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Chilled and frozen foods

Hygienic aspects of construction

The basic design concept

The design of any technological zone for food production should take into account five main components:

  • raw materials and ingredients;
  • technological equipment;
  • staff;
  • packaging materials;
  • finished products.

A widespread strategy is that all other components should be considered secondary to these five main ones and, if possible, located outside the technological zone. These secondary components include:

  • frame of the building;
  • a branch of the main pipelines for water, steam and compressed air; cabling; lighting and ventilation ducts;
  • compressors, chillers and pumps;
  • personnel servicing these systems.

This strategy is well suited for high-risk technology areas. In [8], it is described as the principle of building a “casket in a casket” - by creating isolated clean rooms (rooms) in the building of the enterprise with service and control equipment located in the space under the roof above the ceiling. Refrigeration equipment and pipelines are suspended from construction farms, and access to all service systems is ensured through bridges (see Fig. 13.9). This approach, if implemented correctly, eliminates the main source of pollution from the process area.Basic design principles - separation of production from auxiliary systems and maintenance operations

Fig. 13.9. Basic design principles - separation of production from auxiliary systems and maintenance operations

Floors

Since all technological processes are carried out on the floors, they deserve special consideration and significant initial investments. Guidelines for the design and construction of floors for food production are set forth in [28].

Unsatisfactory condition of the floors increases the likelihood of accidents and accidents, causes difficulties in achieving the necessary sanitary and hygienic standards and increases the cost of preventive measures. Damage to the floor can lead to a long shutdown of production and financial loss during the repair period. Many problems associated with floors arise due to insufficient attention to detail at the design stage, in particular:

  • Plates of overlap;
  • waterproof layer, gripping the wall to a height above the normal level of spills;
  • subfloor seams and the upper deck on the perimeter of the floor, on the supporting walls, around columns and equipment foundations;
  • sewage with regard to the intended location of the equipment;
  • plaster beacons (to obtain a sufficiently flat surface to cover the floor or to form the necessary reductions when they are not provided in the concrete slab);
  • finishing the floor, tile or synthetic polymers;
  • technological issues, including the impact of vehicles, shock loads from technological operations, proposed equipment, the possibility of product spills and potential corrosion problems associated with them, heat shocks and drainage requirements, types of detergents used and requirements for slip resistance, etc. ;

Floor coverings can be divided into three main groups: concrete, fully glazed ceramic tiles and seamless polymer coatings. Concrete coatings, including high-strength concrete (with crushed granite), suitable and widely used in other parts of the enterprise, are not recommended for use in high-risk production areas. This is due to their ability to absorb water, and therefore make it possible to grow microorganisms under the surface of the floor, where it is extremely difficult to use effective cleaning agents.

Pressed or stamped ceramic tiles, widely used in the food industry, have recently been partially replaced (due to their cost) by various seamless polymer floors. Properly laid (a necessary condition for all types of floor coverings) tiles of appropriate quality (fully glazed ceramics) are quite suitable for high-risk production areas and will last a long time. The color of such tiles can be chosen in a wide range.

Tiles are laid with a mixture of sand and cement mortar on the subfloor (thin layer) or on a mixture of semi-dry sand and cement (thick layer). A tile thickness of about 20 mm provides sufficient strength for any of the laying methods. Thinner tiles (12 mm) are used for laying in the polymer layer by vibration. The surface of the tiles can be smooth, studded or (to increase the sliding resistance) include granules of silicon carbide. Studded tiles (with protrusions) are not recommended due to the fact that they are more difficult to wash. Ideally, the most washable coatings should be used, however, in practice, the requirements for non-slip cannot be ignored, and therefore

the final choice should be based on a compromise between different factors, taking into account the significance of each of them.

The joints should be filled with the solution as quickly as possible, otherwise the surfaces of the joints may be contaminated. Cement mortars are considered unsuitable for hygienic reasons, and usually use polymer mortars, but not earlier than three days after laying the tiles (so that the water from the layer under the tile can evaporate). Epoxy resins are widely used for filling joints, but they have limited resistance to high concentrations of sodium hypochlorite and soften at temperatures above 80 ° C. Polyester and furan resins are more resistant to chemical corrosion. Data on the chemical resistance of various resins listed in [9] are given in [22]. Materials for pouring joints must fill the joints completely to a depth of at least 12 mm and be flush with the surface of the tile. Thin joints (1 mm) are obtained when tiles are immersed in a layer of resin by vibration. This procedure provides a flat surface and reduces the possibility of damage to the edges of the tiles during operation. One of the advantages of tiled floors, which are not always appreciated, is that the areas or zones of the damaged surface can be relatively easily replaced with tiles of the original color, that is, the overall quality and appearance of the floor can be maintained.

A good option for obtaining a hygienic surface is seamless polymer-based floors (provided that they are laid on a solid concrete base). The surface layer can be made from a system based on various polymers (mainly epoxy or polyurethane) or from polymer-modified cementing systems. Resin-based systems can be divided into three large groups:

  • for hard modes (systems with a thickness of 5-12 mm with a large amount of filler applied with a trowel); such coatings have great strength, usually they are non-slip;
  • self-leveling (self-flowing) resins (pouring and smoothing systems with a thickness of 2-5 mm, which are sometimes more correctly called self-smoothing); they usually give smooth shiny surfaces;
  • systems with a coating thickness of usually 0,1-0,5 mm (they are not recommended for high-risk areas and other production areas due to their low resistance); damage to such sexes is associated with microbial infection, including Listeria monocytogenes, developing under exfoliated coatings.

The floors offered must comply with regulatory requirements. The UK and EU laws are common, but require floors to be waterproof or impervious and cleanable. CCFRA [23] developed a simple technique for assessing water absorption by floor covering materials (these materials can be easily accepted or rejected for any recorded water absorption by them). The absorption of water by materials is unacceptable, since if the liquid can penetrate the flooring materials, microorganisms can get into places that cannot be chemically cleaned and disinfected.

It is more difficult to interpret the possibility of cleaning materials, but in [21] and [23] appropriate test methods were proposed to assess the ability to remove entrenched microorganisms. Differences in the cleaning ability between the materials were found, but they are not necessarily related to the surface roughness, traditionally measured in µmRa. The authors of these two works showed that the microbiological cleaning ability is determined when the surface defects are 100-1000 times lower than what is considered necessary in terms of slip resistance. For example, flooring materials designed to resist slipping can have an average difference between maximum and minimum in millimeters, while the size of defects in which microorganisms can be found is measured in microns. Therefore, it is possible to obtain rough surfaces with good slip resistance and good microbiological cleaning ability at the micron level, and vice versa, smooth surfaces with limited slip resistance and poor cleaning ability at the micron level. Thus, when choosing materials for flooring, data are needed on their impermeability and cleaning ability. At the junction with walls or other vertical surfaces (the bases of mechanisms or columns), the floor should have a fillet, as this makes it easier to clean.

With a wide selection of polymeric materials / systems, it is important that the manufacturer carefully considers the requirements of the consumer and discusses them in detail with the contractor engaged in flooring. In [19], it is argued that usually higher quality materials can be more expensive, but more durable and cheaper to operate. It also seems that it would be reasonable to use the services of trustworthy contractors to arrange floors and familiarize themselves with the existing floor of the type in question.

Sewerage

It was argued in [8] that sewage systems are often neglected and poorly constructed. A comprehensive analysis of sewage requirements is an important aspect of floor design. Ideally, in order to ensure that the downpipes exit directly into the sewer pipes, the layout and installation of the production equipment should be completed before the floors are constructed. In practice, this is not always possible (and especially in the food industry), and it is likely that the layout of the pipes will often change. Equipment should not be located directly above the drainage channels, as this may limit access to them for cleaning.

Drainage from the equipment should go directly to the sewer pipes so as to avoid flooding the floor. Another option is possible: the construction of a low wall around the equipment from which water and solid waste can be removed. Where the channels are located near the wall, they should not be directly in front of it in order to avoid the gulf connecting the wall with the floor. An additional advantage of the channels located next to the wall is that the equipment is not installed close to the wall, providing access for cleaning.

Adequate sewage can only be ensured if the corresponding differences to the drain points are provided. To determine the optimal or rational difference should take into account a number of factors, for example:

  • volumes of water (“wet” processes require a larger drop);
  • floor finishing (a smoothed polymer surface requires a greater difference than self-leveling, otherwise puddles may form in the depressions on the surface);
  • safety (fluctuations exceeding 1:40 can lead to risk for the operator and create problems for wheeled vehicles).

The type of runoff used depends significantly on the type of process. For operations using a significant amount of water and solids, gutter-shaped drains are most suitable, and for processes in which large volumes of water are formed, but little solid waste, drains in the form of channels with gratings are preferable (Fig. 13.10). Many technologies for processing chilled products do not require branched systems for drains of large volumes of liquid, and a smaller amount of drains leads to less use of water, thereby limiting microbiological contamination of the environment. In such cases, a small amount of rain gutters may be provided in the production area.

In most cases, the sewer channels should have a difference of at least 1 to 100, a round bottom, be no deeper than 150 mm for ease of cleaning and have gratings (for security reasons). Channel grilles should be easy to remove and have wide openings (at least 20 mm) for solid particles. In recent years, there has been a clear increase in the use in the construction of corrosion-resistant materials, in particular stainless steel for drain grates. Stainless steel finds wider application in other sewage valves (for example, in various designs of traps and channels of low-volume drainage systems).

The edge of the channel groove should be properly designed and rounded (Fig. 13.10). This is especially important to prevent damage to the well / floor joint if wheeled vehicles are used and to combat pathogens. The authors are aware of cases where a seal was broken between the well and the floor structure, so that there was a void between them that was completely impossible to clean. Then, when wheeled vehicles are stepping on or passing through such a channel, a small amount of dirty liquid with microorganisms is rammed into the floor surface.

The flow in the wastewater system should move in the opposite direction to the direction of the process (i.e. from a high risk area to a low risk area); wherever possible, backflow from a low risk area to a high risk area should not be possible. This is best achieved with separate drainage systems for these areas, leading to the main sewer system with an air break between each of the headers and the main header. The drainage system should also be designed so that the reinforcement points are outside the high risk areas. Solids should be separated from liquids as soon as possible using filters to avoid leaching and high discharge concentrations. Solids traps should be easily accessible for emptying and located outside the process area.The semi-circular drain channel with power groove grating and stainless steel inlet

Fig. 13.10. The semi-circular drain channel with power groove grating and stainless steel inlet 

Walls

The basics of the design and construction of walls, ceilings and communications are described in [26]. For the construction of walls forming the boundaries of the high-risk zone and individual rooms inside this zone, many different materials can be used. When analyzing various systems, it is necessary to take into account a number of technical factors - hygienic characteristics, insulating properties and structural characteristics of walls.

Modular panels with thermal insulation, consisting of a layer of insulating material with a thickness of 50-200 mm between two steel sheets, are currently widely used for non-load-bearing walls. It is necessary to carefully analyze not only the fire-retardant properties of the insulation of the wall or coating material, but also the toxicity of the gases emitted during combustion, as they can complicate fire fighting. Steel outer sheathing to provide rigidity is usually done slightly ribbed and can be finished with a number of ready-to-use hygienic coatings. The modules are designed so that they can be docked with each other and seal the joints with silicone sealant. Modules can be mounted directly in the I-shaped channel on the floor or concrete ledge (base) (Fig. 13.11). The latter provides useful protection against possible damage during the movement of vehicles (in particular, forklift trucks), however, it should be borne in mind that this design reduces the possibility of relatively simple and cheap redevelopment of premises.

To provide an easy-to-wash and waterproof connection, sections directly attached to the floor must be properly installed in silicone sealant and provided with a fillet. To facilitate cleaning, as in the case of wall and floor joints, it is useful to make a fillet between the wall and the ceiling.

To ensure the integrity of the appearance and surface characteristics in the entire high-risk area, thin sections (50 mm) of the thermal insulation panel are sometimes used to cover external or load-bearing walls. At the same time, places suitable for sheltering pests can form between two layers of wall material. The likelihood of this problem increases if the service openings in the thermal insulation panels are not effectively sealed.

In the UK, load-bearing and fire walls are often made of bricks or slabs. Walls made from such materials usually do not have a sufficiently smooth surface for direct application of various coatings. To obtain the smooth surface necessary for the coating layer, a mortar of sand with cement is usually applied to the brickwork. Walls can also be covered with other materials, such as tiles or plastic sheets. Tiles are more preferable provided that each of them is completely sealed, and the appropriate polymer was used to seal it. In very humid areas with a high probability of mold growth, the use of a fungicidal coating may be considered; There is evidence that some of these coatings do not lose their effectiveness for many years.

In accordance with the sanitary and hygienic requirements of various EU directives, the walls must be made of waterproof, non-absorbent, washable, non-toxic materials and have smooth surfaces without cracks to a height appropriate to the operations to be performed. For high-risk areas, the design and decoration requirements must be observed up to the ceiling level. For wall coverings and finishing coatings, the methods of hygienic assessment of floor materials described above are quite applicable.Modular thermal insulation panel located in 11-shaped channel and fastened to concrete base

Fig. 13.11. Modular thermal insulation panel located in 11-shaped channel and fastened to concrete base

Emergency exits must be equipped with locking devices that open only from the inside (doors must remain closed except in emergency cases). Large technical gates required for periodic movement of equipment into and out of the high-risk area, inoperative conditions, must also be closed and sealed.

Ceilings

When considering the main issues of designing high-risk areas to separate production and auxiliary functions, the idea of ​​using ceilings was discussed. In practice, this is often achieved by applying load-bearing fastening insulating panels or hanging sections (which are used for interior walls) to the supporting structure of the building. The use of such heat-insulating panels meets regulatory requirements, since their surface is easy to clean and particles cannot be separated from it.

It is important that communications passing through the ceiling are sealed so as to prevent access of contaminants. Cables can pass through cable channels or special channels that must be effectively sealed to prevent access of rodents and water. All switching equipment and controls (except emergency stop buttons) should, if possible, be located in separate rooms outside the process zones (especially when performing “wet” operations).

Lighting can be a combination of natural and artificial. Artificial lighting has many advantages, since when properly positioned it gives uniform illumination of sorting belts of conveyors (inspection conveyors). The recommended minimum illumination is 500-600 lux. Fluorescent tubes and lamps should be equipped with devices for protecting glass (usually polycarbonate), which in case of damage remains inside. Hanging devices must be smooth, easy to clean and designed in accordance with certain standards to prevent water from entering them. It is recommended to connect lighting devices with a plug and socket, so that in case of a malfunction it is possible to replace the entire device, and move the malfunctioning from the technological zone to the appropriate workshop for repair. Ideally, for hygienic reasons, recessed lights flush with the ceiling are recommended (Fig. 13.9), but this is not always possible, and repairs can be difficult.

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