Hygiene Survey in Food Plants

Food safety is related to the absence or presence of levels of foodborne hazards in food at the point of consumption. The EC Regulation 852/2004 covers the principal objective of the general hygiene rules to ensure a high level of consumer protection with regard to food safety. However, food safety is the joint responsibility of many people and it is principally ensured through the combined efforts of all the parties in the food chain. Legislative demands set the basic requirements for the manufacturing of safe food products whereas food safety management systems and food safety guidelines and standards based on given legislation help the food industry to keep up with current food safety requirements. Hygiene survey is a practical tool for controlling hygiene in food plants. By using an efficient sampling of the surfaces of the process line, it is possible to reduce the amount of low-quality food leaving the plant. Hygiene survey can include checking of the amount of surface-attached soil including protein, polysaccharides, other organic and inorganic residues, biofilm, dead and/or living microbes in general, or specific pathogens and other harmful microbes. Hygiene survey also helps with tracing contamination sources and in optimising cleaning systems. There are several sources of microbial contamination: raw materials, process equipment, environmental surfaces, air, personnel and the final product. In some cases demands for better hygiene have been made because of prolonged shelf-life of products, centralized production and long-distance transportation, less time spent on cleaning and demands for environmentally safe cleaning agents (Salo, 2006). Quantification of the actual number of microbes from surfaces is difficult due to strong microbial adherence of biofilms. In addition, detection of biofilms using traditional swabbing method often gives incorrect results due to strong microbial adherence. Most techniques underestimate the number of microbes on a surface. Hygiene surveys from surfaces are challenging; the measuring should be quickly performed, directly from the surface and without damaging the surface, and the microbes need to be detached completely. However, it is difficult to measure biofilm and biotransfer potential because the conventional microbiological methods used to assess equipment hygiene have not been developed for detecting biofilm. Reliable results are only possible if the biofilm is properly detached and the cultivation is performed under reproducible conditions or if the measurement can be performed without detaching the microbes. Microscopy is very often used as a reference method for swabbing and cultivation. It has been reported that the cells counted by direct microscopy consistently give results one log unit higher than the cultivation methods. Moreover, observations of surfaces using epifluorescence microscopy have clearly revealed that even when vigorous swabbing is applied only a small part of the actual biofilm including the cells in it is detached (Wirtanen, 1995). On the other hand, use of excessive agitation and strong chemicals for detachment of surface-adherent cells may harm the cells, thus making them unable to grow in the cultivation procedure. Choosing sampling sites in food plants and especially in equipment with complicated structures is challenging, since most likely the microbial residues are in curvatures, con-nections, propellers, or on uneven surfaces which are not easy to reach with sampling tools. Quantification of the swabbed areas in places like these is challenging. Contact agar applications with ridged frames are only suitable for sampling of smooth and straight surfaces (Salo et al., 2008). Preventive risk-based food safety management systems such as HACCP require that hygiene monitoring should provide results rapidly in order to be able to perform corrective actions. ATP bioluminescence and protein detection kits for instance can provide a real time estimation of overall cleaning efficacy or protein residues, respectively. The detection and enumeration of indicator organisms is widely used to assess the efficacy of sanitation procedures. Escherichia coli counts can be used as an indirect measure of faecal contamination. The use of Enterobacteriaceae as hygiene indicators instead of coliforms or E. coli yields much more precise results. Interpretation of the results from hygiene monitoring is often carried out case by case since there are quite many factors affecting an acceptable level of cleanliness. The ac-ceptable level depends on the purpose of the surface. The surfaces in contact with ready-to-eat food products must be much cleaner than other surfaces in the process plant in contact with products which will be pasteurised or surfaces in no direct contact with foods. Special attention should also be paid to the surfaces next to food contact surfaces since there is a high risk of spreading contamination to food products (Salo et al., 2006). The cleanliness level of the processed product depends also on the spoilage sensitivity and the wanted self-life of the product. The available recommended guidelines and standards for aerobic colony counts for clean surfaces vary widely, being 0 - 80 CFU/cm2 (Griffith, 2005). The threshold limit for clean surface must be based upon a perception of a specific risk and the decided acceptable level. Alternatively, microbial yield obtained from surface after correct imple-mentation of a well-designed cleaning programme can be used as a desired value (Griffith, 2005). Comprehensive studies performed by Griffith (2005) have indicated that in many cases levels o