2002

Wirtanen, Gun; Miettinen, Hanna; Pahkala, Satu; Enbom, Seppo; Vanne, Liisa

This literature review deals with air handling in controlled environments in the food industry. The concern to determine the importance of the airflow as a possible source of contamination is growing, because the airborne dust particles can introduce foreign matter including microbial contaminants into the products produced. The following criteria should be used to determine a sampling strategy: the sampling method, specificity and level of sensitivity required as well as the speed with which a result is required. The microbial particles are likely to be more important than the total particle counts, because they can cause infections or be responsible for allergenic and toxic illnesses. Important information needed from the sampling period includes: location and area of the site, date and time of sampling, test temperature and moisture conditions, functions of the ventilation system during sampling, personnel in the area, volume of air sampled, collection media used and incubation time and temperature used as well as sampler used. A careful planning of the plant layout as well as the services are needed to be able to choose an optimal clean air solution. Common methods used to reduce viable microbial counts in the production facilities include filtration, chemical fogging, ozone and UV radiation. The air filters needed in most food-processing environment are of barrier type, in which dust particles and the majority of microbes are captured and retained. The degree of filtration required is dependent largely on the product being manufactured. Since most food production plants are located in industrial areas with heavy atmospheric pollution, consumers need to be assured that these pollutants are excluded from the foodstuffs they consume.The filtration must be efficient enough to eliminate bacteria, fungi and spores from the airstream. The primary air filters protect the mechanical items of an air movement system from gross contamination over years of operation. Secondary filters are employed to remove smaller particulates from the air to a level needed in the process. Tertiary filters offer the best protection in installations where maximum particulate control is required. Some of the topics to be considered when choosing filters for the controlled environment are: cleanroom classification, number of air exchanges needed, classification of filters, efficiency needed, particles to be captured, filter material and type of filter. Filter header frames and cases are usually manufactured from galvanized mild steel or stainless-steel; only prefilters use card frames. The design, installation and sealing of a suitable filter-framing system is essential to guarantee complete filtration integrity. All filters must be compatible with the food-processing environment and employ nonmigrating media. Clean air solutions should be considered in processes, where microbial inactivation, e.g. through termal sterilization or deep-freezing, is not feasible. In a well-designed controlled environment clean airflows help to reduce the airborne contamination rate. It must be taken into account that the personnel itself is one of the main sources in contaminating products produced if the procedures, accessories and garments used are inappropriate. The potential risk situations created by interaction between people, air movements and airborne contaminants are difficult to predict with common microbiological measuring methods. The limitation of risks concept, which includes visualization of air movements, particle challenge testing and calculation of the risk factor, presents a method by which the risks can be limited. In the review methods for assessing viable airborne microbes are given in Chapter 7. In Chapter 8 available reports on the microbial air quality in food processing areas h