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Li J.,Shanghai Ocean University | Lin T.,Shanghai Ocean University | Lu Q.,Guangdong Institute of Eco environmental and Soil Sciences | Wang J.J.,Shanghai Ocean University | And 5 more authors.
LWT - Food Science and Technology | Year: 2014

Acidic electrolyzed water ice (AEW ice) is a new kind of bactericide used in preservation or cold sterilization of food products. The aim of this study was to investigate changes in the physicochemical properties (oxidation reduction potential (ORP), pH value and available chlorine concentration (ACC)), bactericidal efficiency, and decay kinetics of available chlorine in AEW ice during 10h of storage time. Results indicated that pH changes of AEW ice did not have a significant difference (p>0.05) during the first 6-h storage, after 6h, the pH of AEW ice prepared with ≤1g/l NaCl solution changed more slowly than that of AEW ice prepared with >1g/l NaCl solution. Both ORP and ACC decreased with storage time. The ACC of AEW ices prepared from >1.5g/l NaCl solutions decreased faster and in a greater extent than those prepared from ≤1.5g/l NaCl solutions. According to the correlation analysis, the correlation coefficients between pH, ORP, and ACC and Vibrio parahaemolyticus inactivation were -0.831, 0.787 and 0.944, respectively, and those between the above parameters and Listeria monocytogenes inactivation were -0.814, 0.701 and 0.97, respectively. Based on the kinetic study, the decay of ACC fitted the first order kinetics. © 2014 Elsevier Ltd. Source


Liao C.,Shanghai Ocean University | Peng Z.Y.,Shanghai Ocean University | Li J.B.,Shanghai Ocean University | Cui X.W.,Shanghai Ocean University | And 9 more authors.
Letters in Applied Microbiology | Year: 2015

The aim of this study was to simultaneously construct PCR-DGGE-based predictive models of Listeria monocytogenes and Vibrio parahaemolyticus on cooked shrimps at 4 and 10°C. Calibration curves were established to correlate peak density of DGGE bands with microbial counts. Microbial counts derived from PCR-DGGE and plate methods were fitted by Baranyi model to obtain molecular and traditional predictive models. For L. monocytogenes, growing at 4 and 10°C, molecular predictive models were constructed. It showed good evaluations of correlation coefficients (R2 > 0·92), bias factors (Bf) and accuracy factors (Af) (1·0 ≤ Bf ≤ Af ≤ 1·1). Moreover, no significant difference was found between molecular and traditional predictive models when analysed on lag phase (λ), maximum growth rate (μmax) and growth data (P > 0·05). But for V. parahaemolyticus, inactivated at 4 and 10°C, molecular models show significant difference when compared with traditional models. Taken together, these results suggest that PCR-DGGE based on DNA can be used to construct growth models, but it is inappropriate for inactivation models yet. This is the first report of developing PCR-DGGE to simultaneously construct multiple molecular models. Significance and Impact of the Study: It has been known for a long time that microbial predictive models based on traditional plate methods are time-consuming and labour-intensive. Denaturing gradient gel electrophoresis (DGGE) has been widely used as a semiquantitative method to describe complex microbial community. In our study, we developed DGGE to quantify bacterial counts and simultaneously established two molecular predictive models to describe the growth and survival of two bacteria (Listeria monocytogenes and Vibrio parahaemolyticus) at 4 and 10°C. We demonstrated that PCR-DGGE could be used to construct growth models. This work provides a new approach to construct molecular predictive models and thereby facilitates predictive microbiology and QMRA (Quantitative Microbial Risk Assessment). Significance and Impact of the Study: It has been known for a long time that microbial predictive models based on traditional plate methods are time-consuming and labour-intensive. Denaturing gradient gel electrophoresis (DGGE) has been widely used as a semiquantitative method to describe complex microbial community. In our study, we developed DGGE to quantify bacterial counts and simultaneously established two molecular predictive models to describe the growth and survival of two bacteria (Listeria monocytogenes and Vibrio parahaemolyticus) at 4 and 10°C. We demonstrated that PCR-DGGE could be used to construct growth models. This work provides a new approach to construct molecular predictive models and thereby facilitates predictive microbiology and QMRA (Quantitative Microbial Risk Assessment). © 2014 The Society for Applied Microbiology. Source


Yu Y.-X.,Shanghai Ocean University | Yu Y.-X.,Laboratory of Quality and Safety Risk Assessment for Aquatic Products on Storage and Preservation Shanghai | Sun X.-H.,Shanghai Ocean University | Sun X.-H.,Laboratory of Quality and Safety Risk Assessment for Aquatic Products on Storage and Preservation Shanghai | And 6 more authors.
Canadian Journal of Microbiology | Year: 2015

Microorganisms can produce species-specific microbial volatile organic compounds (MVOCs), or odor compounds, which can be characterized by odor fingerprinting. The objective of this study was to characterize the odor fingerprint of Listeria monocytogenes. Solid-phase microextraction - gas chromatography - mass spectrometry (SPME-GC-MS) and electronic nose (E-nose) were used to recognize the MVOCs of L. monocytogenes in pure culture medium. The main MVOCs of L. monocytogenes were identified by SPME-GC-MS analysis as alcohols, aldehydes, ketones, alkanes, and heterocyclics, among which the relative peak area of one compound, 3-hydroxy-2-butanone, increased along with the growth of L. monocytogenes. The odor fingerprint of L. monocytogenes at different growth stages could be clearly discriminated by E-nose. In addition, E-nose signals had a very good linear relationship with the concentration of this bacterium (R2 = 0.9937). Our study may help to establish the analysis of the odor fingerprint of microorganisms as a potential routine method in microbiology. Source


Sun G.,Shanghai Ocean University | Sun G.,Laboratory of Quality and Safety Risk Assessment for Aquatic Products on Storage and Preservation Shanghai | Xiao J.,Shanghai Ocean University | Xiao J.,Laboratory of Quality and Safety Risk Assessment for Aquatic Products on Storage and Preservation Shanghai | And 12 more authors.
Applied Biochemistry and Biotechnology | Year: 2015

The 16S ribosomal RNA (rRNA) gene of marine archaeal samples was amplified using a nested PCR approach, and the V3 region of 16S rRNA gene of crab gut microbiota (CGM) was amplified using the V3 universal primer pair with a guanine and cytosine (GC)-clamp. Unpurified PCR products (UPPs), products purified from reaction solution (PPFSs), and products purified from gel (PPFGs) of above two DNA samples were used for denaturing gradient gel electrophoresis (DGGE) analysis, respectively. In contrast to almost identical band patterns shared by both the UPP and PPFS, the PPFGs were barely observed on the DGGE gel for both the marine archaea and CGM samples. Both PPFS and PPFG of CGM V3 regions were subjected to cloning. A small amount of positive clones was obtained for PPFS, but no positive clones were observed for PPFG. The melt curve and direct sequencing analysis of PPFS and PPFG of E. coli V3 region indicated that the Tm value of PPFG (82.35 ± 0.19 °C) was less than that of PPFS (83.81 ± 0.11 °C), and the number of shorter GC-clamps was significant higher in PPFG than in PPFS. The ultraviolet exposure experiment indicated that the ultraviolet was not responsible for the deletion of the GC-clamps. We conclude that the gel purification method is not suitable for DGGE PCR products or even other GC-rich DNA samples. © 2014, Springer Science+Business Media New York. Source

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