Design and Construction of Equipment in Food Industry
The hygienic design of equipment is necessary to comply with legislative requirements, avoid product contamination and to facilitate cost-effective cleaning and, if necessary, disinfection.
Poorly designed equipment, which cannot be dismantled, may be uncleanable, incapable of being chemically disinfected and may result in product contamination by pathogenic bacteria. Even if equipment can be dismantled, unhygienic design may make cleaning and disinfection prohibitively expensive.
The legal requirements
Food safety legislation requires all articles, fittings and equipment with which food comes into contact to:
- be kept clean;
- be so constructed, of such materials and maintained in such condition and repair as to minimise risk of contamination; and
- enable thorough cleaning and, where necessary, disinfection
Furthermore, equipment must be installed in a way which allows the surrounding area to be cleaned.
The supply of Machinery
The regulations require that new machinery used for preparing and processing foodstuffs carries a CE marking and must be designed and constructed to avoid health risks and in particular:
- contact materials of foodstuffs must satisfy the conditions set down in the relevant directives. Machinery must be designed and constructed to facilitate cleaning;
- all surfaces and joints must be smooth, without ridges or crevices which could harbour organic materials;
- projections, edges and recesses should be minimal. Continuous welding is preferable. Screws and rivets should not be used unless technically unavoidable;
- contact surfaces must be easily cleaned and disinfected. The design of internal surfaces, angles, etc. must allow thorough cleaning;
- cleaning residues must drain from equipment surfaces, pipework, etc., there must be no retention in voids;
- the design should prevent organic accumulations or insect infestation in uncleanable areas, e.g., by the use of castors or sealed bases; and
- lubricants must not come into contact with any product.
Construction materials
Materials in contact with food must be non-toxic, non-tainting and constituents from their surfaces must not migrate into the food or be absorbed by the food in quantities which could endanger health. Materials must have adequate strength over a wide temperature range, a reasonable life, be corrosion and abrasion resistant and be easily cleaned and disinfected. In most meat plants, the use of wood is forbidden except in rooms used for the storage of hygienically packed fresh meat.
The most widely used material is food-grade stainless steel. Some plastics may be suitable, but must be approved for food use. Aluminium should be avoided, as should copper and zinc. Handles of knives, brushes and other equipment should all be made from cleansable materials such as polypropylene or high-density stainless steel.
Surfaces should be smooth, non-porous, continuous, non-flaking and free from cracks, crevices and pits. Surfaces will need to retain a satisfactory finish throughout their life including anticipated abuse and normal wear and tear. Poor surfaces harbour grease, dirt and bacteria and are difficult to clean and disinfect. They may also result in physical contamination. Equipment that is damaged, chipped, cracked and pitted may need to be replaced. Temporary repairs with string or tape are unacceptable. Joints should be made by welding or continuous bonding to reduce projections, edges and recesses to a minimum. Soft wood is unsuitable as it is porous, cracks and splinters and is difficult to clean.
Equipment exterior
The external surfaces of equipment must avoid ledges and dust-traps; for example, round legs are preferred to rectangular. It is important to avoid recessed corners, sharp edges, unfilled seams, uneven surfaces and hollows and projecting bolt heads, threads, screws or rivets that cannot be cleaned. Inaccessible spaces, pockets and crevices where product may accumulate must be absent.
Fixing and siting of equipment
Equipment must be sited so that there is sufficient space to facilitate access to all external and internal surfaces and, where required, to allow for rapid dismantling and reassembly. Machinery may be mounted on coved, raised platforms of concrete to facilitate cleaning. Where necessary, additional space may need to be provided. The bases and lower parts of machines, including motors and gears, may be difficult to clean and consequently collect dust and spillages which make ideal breeding sites for insects. Skirting or cover plates tend to trap dust.
Where practicable, and with due regard for safety, equipment can be mobile to facilitate its removal for cleaning. Gas and electricity supply pipes should be flexible and capable of being disconnected to facilitate cleaning. This will also enable adjacent wall surfaces and the floor to be effectively cleaned.
Drainage
All pipelines, vessels and equipment should be self-draining, not only to enable liquid deriving from foodstuffs to be discharged but also for cleaning and rinsing fluids. U-bends are fitted to sinks, toilets, etc. to stop odours and pests from the drains getting into food rooms.
Preparation surfaces
Preparation surfaces should be jointless, durable, impervious, the correct height and provide a firm base on which to work. If materials other than stainless steel are used, for example food-grade plastic, care should be taken to seal the edges and gaps which may harbour food scraps. They must be able to withstand frequent and repeated cleaning and disinfection without any premature deterioration, pitting or corrosion.
Chopping boards
A variety of non-absorbent materials for chopping boards is now available, including good quality polypropylene. However, some are unsatisfactory. A good board should be durable and not split or warp and it is advantageous if it can be passed through a dishwasher. Boards should be non-toxic, difficult to score and resist stains, chemicals and heat.
As yet no ideal replacement has been found for hardwood chopping blocks. However, these should be maintained in good condition and used solely for chopping or sawing raw meat. A common colour-coding system for chopping boards involves using:
Contamination
To avoid cross-contamination, it is important that the same equipment is not used for handling raw and high-risk products without being disinfected. To prevent the inadvertent use of equipment for high-risk and raw food the use of different colours and/or shapes is advantageous. Colour coding may be extended from knives and chopping boards to include washing facilities, trolleys, protective clothing, cloths and packaging material.
The cleaning of equipment
All operating instructions and procedures must be clearly communicated to the equipment users and cleaners. The equipment should be capable of being cleaned and, if necessary, disinfected safely, thoroughly and rapidly without the need for skilled fitters and specialised tools. If dismantling is necessary this must be achieved relatively easily, as should reassembly.
Sharp edges are a serious hazard for cleaners. A reluctance to clean equipment because of poor design will result in a lowering of hygienic standards. Hinges should be capable of being taken apart for cleaning. Angle-iron is difficult to clean and tubular construction is preferred. Open ends to tubular legs must be sealed.
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