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This content is taken from the Queen's University Belfast's online course, Tackling Global Food Safety. Join the course to learn more.

Skip to 0 minutes and 1 second Testing of food or feed is performed to establish the presence or absence of particular hazards by means of qualitative tests, or to measure the amount of particular hazard by means of quantitative tests. It can be necessary to check for particular hazards in food for a variety of reasons - to ensure compliance with legislation, for monitoring or surveillance of food at primary production level, food company own checks, import control border checks, during foodborne illness outbreak investigations, or for risk assessment. Detecting microbial pathogens and toxins in foods presents many challenges - a wide variety of food sample types to be tested, liquid versus solid, meat versus vegetables, raw versus cooked. And so the same sample preparation protocol may not apply to all.

Skip to 0 minutes and 55 seconds There may also be a complexity of certain food matrices and compositions. This means that the separation of target bacterium or toxin isn’t always easy. In some cases the presence of inhibitors of key test reagents in certain foods may exist, particularly in relation to PCR detection. Generally, pathogens are present in low numbers along with high numbers of harmless bacteria, and also may be in an injured state. Cells, therefore, may need resuscitation or enrichment before detection. And often the target analyte may not be evenly distributed throughout a food sample, so it is important to obtain a representative sample for testing. So there are three important steps in food testing - sampling, sample preparation, and detection.

Skip to 1 minute and 47 seconds Immunomagnetic separation, or IMS, is an example of a sample preparation technique used to capture and concentrate a target pathogen or toxin from the food sample. An antibody based lateral flow assay to detect shellfish toxin, or PCR to detect DNA of a bacterial pathogen previously captured by IMS, are examples of detection methods. Each step in food testing may impact detection sensitivity in overall success of the test.

Detection methods

Given the threats which they pose to food safety and health, we must check and monitor for the presence and levels of particular hazards across our food supply chains.

The process of detection is key to the reduction and prevention of contaminants being introduced into the food chain. A wide range of possible test formats (methods) exist for the detection of various chemical, biological and allergenic hazards - these detection methods may be biochemically-based, culture-based, antibody-based, or nucleic acid-based.

It is imperative that such detection tests are trustworthy to ensure that the detection method is fit for purpose and that there can be confidence in the results reported following their use.

The video above will discuss some of the challenges in detecting microbial pathogens and toxins in food.

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This video is from the free online course:

Tackling Global Food Safety

Queen's University Belfast