The hygienic design of chilled foods plant J. Holah and R.H. Thorpe, Campden and Chorleywood Food Research association 13.1 Introduction The primary concern of chilled food manufacturers is to produce a product that is both wholesome, i.e. it has all the fresh, quality attributes associated with a chilled food, and safe, i.e. free from pathogenic microorganisms and chemical and foreign body contamination. This is particularly important in this product ector as, due to the nature and method of production, many chilled foods are classified as high-risk products The schematic diagram shown in Fig. 13. 1, which is typical for all food factories, shows that the production of safe, wholesome foods stems from a thorough risk analysis. Indeed this is now a legal requirement. The diagram also shows that given specified raw materials, there are four major building block that govern the way the factory is operated to ensure that the safe, wholesome food goal is realised. Hygienic design dictates the design of the production facility and equipment whilst process development enables the design of safe validated processes. Hygienic practices and process control subsequently ensure the respective integrity of these two dependables Risk analysis encompasses identifying the hazards that may affect the quality or safety of the food product and controlling them at all stages of the process such that product contamination is minimised. In the food industry this is commonly referred to as Hazard Analysis Critical Control Point(HACCP) Such hazards are usually described as biological, e.g. bacteria, yeasts, moulds hemical, e.g. cleaning chemicals, lubricating fluids physical, e.g. glass, insects, pests, metal, dust
13.1 Introduction The primary concern of chilled food manufacturers is to produce a product that is both wholesome, i.e. it has all the fresh, quality attributes associated with a chilled food, and safe, i.e. free from pathogenic microorganisms and chemical and foreign body contamination. This is particularly important in this product sector as, due to the nature and method of production, many chilled foods are classified as high-risk products. The schematic diagram shown in Fig. 13.1, which is typical for all food factories, shows that the production of safe, wholesome foods stems from a thorough risk analysis. Indeed this is now a legal requirement. The diagram also shows that given specified raw materials, there are four major ‘building blocks’ that govern the way the factory is operated to ensure that the safe, wholesome food goal is realised. Hygienic design dictates the design of the production facility and equipment whilst process development enables the design of safe, validated processes. Hygienic practices and process control subsequently ensure the respective integrity of these two dependables. Risk analysis encompasses identifying the hazards that may affect the quality or safety of the food product and controlling them at all stages of the process such that product contamination is minimised. In the food industry this is commonly referred to as Hazard Analysis Critical Control Point (HACCP). Such hazards are usually described as • biological, e.g. bacteria, yeasts, moulds • chemical, e.g. cleaning chemicals, lubricating fluids • physical, e.g. glass, insects, pests, metal, dust. 13 The hygienic design of chilled foods plant J. Holah and R. H. Thorpe, Campden and Chorleywood Food Research Association
356 Chilled foods HACCP materials Hygienic design Process development Hygienic practices Process control Safe wholesome Fig. 13.1 Schematic stages required to ensure safe, wholesome chilled products A hazard analysis should be undertaken at the earliest opportunity in the process of food production and if possible, before the design and construction of the processing facility. This allows the design of the production facility to play a major role in hazard elimination or risk reduction Of the four building blocks illustrated in Figure 13. 1, this chapter deals with hygienic design. For the food factory, hygienic design begins at the level f its siting and construction and is concerned with such factors as the design of the building structure, the selection of surface finishes, the segregation of work areas to control hazards, the flow of raw materials and product, the movement and control of people, the design and installation of the process equipment and the design and installation of services(air, water, steam electrics, etc. With regard to legislation, there are some EEC Directives relating to the production of certain foodstuffs, such as meat, fish and egg products, in which requirements for the premises are specified. On the 14 June, 1993,however,a Council Directive on the hygiene of foodstuffs was adopted( Council Directive 93/43/EEC). This Directive applies to the production of all foodstuffs and it is more specific than any previous regulations. The first of ten chapters covers the general requirements for food premises and the second the specific requirements for room where foodstuffs are prepared, treated or processed; only dining areas
A hazard analysis should be undertaken at the earliest opportunity in the process of food production and if possible, before the design and construction of the processing facility. This allows the design of the production facility to play a major role in hazard elimination or risk reduction. Of the four building blocks illustrated in Figure 13.1, this chapter deals with hygienic design. For the food factory, hygienic design begins at the level of its siting and construction and is concerned with such factors as the design of the building structure, the selection of surface finishes, the segregation of work areas to control hazards, the flow of raw materials and product, the movement and control of people, the design and installation of the process equipment and the design and installation of services (air, water, steam, electrics, etc.). With regard to legislation, there are some EEC Directives relating to the production of certain foodstuffs, such as meat, fish and egg products, in which requirements for the premises are specified. On the 14 June, 1993, however, a Council Directive on the hygiene of foodstuffs was adopted (Council Directive 93/43/EEC). This Directive applies to the production of all foodstuffs and it is more specific than any previous regulations. The first of ten chapters covers the general requirements for food premises and the second the specific requirements for room where foodstuffs are prepared, treated or processed; only dining areas Fig. 13.1 Schematic stages required to ensure safe, wholesome chilled products. 356 Chilled foods
The hygienic design of chilled foods plant 357 and premises specified in Chapter 3, e.g. marquees, market stalls etc.are excluded. Within all of these documents. however. advice is at best concise 13.2 Segregation of work zones Factories should be constructed as a series of barriers that aim to limit the entrance of contaminants. The number of barriers created will be dependent on the nature of the food product and will be established from the HACCP study. Figure 13.2 shows that there are up to three levels of segregation that are typical for food plants Level I represents the siting of the factory, the outer fence and the area up to the factory wall. This level provides barriers against environmental conditions e.g. prevailing wind and surface water run-off, unauthorised public access and avoidance of pest harbourage areas Level 2 represents the factory wall and other processes(e.g. UV flytraps) which should separate the factory from the external environment. Whilst it is obvious that the factory cannot be a sealed box, the floor of the factory should ideally be at a different level to the ground outside and openings should be designed to be pest proof when not in use Level 3 represents the internal barriers that are used to separate nanufacturing processes of different risk e. g. pre and post-heat treatment. Such separation should seek to control the air, people and surfaces(e.g. the floor and drainage systems) and the passage of materials and utensils across the barrier Administration and amenity area High-care area+ Preparation area Finished goods storage and dispatch reception and ()Perimeter fence;(2)Main factory buildings; (3)Walls of hiob contamination Fig. 13.2 Schematic layout of a factory site showing 'barriers high-care area
and premises specified in Chapter 3, e.g. marquees, market stalls etc. are excluded. Within all of these documents, however, advice is at best, concise. 13.2 Segregation of work zones Factories should be constructed as a series of barriers that aim to limit the entrance of contaminants. The number of barriers created will be dependent on the nature of the food product and will be established from the HACCP study. Figure 13.2 shows that there are up to three levels of segregation that are typical for food plants. Level 1 represents the siting of the factory, the outer fence and the area up to the factory wall. This level provides barriers against environmental conditions e.g. prevailing wind and surface water run-off, unauthorised public access and avoidance of pest harbourage areas. Level 2 represents the factory wall and other processes (e.g. UV flytraps) which should separate the factory from the external environment. Whilst it is obvious that the factory cannot be a sealed box, the floor of the factory should ideally be at a different level to the ground outside and openings should be designed to be pest proof when not in use. Level 3 represents the internal barriers that are used to separate manufacturing processes of different risk e.g. pre and post-heat treatment. Such separation should seek to control the air, people and surfaces (e.g. the floor and drainage systems) and the passage of materials and utensils across the barrier. Fig. 13.2 Schematic layout of a factory site showing ‘barriers’ against contamination. (1) Perimeter fence; (2) Main factory buildings; (3) Walls of high-care area. The hygienic design of chilled foods plant 357
358 Chilled foods 13. 2.1 The factory site Attention to the design, construction and maintenance of the site surrounding the factory provides an opportunity to set up the first(outer)of a series of barriers to protect production operations from contamination. It is a sound principle to take all reasonable precautions to reduce the pressures'that may build up on each of the barriers making up the overall protective envelope. A number of steps can be taken. For example, well-planned and properly maintained landscaping of the grounds can assist in the control of rodents, insects, and birds by reducing food supplies and breeding and harbourage sites. The use of two lines of rodent baits located every 15-2lm along the perimeter boundary fencing and at the foundation walls of the factory, togethe with a few mouse traps near building entrances is advocated by Imholte (1984) Both Katsuyama and Strachan(1980)and Troller(1983)suggest that the area ediately adjacent to buildings be kept grass free and covered with a deep layer of gravel or stones. This practice helps weed control and assists inspection of bait boxes and traps The control of birds is important, otherwise colonies can become established and cause serious problems. Shapton and Shapton(1991)state there should be a strategy of making the factory site unattractive by denying birds food and harbourage. They stress the importance of ensuring that waste material is not left in uncovered containers and that any spillages of raw materials are cleared up promptly Shapton and Shapton(1991)state that many insects are carried by the wind nd therefore are inevitably present in a factory. They point out the importance of preventing the unauthorized opening of doors and windows and the siting of rotective screens against flying insects. Imholte (1984)considers such screens present maintenance problems. These authors draw attention to lighting for warehouses and outdoor security systems attracting night-flying insects and recommend high pressure sodium lights in preference to mercury vapour lamp Entrances that have to be lit at night should be lit from a distance with the light directed to the entrance, rather than lit from directly above. This prevents flying insects being attracted directly to the entrance. Some flying insects require water to support part of their life cycle e.g. mosquitoes, and experience has shown that where flying insects can occasionally be a problem, all areas where water could ollect or stand for prolonged periods of time(old buckets, tops of drums, etc. need to be removed or controlled Good landscaping of sites can reduce the amount of dust blown into the factory, as can the sensible siting of any preliminary cleaning operations for raw materials such as root vegetables, which are often undertaken outside the factory. Imholte(1984)advocates orientating buildings so that prevailing winds do not blow directly into manufacturing areas. The layout of vehicular routes around the factory site can affect the amount of soil blown into buildings Shapton and Shapton(1991) suggest that for some sites it may be necessary to restrict the routes taken by heavily soiled vehicles to minimize dust contamination
13.2.1 The factory site Attention to the design, construction and maintenance of the site surrounding the factory provides an opportunity to set up the first (outer) of a series of barriers to protect production operations from contamination. It is a sound principle to take all reasonable precautions to reduce the ‘pressures’ that may build up on each of the barriers making up the overall protective envelope. A number of steps can be taken. For example, well-planned and properly maintained landscaping of the grounds can assist in the control of rodents, insects, and birds by reducing food supplies and breeding and harbourage sites. The use of two lines of rodent baits located every 15–21m along the perimeter boundary fencing and at the foundation walls of the factory, together with a few mouse traps near building entrances is advocated by Imholte (1984). Both Katsuyama and Strachan (1980) and Troller (1983) suggest that the area immediately adjacent to buildings be kept grass free and covered with a deep layer of gravel or stones. This practice helps weed control and assists inspection of bait boxes and traps. The control of birds is important, otherwise colonies can become established and cause serious problems. Shapton and Shapton (1991) state there should be a strategy of making the factory site unattractive by denying birds food and harbourage. They stress the importance of ensuring that waste material is not left in uncovered containers and that any spillages of raw materials are cleared up promptly. Shapton and Shapton (1991) state that many insects are carried by the wind and therefore are inevitably present in a factory. They point out the importance of preventing the unauthorized opening of doors and windows and the siting of protective screens against flying insects. Imholte (1984) considers such screens present maintenance problems. These authors draw attention to lighting for warehouses and outdoor security systems attracting night-flying insects and recommend high pressure sodium lights in preference to mercury vapour lamps. Entrances that have to be lit at night should be lit from a distance with the light directed to the entrance, rather than lit from directly above. This prevents flying insects being attracted directly to the entrance. Some flying insects require water to support part of their life cycle e.g. mosquitoes, and experience has shown that where flying insects can occasionally be a problem, all areas where water could collect or stand for prolonged periods of time (old buckets, tops of drums, etc.) need to be removed or controlled, Good landscaping of sites can reduce the amount of dust blown into the factory, as can the sensible siting of any preliminary cleaning operations for raw materials such as root vegetables, which are often undertaken outside the factory. Imholte (1984) advocates orientating buildings so that prevailing winds do not blow directly into manufacturing areas. The layout of vehicular routes around the factory site can affect the amount of soil blown into buildings. Shapton and Shapton (1991) suggest that for some sites it may be necessary to restrict the routes taken by heavily soiled vehicles to minimize dust contamination. 358 Chilled foods
The hygienic design of chilled foods plant 359 13.2.2 The factory building The building structure is the second and a major barrier, providing protection for aw materials, processing facilities and manufactured products from contamina- tion or deterioration. Protection is both from the environment, including rain, wind, surface runoff, delivery and dispatch vehicles, dust, odours, pests and uninvited people etc. and internally from microbiological hazards(e.g. raw material cross-contamination), chemical and physical hazards (e.g. from plantrooms and engineering workshops). Ideally, the factory buildings should be designed and constructed to suit the operations carried out in them and should not place constraints on the process or the equipment layout The type of building, either single-or multistorey, needs to be considered Imholte(1984), comments that the subject has always been a controversial one and describes the advantages and disadvantages of both types of buildings. He also suggests a compromise may be achieved by having a single-storey building with varying headroom featuring mezzanine floors to allow gravity flow of materials, where this is necessary. Single-storey buildings are preferred for the majority of chilled food operations and generally allow the design criteria for high-risk areas to be more easily accommodated. However, it should be appreciated that where production is undertaken in renovated buildings, it may not be possible to capitalize on some of the advantages quoted by Imholte (1984). Of particular concern in multistorey buildings is leakage, of both air and fluids, from areas above and below food processing areas. The authors have undertaken investigative work in a number of factories in which contamination has entered high-risk areas via leakage from above, through both floor defects and badly maintained drains. In addition, on a number of occasions the drainage systems have been observed to act as air distribution channels, with air from low-risk areas(both above and below) being drawn into high risk. This can typically occur when the drains are little used and the water traps dry out The factory layout is paramount in ensuring both an economic and safe processing operation and should be such that processing operations are as direct as possible. Straight line flow minimises the possibility of contamination of processed or semi-processed product by unprocessed or raw materials and is more efficient in terms of handling. It is also easier to segregate clean and dirty process operations and restrict movement of personnel from dirty to clean areas Whilst ideally the process line should be straight, this is rarely possible, but must be no backtracking and, where there are changes in the direction of process flow, there must be adequate physical barriers The layout should also consider that provision is made for the space necessary to undertake the process and associated quality control functions, both immediately the factory is commissioned and in the foreseeable future Space should also be allowed for the storage and movement of materials and personnel Surrounding equipment, Imholte (1984) states 915 mm(3.0 feet)should be considered as the bare minimum for most units however he recom 1830 mm(6.0 feet) as a more practical figure to allow production, cleaning maintenance operations to be undertaken in an efficient manner
13.2.2 The factory building The building structure is the second and a major barrier, providing protection for raw materials, processing facilities and manufactured products from contamination or deterioration. Protection is both from the environment, including rain, wind, surface runoff, delivery and dispatch vehicles, dust, odours, pests and uninvited people etc. and internally from microbiological hazards (e.g. raw material cross-contamination), chemical and physical hazards (e.g. from plantrooms and engineering workshops). Ideally, the factory buildings should be designed and constructed to suit the operations carried out in them and should not place constraints on the process or the equipment layout. The type of building, either single- or multistorey, needs to be considered. Imholte (1984), comments that the subject has always been a controversial one and describes the advantages and disadvantages of both types of buildings. He also suggests a compromise may be achieved by having a single-storey building with varying headroom featuring mezzanine floors to allow gravity flow of materials, where this is necessary. Single-storey buildings are preferred for the majority of chilled food operations and generally allow the design criteria for high-risk areas to be more easily accommodated. However, it should be appreciated that where production is undertaken in renovated buildings, it may not be possible to capitalize on some of the advantages quoted by Imholte (1984). Of particular concern in multistorey buildings is leakage, of both air and fluids, from areas above and below food processing areas. The authors have undertaken investigative work in a number of factories in which contamination has entered high-risk areas via leakage from above, through both floor defects and badly maintained drains. In addition, on a number of occasions the drainage systems have been observed to act as air distribution channels, with air from low-risk areas (both above and below) being drawn into high risk. This can typically occur when the drains are little used and the water traps dry out. The factory layout is paramount in ensuring both an economic and safe processing operation and should be such that processing operations are as direct as possible. Straight line flow minimises the possibility of contamination of processed or semi-processed product by unprocessed or raw materials and is more efficient in terms of handling. It is also easier to segregate clean and dirty process operations and restrict movement of personnel from dirty to clean areas. Whilst ideally the process line should be straight, this is rarely possible, but there must be no backtracking and, where there are changes in the direction of process flow, there must be adequate physical barriers. The layout should also consider that provision is made for the space necessary to undertake the process and associated quality control functions, both immediately the factory is commissioned and in the foreseeable future. Space should also be allowed for the storage and movement of materials and personnel. Surrounding equipment, Imholte (1984) states 915 mm (3.0 feet) should be considered as the bare minimum for most units; however, he recommends 1830 mm (6.0 feet) as a more practical figure to allow production, cleaning and maintenance operations to be undertaken in an efficient manner. The hygienic design of chilled foods plant 359
360 Chilled foods In addition to process areas, provision may have to be made for a wide rar of activities including raw material storage, packaging storage, water storage wash-up facilities; plantroom; engineering workshop; cleaning stores, micro- biology, chemistry and QC laboratories, test kitchens, pilot plant; changing facilities: restrooms: canteens: medical rooms: observation areas/viewing galleries and finished goods dispatch and warehousing Other good design principles given by Shapton and Shapton(1991)are The flow of air and drainage should be away from clean areas towards The flow of discarded outer packaging materials should not cross, or run counter to, the flow of either unwrapped ingredients or finished products Detailed information on the hygienic design requirements for the construction of the external walls or envelope of the factory is not easily found. Much of the data available is understandably concerned with engineering specifications, which are not considered in this chapter. Shapton and Shapton(1991), Imholte 1984) and Timperley(1994)discuss the various methods of forming the external walls and give a large amount of advice on pest control measures, articularly for rodents. A typical example of a suitable outside wall structure shown in Figure 13.3. The diagram shows a well sealed structure that resists pest ingress and is protected from external vehicular damage. The ground floor of the factory is also at a height above the external ground level. By preventing direct access into the factory at ground floor level, the entrance of contamination(mud, soil, foreign bodies etc. ) particularly from vehicular traffic(forklift trucks, raw material delivery etc. )is restricted In addition, the above references provide considerable information on the hygienic requirements for the various openings in the envelope, particularly doors and windows. Points of particular interest are Doors should be constructed of metal, glass reinforced plastic (GRP)or plastic, self-closing, designed to withstand the intended use and misuse and be suitably protected from vehicular damage where applicable Exterior doors should not open directly into production areas and should emain closed when not in use. Plastic strip curtains may be used as inner doors If possible, factories should be designed not to have windows in food processing areas. If this is not possible, e.g. to allow visitor or management observation, windows should be glazed with either polycarbonate or and their locationg, si ister, detailing all types of glass used in the factory laminated A glass reg Metal or plastic frames with internal sills sloped(200-40.)to prevent their use as temporary storage places and with external sills sloped at 60 to prevent bird roosting, should be used Opening windows must be screened in production areas and the screens be designed to withstand misuse or attempts to remove them
In addition to process areas, provision may have to be made for a wide range of activities including raw material storage; packaging storage; water storage; wash-up facilities; plantroom; engineering workshop; cleaning stores; microbiology, chemistry and QC laboratories; test kitchens; pilot plant; changing facilities; restrooms; canteens; medical rooms; observation areas/viewing galleries and finished goods dispatch and warehousing. Other good design principles given by Shapton and Shapton (1991) are: • The flow of air and drainage should be away from ‘clean’ areas towards ‘dirty’ ones. • The flow of discarded outer packaging materials should not cross, or run counter to, the flow of either unwrapped ingredients or finished products. Detailed information on the hygienic design requirements for the construction of the external walls or envelope of the factory is not easily found. Much of the data available is understandably concerned with engineering specifications, which are not considered in this chapter. Shapton and Shapton (1991), Imholte (1984) and Timperley (1994) discuss the various methods of forming the external walls and give a large amount of advice on pest control measures, particularly for rodents. A typical example of a suitable outside wall structure is shown in Figure 13.3. The diagram shows a well sealed structure that resists pest ingress and is protected from external vehicular damage. The ground floor of the factory is also at a height above the external ground level. By preventing direct access into the factory at ground floor level, the entrance of contamination (mud, soil, foreign bodies etc.), particularly from vehicular traffic (forklift trucks, raw material delivery etc.) is restricted. In addition, the above references provide considerable information on the hygienic requirements for the various openings in the envelope, particularly doors and windows. Points of particular interest are: • Doors should be constructed of metal, glass reinforced plastic (GRP) or plastic, self-closing, designed to withstand the intended use and misuse and be suitably protected from vehicular damage where applicable. • Exterior doors should not open directly into production areas and should remain closed when not in use. Plastic strip curtains may be used as inner doors. • If possible, factories should be designed not to have windows in food processing areas. If this is not possible, e.g. to allow visitor or management observation, windows should be glazed with either polycarbonate or laminated. A glass register, detailing all types of glass used in the factory, and their location, should be composed. • Metal or plastic frames with internal sills sloped (20º40º) to prevent their use as ‘temporary’ storage places and with external sills sloped at 60º to prevent bird roosting, should be used. • Opening windows must be screened in production areas and the screens be designed to withstand misuse or attempts to remove them. 360 Chilled foods
The hygienic design of chilled foods plant 361 LAOOOOOY Soffit sealed to wall ashing Cover detail Screed : 4∴:…:← Floor slab Fig. 13.3 Outside wall configuration showing a well sealed structure with elevated factory floor level 13. 2.3. High-risk production area It is unfortunate that the term high risk,, which is also used to describe other foods, for example low-acid canned foods, has become associated with the particular area of the factory where chilled foods are produced. The terms high risk areaand "low-risk area are often used to describe parts of a chilled foods factory where different hygiene requirements apply It is considered that such terminology is misleading, and its use can imply to employees and other people that lower overall standards are acceptable in those areas where, for example, operations concerned with raw material reception, storage and initial preparation are undertaken. In practice, all operations concerned with food production should be carried out to the highest standard Unsatisfactory practices in so-called low-risk areas may put greater pressures on barrier system'separating the two areas. Whilst undesirable, however, it is pable that such terminology will remain for the near future. The advent of the use of more 'pharmaceutical techniques in hygienic food manufacture may lead to the use of appropriate pharmaceutical terminology, e.g. clean'zones
13.2.3. High-risk production area It is unfortunate that the term ‘high risk’, which is also used to describe other foods, for example low-acid canned foods, has become associated with the particular area of the factory where chilled foods are produced. The terms ‘highrisk area’ and ‘low-risk area’ are often used to describe parts of a chilled foods factory where different hygiene requirements apply. It is considered that such terminology is misleading, and its use can imply to employees and other people that lower overall standards are acceptable in those areas where, for example, operations concerned with raw material reception, storage and initial preparation are undertaken. In practice, all operations concerned with food production should be carried out to the highest standard. Unsatisfactory practices in so-called low-risk areas may put greater pressures on the ‘barrier system’ separating the two areas. Whilst undesirable, however, it is probable that such terminology will remain for the near future. The advent of the use of more ‘pharmaceutical’ techniques in hygienic food manufacture may lead to the use of appropriate pharmaceutical terminology, e.g. ‘clean’ zones. Fig. 13.3 Outside wall configuration showing a well sealed structure with elevated factory floor level. The hygienic design of chilled foods plant 361
362 Chilled foods More recently, the Chilled Food Association in the UK(Anon. 1997a) established guidelines to describe the hygiene status of chilled foods and indicate the area status of where they should be processed after any heat treatment. Three levels were described, high-risk area(HRA), high-care area HCA)and good manufacturing practice(GMP). Their definitions were HRa An area to process components, ALL of which have been heat treated to >90%C for 10 mins or>70C for 2 mins and in which there is a risk of contamination between heat treatment and pack sealing that may present a food safety hazard HCA An area to process components, SoME of which have been heat treated to >70C for 2 mins. and in which there is a risk of contamination between heat treatment and pack sealing that may present a food safety GMP An area to process components, NoNE of which have been heat treated to>70C for 2 mins. and in which there is a risk of contamination prior to pack sealing that may present a food safety hazard In practice, the definition of HCa has been extended to include an area to further process components that have undergone a decontamination treatment e.g. fruit and vegetables after washing in chlorinated water or fish after low temperature smoking Most of the requirements for the design of HRa and HCa operations are the same, with the emphasis on preventing contamination in HRA and minimising contamination in HCA operations(Anon. 1997a). In considering whether a high risk or high care is required and therefore what specifications should be met. chilled food manufacturers need to carefully consider their existing and future product ranges, the hazards and risks associated with them and possible developments in the near future. If budgets allow, it is al ways cheaper to build to he highest standards from the onset of construction rather than try to retrofit or refurbish at a later stage. Guidance within this chapter is aimed at satisfying the equirements for high-risk operations Listeria philosophy In terms of chilled food product safety, the major contamination risk is microbiological, particularly from the pathogen most commonly lated with the potential to grow in chilled foods, Listeria monocytogenes. For many chilled food products, L. monocytogenes could well be associated with the raw materials used and thus may well be found in the low-risk area. After the product has been eat processed or decontaminated (e.g. by washing), it is essential that all measures are taken to protect the product from cross-contamination from low risk, L. monocytogenes sources. Similarly, foreign body contamination that would jeopardize the wholesomeness of the finished product, could also be found in low risk. A three-fold philosophy has been developed by the authors to help reduce the incidence of L. monocytogenes in finished product and at the same time control other contamination sources
More recently, the Chilled Food Association in the UK (Anon. 1997a) established guidelines to describe the hygiene status of chilled foods and indicate the area status of where they should be processed after any heat treatment. Three levels were described, high-risk area (HRA), high-care area (HCA) and good manufacturing practice (GMP). Their definitions were: HRA An area to process components, ALL of which have been heat treated to > 90ºC for 10 mins or > 70ºC for 2 mins, and in which there is a risk of contamination between heat treatment and pack sealing that may present a food safety hazard. HCA An area to process components, SOME of which have been heat treated to > 70ºC for 2 mins, and in which there is a risk of contamination between heat treatment and pack sealing that may present a food safety hazard. GMP An area to process components, NONE of which have been heat treated to > 70ºC for 2 mins, and in which there is a risk of contamination prior to pack sealing that may present a food safety hazard. In practice, the definition of HCA has been extended to include an area to further process components that have undergone a decontamination treatment e.g. fruit and vegetables after washing in chlorinated water or fish after low temperature smoking and salting. Most of the requirements for the design of HRA and HCA operations are the same, with the emphasis on preventing contamination in HRA and minimising contamination in HCA operations (Anon. 1997a). In considering whether a high risk or high care is required and therefore what specifications should be met, chilled food manufacturers need to carefully consider their existing and future product ranges, the hazards and risks associated with them and possible developments in the near future. If budgets allow, it is always cheaper to build to the highest standards from the onset of construction rather than try to retrofit or refurbish at a later stage. Guidance within this chapter is aimed at satisfying the requirements for high-risk operations. Listeria philosophy In terms of chilled food product safety, the major contamination risk is microbiological, particularly from the pathogen most commonly associated with the potential to grow in chilled foods, Listeria monocytogenes. For many chilled food products, L. monocytogenes could well be associated with the raw materials used and thus may well be found in the low-risk area. After the product has been heat processed or decontaminated (e.g. by washing), it is essential that all measures are taken to protect the product from cross-contamination from low risk, L. monocytogenes sources. Similarly, foreign body contamination that would jeopardize the wholesomeness of the finished product, could also be found in low risk. A three-fold philosophy has been developed by the authors to help reduce the incidence of L. monocytogenes in finished product and at the same time, control other contamination sources. 362 Chilled foods
The hygienic design of chilled foods plant 363 1. Provide as many barriers as possible to prevent the entry of Listeria into the high-risk area 2. Prevent the growth and spread of any Listeria penetrating these barriers during production 3. After production, employ a suitable sanitation system to ensure that all Listeria are removed from high risk prior to production recommencing 13.3 High-risk barrier technology The building structure, facilities and practices associated with the high-risk production and assembly areas provide the third and inner barrier protecting chilled the use of combinations of a number of separate components or sub-barriers, to control contamination that could enter high risk from the following routes product entering high risk via a heat process product entering high risk via a decontamination process. Product entering high risk that has been heat processed/decontaminated off-site but whose outer packaging may need decontaminating on entry to high risk other product transfer iquid and solid waste materials urfaces, usually associated with low/high-risk physical junctions and concerned with floors, walls, doors, and false or suspended ceilings food operatives entering high risk the air utensils, which may have to be passed between low and high risk 13.3. 1. Heat treated product Where a product heat treatment forms the barrier between low and high risk(e.g an oven, fryer or microwave tunnel), two points are critical to facilitate 1. All product passing through the heat barrier must receive its desired cooking time/temperature combination. This means that the heating device should be performing correctly (e.g. temperature distribution and maintenance are established and controlled and product size has remained constant)and that it should be impossible, or very difficult, for product to pass through the heat treatment without a cook process being initiate 2. The heating device must be designed such that as far as is possible, the device forms a solid, physical barrier between low and high risk. Where it is not physically possible to form a solid barrier, air spaces around the heating equipment should be minimised and the low/high-risk floor junction should be fully sealed to the highest possible height
1. Provide as many barriers as possible to prevent the entry of Listeria into the high-risk area. 2. Prevent the growth and spread of any Listeria penetrating these barriers during production. 3. After production, employ a suitable sanitation system to ensure that all Listeria are removed from high risk prior to production recommencing. 13.3 High-risk barrier technology The building structure, facilities and practices associated with the high-risk production and assembly areas provide the third and inner barrier protecting chilled food manufacturing operations from contamination. This final barrier is built up by the use of combinations of a number of separate components or sub-barriers, to control contamination that could enter high risk from the following routes: • product entering high risk via a heat process • product entering high risk via a decontamination process. Product entering high risk that has been heat processed/decontaminated off-site but whose outer packaging may need decontaminating on entry to high risk • other product transfer • packaging materials • liquid and solid waste materials • surfaces, usually associated with low/high-risk physical junctions and concerned with floors, walls, doors, and false or suspended ceilings • food operatives entering high risk • the air • utensils, which may have to be passed between low and high risk 13.3.1. Heat treated product Where a product heat treatment forms the barrier between low and high risk (e.g. an oven, fryer or microwave tunnel), two points are critical to facilitate its successful operation. 1. All product passing through the heat barrier must receive its desired cooking time/temperature combination. This means that the heating device should be performing correctly (e.g. temperature distribution and maintenance are established and controlled and product size has remained constant) and that it should be impossible, or very difficult, for product to pass through the heat treatment without a cook process being initiated. 2. The heating device must be designed such that as far as is possible, the device forms a solid, physical barrier between low and high risk. Where it is not physically possible to form a solid barrier, air spaces around the heating equipment should be minimised and the low/high-risk floor junction should be fully sealed to the highest possible height. The hygienic design of chilled foods plant 363
364 Chilled foods The fitting of heating devices that provide heat treatment within the structure of a building presents two main difficulties. Firstly, the devices have to be designed to load product on the low-risk side and unload in high risk. Secondly, he maintenance of good seals between the heating device surfaces, which cycle through expansion and contraction phases, and the barrier structure which has a different thermal expansion, is problematical. Of particular concern are ovens and the authors are aware of the following issues Some ovens have been designed such that they drain into high risk. This is unacceptable for the following reason. It may be possible for pathogens present on the surface of product to be cooked (which is their most likely location if they have been derived from cross-contamination in low risk)to fall to the floor through the melting of the product surface layer(or exudate n overwrapped product)at a temperature that is not lethal to the pathogen The pathogen could then remain on the floor or in the drain of the oven in such a way that it could survive the cook cycle. On draining, the pathogen would then subsequently drain into high risk Pathogens have been found at the exit of ovens in a number of food factories Problems have occurred with leakage from sumps under the ovens into higl risk. There can also be problems in sump cleaning where the use of high pressure hoses can spread contamination into high risk Where the floor of the oven is cleaned, cleaning should be undertaken in such a way that cleaning solutions do not flow from low to high risk. Ideall cleaning should be from low risk with the high-risk door closed and sealed. If leaning solutions have to be drained into high risk, or in the case of ovens that have a raining water cooling system, a drain should be installed immediately outside the door in high risk. Other non-oven related issues to consider include the following The design of small batch product blanches or noodle cookers (i.e. small vessels with water as the cooking medium) does not often allow the uipment to be sealed into the low/high-risk barrier as room ha created around the blancher to allow product loading and unloading Condensation is likely to form because of the open nature of these cooking vessels and it is important to ventilate the area to prevent microbial build-up where water condenses. Any ventilation system should be designed so that the area is ventilated from low risk; ventilation from high risk can draw into high risk large quantities of low-risk Early installations of kettles as barriers between low and high risk, together with the associated bund walls to prevent water movement across the floor and barriers at waist height to prevent the movement of people, whilst innovative in their time, are now seen as hygiene hazards. It is virtually impossible to prevent the transfer of contamination, by people, the air and via leaning, between low and high risk. It is now possible to install kettles within low risk and transfer product(by pumping, gravity, vacuum etc
The fitting of heating devices that provide heat treatment within the structure of a building presents two main difficulties. Firstly, the devices have to be designed to load product on the low-risk side and unload in high risk. Secondly, the maintenance of good seals between the heating device surfaces, which cycle through expansion and contraction phases, and the barrier structure which has a different thermal expansion, is problematical. Of particular concern are ovens and the authors are aware of the following issues: • Some ovens have been designed such that they drain into high risk. This is unacceptable for the following reason. It may be possible for pathogens present on the surface of product to be cooked (which is their most likely location if they have been derived from cross-contamination in low risk) to fall to the floor through the melting of the product surface layer (or exudate on overwrapped product) at a temperature that is not lethal to the pathogen. The pathogen could then remain on the floor or in the drain of the oven in such a way that it could survive the cook cycle. On draining, the pathogen would then subsequently drain into high risk. Pathogens have been found at the exit of ovens in a number of food factories. • Problems have occurred with leakage from sumps under the ovens into high risk. There can also be problems in sump cleaning where the use of high pressure hoses can spread contamination into high risk. • Where the floor of the oven is cleaned, cleaning should be undertaken in such a way that cleaning solutions do not flow from low to high risk. Ideally, cleaning should be from low risk with the high-risk door closed and sealed. If cleaning solutions have to be drained into high risk, or in the case of ovens that have a raining water cooling system, a drain should be installed immediately outside the door in high risk. Other non-oven related issues to consider include the following: • The design of small batch product blanchers or noodle cookers (i.e. small vessels with water as the cooking medium) does not often allow the equipment to be sealed into the low/high-risk barrier as room has to be created around the blancher to allow product loading and unloading. Condensation is likely to form because of the open nature of these cooking vessels and it is important to ventilate the area to prevent microbial build-up where water condenses. Any ventilation system should be designed so that the area is ventilated from low risk; ventilation from high risk can draw into high risk large quantities of low-risk air. • Early installations of kettles as barriers between low and high risk, together with the associated bund walls to prevent water movement across the floor and barriers at waist height to prevent the movement of people, whilst innovative in their time, are now seen as hygiene hazards. It is virtually impossible to prevent the transfer of contamination, by people, the air and via cleaning, between low and high risk. It is now possible to install kettles within low risk and transfer product (by pumping, gravity, vacuum etc.) 364 Chilled foods