302 Chilled foods recirculated in aerosols over open containers, by the air flow. The importance of chilling after preparation, chilled storage and distribution have been discussed by Baird-Parker (1994)as critical control points in the manufacture of raw and cooked chilled foods. Farquhar and Symons(1992) have noted a US code of practice with recommendations for the preparation of safe chilled foods, it covers chilling, chilled storage, pre-distribution storage and handling and temperature management practices Chilled storage Chilled storage should be designed to maintain the existing or specified temperature in a product. Product or ingredient containers should enter storage chills at their target temperature, because the performance of the air system ( temperature and air velocity)and the way product is stacked are normally not designed to allow a significant reduction in temperature to take place Manufacturing area (MA) A manufacturing area is a part of the factory that handles all types of ingredients The process intermediates made in this area will be heat-treated before they are sold as products and will pass through hygienic or high-care areas during processIng. Hygienic area(HA) a hygienic area is a defined processing area designed for the handling and preparation of low-risk raw materials and products containing a mixture of heat treated and undecontaminated ingredients( Class 1). It should be designed and onstructed for easy cleaning, so that high standards of hygiene can be achieved and especially to prevent bacteria, such as Listeria, becoming established in it and contaminating products. When it is used for the assembly of final products containing undecontaminated components such as cheese, it should not be used for the processing or preparation of any ingredients likely to carry pathogens and hence likely to increase the risks of products containing infectious pathogens Areas conforming to this standard of hygiene should be used for the post-process andling of in-pack pasteurised products( Class 4) High-care area(HCA) This is a well-defined, physically separated part of a factory which is designed and operated specifically to prevent the recontamination of cooked ingredients and products after completion of the cooking process, during chilling, assembly and primary packaging. It is an integral part of the factory layout shown in Fig 11.3 and is used for the preparation of products in Classes 2 and 3. Usually there are specific hygiene requirements covering layout, standards of construction and equipment, the training and hygiene of operatives, engineers and management and a distinct set of operational procedures(especially covering the intake and exit of food components and packaging material), all designed to limit the
recirculated in aerosols over open containers, by the air flow. The importance of chilling after preparation, chilled storage and distribution have been discussed by Baird-Parker (1994) as critical control points in the manufacture of raw and cooked chilled foods. Farquhar and Symons (1992) have noted a US code of practice with recommendations for the preparation of safe chilled foods, it covers chilling, chilled storage, pre-distribution storage and handling and temperature management practices. Chilled storage Chilled storage should be designed to maintain the existing or specified temperature in a product. Product or ingredient containers should enter storage chills at their target temperature, because the performance of the air system (temperature and air velocity) and the way product is stacked are normally not designed to allow a significant reduction in temperature to take place. Manufacturing area (MA) A manufacturing area is a part of the factory that handles all types of ingredients. The process intermediates made in this area will be heat-treated before they are sold as products and will pass through hygienic or high-care areas during processing. Hygienic area (HA) A hygienic area is a defined processing area designed for the handling and preparation of low-risk raw materials and products containing a mixture of heattreated and undecontaminated ingredients (Class 1). It should be designed and constructed for easy cleaning, so that high standards of hygiene can be achieved and especially to prevent bacteria, such as Listeria, becoming established in it and contaminating products. When it is used for the assembly of final products containing undecontaminated components such as cheese, it should not be used for the processing or preparation of any ingredients likely to carry pathogens and hence likely to increase the risks of products containing infectious pathogens. Areas conforming to this standard of hygiene should be used for the post-process handling of in-pack pasteurised products (Class 4). High-care area (HCA) This is a well-defined, physically separated part of a factory which is designed and operated specifically to prevent the recontamination of cooked ingredients and products after completion of the cooking process, during chilling, assembly and primary packaging. It is an integral part of the factory layout shown in Fig. 11.3 and is used for the preparation of products in Classes 2 and 3. Usually there are specific hygiene requirements covering layout, standards of construction and equipment, the training and hygiene of operatives, engineers and management and a distinct set of operational procedures (especially covering the intake and exit of food components and packaging material), all designed to limit the 302 Chilled foods
Microbiological hazards and safe process design 303 chances of contamination. The usage of re-pack and re-work materials in high- care areas should be discouraged, and if this is not possible then very strict rules of segregation in time should be enforced Air handling ir is a significant means of dispersing contaminants, therefore particular attention should be paid to the direction of flow of air within a manufacturing ea or between areas. Within manufacturing areas the flow should be from clean'to 'dirty' to minimise the chances of contaminants being carried from raw to decontaminated product. The quality of the air should be related to the hygiene category of the area, see Manufacturing area(MA), Hygienic area(H and High-care area(HCA)requirements(CFDRA 1997) aning should remove food debris from process equipment, manufacturing and storage areas. Effective cleaning should remove all food debris from work surfaces, machines or an area, so that microbes cannot grow and subsequent production is not contaminated. Effective cleaning cannot be achieved unless equipment is hygienically designed and maintained. In practice, complete removal of food residues is rarely achieved by the techniques used for cleaning open plant(e.g. in slicers and dosing equipment). In factories manufacturing chilled foods, the residues after cleaning may provide growth substrates for the factory microflora, and experience has shown that many modern cleaning techniques and chemicals, when used in chilled areas, may actually select for Listeria High-pressure(HPL V) cleaning if used in an uncontrolled fashion will generate aerosols that may contaminate products and equipment with food debris and bacteria. To minimise the risks of contamination, food and packagin materials should be removed from areas during cleaning. haCCP can make a valuable contribution in this area by identifying those process stages where hygiene is critical to the product quality and safety and also by checking from the process flow diagram that there is good access for cleaning within the factory layout. Disinfection infection procedures should destroy any microbes left on cleaned surfaces and should be used at process stages where product re-contamination is a safety hazard. In practice, these procedures must often destroy or inhibit microbes remaining in the food residues invariably left after cleaning. Cleaning alone is able to achieve a satisfactory level of hygiene in hygienic or GMP areas, but high-care areas will require additional disinfection to provide extra confidence that viable bacteria are absent. Heat and a variety of chemicals are used as disinfectants The effectiveness of disinfection will be reduced if the disinfectant is prevented from reaching the microbes by food debris; hence, thorough cleaning is always required to ensure effective disinfection. The assurance of good access of disinfectants is a primary objective of the hygienic design of
chances of contamination. The usage of re-pack and re-work materials in highcare areas should be discouraged, and if this is not possible then very strict rules of segregation in time should be enforced. Air handling Air is a significant means of dispersing contaminants; therefore particular attention should be paid to the direction of flow of air within a manufacturing area or between areas. Within manufacturing areas the flow should be from ‘clean’ to ‘dirty’ to minimise the chances of contaminants being carried from raw to decontaminated product. The quality of the air should be related to the hygiene category of the area, see Manufacturing area (MA), Hygienic area (HA) and High-care area (HCA) requirements (CFDRA 1997). Cleaning Cleaning should remove food debris from process equipment, manufacturing and storage areas. Effective cleaning should remove all food debris from work surfaces, machines or an area, so that microbes cannot grow and subsequent production is not contaminated. Effective cleaning cannot be achieved unless equipment is hygienically designed and maintained. In practice, complete removal of food residues is rarely achieved by the techniques used for cleaning open plant (e.g. in slicers and dosing equipment). In factories manufacturing chilled foods, the residues after cleaning may provide growth substrates for the factory microflora, and experience has shown that many modern cleaning techniques and chemicals, when used in chilled areas, may actually select for Listeria. High-pressure (HPLV) cleaning if used in an uncontrolled fashion will generate aerosols that may contaminate products and equipment with food debris and bacteria. To minimise the risks of contamination, food and packaging materials should be removed from areas during cleaning. HACCP can make a valuable contribution in this area by identifying those process stages where hygiene is critical to the product quality and safety and also by checking from the process flow diagram that there is good access for cleaning within the factory layout. Disinfection Disinfection procedures should destroy any microbes left on cleaned surfaces and should be used at process stages where product re-contamination is a safety hazard. In practice, these procedures must often destroy or inhibit microbes remaining in the food residues invariably left after cleaning. Cleaning alone is able to achieve a satisfactory level of hygiene in hygienic or GMP areas, but high-care areas will require additional disinfection to provide extra confidence that viable bacteria are absent. Heat and a variety of chemicals are used as disinfectants. The effectiveness of disinfection will be reduced if the disinfectant is prevented from reaching the microbes by food debris; hence, thorough cleaning is always required to ensure effective disinfection. The assurance of good access of disinfectants is a primary objective of the hygienic design of Microbiological hazards and safe process design 303
4 Chilled foods equipment and the development of cleaning schedules. The systematic monitoring of specified sites in equipment or production areas either visually or microbiologically checks the effectiveness of cleaning. The effectiveness of disinfection can be checked by swabbing or chemical means 11.3 The microbiological hazards The microbiological hazards of chilled foods can be roughly classified according to whether harmful microbes can infect the consumer or whether they multiply in the food and produce toxins that then cause disease soon after the food is eaten. The micro-organisms of greatest concern are listed in Table 1 1.2. All realistic microbiological hazards should be controlled by the product and process design. The real, not the specified, storage temperature and the length of the shelf-life must be assessed to determine whether a particular hazard is realistic in a particular product Infectious pathogens can be hazardous at very low levels, whereas appreciable levels or growth of toxigenic micro-organisms are needed to cause a hazard When designing a product or process it is very risky to assume that a particul microbiological hazard will be absent, e.g. because it has not been detected in a component. Processes should be designed to control all realistic hazards The infectious pathogens(see Table 11. 2 and Ch. 8)include Salmonella, E coli O157 H7 and Listeria monocytogenes. They may be present in raw Table 11.2 Food-poisoning organisms of major concern and their heat resistance and growth temperature characteristics Heat resistance growth Vegetative cells Spores Listeria monocytogenes (INF) Clostridium botulinum type e non-proteolytic B&F (TOX) Yersinia enterocolitica(INF) brio oticus (INF) Bacillus cereus(TOX) Medium Aeromonas hydrophilia(Inf) Bacillus subtillis(TOX) Salmonella species(INF) Clostridium perfringens(INF) H Escherichia coli O157(INF) Clostridium botulinum type a proteolytic B(TOX (TOX)° Campylobacter jejuni coli (INF) infectious; TOX, toxigenic
equipment and the development of cleaning schedules. The systematic monitoring of specified sites in equipment or production areas either visually or microbiologically checks the effectiveness of cleaning. The effectiveness of disinfection can be checked by swabbing or chemical means. 11.3 The microbiological hazards The microbiological hazards of chilled foods can be roughly classified according to whether harmful microbes can infect the consumer or whether they multiply in the food and produce toxins that then cause disease soon after the food is eaten. The micro-organisms of greatest concern are listed in Table 11.2. All realistic microbiological hazards should be controlled by the product and process design. The real, not the specified, storage temperature and the length of the shelf-life must be assessed to determine whether a particular hazard is realistic in a particular product. Infectious pathogens can be hazardous at very low levels, whereas appreciable levels or growth of toxigenic micro-organisms are needed to cause a hazard. When designing a product or process it is very risky to assume that a particular microbiological hazard will be absent, e.g. because it has not been detected in a component. Processes should be designed to control all realistic hazards. The infectious pathogens (see Table 11.2 and Ch. 8) include Salmonella, E.coli O157:H7 and Listeria monocytogenes. They may be present in raw Table 11.2 Food-poisoning organisms of major concern and their heat resistance and growth temperature characteristics Minimum Heat resistance growth temperature Low Medium High Vegetative cells Spores Low Listeria monocytogenes (INF)a Clostridium botulinum type E, non-proteolytic B&F (TOX) Yersinia enterocolitica (INF) Vibrio parahaemolyticus (INF) Bacillus cereus (TOX) Medium Aeromonas hydrophilia (INF) Bacillus subtillis (TOX) Salmonella species (INF) Bacillus licheniformis (TOX) Clostridium perfringens (INF) High Escherichia coli O157 (INF) Clostridium botulinum type A & proteolytic B(TOX) Staphylococcus aureus (TOX)b Camplylobacter jejuni & coli (INF) Notes a INF, infectious; b TOX, toxigenic. 304 Chilled foods