Chilled and frozen foods

Aspects of the design of the barriers to high-risk areas

Building structures, equipment and production methods associated with high-risk areas and production areas provide an internal third barrier that protects the production of chilled products from contamination. The last barrier is formed by a combination of individual components to combat pollution, which can fall into the high risk zone with the following components:

  • A product entering a high-risk area after heat treatment;
  • A product entering the high-risk area after the disinfection process; A product that has undergone heat treatment / disinfection outside the production area, but whose external packaging may need to be decontaminated at the entrance to the high-risk zone;
  • Other incoming products;
  • packaging materials;
  • Liquid and solid waste;
  • surfaces usually associated with the physical boundaries of low and high risk areas — floors, walls, doors, and suspended ceilings;
  • Personnel entering high risk areas;
  • air;
  • Equipment and tools that may be necessary to move between low and high risk areas.

A product that has been cooked

Where the equipment for heat treatment of a product creates a barrier between low and high risk zones (for example, a stove, fryer or microwave tunnel), two things are important to facilitate successful operation of the barrier.

 All products passing through the thermal barrier must be processed with the required combination of duration and temperature. This means that the heating device must work properly (for example, the temperature distribution must be set and maintained, and the size of the product must remain constant). At the same time for the product passage of the heat treatment zone without a treatment process should be impossible or as difficult as possible.

 The heating device should be designed to form a continuous physical barrier between high and low risk areas. Where it is physically impossible to form a continuous barrier, the air gaps around this equipment should be minimal, and the combination of high and low risk areas on the floor should be completely closed to the maximum possible height.

Installation of heating devices is associated with two main difficulties. First, the devices must be designed so that products are loaded on the low-risk side, and unloaded on the high-risk side. Secondly, it is difficult to maintain good insulation between the surfaces of the heating device, which go through the expansion and contraction phases, and the construction of the barrier, which has a different coefficient of thermal expansion.

Furnaces are a matter of particular concern, since some of them are designed to discharge the product to a high-risk area. This is unacceptable for the following reason. The most likely place of presence of pathogens resulting from cross-contamination in the low-risk area is the product surface. A pathogen that is present on the surface of the processed product can get on the floor when the surface layer of the product is defrosted (or stand out on its outer packaging) at a temperature that is not lethal for it and linger on the floor or in the oven’s drain, maintaining the heat treatment cycle. When discharging from the oven, this microorganism can then enter a high-risk zone (they were repeatedly found at the exit from the ovens of a number of food production facilities).

In addition, there are problems with leakage to high-risk areas from the settling tanks under the furnaces. There may also be problems with cleaning the septic tanks if the use of high pressure hoses can lead to the spread of contamination to a high-risk area.

Where the furnace is being cleaned, cleaning should be done in such a way that detergent solutions do not flow from the low-risk area to the high-level area. Ideally, the sink should come from a low-risk area with the high-risk door closed and sealed. If cleaning solutions should drain into the high-risk zone, the drain should be installed from the outside directly behind the door leading to the high-risk zone.

Other issues that require attention, not related to the ovens, include the design of small batch blanchers or noodle cookers (i.e., small water tanks as cooking medium). They rarely allow equipment to be built directly into the boundary between low and high risk zones, since there should be space around the blancher for loading and unloading the product. Due to the fact that these tanks are open, the formation of condensate is very likely, and therefore the ventilation of this zone is important to prevent the accumulation of microorganisms in places of water condensation. Any ventilation system should be designed so that the zone is ventilated from the low-risk area; ventilation from the high-risk area can lead to the drawing of large amounts of air into it from the low-risk area.

The previously used installation of boilers as barriers between low and high risk zones, along with walls to prevent water from moving across the floor and barriers about one and a half meters high to prevent people from moving, is now considered sanitary and hygienic. It is almost impossible to prevent the transfer of pollution between areas of low and high risk with people, air, while washing and cleaning. It is possible to install boilers in the low-risk zone and move the product (by pumping, due to drift, vacuum, etc.) to the high-risk zone through a pipeline in the separation wall. Boilers should be located in a low-risk zone at such a height that product transfer to a high-risk zone would occur well above ground level. There are installations where the receiving vessels for the incoming product had to be placed on the floor.

Product remission

Fresh product, which must be processed in the HRA, must enter it after disinfection, which usually involves washing with running water with biocides. The most common use of chlorinated solutions (although other biocides are used, for example, bromine, chlorine dioxide, ozone, organic acids, peracetic acid, hydrogen peroxide, etc.), mechanically stirred washing baths or washing baths such as a jacuzzi.

In addition, after appropriate risk assessment, it is now increasingly important to disinfect the outer packaging of various ingredients at the entrance to a high-risk zone (for example, products prepared elsewhere and received for processing in a high-risk zone, canned foods and some processed ingredients in packaging). If it is likely that the outer packaging is contaminated with food materials, it is best to carry out disinfection using washing with a disinfectant (quaternary ammonium compounds are usually used). If the packaging is clean, it is preferable to use ultraviolet radiation, since such a dry method limits the growth of microorganisms from the environment.

Disinfection systems must be designed and installed so that they meet the three main criteria.

 As in the case of thermal barriers, disinfection systems to minimize the free space around them must be installed inside the barrier between the zones of low and high risk; The minimum clearance around the disinfection system must be less than the size of the product being disinfected, which ensures that all ingredients in the high-risk zone pass through the disinfection system and, therefore, their mandatory disinfection (unlike the heat treatment situation, it is not visually possible to assess whether the entire external ingredient surface).

 Before implementation, the decontamination process should be checked; for liquid treatment, this implies the determination of an appropriate disinfectant that properly combines the washing ability and disinfecting properties with an appropriate temperature of application, concentration and duration of contact; similarly, the appropriate wavelength, intensity and time of contact must be determined for ultraviolet radiation; the same degree of decontamination should be applied to all surfaces of products, and if this is not possible, the process should be applied to the surface undergoing minimal treatment.

 After implementation, controls should be identified using automatic dispensing of disinfectants, conveyors with a fixed speed, UV-intensity meters, etc. To ensure that all surfaces of the product are processed, the monitoring of the process may include periodic checking of critical parameters (for example, clogging of spraying nozzles or intensity of UV lamps) and loading the transfer conveyor from the lower risk side.

Transfer of other products

The introduction of external packaging materials into the high-risk zone is currently considered to be incorrect. All ingredients and packaging materials for the manufactured product should be removed from the boxes and transferred to a high-risk area.

Some ingredients (heat-treated liquid in tanks or stable in nature) - for example, butter or pasteurized dairy products, are best transported by pumping through a barrier between low and high risk areas directly to the point of use. Dry, stable bulk storage ingredients (eg, sugar) can also be moved to a high-risk area using hermetically sealed conveyors.

Ingredients in the container can be opened at the barrier between the zones and poured into the high risk zone through appropriate transportation systems - for example, into the receiving tank through a simple funnel built into the wall. It is desirable to be able to shut off the transportation systems when they are idle; they must be designed to be washable and disinfectable from a high-risk area before use.


Packaging materials (film reels, cardboard boxes, containers, trays, etc.) are best supplied in double-bag manufacturing. At the same time, cardboard is used outside, and then two layers of plastic surrounding the packaging materials. The packaging is delivered to production, the box is removed, and the material is stored in double bags until used at an appropriate warehouse of packaging materials. When packing material is required in a high-risk zone, it is delivered to the barrier between zones, the outer plastic bag is removed, and the inner bag with the packaging material enters the high-risk zone through the corresponding hatch. The packaging materials are in a second plastic bag before being delivered to the line or to the packaging machine.

The hatch, like all openings in the barrier between the low and high risk zones, should be as small as possible and close when not in use. This is necessary to reduce the air flow through the hatch and thereby to reduce air consumption by air conditioning systems that maintain excess pressure in the high-risk zone. For some packaging materials (especially for heavy film reels), a special system for transporting them through the hatch may be required. A door that opens or, preferably, an airlock with a double door, should be used only in cases where it is technically impossible to use the hatch (it is necessary to take appropriate precautions to decontaminate the airlock after use).

Liquid and solid waste

In no case should liquid and solid waste from low-risk areas be removed from an enterprise through a high-risk area. Attention should also be paid to procedures for removing waste from high-risk areas. Disposal of liquid waste from low and high risk areas is described below in the section on sewage.

Solid waste that has fallen on the floor, on equipment, etc., should be immediately collected in bags or placed in easily cleanable bins. It may also be necessary to remove solid waste from the line during business interruptions or to facilitate the replacement of the product being produced. Garbage bags should be removed from the high-risk zone so as to minimize any possible cross-contamination of already processed products, and it is desirable that they do not move in the opposite direction to the movement of the product. For small amounts of waste in bags, it is better to use existing hatches (for example, hatches for unloading packaged product or hatches for receiving packaging materials), since additional hatches increase the risk of external contamination and place additional demands on the air conditioning system. For waste collected in bins, it may be necessary to dispose of them through specially designed, easily cleaned from a high-risk area, refuse chutes leading directly to waste trolleys. Garbage bins must be color coded to distinguish them from food containers and used only for waste.


In this context, surfaces are defined as tight physical connections between low and high risk areas, namely floors, walls, doors and suspended ceilings. For more information, see the sections 13.4.1 and 13.4.2 below.


Inside the enterprise building, appropriate household facilities and rooms for staff catering should be provided. Individual lockers should be provided for the storage of outer clothing, which should be separated from the working clothes storage areas. Toilets should not open directly to food processing areas, and all toilets should be equipped with uncomplicated handwashing equipment. In addition, staff (as well as visitors, contractors, etc.) should be personally responsible for their implementation of appropriate hygiene measures. Usually they are formulated in the form of sanitary-hygienic strategy of the enterprise, which usually includes:

  • use and timely replacement of protective clothing, shoes and hats; in some cases, in addition to the protective headgear, a thin hairnet should be worn (clips and barrettes are not recommended);
  • prohibition of the use of protective clothing outside the enterprise;
  • beard cover (short and neatly trimmed) with special devices;
  • prohibition of using nail polish, false nails and make-up in production areas, as well as false eyelashes, wrist watches and jewelry;
  • Observance of cleanliness of hands;
  • prohibition of bringing personal items into the production area (handbags, shopping bags, etc., should be left in individual wardrobe lockers);
  • Permission to enter and consume food only in recreation areas and dining room for staff;
  • Banning the use of sweets and chewing gum in the work areas;
  • smoking is allowed only in specially designated areas marked as “Smoking Area”;
  • In all areas of the enterprise, spitting is prohibited;
  • About superficial injuries (for example, cuts, scratches, abscesses, wounds and skin infections) should be reported in time to the medical unit or the attendant on duty through the site's master; Before the entry of such an employee into production zones, he must receive a special permit;
  • dressings should be waterproof, appropriately colored (to distinguish them from the product), and contain a metal strip (to facilitate their detection with metal detectors in case of loss);
  • Infectious diseases (including indigestion, diarrhea (diarrhea), skin diseases and discharge from the eyes, nose or ears) should be promptly reported to the medical unit or the orderly attendant through the site master; this also applies to personnel who have returned from trips abroad with a possible risk of infection;
  • after the illness, it is necessary to report to the medical unit about the disease.

For operators working in a high-risk area, facilities and requirements for personnel should ensure the minimization of any possible contamination in the area. The main sources of potential pollution are the operators themselves and technological operations. This requires additional attention to protective clothing and special organization of places for dressing in overalls for work in a high-risk area. Methods relating to staff hygiene are constantly evolving, and their reviews are given in [16, 24, 25].

Overalls for high-risk zones do not necessarily differ from those used in low-risk zones in terms of style or quality, although the requirements for its washing may be higher (this applies primarily to the washing temperature sufficient to significantly reduce the number of microorganisms). In fact, many laundries currently work on the same principles of low and high risk zones as the food industry: dirty things enter the low risk zone, are loaded into a washing machine that serves as the interface between zones, then things are erased, disinfected, and then for drying and packaging come in a high risk zone.

For additional protection of processed foods in the high-risk zone from contamination from the operator's body, additional means (gloves, sleeves, masks, helmets, hooded clothing, overalls, etc.) may be used. All clothes and shoes used in the high-risk zone should have a certain color, which allows you to quickly detect a possible violation of sanitary and hygienic requirements.

Operators should wear and take off shoes at the high risk zone at the border of low and high risk zones. This requirement is based on studies [25], which showed that shoe washing devices (bathtubs and sinks) cannot sufficiently disinfect shoes so that they can be worn in both low and high risk zones and disinfected between zones. In addition, shoe washers can spread contamination through aerosols and water droplets, which, moreover, provide moisture for the growth of microorganisms on the floor of a high-risk area. At the same time, it was shown that shoe washers remove organic material well from shoes and are therefore useful in low-risk areas.

For personnel working in high-risk areas or visitors, the changing room serves as the only entry and exit point. It is designed and planned in such a way as to minimize the risk of contamination from the low-risk zone and ensure that the hygienic procedures necessary for personnel are performed. In practice, there are some options in the planning of such dressing rooms. Their location depends, for example, on space availability, food production volume and their type (this affects the estimated number of employees) and whether the dressing room serves as a barrier between operators of low and high risk zones or between visitors and operators of high traffic areas. risk. Usually, for barriers between low and high risk areas, construction requirements are higher than for barriers between the environment outside the enterprise and the high risk zone, since the level of potential pollution in the low risk zone (both at the hands of operators and in the area environment) is usually higher [24 ]. In each case, the firm must evaluate the effectiveness of both the location of the changing room and the procedure that allows not to endanger the high-risk zone and the products prepared in it. This is best done using the HACCP methodology, which allows to obtain the necessary data.

Based on the CCFRA research, we propose the following sequence of operations to maintain hand hygiene when entering the high-risk zone [24] in order to maximize the purity of the hands, minimize the level of microorganisms carried on the hands, and make the hands as dry as possible (but at the same time reduce excessive contact with water and chemicals that can cause dermatitis among operators) and reduce the likelihood of water being transferred to a high-risk area.

  • Remove clothing from low-risk areas or outer clothing.
  • Remove shoes from a low-risk or outdoor area and place it in the cage compartment designed for it.
  • Cross the barrier separating the low and high risk areas.
  • Dress in the following order:
  • To put on shoes constantly in the high-risk zone;
  • wear a hair net; close all hair (if necessary, wear a beard dressing / mesh and headdress);
  • Wear overalls (fully fastened to the top).
  • Check clothes and appearance in the mirror in the room.
  • Enter the high-risk production area and apply an alcohol-based disinfectant.
  • Wear disposable gloves, arm ruffles and apron (if necessary).
  • A typical layout of the changing room is shown in Fig. 13.4. It is designed to perform the above procedure and should be provided by the following:
  • A zone for storing outer clothing or clothing for a low risk zone (at the entrance); Individual lockers must have an inclined top;
  • Barrier for the separation of the sexes of low and high risk areas; This should be a physical barrier such as a low wall (about 60 cm in height), which allows washing floors on both sides of the barrier without splashing;
  • open individual lockers at this barrier for storing shoes of low-risk areas;
  • Stand for monitoring / drying shoes;
  • an area equipped with an appropriate wastewater system for washing shoes; [25] research has shown that both manual washing and the use of shoe washing machines give acceptable results;
  • shells for one person; water supply for handwashing should be automatic or foot-operated; water should be supplied at the temperature required for handwashing; sewage must be discharged directly into the sewer; hand washing shells placed at the entrance to the high-risk zone (which was previously considered correct, as it allowed to observe compliance with the hand washing requirements), lead to the occurrence of a large amount of aerosol with staphylococcal strains that can infect the product;
  • appropriate equipment for drying hands (for example, a paper towel dispenser or a device for drying with heated air), and for used paper towels - an appropriate container;
  • Access to clean overalls and storage for contaminated clothing (for large industries this can be done with the help of adjoining and connected hatches);
  • blocking doors that make it possible to enter a high-risk area only if a certain important operation has been performed - for example, hand washing (if possible);
  • Camcorders (security cameras) for monitoring the implementation of the procedure for washing hands;
  • devices for dispensing alcohol solution for cleaning hands immediately after entering a high-risk production area.

In the high-risk zone, it is also possible to install additional hand washing sinks if the manufacturing process requires frequent operation. Alternatively alcohol wipes may be used.

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