Your Metal Detector Is Not a Foreign Body Programme: Why Food Factories Must Prevent, Not Just Detect

By Isaac Muthui, CEO, Tamalaki Business Network Ltd. Originally published at factoraerp.com.

A customer opens a packet and finds something that should not be there: a sliver of glass, a metal shard, a piece of blue plastic, a bristle, a plaster. From that moment, nothing else about your product matters to them. A taste problem loses you a sale. A hard object in food can break a tooth or cause a choking injury, and it ends up on social media within the hour.

Most food factories respond to that risk by buying a metal detector. That is a good start, but it is not a foreign body programme. A metal detector does not see glass, most plastics, wood or a plaster without a metal strip. It only catches what it was set up to catch, at the sensitivity someone last checked, on the line where it is installed. Everything else depends on what happens upstream.

This article is for production leads, QA officers, engineers and owners of small and mid-sized food and agro factories in Kenya and East Africa: millers, bakeries, dairies, juice and beverage makers, edible-oil processors, meat and poultry plants, and spice and snack packers. It gives you an eight-step foreign body control checklist for food factories that covers prevention, detection and what to do when something is found. It is operations guidance, not legal advice; confirm the specifics with KEBS, your county public health office and your customers' specifications.

What the standards and the law actually say

Codex, the international baseline. The General Principles of Food Hygiene (CXC 1-1969) deals with physical contamination in section 13.2.5. It says systems should be in place throughout the food chain to prevent contamination by extraneous materials, "especially any hard or sharp object(s), e.g. jewellery, glass, metal shards, bone(s), plastic, wood fragments, that could cause injury or present a choking hazard". It names prevention first ("maintenance and regular inspection of equipment"), then detection: "Detection or screening devices which are appropriately calibrated should be used where necessary (e.g. metal detectors, X-ray detectors)". It also asks for procedures for staff to follow "in the case of breakages (e.g. breakage of glass or plastic containers)".

Elsewhere Codex asks that premises and equipment be maintained to prevent contamination "from pests, metal shards, flaking plaster, debris, chemicals, wood, plastic, glass, paper" (11.1.1), that jewellery, watches, pins, false nails and eyelashes stay out of food handling areas where they pose a threat (section 12), and that plasters be of a contrasting colour and/or detectable by a metal or X-ray detector. Its HACCP annex is direct about being specific: hazards should be named, "e.g. metal fragments", with their source, "e.g. metal from broken blades after chopping", and it uses "a broken sieve" as an example of a deviation that monitoring must catch in time to isolate the affected product.

The East African hygiene code. EAS 39:2001, the hygiene code of practice for the food and drink manufacturing industry, has a clause on foreign matter (4.4). It makes the manufacturer responsible for precautions including "inspection of raw materials, keeping the production area free from extraneous material" and pest control (4.4.1). It says no glass containers other than finished-product packaging should be brought into the production area, including ingredients in glass, measuring jugs, analytical equipment and glass thermometers not encased in metal (4.4.4). Glass pipes, flow meters and glass equipment should be avoided, or routinely inspected for cracks and splinters under a documented procedure (4.4.5). A broken window must be reported at once to a designated person, who is responsible for identifying and destroying any food that could have been contaminated (4.4.6).

On detection, EAS 39 says a metal detector shall be installed, where appropriate, on all consumer lines, positioned to inspect the finished pack where technically possible, capable of detecting 2 mm ferrous and 2.5 mm non-ferrous test spheres unless the food makes that impossible, with sensitivity "checked at least once per 8-hour shift by a designated person" (4.4.7). Detectors should have an automatic reject into a locked, inaccessible container, with the reject mechanism checked at the same time, or automatic line stop where rejection is not feasible (4.6.5). It also covers the small things: plain wedding rings and sleeper earrings or studs only (5.6.1), coloured waterproof dressings with a metal strip (5.2.2.4), shatterproof material instead of glass where breakage could contaminate food (12.11.5), sieves and filters checked regularly (13.3.8), and records showing glass equipment has been inspected for cracks and splinters (clause 14).

Kenyan law. The Food, Drugs and Chemical Substances (Food Hygiene) Regulations, 1978, made under Cap. 254, require light bulbs, fixtures, skylights and other glass suspended over exposed food to be of the safety type or otherwise protected in case of breakage (regulation 9(4)). Equipment and utensils must be designed, built and used so as to prevent contamination of food by "lubricants, fuel, metal fragments" and other contaminants (10(3)). Extraneous material testing procedures are to be used where necessary to identify contamination, and contaminated food and ingredients rejected or adequately treated (14(f)). People working in direct contact with food must remove all jewellery and take other precautions to prevent contamination with foreign substances (Part B of regulation 15).

Put together, the floor rule is: know where hard objects can come from, keep them out, catch what gets through with checked equipment, and when something is found, act on the product and find the source.

Why a metal detector alone is not enough

Kenyan consumers are watching. On 9 October 2026, Kenyans Living It reported that a shopper said he found what appeared to be a plaster inside packaged beef bought from a Naivas branch in Utawala, Nairobi, and shared a video that was then reposted on Instagram. The site noted that the allegation had not been independently confirmed by authorities and that Naivas had not issued a statement at the time of publishing. Whatever the facts of that case, the lesson for any processor is the same: a foreign body complaint is now public within hours, and your answer will be judged on what records you can show.

The harder problem inside the factory is that most foreign bodies are not metal, and most metal is not caught at the end of the line by luck.

Illustration (not real customer data): a maize mill has a metal detector on its 2 kg packing line and a magnet at intake. Nobody has a schedule to clean or inspect the magnet, and the sieve screen is checked "when there is time". A torn sieve lets through hard fragments and a piece of a plastic scoop for a whole shift. The detector passes all of it, because it is not metal. The complaint comes three weeks later. With a sieve check recorded at the start and end of each shift, the mill could have held only the product made since the last good check, instead of guessing.

The 8-step foreign body control checklist

1. Map where foreign bodies can come from

• Walk the process from intake to dispatch and list, at each step, the physical hazards that could get into the product and where they would come from: stones and metal in raw grain, bone in meat, wire and nails from sacks and pallets, metal from worn blades and screens, glass from lights and jars, hard plastic from scoops, buckets and machine guards, wood from pallets, flaking paint, string, bristles, personal items.
• Be specific, as Codex asks: "metal fragments from the cutter blade", not "physical hazards".
• Rate each one by how likely it is and how much harm it could cause, and decide where it will be prevented, removed or detected. That map feeds your HACCP plan.

2. Control what comes in

• Set physical-quality limits in your raw material and packaging specifications: stones, metal, glass, extraneous matter.
• Inspect at intake. EAS 39 names "inspection of raw materials" first among foreign matter precautions. Our supplier intake checklist covers how to sample, record and reject.
• Remove outer packaging, strings and staples before materials enter production, and debox in a separate area where you can.
• Use removal steps that suit the material: cleaners, destoners, sieves and magnets for grain and powders, filters and strainers for liquids.

3. Run a glass and brittle plastics register

• List every item of glass, brittle plastic and ceramic in or above production and storage areas: light fittings, windows, gauges, sight glasses, clock faces, display screens, inspection hatches, lab equipment.
• Replace glass with shatterproof material where breakage could contaminate food (EAS 39, 12.11.5). Make sure lights over exposed food are the safety type or covered, as regulation 9(4) of the Food Hygiene Regulations requires.
• Keep glass containers out of production except finished-product packaging (EAS 39, 4.4.4).
• Inspect each item on the register on a fixed schedule, record its condition, and log any damage. EAS 39 expects records of glass equipment inspections.

4. Write and practise a breakage procedure

• Decide in advance what happens when glass or hard plastic breaks: stop the line, keep people and product in place, call the designated person, and cordon off the area.
• Hold all exposed product, ingredients and packaging within a defined radius, and anything that may have been affected since the last good check. EAS 39 (4.4.6) puts responsibility for identifying and destroying possibly contaminated food on the designated person.
• Clean up with dedicated, identifiable tools that never go back into general use, check footwear, and inspect and clean the area before production restarts.
• Account for the pieces: try to reassemble the broken item to see whether anything is missing. Record what broke, where, when, what was held and who released the line.

5. Look after the equipment, sieves and magnets

• Include blades, screens, mesh belts, scrapers and guards in preventive maintenance and inspect them for wear, cracks and missing pieces.
• Check sieves and filters for tears at the start and end of each shift, and record the result (EAS 39, 13.3.8). Clean and inspect magnets on a schedule and record what they collect: a sudden rise in metal on a magnet is an early warning of a wearing part.
• After any maintenance or repair, account for all tools and parts, remove swarf and debris, and inspect before handover. This fits naturally into line clearance.
• Use food-grade lubricants and keep fasteners, wire and cable ties out of open-product zones where you can.

6. Set people rules

• No jewellery except what your policy allows (EAS 39 permits plain wedding rings and sleeper earrings or studs; the Food Hygiene Regulations require food handlers to remove all jewellery), no watches, pins, false nails or false eyelashes.
• Coloured, detectable plasters, issued and logged by a supervisor. Hairnets and beard covers. Pens and tools that are metal-detectable or tethered where practical.
• No loose items in top pockets. Keep personal items in lockers outside production.
• Train new starters on why this matters, and check it at every entry to the floor.

7. Detect, reject and check the detector

• Install metal detection (or X-ray where the product or packaging needs it) on consumer lines, positioned to inspect the finished pack where technically possible (EAS 39, 4.4.7).
• Set sensitivity using certified ferrous, non-ferrous and stainless steel test pieces. EAS 39 gives 2 mm ferrous and 2.5 mm non-ferrous spheres as the target unless the product makes that impossible.
• Check the detector at start-up, at least once per 8-hour shift (EAS 39), after product changes and at the end of the run. Pass each test piece through in the product, record the result and the person, and confirm the reject works.
• Reject into a locked container that only QA can open (EAS 39, 4.6.5). Every reject is investigated, not tipped back onto the line.
• Treat the detector like any other measuring instrument and keep it in your calibration programme.

8. When something is found, act on the product, then find the source

• If a detector check fails, everything packed since the last good check goes on QA hold and is rechecked on a working detector. The same rule applies to a torn sieve or a missing piece of a blade or scoop.
• Examine every reject and every found object. Identify the material and compare it with your hazard map. A piece of blue plastic is easier to trace when you know where blue plastic is used in the plant.
• Log a non-conformance with the cause, corrective action, owner and closing date, and trend the results by line and object type.
• Handle customer complaints about foreign bodies quickly: ask for the object and the pack, check the batch records for that lot, and decide whether other lots may be affected. If product has already gone out, you need to find it fast, which is what a mock recall tests.

Habits that make foreign body control stick

• Prevention first, detection second. The detector is the last net, not the plan.
• Every piece accounted for. After a breakage or a repair, the line restarts only when the missing pieces are found or the product is held.
• The test piece goes through every shift. A detector nobody tests is an ornament.
• Rejects belong to QA. They are locked away and investigated, never put back.
• Hold back to the last good check. That rule decides how much product a failure costs you.

Foreign body control links to the rest of your quality system: pest control keeps insects and droppings out, cleaning and sanitation uses coloured tools so a lost bristle is visible, and the dairy milk intake checklist includes filtering milk at reception.

Where an ERP helps

A clipboard and a disciplined QA officer can run this checklist in one small plant. It gets harder with several lines and shifts, because the question after a failed detector check or a torn sieve is "which lots were packed since the last good check?"

FactoraERP tracks production batches and lots, stock status including QA holds, non-conformance records, stock adjustments with reason codes, and batch costs and yields. That means a failed detector check, a breakage or a foreign body complaint can be logged as a non-conformance with an owner, linked to the lots produced since the last good check, those lots can be put on hold until QA decides, and any product destroyed gets a reason code instead of disappearing into an unexplained stock count difference or a strange batch yield. See factoraerp.com.

Free download: eTIMS readiness checklist for factories

Quality records, stock records and invoices increasingly have to tell the same story for Kenyan manufacturers, and product destroyed after a foreign body incident touches all three. If you want a free eTIMS readiness checklist for factories, sign up for the FactoraERP Insights newsletter at https://isaacmuthui.substack.com. You will get practical operations notes for food and agro manufacturers. No spam; unsubscribe anytime. For background, see our guide to eTIMS for food and agro manufacturers.

FAQ

What should a foreign body control checklist for a food factory include?
A map of where physical hazards can enter the process, controls on incoming materials, a glass and brittle plastics register with scheduled inspections, a breakage procedure, maintenance and inspection of blades, sieves and magnets, people rules on jewellery and plasters, metal detection or X-ray with recorded checks and a locked reject, and a procedure for holding product and investigating when something is found.

What counts as a foreign body in food?
Any material that should not be in the product. Codex highlights hard or sharp objects that could cause injury or choking, such as jewellery, glass, metal shards, bone, plastic and wood fragments. Others include stones, string, paper, bristles, plasters and insects.

How often should a metal detector be checked?
EAS 39 says the sensitivity of the search head should be checked at least once per 8-hour shift by a designated person, and that the reject mechanism should be checked at the same time. Many plants also check at start-up, after product changes and at the end of the run.

What size should a metal detector detect?
EAS 39 says the detector should be capable of detecting 2 mm ferrous and 2.5 mm non-ferrous spheres unless the composition of the food makes this impossible. Your customers may set tighter limits, including for stainless steel.

Can a metal detector find glass or plastic?
No. Standard metal detectors do not detect glass, most plastics, wood or stones. X-ray inspection can detect some dense non-metal materials, but prevention through a glass register, a breakage procedure, sieves and equipment inspection remains the main control.

What should we do when glass breaks in production?
Stop the line, alert the designated person, hold exposed product and materials in the affected area, clean up with dedicated tools, account for the pieces, inspect before restarting, and record what happened. EAS 39 makes the designated person responsible for identifying and destroying any food that could have been contaminated.

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Isaac Muthui, CEO, Tamalaki Business Network Ltd