DNA-based techniques for authentication of processed food and food supplements.

Foodborne pathogens have been a cause of a large number of diseases worldwide and more so in developing countries. This has a major economic impact. It is important to contain them, and to do so, early detection is very crucial. Detection and diagnostics relied on culture-based methods to begin with and have developed in the recent past parallel to the developments towards immunological methods such as enzyme-linked immunosorbent assays (ELISA) and molecular biology-based methods such as polymerase chain reaction (PCR). The aim has always been to find a rapid, sensitive, specific and cost-effective method. Ranging from culturing of microbes to the futuristic biosensor technology, the methods have had this common goal. This review summarizes the recent trends and brings together methods that have been developed over the years.

A review on detection methods used for foodborne pathogens.

Identification of meat origin in food products – A review

Comparison between digital PCR and real-time PCR in detection of Salmonella typhimurium in milk.

Development of a multiplex real-time PCR method for simultaneous detection of Vibrio parahaemolyticus, Listeria monocytogenes and Salmonella spp. in raw shrimp

In this project, a highly precise quantitative method based on the digital polymerase chain reaction (dPCR) technique was developed to determine the weight of pork and chicken in meat products. Real-time quantitative polymerase chain reaction (qPCR) is currently used for quantitative molecular analysis of the presence of species-specific DNAs in meat products. However, it is limited in amplification efficiency and relies on standard curves based Ct values, detecting and quantifying low copy number target DNA, as in some complex mixture meat products. By using the dPCR method, we find the relationships between the raw meat weight and DNA weight and between the DNA weight and DNA copy number were both close to linear. This enabled us to establish formulae to calculate the raw meat weight based on the DNA copy number. The accuracy and applicability of this method were tested and verified using samples of pork and chicken powder mixed in known proportions. Quantitative analysis indicated that dPCR is highly precise in quantifying pork and chicken in meat products and therefore has the potential to be used in routine analysis by government regulators and quality control departments of commercial food and feed enterprises.

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Quantitative Analysis of Pork and Chicken Products by Droplet Digital PCR

Molecular typing of Vibrio parahaemolyticus isolates from the middle-east coastline of China.

Comparative proteomic analysis by iTRAQ-2DLC-MS/MS provides insight into the key proteins involved in Cronobacter sp. biofilm formation

Salmonella is the most common cause of bacterial food poisoning in humans worldwide. Thus, rapid and reliable methods for the detection of this pathogen are required. Real-time reverse-transcriptase polymerase chain reaction (rt-RT-PCR), which detects the presence of mRNA (shorter half-life than DNA) has shown great potential for detecting viable pathogens. We recently identified a few new potential specific DNA sequences for Salmonella enterica using a comparative genomics method (Chen et al., 2010). In the present study, we examined the expression of the Salmonella-specific sigDE operon (encoding invasion proteins within the pathogenicity island 5) under typical growth conditions to determine whether sigDE could be a useful viability marker for the bacterium. We then assayed sigDE mRNA from cells heat-treated at 60°C, 100°C, and 121°C (autoclaved), and found that mRNA was degraded in autoclaved bacterial samples. These results showed that the sigDE transcript is a suitable mRNA target for rt-RT...

Development of a sigDE-based real-time reverse-transcriptase PCR for the detection of viable Salmonella enterica.

To date, over 150 genetically modified (GM) crops are widely cultivated. To comply with regulations developed for genetically modified organisms (GMOs), including labeling policies, many detection methods for GMO identification and quantification have been developed. To detect the entrance and exit of unauthorized GM crop events in China, we developed a novel quadruplex real-time PCR method for simultaneous detection and quantification of GM cotton events GHB119 and T304-40 in cotton-derived products (based on the 5′-flanking sequence) and the insect-resistance gene Cry2Ae. The limit of detection was 10 copies for GHB119 and Cry2Ae and 25 copies for T304-40. The limit of quantification was 25 copies for GHB119 and Cry2Ae and 50 copies for T304-40. Moreover, low bias and acceptable standard deviation and relative standard deviation values were obtained in quantification analysis of six blind samples containing different GHB119 and T304-40 ingredients. The developed quadruplex quantitative method could be used for quantitative detection of two GM cotton events (GHB119 and T304-40) and Cry2Ae gene ingredient in cotton derived products.

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Jielin Yang

Papers

Quantitative Analysis of Pork and Chicken Products by Droplet Digital PCR

Molecular typing of Vibrio parahaemolyticus isolates from the middle-east coastline of China.

Comparative proteomic analysis by iTRAQ-2DLC-MS/MS provides insight into the key proteins involved in Cronobacter sp. biofilm formation

Development of a sigDE-based real-time reverse-transcriptase PCR for the detection of viable Salmonella enterica.

A novel quadruplex real-time PCR method for simultaneous detection of Cry2Ae and two genetically modified cotton events (GHB119 and T304-40)