Changing perspectives in food microbiology: Implementation of rapid microbiological analyses in modern food processing

Impact of animal husbandry and slaughter technologies on microbial contamination of meat: Monitoring and control

The microbial flora transferred to carcasses during slaughter is a reflection of the care taken on the slaughter floor and of the types and numbers of microorganisms acquired by the animal on the farm or during the period of transportation to the slaughter house. These microogranisms may include those able to cause illness in the consumer, or microorganisms responsible for spoilage of the product. Considerable progress has been made in reducing contamination at slaughter and thereby extending the shelf-life of meat. In contrast, international statistics still clearly show that meat and meat products are responsible for a major proportion of all foodborne infections. This latter aspect is not determined by the overall number of microorganisms present but by the bacterial composition of the animal's gut flora at slaughter. Preventive quality assurance along the whole productions and processing line is therefore the only effective means of controlling the microbiological safety and quality of meat. This includes hazard analysis techniques to identify critical control points and procedures for monitoring the microbiological status of both animals and carcasses since most of the critical points cannot be totally controlled. At early stages in the production line, colonisation of meat animals with pathogens should be prevented. Subsequently, good slaughter practices will ensure carcasses of good overall microbiological quality. This paper deals with microbiological monitoring systems that can be used at different stages of production and processing to control the microbiological quality of poultry and pig meat.

An outline of a risk assessment-based system of meat safety assurance and its future prospects

Discussed are the outlines of a risk assessment-based system of meat safety assurance to replace the current meat inspection. An example of a system that uses the Hazard Analysis of Critical Control Points (HACCP)-principles in the entire production chain from stable to table is also given. Continuous evaluation of risks is the main driving force of the new system. Only then the system has the means to remain flexible and provide for the data necessary to convince trade partners that the products they buy are safe. A monitoring system that keeps track of the important health hazards in the entire chain from stable to table is therefore necessary. This includes monitoring of cases of disease in the human population caused by the hazardous agents of concern. Coordination of the monitoring and control and processing of the information is done by an independent body. Furthermore, the system demands a production from stable to table that is based on the ideas of Integrated Quality Control (IQC), HACCP, and certification of production processes and quality control procedures. Clear legislation provides for criteria about acceptable or unacceptable health risks for the consumer and determines at what moments which risks should be controlled by the producers. Simultaneously, the legislation has to be flexible enough to be able to adapt quickly to any changes in risks, or in the way risks should be controlled. In the new system current meat inspection can easily be carried out by employees of the slaughter houses and is no longer a direct responsibility of the authorities. The authorities only demand certain safety levels and verify whether producers stick to these. Producers remain fully responsible for the safety and quality of their products, and fully liable in case of any damage to the consumers' health. However, it is to be expected that some EU Member-States miss the organizational and agricultural basis for a successful application of the new system. Consequences are that two parallel flows of meat and meat products may come to existence. One flow will exist of meat produced according to the new, and with respect to safety assurance, superior system. The other flow will consist of meat produced and inspected in the traditional way. However, this meat will contain all the flaws that required a revision of the system in the first place. This, and the fact that EU policy ordains that part-taking in an alternative meat inspection system should be voluntary, may very well result in a very slow start-up of the new system. One of the easiest solutions, however, would be to implement a decontamination step in the slaughtering process, provided that this is accompanied by strict codes of hygienic practices and good manufacturing practices. Not only would this lead to safer meat, but also result in the two separate flows of meat becoming one flow again as well as an easier to organize livestock production according to HACCP-principles.

Microbes in food processing technology

There is an increasing understanding that the microbial quality of a certain food is the result of a chain of events. It is clear that the microbial safety of food can only be guaranteed when the overall processing, including the production of raw materials, distribution and handling by the consumer are taken into consideration. Therefore, the microbiological quality assurance of foods is not only a matter of control, but also of a careful design of the total process chain. Food industry has now generally adapted quality assurance systems and is implementing the Hazard Analysis Critical Control Point (HACCP) concept. Rapid microbiological monitoring systems should be used in these cases. There is a need for rapid and simple microbiological tests which can be adapted to the technology and logistics of specific production processes. Traditional microbiological methods generally do not meet these high requirements. This paper discusses the tests, based on molecular biological principles, to detect and identify microbes in food-processing chains. Tests based on DNA technology are discussed, including in vitro DNA amplification like the polymerase chain reaction (PCR) method and identifications based on RFLP, RAPD and DNA fingerprinting analysis. PCR-based methodology can be used for the rapid detection of microbes in food manufacturing environments. In addition, DNA fingerprinting methods are suitable for investigating sources and routes of microbial contamination in the food cycle.

Immunological methods for detection of foodborne pathogens and their toxins

Improved methods to detect microorganisms and their toxins introduced during the last decade involve among others recombinant DNA techniques and various immuno-assays such as the enzyme-linked immunosorbent assay and the latex agglutination. Immuno-assays are based on a quantitative reaction of an antigen (bacterial metabolite, e.g., toxin) with its antibody. Therefore, they are suited for detection of microorganisms based on their production of specific antigens and for quantitative detection of bacterial toxins. Sensitivity and specificity of immuno-assays are mainly determined by the antiserum used. In this respect the use of well selected monoclonal antibodies can be of advantage. With the enzyme-linked immunosorbent assay and latex agglutination test quantities of 0.1-1 ng of antigen/ml can be detected. Of both techniques the latex agglutination method has several advantages; the method is simple, inexpensive and rapid. Since each immuno-assay is sensitive to non-specific reactions, recognition of false positive results is necessary. The most appropriate method for this is to add an inhibitor to the test sample which blocks specifically the paratope of the immunoglobulin. Another general disadvantage of immuno-assays is that only the antigenicity is determined and this may differ from the actual toxicity. Therefore, antibodies should be used that react with the toxic centre(s) of the molecule, which can be accomplished by using well selected monoclonal antibodies.