Preservation | Ragaert P.,Laboratory of Food Microbiology and Food Preservation | Pauwels D.,Laboratory of Food Microbiology and Food Preservation | Anthierens T.,Laboratory of Food Microbiology and Food Preservation | And 4 more authors.
Journal of Agricultural and Food Chemistry | Year: 2010

Selective ion flow tube mass spectrometry (SIFT-MS) is a direct mass spectrometric technique that allows qualitative and quantitative analysis of a large number of volatile organic compounds. Because of its speed and ease of use, this nondestructive technique could be considered as a practical tool for quality control. This research focuses on the possibilities of direct headspace sampling by SIFT-MS for the quantification of the volatile basic nitrogen content (TVB-N) of fish fillets. These volatile bases [trimethylamine (TMA), dimethylamine (DMA), and ammonia] give additional information in conjunction with the sensory scoring and microbiological analysis about the quality of the fish fillets. This research validates in a first part the SIFT-MS method for the quantification of the volatile bases in mixed cod samples. With regard to the investigated linearity, repeatability, reproducibility, recovery, limit of detection, and limit of quantification, SIFT-MS appeared to be an adequate technique for measuring volatile bases spiked on cod. In the second part of this research, the technique was validated for the analysis of volatile bases on cod fillets during a storage experiment under ice. A good correlation was obtained between the proposed direct headspace sampling and traditional methods. The sensitivity of the SIFT-MS method can be improved when cod fillets are made more alkaline (pH >11) during sampling. © 2010 American Chemical Society.


PubMed | Laboratory of Food Microbiology and Food Preservation
Type: Evaluation Studies | Journal: Food microbiology | Year: 2011

Previous study showed that repetitive mild decontamination treatments with intense light pulses (ILP) and lactic acid (LA) can induce increased resistance in surviving pathogenic cells. Research has evaluated the potential of increased resistance to enhance the persistence of resistant variants of Listeria monocytogenes and Escherichia coli O157:H7 under suboptimal growth conditions. Growth of resistant variants and parental strains was determined by optical density (OD) measurements in nutrient broths with different pH values and NaCl concentration, at low temperature. The real lag phase was calculated, and results indicated that intense light pulses (ILP) resistant variants needed longer time to initiate growth compared to their parental strains, for both L. monocytogenes and E. coli O157:H7 when incubated at 7 C and 10 C, respectively. These selected variants were of the similar resistance towards heat and low pH (no cross-tolerance). Nevertheless, lactic acid (LA) resistant variant of L. monocytogenes was cross-protected when exposed to low pH, but not when treated with heat.


PubMed | Laboratory of Food Microbiology and Food Preservation, Ghent University and Belgium Institute for Agricultural and Fisheries Research
Type: Journal Article | Journal: Journal of food protection | Year: 2015

Food is an important dissemination route for antibiotic-resistant bacteria. Factors used during food production and preservation may contribute to the transfer of antibiotic resistance genes, but research on this subject is scarce. In this study, the effect of temperature (7 to 37C) and modified atmosphere packaging (air, 50% CO2-50% N2, and 100% N2) on antibiotic resistance transfer from Lactobacillus sakei subsp. sakei to Listeria monocytogenes was evaluated. Filter mating was performed on nonselective agar plates with high-density inocula. A more realistic setup was created by performing modified atmosphere experiments on cooked ham using high-density and low-density inocula. Plasmid transfer was observed between 10 and 37C, with plasmid transfer also observed at 7C during a prolonged incubation period. When high-density inocula were used, transconjugants were detected, both on agar plates and cooked ham, under the three atmospheres (air, 50% CO2-50% N2, and 100% N2) at 7C. This yielded a median transfer ratio (number of transconjugants/number of recipients) with an order of magnitude of 10(-4) to 10(-6). With low-density inocula, transfer was only detected under the 100% N2 atmosphere after 10-day incubation at 7C, yielding a transfer ratio of 10(-5). Under this condition, the highest bacterial density was obtained. The results indicate that low temperature and modified atmosphere packaging, two important hurdles in the food industry, do not necessarily prevent plasmid transfer from Lactobacillus sakei subsp. sakei to Listeria monocytogenes.

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