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Chilled and frozen foods

Hygienic aspects of the design of air conditioning.

Air is a potential source of pathogens, and air intake into the high-risk area must be regulated.

Air can enter this zone through special air conditioning systems or can come from external unregulated sources (for example, low-risk production, workshop). packaging environmentTypical room layout changing.

13.4. Typical room layout changing.

For high-risk areas, the task of air conditioning systems is to supply appropriately filtered fresh air of the required temperature and humidity (with a slight overpressure to prevent air from entering outside).

The costs of air conditioning systems are one of the main cost items associated with the construction of a high-risk zone, and before starting the development of air conditioning systems, you should always consult a specialist. Based on an appropriate risk analysis, it can be concluded that the system requirements for high purity zones may be less stringent, especially in terms of filtration levels and overpressure. After installation, any changes to the layout of the high-risk area (for example, rebuilding / reconstruction of walls, doors or openings) should be carefully analyzed, since they have a big impact on the air conditioning system.

on air quality standards for the food industry have been considered by a working group with the US, and then [10] was prepared by appropriate guidance. air conditioning systems design should consider the following factors:

  •  the degree of filtering incoming air;
  •  overpressure;
  •  air consumption (taking into account operational requirements and comfortable working conditions);
  •  the direction of air flow;
  •  temperature requirements;
  •  local cooling and maintenance of barriers;
  •  humidity requirements;
  •  installation and maintenance complexity.

The main air flows in the high-risk zone are shown in Fig. 13.5, and a more detailed diagram of the air conditioning system is shown in Fig. 13.6.

The main danger from air pollution of the high-risk zone comes from the technological operations of the low-risk zone (especially from the processing of raw materials, the probability of infection of which by pathogenic microorganisms is quite high). Therefore, the main role of the air conditioning system is to ensure that filtered air enters the high-risk zone at a higher pressure than in the low-risk zone. This means that if there is a physical violation of the barrier of low and high risk areas (for example, opening the hatch), air will flow through the hole from the high risk zone to the low risk zone. The level of microorganisms in the air of the low-risk zone (depending on the type of product and technology) can be very high [18], and overpressure should prevent particles in the air from entering the high-risk zone, some of which may contain viable pathogenic microorganisms.

To facilitate the operation of the air conditioning system, it is important to control potential sources of aerosols from personnel and technological processes.The main air flow in the high risk zone.

Ris.13.5. The main air flow in the high risk zone.Driving conditioning.


Figure 13.6. Air conditioning system diagram.

etc. Air filtration is a complex process where in-depth knowledge of filter types and available installations is required. The choice of filter type is dictated by the required degree of removal of microorganisms and particles from the air (see [10] for more on this). For high-risk areas, in order to obtain air that meets specified requirements, a number of filters are required (Fig. 13.6).

To increase the efficiency, the pressure drop between the low and high risk areas should be 5-15 Pa. The desired pressure drop will be determined by the number and size of the holes, as well as the temperature drops between the low and high risk areas. For example, if in the low-risk zone the temperature is 20 ° С, and in the high-risk zone –10 ° С, warm air from the low-risk zone tends to rise through the openings, and cold air through the same openings from the high-risk zone tends to fall, which leads to to movement in two directions. To ensure a one-way flow, air from a high-risk zone through such a hole of 1,5 m / s or higher may be required.

In addition to creating excessive pressure, the air flow rate should be sufficient to cope with the heat load created by the production environment (technological processes and personnel) and provide workers with fresh air. A 5–25-fold change of air per hour is usually sufficient, although in a high-risk area with large hatches or doors that often open, a 40-fold exchange of air may be required.

Air is usually supplied to a high-risk area or through ceiling grilles or woven sleeves (usually made to reduce their shrinkage from polyester fiber or polypropylene). The advantage of ceiling grilles is that they are relatively cheap and do not require frequent maintenance, but their speed and intensity of silent air supply through them without drafts is limited. As for the latter, the air speed next to the employee to minimize discomfort due to wind cooling should be 0,3 m / s. Air distribution over the air hoses can be carried out at low air flow rates and with minimal channel connections, however, they require periodic washing, and therefore their spare set is necessary. If an additional air supply is not used to maintain excess pressure, then ceiling air coolers that cause its recirculation are the only really acceptable option for operations in the air conditioner.

A collaboration between CCFRA and the Silsoe Institute, funded by the UK Department of Fisheries and Food Industry (MAPE) since 1995, has analyzed the control of airborne microbial contamination in high-risk production areas. This work has led to the creation of a guidance document for airflow guidance in high-risk areas and has led to innovation in two main areas. First, it is the modernization of high-risk areas to achieve balances of air flows and overpressure based on computer models. Secondly, such models allow predicting the movement of microorganisms in the air from known sources of infection (for example, operators). This has led to the design of air conditioning systems that provide directional air movement that moves particles away from the source of contamination in a direction that does not compromise product safety. As an illustration (see Fig. 13.7a), the predicted air flows in real production are shown, simulated using the CFD software package developed by Silsoe (Computational Fluid Dynamics, computer analysis of fluid dynamics). This model was then applied to predict the movement of 10 µm particles away from line operators (like peeling skin flakes) (see Figure 13.76). The predicted routes show that in some cases the air flow is directed in the desired direction and moves these separated particles away from the product, while in other cases the particles move directly over and along the conveyors with the product, thereby presenting a hygienic hazard (risk).

Chilled food manufacturers have traditionally preferred to use low temperatures (typically around 10-12 ° C) in high-risk areas to control and prevent the growth of some (eg Salmonella, but not all — eg Listeria) foodborne pathogens. Cooling the zone to this temperature is also beneficial to reduce heat absorption by the product and thereby maintain the cold chain. In addition, refrigerated food manufacturers in the UK must ensure that their products comply with the Food Safety Regulations (Temperature Control Section) 1995 [4], as well as with retail requirements.

In the United Kingdom, the "Occupational Health, Safety and Conditions" [2] requires that "in buildings, the temperature in all industrial areas should be within reasonable limits", for which the complementary document [3] usually takes a temperature of at least 16 ° C (or where work generally requires a lot of physical effort - at least 13 ° C). To help resolve this conflict between product and room temperatures, the CCFRA established a 1996 Occupational Safety and Health (HSE) Working Group and Chilled Food Processors working group that created a document titled Guidelines to achieve rational operating temperatures and conditions in the production of chilled products ”[11] - an addition to [1]. In [R] it is argued that in order to meet the requirements of [4], and not just use the lower temperature of the working rooms, it is first necessary to consider alternative ways of regulating the product temperature. Only if alternative measures are not applicable can it be justified for hygienic reasons to maintain the temperature of the production area below 16 ° C (or 13 ° C). Where such lower temperatures apply, management must be able to demonstrate that appropriate measures have been taken to ensure the thermal comfort of workers. Complete information on these issues is given in [11].

Another MAFF-funded CCFRA / Silsoe joint project explored the use of local cooling for the following purposes:

♦ providing well filtered, cooled air directly above or around the product, which can reduce cooling requirements for the entire high risk area to 10 (13) ° C and reduce the required filtration rate (paramount, however, the requirement forDiagram: a) predicted air flows in real production of refrigerated products based on air flow measurements. The length and size of the arrow indicates the air speed, and its direction indicates the direction of flow; b) predicted flow from line operators. Product flow along five lines moves in the direction from Y to Z

Figure: 13.7. Diagram: a) predicted air flows in real production of refrigerated products based on air flow measurements. The length and size of the arrow indicates the air speed, and its direction indicates the direction of flow; b) predicted flow from line operators. Product flow along five lines moves from Y to Z

overpressure in the low-risk zone, and the number of air exchanges per hour remains unchanged);

♦ using air flow to create a barrier to prevent the entry of aerosol particles, some of which may contain viable microorganisms.

An example of such a technology is shown in Fig. 13.8, where a diagram of a conveyor is given, to which cooled filtered air is directed in an amount sufficient to maintain a low product temperature. When an aerosol containing microorganisms is formed around the operating conveyor, microbiological sampling of air indicates a decrease in the number of microorganisms in the protected area by 10–100 times [12].

The choice of relative air humidity is a compromise between the comfort of operators, the quality of the product and the drying out of the production environment.Scheme a) the direction of the cooled filtered air across the conveyor belt with the product; B) decrease in the number of microorganisms (some) on the conveyor during the operation. The diameter of the circles is directly proportional to the fixed amount of

Fig. 13.8. Scheme a) the direction of the cooled filtered air across the conveyor belt with the product; B) decrease in the number of microorganisms (some) on the conveyor during the operation. The diameter of the circles is directly proportional to the fixed amount of

A relative humidity of 55-65% helps to limit the growth of microorganisms in the production environment and increases the rate of drying of equipment and environment after cleaning operations. Low humidity can, however, cause drying of the product, that is, loss of weight and quality (especially at high air velocities). Higher humidity maintains product quality, but can lead to drying and condensation problems, increasing the microorganisms' ability to survive and grow. Most often, a compromise humidity of 60-70% is recommended, which is optimal for operators.

Finally, air conditioning systems should be installed so that they are easy to maintain and clean. As a commissioning program, both their operability under normal use and their ability to perform other functions should be verified (e.g. direct air venting during washing / cleaning operations to prevent air contaminated with potentially corrosive detergent chemicals from entering the air conditioner, recirculation of the surrounding or heated air after washing operations to dry the production environment, etc.).

Work accessories

Any equipment, supplies, tools, etc., regularly used in the high-risk area, should, if possible, remain in it. This means that it is necessary to provide storage areas or zones in which accessories can be serviced and cleaned.

So, the need for ingredients, for transport containers for them or for a product (trays, trays, etc.) should be minimized, but where they are unavoidable, the transport container should remain in a high-risk area, and it should be cleaned, washed and disinfect in a separate area; any accessories (eg agitators, spoons, buckets) or other non-stationary equipment (eg jiggers or bins) used to handle the product should remain in the high risk area; they should be cleaned / washed and disinfected in a separate area.

A special room should be provided for all production operations of wet cleaning, which is better located on the side of the outer wall, which facilitates the removal and supply of air. The outer wall also allows an external storage for bulk storage of detergents that can be directly dispensed into the ring main pipeline through the wall. This room should have its own separate sewerage system, which, in the case of operations with large volumes of water, may include drainage at the inlet and outlet to prevent water from leaving the room. It should include a “waiting area” for equipment, etc., a washing area (for manual or automatic) as appropriate, and a waiting (drying) area where equipment can be stored prior to use. These areas should be separated from each other as much as possible.

All washing equipment, including hand tools (brushes, rubber squeegees / squeegees, scoops, etc.) and large equipment (pressure washers, scrubber driers, etc.) must remain in the high risk and have special color coding (to distinguish equipment of high and low risk areas, if necessary). Provision should also be made for storing such equipment when not in use.

Detergent affinities should preferably be piped into the high-risk area through an annular main pipeline (which must be separated from the low-risk annular main pipeline). If this is not possible, detergents should be stored in a specially equipped area.

The most frequently used equipment maintenance tools, spare parts, etc. (with the necessary hand tools to perform this maintenance) should be stored in a high risk area. For certain operations (for example, sharpening the cutting inserts of meat slicers), it may be necessary to provide special mechanical workshops.

High-risk areas should provide storage facilities for accessories that are not used regularly but are too large to pass the barrier between low-risk and high-risk areas (eg ladders to replace air distribution hoses).

There should also be written instructions with detailed instructions on how and where to decontaminate equipment that cannot be stored in a high-risk area, but is periodically used there, or new equipment entering a high-risk area. If necessary, these instructions may also require instructions for decontamination of the area where the equipment is decontaminated.

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