In the latter part of the 20th century, the food industry has evolved in response to the consumer demand for even greater convenience and utility.
Frozen foods, chilled foods and a variety of other manufacturing techniques were further developed to deliver to consumers’ requirements. This was all accompanied by an increase in the risk posed by microbial contaminants to consumer safety and to the survival of food manufacturers. Food poisoning and spoilage in the 21st century can now lead to food manufacturers’ bankruptcy and the destruction of hard fought for reputations of quality and safety. Unfortunately, the solution will not be the elimination of risk as the variables and possibilities of contamination from “farm to fork” are so myriad. The fact remains that a single breach can be catastrophic. Instead, the food industry as meticulously as it can, both economically and technically, continues to strive to reduce the risk with the microbiological monitoring of products and processes.
Consequences
Reports posted by the Canadian Food Inspection Agency in Ottawa for the first month of this year alone highlight the pressure the food industry is under to guarantee the safety of food. Two of the most virulent and deadly species, Salmonella and Listeria have already made an appearance in vegetables and health food products, showing that it is not just eggs, soft cheeses and chicken that present a potential threat to human health. New threats and old threats appear to defy our efforts to get ahead.
An international issue
Food safety is an international issue facing methods and testing regimes across international borders. However, farming practices and permissible interventions in the food chain such as the use of antibiotics vary enormously.
As a result food safety practices can affect international trade and reduce access to international markets because these practices are not harmonized. The trade agreement between the European Union (EU) and the U.S., The Transatlantic Trade and Investment Partnership (TTIP), has raised a number of contentious issues including the use of antibiotics. The public is, so far, reassured by statements made by the Food Standards Agency that antibiotic and growth hormone treated meat products will not be forced onto the plates of EU citizens.
The Canada-European Union Comprehensive Economic and Trade Agreement (CETA) adopts a more harmonized approach with existing EU standards. The EU rules on food safety are designed to protect human life and health, as are the current Canadian standards. Broadly, imports of foodstuffs must comply with general conditions including traceability, hygiene and microbiological criteria. Specific rules apply on genetically modified food and feed, bio proteins and novel foods and the use of antibiotics and pesticides.
Countries in the Far East keen to access western markets have found that applying accepted western testing and hygiene practices to export food products have made EU and North American markets easier to access. That all said, the key focus of food hygienists still remains on protecting consumers at home where new and unpleasant surprises often fill the headlines.
Unpleasant surprises
A recent survey of chicken meat purchased from major UK retailers has demonstrated the ubiquitous presence of campylobacter species awaiting the unwary or poorly skilled cook. The project was undertaken by the Food Standards Agency (UK) and used both public and private microbiology laboratories to produce the data. The samples processed were chicken skin and sponge swabs taken from chicken carcasses. The FSA is working with government and industry to try to reduce the incidence of campylobacter in chicken meat by 2015, a target the report suggests they will struggle to achieve.1
In order to process swabs and skin prior to microbiological analysis within the FSA campylobacter project, it was necessary to maximize microorganism recovery at the pre-enrichment phase to obtain reliable and reproducible analytical results within given limits and tolerances. The protocol adopted also stressed the need for preventing cross contamination between samples. The homogenisation technique used therefore needed to address both issues. This was achieved by using the Stomacher® laboratory paddle blender which ensured efficient circulation of the sample and buffer within the Stomacher® bag to maximise organism recovery and enable smaller subsamples to be taken for fully representative analysis of the whole. The sponge swab technique followed by extraction in the Stomacher® has been shown to be a superior method to traditional swab sticks generating a more representative result.2
If elimination of campylobacter is proving a struggle, then close monitoring and epidemiological studies will be keeping microbiologists busy for the foreseeable future.
Rapid methods
The traditional techniques of horizontal isolation of campylobacter are reliable but slow. New real time PCR techniques require shorter preenrichment following Stomaching. The possibility of reducing the time to 24hours allows the possibility of processors being able to clear products before shipping. However, the reliability of the final result still depends entirely on the quality of the sample provided, whatever the speed or sophistication of the method. A study of this technique applied to salmonella in chicken demonstrates the advantages of a rapid and reliable method.3
Sample size matters
An approach recently adopted by the FDA in the U.S. has addressed the statistical disadvantage the microbiologist has to work with by increasing the sample size to up to 375g. These methods, which can be found in the Bacteriological Analytical Manual, have gained favour beyond the U.S. jurisdiction and have been adopted in Australia and South Korea.4 The largest sample volumes apply to meat products and not only applied to poultry but also red meat and in particular for the analysis for e. coli 0157.
The problem
Microbiology as a science has a problem.The techniques used whether they be the latest DNA probe technology or the traditional techniques, which Pasteur himself would not be unfamiliar with, are dealing with the detection of life. Food materials are inherently variable and microorganisms unpredictable. Therefore, it is essential that this variability, both within and between samples, is minimized as far as possible prior to microbiological analyses with proper sampling and also sample preparation techniques.
The solution
Sample preparation is a critical step in all food microbiology globally. High quality sample preparation delivering subsamples that are fully representative of the whole is vital to the ultimate delivery of good quality, accurate results and is a key consideration in food microbiology.
To borrow a phrase from the computer industry, “garbage in, garbage out.” No matter how sophisticated your analytical technique, without a good quality sample the result will be meaningless.
References:
1. https://www.food.gov.uk/sites/default/files/campylobacter-survey-q2-report.pdf
2. Thom K.A. et al.. Comparison of swab and sponge methodologies for identification of Acinetobacter baumannii from the hospital environment. Journal of Clinical Microbiology 2012, 50(6):2140.
3. http://tools.lifetechnologies.com/content/sfs/manuals/4476867A.pdf
4. http://www.fda.gov/Food/Food-ScienceResearch/Laboratory-Methods/ucm072616.htm
About the Author
Stuart Ray is a technical director with Seward Ltd.
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