9 FOREIGN BODY CONTROLS – Food and Drink – Good Manufacturing Practice, 7th Edition



The protection of food against contamination with foreign bodies requires the use of hazard analysis critical control point (HACCP) to identify potential sources, with assessment of the types of foreign bodies associated with them and their degree of seriousness. It is important to determine if the foreign bodies are intrinsic, that is, derived from the product, for example fruit stones or fish bone, or extrinsic, that is, derived from the manufacturing environment, as the method of control will be different. Preventive methods are progressively applied at various points in the process flow, manufacturing, packaging, storage and distribution chain to minimise the risk of the presence of foreign bodies in the product. While the use of automatic inspection devices (metal detectors, X‐ray machines and vision systems) is recommended as appropriate, it must be remembered that none of these devices is capable of detecting all foreign body contaminants. The major emphasis must always be prevention. Foreign body control procedures are a key prerequisite to ensuring good manufacturing practice (GMP).

Sources of Foreign Bodies

9.1 It is convenient for practical control to divide sources of foreign bodies into those external to the manufacturing plant and those within the plant and premises. Incoming materials and their packaging originating from external sources then immediately become potential internal sources as they enter the manufacturing premises. The types of physical contamination that need to be considered in any food safety management system (FSMS) include glass, ceramic, plastic (hard and soft), wood, metal, paint, paper, cardboard, string, stones, pests and parts of pests, building materials and human‐origin foreign bodies.

9.2 External sources are frequently associated with characteristic contaminants such as pest predators on fruits and vegetables or parasites in animals. Similarly, particular methods of production, handling and packaging of incoming materials can give rise to characteristic foreign bodies, for example metal or plastic tags in carcass meat, stones in root crops or slivers of wood in herbs or tea packed in wooden containers. Incoming materials may arrive in primary and secondary packaging, made from materials such as metal, glass, plastic, ceramic, textile, paper or cardboard, and often on wooden pallets (tertiary packaging). Food safety risk assessment approaches, such as HACCP, should be used to assess each incoming material to identify the potential food safety hazards associated with it and its packaging and the appropriate action necessary to minimise their effects. Preventive measures should start at the source of supply and all raw material specifications should include considerations concerning foreign body control and limitation (see Chapter 3).

9.3 Internal sources of foreign bodies include the following:

  1. the building and installations (see Chapter 19);
  2. the plant and equipment (see Chapter 19);
  3. surface coatings and finishes (see Chapter 19);
  4. extraneous materials (packaging, cleaning materials and equipment, maintenance, engineering and production tools, spare parts, etc.) (see Chapters 19, 21 and 23);
  5. personnel (see Chapter 17);
  6. water supply (see Chapter 20);
  7. pest infestation (see Chapter 22); and
  8. recovered or reworked product (see Chapter 29).


9.4 Preventive concepts should be considered in:

  1. the design of the plant, equipment and buildings and their maintenance;
  2. the management of non‐conforming materials, recovered or reworked product;
  3. personnel training and management;
  4. housekeeping and general hygiene; and
  5. processing and packaging.

9.5 The examination and analysis of quality control data and consumer complaints records should be used to monitor the effectiveness of preventive action (see Chapter 27).

9.6 All plant, equipment and buildings should be inspected regularly to ensure that nothing has deteriorated, become dirty or become detached, or is likely to do so, and thereby create a risk of physical contamination of a product (see Chapter 19). Mobile equipment, for example forklifts and pallet trucks, should be used in designated areas, for example external and internal, and be specific to high‐ or low‐care areas in order to minimise the potential for cross‐contamination between the different areas established. The Food Standards Agency (FSA) publication E. coli O157 – Control of cross‐contamination: Guidance for food business operators and enforcement authorities revised guidance (December 2014) focuses on the controls that need to be implemented to prevent cross‐contamination.1 In this context cross‐contamination is the transfer of harmful bacteria either directly by food sources coming into contact or indirectly via contact with, for example, a work surface, utensil (e.g. knife) or hands. However, many preventive measures, such as training, sanitation procedures etc., implemented as part of a GMP programme are effective to address not only biological hazards, but also chemical and physical hazards.

9.7 Personnel should be instructed and encouraged to report immediately any incident of contamination/cross‐contamination or potential contamination of people, materials, packaging, equipment or the product whatever the potential hazard may be. Contamination with a physical item can also lead to biological contamination as the physical item acts as a vehicle to transfer bacteria, e.g. dust, human hair, cleaning cloth, glove and so forth.

9.8 A risk assessment must be undertaken to identify in which areas of the manufacturing site and at which stages of the manufacturing process personnel could present a contamination risk to the product. In areas where personnel are deemed of risk to the product they must be issued with suitable protective clothing which is designed to prevent physical contamination. Overalls should be knee length, have internal pockets only and non‐detachable fastenings. Loose items, unless required to carry out necessary work, should be banned in production areas. These include keys, coins, mobile phones and so on. In the event that loose items, for example keys, are required, a ‘sign out and sign back in’ control protocol should be in place that also identifies the corrective action required in the event an item is lost. All wristwatches, jewellery and bracelets should be prohibited. Plain wedding rings, or wedding wristbands, and secure ‘sleeper’ continuous loop earrings are possible exceptions if control procedures have been developed to manage these items effectively within the production area. These procedures should also cover rings and studs on exposed parts of the skin such as the face, ears or nose. Fingernails should be clean, short and unvarnished and false nails should not be worn. Adequate head, body and facial hair coverings must be provided and properly used, and should not be kept in place with the aid of hairpins or other fastenings, which could drop off. All head hair should be fully contained in the head covering; sleeves should come to the wrist to prevent the loss of arm hair and potential contamination of the product. Any hoods on personal items of clothing should be under the protective clothing at all times. Clothing with high collars, including those that have zips with metal ‘fobs’, which could dislodge and fall into the product, should be underneath the protective clothing at all times. Cuts and grazes on exposed skin must be covered by a waterproof dressing, which should be metal detectable, brightly coloured and easily seen against the background of the product. These should be subject to an issue procedure so they are effectively monitored. If disposable gloves are used, they should be checked regularly for any signs of damage or loose pieces that could fall off and contaminate the product. Gloves should be of a distinctive colour, be made of non‐allergenic material and must not shed fibres or particles. Gloves should also be subject to an issue control procedure to ensure they are adequately controlled to prevent physical loss and potential product contamination. Smoking, eating and drinking and the use of chewing gum should be restricted to designated areas, away from food production and storage areas, with adequate waste disposal and hand‐washing facilities being provided. Employee facilities such as lockers, changing areas, toilets, smoking areas and rest and food areas should be designed and constructed so that they can be maintained in a clean and hygienic manner. The use of clear lockers in food production entry areas aids inspection during hygiene audits. The training programme should explain the necessity for the restrictions and disciplines required in production and storage areas (see Chapter 17).

9.9 Good housekeeping (see Chapters 10, 19 and 21) requires clear instructions concerning the use and disposition of general materials to appear in master manufacturing instructions, plant operating instructions, work instructions, maintenance and service instructions and cleaning manuals. Good housekeeping includes the general tidiness and cleanliness of production and storage areas and also covers infestation control. Buildings must be protected against penetration by animals, birds, rodents and insects by adequate maintenance and proofing. Secondary defences such as poisoned baits, flying insect electrocutors, sticky boards and sprays should be used in appropriate areas to deal with animals and insects that penetrate the building, but should not be seen as the primary means of control. It is generally accepted practice to use non‐toxic rodent baits internally within a food manufacturing unit unless a pest infestation has been identified. Due care should be taken to ensure that the infestation controls in themselves do not prove a means of food contamination so they must be sited in suitable locations and securely fastened in place. Wood, glass and paint should, where practicable, be eliminated from open food areas and equipment.

Metal/Foreign Body Detection and Removal

9.10 Manufacturing processes should be designed to include process steps and/or procedures that will minimise the risk of foreign body contamination of the product. A formal risk assessment should be undertaken to determine whether foreign body detection equipment should be used within the manufacturing process to detect and/or remove foreign body contamination (see Chapter 3). This risk assessment should be undertaken by competent staff and be formally recorded. The frequency of subsequent review of the risk assessment should also be defined and complied with.

Containers may be kept inverted, where practicable, and should be cleaned by jets of filtered air or potable water before being filled. Typical detection and removal activities in a manufacturing process include visual inspection and sorting, air and liquid flotation, spinning, sieving, sifting, washing, filtration, magnets and magnetic grids and plates, metal detection, optical grader/sorter, and X‐ray detection and other forms of scanning.

Effective metal detectors should be employed on the production lines and plant at suitable points in the process. More elaborate methods, such as X‐ray examination or scanning equipment, exist and may be useful. In addition to the use of X‐ray examination and scanning equipment in factories, cargoes in containers or road vehicles may be X‐rayed at some ports during import/export. Where metal detectors are used within the manufacturing process, they should always include automatic rejection systems and closed containers to hold reject materials. The closed containers should be locked at all times unless being opened by a designated person during monitoring checks. Detection of foreign matter during metal detection may lead to material that can in some instances be reprocessed. This decision on whether to reject or reprocess must be undertaken by suitably competent people who understand the full implications of allowing the product to re‐enter the food supply chain. Those responsible for the decision should provide adequate instructions to staff and ensure that suitable monitoring activities are in place.

9.11 Methods of foreign body control should be defined in formal documented procedures. These should include instructions for undertaking the foreign body control procedure, or how to monitor the process step which is designed to eliminate or reduce foreign bodies to a safe level, and the actions to be taken in the event that monitoring identifies product, procedural and/or equipment failure. These foreign body control procedures should address the action to be taken to identify the product that may be affected, its location, the protocol for recall back to the production unit and the procedure for re‐inspection. All materials and/or products that have passed through the inspection method or detection equipment since the procedure was last known to be fully operational, that is, working correctly, should be re‐inspected. All foreign body detection and removal measures should be validated and re‐validated as required (see Chapter 3).

9.12 As previously identified, foreign body controls can include specific process steps such as sieving and filtering. An inventory of filters and sieves should be in place that details the unique equipment identification number, location, type, size in millimetres or microns, and the frequency of inspection. Magnets should also be included on the list if applicable. Sieves and filters should be risk assessed to ensure that they themselves do not present a foreign body risk. This assessment should include reviewing if the sieves are made of metal detectable material or are of a contrasting colour to the food. The review should also ensure the equipment is controlled by documented inspection procedures that identify the action to be taken if the sieves or filters are found to be broken or damaged, the maintenance procedures that have been established for the equipment and the level of training required for operators and those inspecting the equipment. If foreign bodies are found during sieve or filter inspection, then the nature and number of the foreign bodies and the corrective action that has been taken to rectify the problem should be recorded.

9.13 Consideration should also be given to:

  • the type of food being analysed, especially particle size and the packaging type (if detection is undertaken following packing). A risk assessment should be undertaken if metal detection is deemed appropriate as to the type of detector and its sensitivity to ferrous, non‐ferrous and stainless‐steel metal and the degree of sensitivity required. Product packed into metal, metal‐laminated or foil packaging should be considered in terms of the alternative metal controls that may be required within the manufacturing process;
  • the design of detector required. In‐line pipe metal detectors and conveyor‐type systems (suitable for large items), which have a belt stop system in place if metal is detected, should be fitted with an audible or visible alarm. Personnel working in the area need to be trained to understand the reasons why such an alarm should go off and the actions that need to be taken. For smaller items, a conveyor‐type metal detection system should be fitted with an automatic reject system that has been validated and is routinely monitored to ensure effectiveness. Rejected product should be transferred automatically into a secure, locked box, and there should be an alarm system in place should metal be detected. Personnel working in the area should be aware of the significance of items being rejected and be able to take appropriate corrective action;
  • the appropriate mesh/sieve size of filters or sieves;
  • the means of validation and the limit of detection of the equipment and whether this represents an acceptable food safety limit. This information will normally be held in the HACCP plan (see Chapter 3);
  • the location, that is, where the detector is to be positioned on the process line and whether this location could be bypassed by product in the event of a specific production activity;
  • the frequency of monitoring or inspection of the equipment/method and the verification activities employed to ensure such measures are effective;
  • the mechanism for rejection following failure (reject arm, locked box system, automatic line stop). The level of security at such devices must be determined as well as the authority for overriding fail‐safe mechanisms, if fitted. Changes to settings or the turning off of reject mechanisms should only be authorised by designated personnel and such decisions must be recorded. Rejection procedures should be formalised, and only authorised personnel should be able to access the locked box or product that has been rejected by the foreign body detector;
  • the method of detector calibration (either manual or automatic) as well as servicing and maintenance requirements;
  • developing documented procedures that define equipment start‐up and operating instructions, and the routine monitoring, testing and calibration of detector equipment, including metal detectors;
  • the reporting of incidents and the implementation of effective, timely corrective action. The incident and the corrective action taken should be recorded in the event of a failure of the foreign body detector. This will include stopping the process, and the subsequent isolation, quarantine and re‐inspection of all items produced since the last acceptable test result.

All materials and/or products that have passed through the inspection method or detection equipment since the procedure was last known to be fully operational, that is, working correctly, should be re‐inspected. Material detected or removed by the equipment in the case of filters or sieves should be inspected. It should be retained as evidence or, if more appropriate, digital photographs should be taken, so that a full examination can be undertaken and appropriate preventive and/or corrective action adopted.

9.14 Where recycled glass containers are used, provision should be made for the inclusion of automated vision inspection systems to inspect the containers for damage and contamination, including cleaning residues.

9.15 The delivery or storage of materials may involve intermediate packaging to prevent damage. This will subsequently have to be removed. This should be designed to minimise the risk of contaminating the product during its removal. For example, pastry materials are sometimes filled hot into boxes lined with a loose plastic film bag. Creases in the bag become surrounded by pastry that traps the film firmly when it cools. This type of packaging should be avoided, where complete removal cannot be assured. In other cases, if used, internal liners or the film should be highly and contrastingly coloured. Packaging should be clean prior to removal of contents. Materials packed in sealed (seamed) metal containers have the obvious hazard of metal swarf being created when they are opened. Cartons should be staple free; paper sacks should be easy‐open, string free and not cut with blunt knives. Plant operatives should be trained to open packaging carefully to avoid product contamination, for example by the misuse of case‐opening knives. The use of a deboxing/debagging area with the transfer of ingredients into internal packaging/containers before being transferred to the processing area is recommended to minimise the potential for foreign body contamination. Knife control procedures should be implemented (see 19.43). Other sources of metal to be considered are cutting blades on equipment, chain mail gloves, aprons and arm protection, needles, nuts and bolts, and wires. Control procedures should be in place to monitor metal items in the production area that can become loose and/or damaged, and appropriate corrective action procedures should be in place in the event of such loss or damage.

9.16 All final packaging used by the manufacturer for products should be examined to ensure compliance with the specification against which it is purchased. In addition to this examination, the detailed appraisal of a manufacturing‐scale sample, such as a pallet load on a production line, is strongly recommended. This allows the performance of a high‐risk packaging material such as glass to be better assessed before acceptance of the bulk delivery for use. In order to implement this protocol, effective lot traceability of packaging material is required. Packaging materials should be brought to their points of usage in minimal quantities (see Chapter 14).

9.17 Brittle material control procedures to control glass, hard plastic or ceramics should be developed (see Chapter 19, 19.36–19.42 check).

9.18 When product containers are cleaned before use, filtered air or potable water should be used. The effectiveness of these cleaning procedures should be routinely monitored and verified, and appropriate action taken based on the results. Where equipment is used to transport, store or hold the product, then the cleaning of these items should be monitored to ensure suitable efficacy. A reject system should be in place to prevent the use of dirty containers that come into direct contact with the product and therefore could present a foreign body risk.

9.19 Where contamination occurs intermittently or infrequently, either systematically or randomly, no practical sampling scheme is likely to detect the fault. Analysis of data produced as a result of monitoring, verification and consumer complaints will indicate any pattern of foreign body contamination and any changes can be subjected to trend analysis that may show the significance or otherwise of the changes (see Chapter 27).

9.20 A risk assessment should be undertaken of offices that open directly into production/storage areas or workstations within production areas. Office equipment, chairs, tables and desks should not be made of wood and should be constructed so that they are easy to clean. Pencils should not be used. Personal items should be kept to a minimum, and no eating or drinking should take place unless water is consumed following an appropriate risk assessment having been made. Stationery items such as paper clips, staples, pens and so on all present a potential foreign body hazard and should be adequately controlled. Quality control workstations should also be risk assessed for the potential for equipment to become lost or damaged and then present a foreign body risk to the product.

9.21 Regrettably, contamination of products by foreign bodies may on occasion be caused deliberately:

  1. during production by an unstable, malicious or disgruntled person;
  2. somewhere in the distribution/retailing chain, by an individual seeking to harm or blackmail a company; or
  3. after purchase, by an individual seeking financial gain or publicity.

While it is difficult to establish complete safeguards against case (a), it is less likely where good industrial relations are fostered. In addition, management should carefully weigh the dangers of allowing particular persons under notice of dismissal or redundancy to work out the period of their notice (see Chapters 5 to 7). Case (b) hazards should be minimised wherever practicable by the use of tamper‐evident packaging and tamper‐evident seals. As regards (c), careful study of the relevant facts and laboratory examination of the foreign body should be carried out, the results of which may sometimes demonstrate the probability (or even certainty) that it had been introduced subsequent to the pack having been opened.