Polymerase Chain Reaction (PCR) - Articles and news items

New applications of PCR in food control

Issue 3 2010, Past issues / 30 June 2010 / Jeffrey Hoorfar Research Manager & Professor of Food Microbiology, National Food Institute, Technical University of Denmark

PCR testing of pathogens has gained widespread use in quality control laboratories throughout the food industry. Many excellent easy-to-use commercial kits are now available for a wide range of microorganisms. But are there any other potential uses for PCR other than a simple plus/minus response that indicates presence or absence of a pathogen harmful to consumers? And why is it important for the food industry to make more use out of PCR testing? (more…)

PCR as a molecular method in the food industry

Issue 1 2010, Past issues / 22 February 2010 / Luca Cocolin, Paola Dolci & Kalliopi Rantsiou, DIVAPRA, Agricultural Microbiology and Food Technology Sector, Faculty of Agriculture, University of Turin

The presence of pathogens is a serious problem that industries producing foodstuffs have to face on a daily base. Foodborne pathogens can survive during processing or they can come in contact with the product due to recontamination or cross-contamination. Food products that contain pathogens represent a risk for human health since consumption of a contaminated product may lead to disease for the consumer. Consequently, there is a strong need for food industries to have methods for detection that are rapid, sensitive, specific and reliable.

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Detecting bacterial spores in soup manufacturing

Issue 3 2009 / 10 September 2009 / A.C.M van Zuijlen & S.J.C.M Oomes, Unilever R&D; P. Vos, Check-Points B.V. and S. Brul, University of Amsterdam

Spores from mesophilic aerobic sporeforming bacteria (Bacillus) are sometimes able to survive the thermal process of commercial sterile products and sporadically cause spoilage or food poisoning. Because of an increasing demand for more fresh products, ideally the processing temperatures should be tailored to inactivate the actual spore load rather than applying worst case scenarios. In doing that, unnecessary loss of product quality can be prevented without running the risk that the product will spoil or cause safety issues.

In that respect, high heat resistant spores are of growing concern. These spores are introduced either into the product through ingredients with a high spore load or through growth and successive sporulation in the line during processing. To ensure an adequate level of thermal treatment to inactivate all spores in the process, their level in the ingredients must be known.

This paper describes new genomics based methods that allow for the rapid detection of bacterial spores in ingredients and semi final products. (more…)

Use of molecular techniques in the food industry

Issue 2 2009 / 1 June 2009 / Mieke Uyttendaele and Andreja Rajkovic, Laboratory of Food Microbiology and Food Preservation, Ghent University

Microbial analysis in foods is an integrated part of management of microbial safety in the food chain. Both competent authorities and individual food business operators use microbial analysis for monitoring of the actual situation and trend analysis in order to detect emerging risks. For compliance testing to defined microbiological criteria or assessment of the performance of management strategies based upon HACCP, microbial analysis is also a valuable tool. Molecular techniques, especially the polymerase chain reaction (PCR), are one of the most important rapid methods for the sensitive and specific detection of pathogenic micro-organisms.

The PCR technique, first described by Kary Mullis in the mid-1980s is a three-step cyclic in vitro procedure based on the ability of the DNA polymerase to copy a strand of DNA. When two primers bind to complementary strands of target DNA, the sequence in between is amplified exponentially with each cycle making the technique a very sensitive tool. The presence of even one copy of the template within the reaction mixture can be detected within a couple of hours as approximately a million-fold of copies are created. The results of PCR are traditionally (conventional PCR) detected by agarose gel electrophoreses and staining and specificity of the bands may be further identified by sequencing. In the early 1990’s, the ‘second’ generation of PCR technologies was introduced by the use of fluorescent double stranded DNA dyes e.g. SYBR@ Green or DNA probes e.g. Molecular beacons® or TaqMan® probes. Real-time PCR enables both the on-line detection (Figure 1) and quantification of the amplification product signal by continuously measuring a fluorescent reporter during the PCR reaction. The potential application of PCR also in routine labs was boosted not only the fact that PCR is no longer a black box reaction but also the fact that real-time PCR consists of a closed-tube format, reducing the risk of contamination potentially leading to false-positive results. (more…)