Hygiene Zone Demarcation for Food Manufacturing Facilities

Good Hygienic Practices

Food can be contaminated at many stages during a production process. There is a global trend in the food industry towards minimal food processing and preservation. Consumer demand for “fresh-like” additive-free foods, that maintain their nutritional and sensorial properties during preparation, conservation, packaging, storage and finally consumption, is on the rise. But the general tendency to apply mild processing and conservation techniques to achieve that purpose, often shortens the shelf-life of food, may put foods at risk and may compromise consumer health. Therefore, more than ever, good hygienic engineering and design practice is one of the tools to reduce or exclude microbial (e.g. pathogens), chemical (e.g. lubricating fluids, cleaning chemicals) or physical (e.g. glass, wood) contamination of food. Proper hygienic design also may eliminate product 'held-up' within the process equipment where it could deteriorate and affect product quality on rejoining the main product flow. As such, good hygienic design may prevent that one batch cross-contaminates a subsequent batch. Good hygienic design further reduces the downtime required for an item of process equipment to be cleaned, while at the same time allowing to increase the time to produce. Therefore, although initially more expensive than similarly performing poorly designed infrastructure and equipment where, hygienically designed facilities and equipment will be more cost effective in the long term.

One GHP method to manage the risk of contamination is to divide a food producing facility into zones in which different hygiene levels apply and ensuring that products flow only from levels of basic hygiene in direction of levels of higher hygiene.

Deciding upon how to apply these zones is done by

1. Identifying process steps where products or intermediate products are easily contaminated, for example because they are still unpacked.
2. Deciding on how to demark or enclose those rooms/areas so that strict hygiene rules can be applied. This might require some reorganization of the flow of process.
3. Deciding on rules that need to be applied in each defined zone.

The ideal production plant would be designed in such a way that raw material would enter at one end of the building and follow a linear path through zones of increasing hygiene before exiting as a final product at the other end. This ideal situation would minimize cross-contamination and should be applied to the design of new food plants. In reality, businesses often have to make do with less than ideal buildings.

However, most processes can be (re)arranged in order to comply as much as possible with the ideal flow of product through a plant. In addition, identification of potential cross-contamination in the flow of material and processes and taking actions to prevent contamination will significantly enhance the level of product safety.

Not all production types require exactly 3 hygiene zones. In certain cases only 2 zones are required whereas in others perhaps 4 might be more appropriate. What is important is to understand and follow the principle of differentiating between process steps where contamination is more likely to occur and defining the necessary design and corresponding behaviour to prevent contamination from happening at these steps.

Zoning – A Cornerstone in Prevention of Food Contamination

Zone B:

Zone B is an area in which a basic level of hygienic design requirements suffices. It encompasses areas in which products are produced that are not susceptible to contamination or that are protected in their final packages. A B0 zone is the area outside the buildings within the perimeter of the site where the objective is to control or reduce hazards created by unauthorized personnel entry and hazards created by water, dirt, dust and presence of animals. B1 zones include warehouses that store both raw materials and packed processed products, offices, workshops, power supply areas, canteens and redundant buildings/rooms. The objective for a B1 zone is to control or reduce hazards created by birds and pests.

Zone M:

Zone M is an area in which a medium level of hygiene suffices. It includes process areas where products are produced that are susceptible to contamination, but where the consumer group is not especially sensitive and where no further microbial growth is possible in the product in the supply chain. In this area, product might be exposed to the environment, during sampling and during the opening of equipment to clear blockages. The objective for zone M is to control or reduce the creation of hazardous sources that can affect an associated area of higher zone classification. Another objective is the protection of the interior of food processing equipment from contamination when exposed to the atmosphere.

Zone H:

Zone H applies to an area where the highest level of hygiene is required. A “High Hygiene” room, which, in food processing is the equivalent of a cleanroom, must be completely contained. Zone H is typical for open processing, where even short exposure of product to the atmosphere can result in a food safety hazard. Products and ingredients that are processed or stored and are destined for a highly susceptible consumer group (e.g., infant nutrition), are instant in nature or ready for consumption. They must be handled in a refrigerated supply chain, as they are susceptible to growth of pathogenic microorganisms. The objective for H zones is to control all product contamination hazards and to protect the interior of food processing equipment from exposure to atmosphere. Filtered air must be supplied to this area.

These areas should be limited in size, must have a simple equipment layout to facilitate process, cleaning and maintenance operations and should have utilities located outside. However, investing in an enclosed line that brings barriers very close to the product is more logical than trying to create a complete cleanroom around a partially open line.

Zoning and the establishment of barriers to ensure that product of acceptable hygienic quality is produced should only be applied where their use will help significantly to protect products. Designing the entire factory as a cleanroom is not the purpose of food area segregation to protect both product and consumer. Zoning and barrier technology must be applied in an appropriate and consistent way, thereby avoiding unnecessary investment.

Construction of Facilities: Appropriate Layout

The layout and design of the food factory must be adapted to the hygienic requirements of a given process, packaging or storage area. The interior of the factory must be designed so that the flow of material, personnel, air and waste can proceed in the right direction. As they become incorporated into food products, raw materials and ingredients should move from the ‘dirty’ to the ‘clean’ areas. However, the flow of food waste and discarded outer packaging materials should be in the opposite direction. Before building begins, simulation of the flow of people, materials, products and waste can help the designer determine the most appropriate place for installing the process equipment and where the process and utility piping should enter the process area. Even the simulation of maintenance and cleaning operations can be useful to determine the most appropriate factory layout. Graphical computer-aided design and 3D visualization programs can help in the hygienic design, positioning and routing of processes, process supports and utility systems. These programs allow the observer to “walk through” the facility, seeing the inside of the facility from different angles and locations. To save building and renovation costs, potential problems can be solved before the onset of construction. Additionally, in the development of high hygiene areas, computational fluid dynamics can help simulate and visualize expected air-flows.

To meet a possible increase of processing activities within the food plant in the future, the building and its food processing support systems should be designed so they can either be expanded, or another building and/or utilities can be added. Over-sizing the main utility systems is a common practice. If possible, the factory should also be made adaptable (i.e., the ability to modify the production area for other manufacturing purposes) and versatile (i.e., the ability to do different things within the same room).

Construction of Facilities: Pest Prevention

To exclude flooding and the entry of rodents, factories should be built at a higher level than the ground outside. Exterior doors should not open directly into production areas, and windows should be absent from food processing areas. The number of loading docks should be minimal and be 1–1.2 m above ground level. Preferably, outside docks should have an overhanging lip, with smooth and uncluttered surfaces that are sloped slightly away from the building to encourage water run-off. Areas beneath docks should not provide harborages for pests, should be paved and should drain adequately. To provide protection for products and raw materials, docks can be shielded from the elements by roofs or canopies. However, these structures can become a serious sanitation problem due to roosting or nesting of birds. Bird spikes or nets can solve that problem. To prevent the entry of insects, dock openings should be provided with plastic strips or air curtains, and external lighting to illuminate these factory entrances should be placed in locations away from the factory building. Intruding insects can still be attracted and killed within the food factory by strategically positioned ultraviolet (UV) light electric grids or adhesive glue board traps.

Construction of Facilities: Interior Hygienic Design and Construction Materials

Construction materials for equipment and utility piping should be hygienic (smooth, non-absorbent, non-toxic and easily cleanable), chemical-resistant (to product, process chemicals, cleaning and sanitizing agents), physically durable (unbreakable, resistant to steam, moisture, cold, abrasion and chipping) and easy to maintain. Materials used to construct process and utility systems located in the non-food contact area may be of a lower grade than those applied in the food contact zone. Surfaces that are frequently wet should not be painted as the paint can crack, flake and chip.

Lead, mercury and cadmium should not be used within the factory. However, as part of many electric components, it is very difficult to exclude their presence. In the food contact area, electric components must always be enclosed in junction boxes, casings, closed cable housings, cabinets, etc. or should be installed in non-product contact zones or in technical corridors. Alloys for food contact may only contain aluminum, chromium, copper, gold, iron, molybdenum, nickel, platinum, silver, titanium, zinc, carbon, etc. However, zinc, copper, aluminum, bronze, brass, carbon and galvanized and painted steel have poor resistance to detergents, disinfectants, acidic food and steam and must be avoided in food contact areas.

Polytetrafluoroethylene, polyethersulfone, polyvinylidene fluoride, phenol-formaldehyde, urea-formaldehyde, melamine-formaldehyde, epoxy and unsaturated polyester resins are used in the construction of electric components, while other plastics like polypropylene (PP), low-density polyethylene (PE), polyvinyl chloride (PVC), polyurethane (PU), ethylene propylene diene monomer (EPDM), silicone, etc. are applied as jacket materials for electrical cables or for the construction of pneumatic hoses and compressed air tubing. PP, PE and PVC are also used to construct drain pipes, while shields of polycarbonate can protect the food area below light sources from shattered glass after accidental breakage of lamps. Silicone, nitrile, PU, EPDM and butyl rubber are largely used as materials for gaskets, seals, etc. Epoxy is widely used as floor, wall and ceiling coatings. Remember that many plastics perform differently at -25 °C than they do at 20 °C.