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