Introduction

Packaging is the last step before food leaves the factory, and the last chance to stop a problem from reaching a customer. A piece of metal from a worn machine part, an underweight pack, a mislabelled allergen or a contaminated seal can lead to complaints, recalls, rejected export consignments and lasting damage to a brand.

Automated packaging machines reduce many risks by minimising handling and producing consistent packs. But machines also introduce their own risks: product can build up in hard-to-clean areas, parts can wear and break, and settings can drift. Keeping a packaging line food-safe requires good machine design, disciplined cleaning, effective inspection and clear records.

This article explains the basics of food safety on packaging lines, with practical advice for Sri Lankan food producers and exporters.

Food safety systems and standards

Most food businesses manage safety through systems such as:

• Good Manufacturing Practice (GMP): basic hygiene, facilities and procedures.
• HACCP (Hazard Analysis and Critical Control Points): identifying hazards and controlling them at critical points.
• ISO 22000: an international food safety management system standard.
• Customer standards: many retailers and export buyers require certification to recognised schemes.

In Sri Lanka, food businesses must also comply with the Food Act and its regulations. Exporters must meet destination market requirements.

Packaging lines play an important part in these systems, often hosting critical control points such as metal detection.

Hygienic machine design

When choosing machines, look for features that support hygiene:

• Stainless steel contact parts: resistant to corrosion and easy to clean.
• Smooth surfaces: with minimal crevices where product can collect.
• Easy access: doors, panels and quick-release parts for cleaning.
• Sloped surfaces: so product and water drain away.
• Sealed electrical components: suitable for the cleaning method used.
• Dust control: for powders, enclosed dosing and extraction points.
• Food-grade lubricants: where lubrication near product is needed.

Many machines in the range Dsigngo Group supplies use stainless steel construction for product contact areas and protective covers, and some feature waterproof and dustproof designs.

Cleaning routines

Effective cleaning depends on clear, documented routines:

Daily cleaning

• Remove product build-up from hoppers, chutes, weigh buckets and forming tubes.
• Clean sealing jaws to maintain seal quality.
• Wipe down surfaces and conveyors.
• Remove waste film and packaging.

Weekly cleaning

• Disassemble removable parts for thorough cleaning.
• Inspect for wear, damage and missing parts.
• Clean areas around and under machines.

Changeover cleaning

• Clean thoroughly between products, especially when changing allergens or colours.

Cleaning methods

• Dry cleaning: brushes, vacuums and air for dry products such as powders and snacks, avoiding moisture.
• Wet cleaning: washing and sanitising for wet or sticky products, where machines are designed for it.

Cleaning schedules should state who cleans what, how, with which materials and how often, with records signed after each clean.

Allergen control

Many products contain allergens such as nuts, milk, wheat, soy, sesame or shellfish. Allergen control on packaging lines includes:

• Scheduling allergen-free products before allergen-containing products where possible.
• Thorough cleaning and verification between allergen changeovers.
• Dedicated tools or equipment for high-risk allergens.
• Correct labelling: wrong labels or film are a common cause of allergen recalls.
• Checking that the correct film or pouch is loaded at every changeover.

Foreign body control

Foreign bodies such as metal, glass, plastic, stones and wood can enter products from raw materials, equipment or the environment. Controls include:

• Sieves and magnets in raw material handling.
• Glass and brittle plastic policies.
• Regular inspection of machines for loose or missing parts.
• Metal detection at the end of the packaging line.

Metal detection

How metal detectors work

Metal detectors create an electromagnetic field through an aperture. When a pack containing metal passes through, the field is disturbed and the detector signals a reject. Detectors can find ferrous metals, non-ferrous metals and stainless steel, though stainless steel is usually hardest to detect.

Key considerations

• Sensitivity: the smallest metal size the detector can reliably find, which depends on aperture size, product effect and settings.
• Product effect: wet, salty or conductive products can affect detection.
• Reject systems: automatic rejection into a locked bin, so contaminated packs cannot return to the line.
• Testing: regular tests with certified test pieces of ferrous, non-ferrous and stainless steel.
• Records: documentation of tests and actions taken.

The metal detector in the range Dsigngo Group supplies has a 400 mm belt, accommodates product widths up to 460 mm and heights of 80 to 120 mm, with belt speeds of 10 to 50 metres per minute.

Testing routine

A typical routine includes testing at start-up, at regular intervals during production, at changeovers and at the end of production. If a test fails, products since the last successful test should be held and rechecked.

Check weighing

Why it matters

Check weighers weigh every pack and reject those outside set limits. They help:

• Ensure packs meet declared weights and legal requirements.
• Reduce giveaway by providing feedback to filling machines.
• Detect missing items in multipacks.
• Provide production data.

Weight requirements

Packaged goods must meet legal metrology requirements on declared quantities. In Sri Lanka, the Measurement Units, Standards and Services Department oversees weights and measures. Many export markets apply average quantity systems with tolerances for individual packs.

Using check weigher data

Check weighers can store detection data, showing trends such as gradually increasing weights. Feeding this information back to the filling machine or operators helps keep weights on target and reduces giveaway.

Positioning inspection equipment

Where inspection equipment sits on the line affects how well it works:

• Metal detectors are usually placed after sealing, so the final pack is checked and no contamination can enter afterwards. For bulk products, an additional detector or magnet before packing can protect machines from damage.
• Check weighers are placed after sealing and before cartoning, so every pack is weighed individually.
• Combination units that integrate check weighing and metal detection save space and share a single reject system.
• **Reject systems** must suit the pack: air blasts for light packs, pushers for heavier packs and drop-flap conveyors for some products.

Leave enough conveyor length for products to be spaced correctly, and make sure rejects cannot fall back onto the line.

Seal integrity

A poor seal can allow contamination, leaks and spoilage. Checks include:

• Visual inspection of seals.
• Seal strength tests.
• Leak tests for vacuum and MAP packs.
• Monitoring sealing temperature, pressure and time.
• Keeping seal areas free of product.

Coding and labelling checks

Correct codes and labels are essential for traceability and safety:

• Check date and batch codes at start-up and regularly during production.
• Verify that the correct film, pouch or label is loaded.
• Keep samples of each batch.
• Use vision systems where appropriate to check codes automatically.

Hygiene by product type

Different products bring different hygiene challenges:

• Powders and spices: dust builds up in machines and the room, and can affect seals. Use dust extraction, enclosed dosing and dry cleaning.
• Snacks and fried foods: oil and crumbs collect on surfaces and conveyors. Clean regularly to prevent rancid build-up and pests.
• Sugar and confectionery: sticky residues form when sugar absorbs moisture. Control humidity and clean promptly.
• Meat, poultry and seafood: high microbiological risk. Use washdown-capable machines, chilled rooms and strict sanitation.
• Dairy and liquids: spills and residues support microbial growth. Clean and sanitise filling systems thoroughly.
• Pharmaceuticals: cross-contamination and documentation requirements are strict, with validated cleaning procedures.

Matching cleaning methods and frequencies to the product ensures that hygiene efforts are focused where they matter most.

Machine safety for operators

Food safety and operator safety go together. Packaging machines should include:

• Fixed and interlocked guards around moving parts, knives and sealing jaws.
• Emergency stop buttons within easy reach.
• Safety doors that stop the machine when opened.
• Fault alarms.
• Lockout and tagout procedures for cleaning and maintenance.

International standards such as ISO 12100 provide principles for machinery safety and risk assessment. Many machines in the range include safety doors, fault alarms and no-bag, no-fill, no-seal logic.

Operators must be trained not to bypass guards and to follow lockout procedures before cleaning or clearing jams.

Maintenance and food safety

Maintenance activities can introduce risks if not controlled:

• Account for all tools and parts after maintenance.
• Clean and sanitise equipment before restarting production.
• Use food-grade lubricants where required.
• Record maintenance work.
• Inspect wear parts regularly to prevent breakage.

Planned preventive maintenance reduces unexpected breakdowns and the risks that come with rushed repairs.

Packing room environment

The machine is only part of the picture. The packing room itself must support hygiene:

• Separation: keep packing areas separate from raw material handling and waste areas.
• Floors, walls and ceilings: smooth, cleanable surfaces without flaking paint or damage.
• Air: control dust and, where needed, temperature and humidity. Chilled products need cool packing rooms.
• Pest control: sealed doors, screens and a documented pest control programme.
• Lighting: sufficient for inspection, with shatterproof covers.
• Hand washing: stations at entry points, with clear rules.
• Clothing: clean uniforms, hair nets and, where required, gloves and masks.
• Packaging material storage: films, pouches and cartons stored off the floor, covered and away from contamination.

Packaging materials are often overlooked as a contamination route. Dusty or damaged film rolls and cartons stored near raw materials can introduce hazards directly into the pack.

Packaging materials and food contact

Materials that touch food must be suitable for food contact. Producers should:

• Obtain declarations of compliance or food contact suitability from material suppliers.
• Check that inks and adhesives used in printed packaging are suitable for food packaging.
• Store materials correctly to avoid contamination.
• Control changes in material suppliers or structures, as they may affect sealing and safety.

Export markets often have specific food contact material regulations, so exporters should confirm requirements with their buyers. Dsigngo Group’s packaging and print teams can help source and print materials suitable for food packaging.

Handling rejects and non-conforming product

Every inspection system needs a clear process for rejected packs:

• Rejects go to a locked or clearly marked bin.
• Only authorised staff open reject bins.
• Each reject is investigated: was it a genuine fault, and what caused it?
• Products held after a failed test are rechecked or disposed of according to procedure.
• Repeated rejects trigger corrective actions, such as machine adjustment or raw material checks.

A clear reject process prevents faulty packs from accidentally returning to the line and turns inspection data into improvement.

Validation and verification

Food safety systems distinguish between:

• Validation: proving that a control works, for example showing that the metal detector can find the specified test pieces in your product.
• Verification: checking that the control is working as intended during production, for example routine tests and record reviews.

Both are important. Validation is usually done when a machine is installed or a product changes, while verification is part of daily routines.

Records and traceability

Good records demonstrate that controls are working:

• Cleaning records.
• Metal detector test records.
• Check weigher reports.
• Changeover and allergen checks.
• Maintenance records.
• Batch and production records.

Records support audits by customers and authorities and make it easier to investigate any issue quickly. Keeping them simple, consistent and easy to find matters as much as keeping them at all. Many factories now use tablets or simple digital forms, which reduce paperwork, prevent missing entries and allow managers to review records in real time. Whatever the format, records should be completed at the time of the check, signed by the person responsible and reviewed regularly by a supervisor.

Food safety checklist for a new packaging machine

Before a new machine starts production, check:

• Product contact parts are suitable for food and have been cleaned and sanitised.
• Cleaning procedures for the machine are written and staff are trained.
• Guards, interlocks and emergency stops work correctly.
• Metal detector sensitivity has been validated with your product.
• Check weigher limits are set according to declared weights.
• Coding equipment prints correct, legible codes.
• Seal quality has been tested.
• Allergen changeover procedures are defined.
• Records and forms are ready for cleaning, testing and production.
• The food safety plan and HACCP documents have been updated to include the new machine.

Completing this checklist ensures the machine starts production safely and supports audits from the very first day.

Common mistakes

• Treating the metal detector as a substitute for good maintenance and raw material controls.
• Testing metal detectors only occasionally, or not at all.
• Allowing operators to bypass rejects or guards to keep production running.
• Cleaning without written procedures or records.
• Ignoring packaging material storage and handling.
• Not updating the food safety plan when machines or products change.

Training

Everyone working on the packaging line should understand:

• Basic hygiene and personal hygiene rules.
• Cleaning procedures for their machines.
• How to test metal detectors and check weighers.
• How to handle rejected packs.
• Allergen and changeover procedures.
• Machine safety and emergency stops.

Training should be refreshed regularly and documented, with extra sessions whenever new machines, products or procedures are introduced.

Illustrative example

The following example is illustrative and does not describe a real client.

A Sri Lankan snack producer preparing for its first export contract is told by the buyer that its packing line needs metal detection and check weighing, with documented procedures. The producer installs a check weigher and metal detector after its VFFS machine, sets up hourly test routines with certified test pieces, introduces cleaning schedules and allergen changeover checks, and trains operators. During the buyer’s audit, the documented controls and records help the producer pass, and the line’s consistent weights reduce giveaway at the same time.

How Dsigngo Group can help

Dsigngo Group supplies packaging machines, check weighers, metal detectors and conveyors, and can advise on hygienic layout, cleaning access and inspection points. Training for operators covers machine operation, cleaning and testing routines. Our design and print teams also produce clear, accurate labels and packaging that support traceability.

Frequently asked questions

Do all food producers need metal detectors?

Not all are legally required to, but metal detection is widely expected by retailers and export buyers, and it is a key control for many products. Assess the risk for your products and customers.

How often should metal detectors be tested?

Common practice is at start-up, at regular intervals during production, at changeovers and at the end of production, as defined in your food safety plan.

Can a check weigher reduce giveaway?

Yes. By monitoring weights and providing feedback, check weighers help keep filling machines on target.

What is the hardest metal to detect?

Stainless steel is usually the most difficult, so test with stainless steel test pieces.

Do you provide training on these routines?

Yes. Training covers operation, cleaning and testing.

Conclusion

Keeping packaging machines food-safe requires hygienic machine design, disciplined cleaning, allergen control, metal detection, check weighing, seal integrity checks, accurate coding, operator safety, maintenance control and good records. Together, these practices protect consumers, satisfy customers and auditors, and safeguard the brand.

Need help building a food-safe packaging line? Talk to Dsigngo Group.

Plan a Food-Safe Line

Sources

• ISO 22000 (food safety management) and HACCP principles (Codex Alimentarius).
• ISO 12100 (safety of machinery, risk assessment).
• Food Act, No. 26 of 1980 (Sri Lanka), and the Measurement Units, Standards and Services Department (weights and measures).
• Machine specifications from the machine catalogue supplied by Dsigngo Group.