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A multiplex polymerase chain reaction (PCR) assay was developed for simultaneous detection of Escherichia coli O157:H7, Bacillus cereus, Vibrio parahaemolyticus, Salmonella spp., Listeria monocytogenes, and Staphylococcus aureus in various Korean ready-to-eat foods. The six specific primer pairs for multiplex PCR were selected based on the O157 antigen (rfbE) gene of E. coli O157:H7, the DNA gyrase subunit B (gyrB) gene of B. cereus, the toxin regulatory protein (toxR) gene of V. parahaemolyticus, the invasion protein A (invA) gene of Salmonella spp., the hemolysin (hly) gene of L. monocytogenes, and the thermonuclease (nuc) gene of S. aureus. The 16S rRNA gene was targeted as an internal control gene in the presence of bacterial DNA. The specificity and sensitivity assays for multiplex primer pairs were investigated by testing different strains. When this multiplex PCR assay was applied to evaluate the validity of detecting six foodborne pathogens in artificially inoculated several ready-to-eat food samples, the assay was able to specifically simultaneously detect as few as 1 colony-forming unit/mL of each pathogen after enrichment for 12 h. Their presence in naturally contaminated samples also indicates that the developed multiplex PCR assay is an effective and informative supplement for practical use.

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The aim of the present work was to investigate the feasibility of employing the molecular imprinting polymer technique for detecting the mycotoxin zearalenone using a surface plasmon resonance (SPR) transducer. The molecularly imprinted polypyrrole (MIPPy) film was prepared by electropolymerization of pyrrole onto the bare Au chip in the presence of a template zearalenone molecule. The MIPPy-SPR sensor exhibited a linear response in the range of 0.3-3000 ng/mL (R (2) = 0.993) for detection of zearalenone. The selectivity efficiencies of zearalenone and other structurally related analogues were 1.0 and 0.15-0.27, respectively. The limit of detection and average recovery of blank corn matrix spiked with 30 ng/g zearalenone were 0.3 ng/g and 89%, respectively, and these were found to be comparable to those obtained by enzyme-linked immunosorbent assay. These results suggest that a combination of SPR sensing with MIPPy film is a promising alternative method for the detection of zearalenone.

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Unlike X-ray systems, a terahertz imaging system can distinguish low-density materials in a food matrix. For applying this technique to food inspection, imaging resolution and acquisition speed ought to be simultaneously enhanced. Therefore, we have developed the first continuous-wave sub-terahertz transmission imaging system with a polygonal mirror. Using an f-theta lens and a polygonal mirror, beam scanning is performed over a range of 150 mm. For obtaining transmission images, the line-beam is incorporated with sample translation. The imaging system demonstrates that a pattern with 2.83 mm line-width at 210 GHz can be identified with a scanning speed of 80 mm/s.

We develop a theoretical model for a fluidic current source consisting of a via, a detour channel, and a push-up type micro-valve. The model accurately describes the non-linear behaviour of this type of device, which has been previously measured experimentally. We show how various structural parameters and material properties of the device influence the saturated flow rate and the minimum driving pressure required for the device to function as a current source. Conversely, the model can be used to design a fluidic current source with a desired saturated flow rate and low operational pressure. The present model can be straightforwardly applied to microfluidic circuits composed of many functional autoregulatory devices.