Foreign Material Control: Validating the CCP and Defending the Reject Log

Metal detection finds ferrous, non-ferrous and stainless metal contaminants by electromagnetic field disturbance — fast, cheap, well-understood, but degraded by product effect (high-moisture, high-salt or warm product creates a signal that masks small contaminants). Detection sensitivity is typically 1.5–2.5 mm ferrous, 2.0–3.0 mm non-ferrous, 2.5–3.5 mm stainless on a wet product line; tighter on dry product. X-ray inspection finds metal, glass, stone, dense plastic and bone by density difference — slower, more capex, but unaffected by product effect and can find non-metal contaminants metal detection misses. The right CCP is usually metal detection on dry/packaged finished product, X-ray on wet/high-care or where bone or glass is the credible hazard. Some lines run both.

Validation is the science exercise that establishes the detector's reliable detection limit on a specific product on a specific line under worst-case conditions. The deliverable is a validation report with the test piece sizes (ferrous, non-ferrous, stainless), the product matrix tested, the detector settings, the conveyor speed, the position of the test piece in the product flow, the number of trials, and the false-reject rate. Validation runs at first introduction, at any change to the product formulation or packaging that affects detection, and on a defined frequency (annually is typical). A reject log without a current validation file underneath is a Major NC in BRCGS Issue 9 and FSSC 22000.

Verification is the routine confirmation, on every shift or every defined run, that the detector still detects the validated test piece sizes — typically at start-up, end-of-run, and at a defined interval (every 30–60 minutes is common, sometimes more frequent for high-risk products). Verification uses certified test pieces (NIST-traceable or supplier-certified spheres at the validated sizes). A failed verification implicates all product made since the last successful verification — that's the hold-and-test event most operators don't want to face. GFSI auditors will pull the verification log, count gaps, and look for failed verifications that didn't trigger a product hold.

Every reject must be logged, identified (visual inspection of the rejected unit to confirm whether it actually contains foreign material), and investigated if it does. Reject reconciliation — counting the rejected packs and matching against the reject counter — proves that the reject mechanism worked and that no contaminated pack continued down the line. Common 483 and audit findings: rejects not logged; rejects logged but not investigated; reconciliation absent (so a contaminated pack could have been recovered onto the line without record); positive finds (real metal in a rejected pack) not escalated into root-cause and CAPA.

Metal detection is the last line of defence — the upstream programme catches contamination earlier and cheaper. Magnets (rare-earth, typically 10,000+ gauss) on ingredient feed and finished-product flow remove ferrous before it reaches the detector. Sieves and screens (per ingredient particle size) catch oversize and foreign objects. Filters on liquid streams catch finer particulates. Each requires its own inspection cadence, integrity test, and replacement schedule — magnets cleaned and inspected per shift, sieve integrity verified per batch, filter integrity tested per defined cycle. A broken sieve or a magnet found loose during routine inspection implicates production back to the last documented intact check.

Glass and brittle plastic in the production environment are themselves a foreign-material risk — a broken light cover, a snapped polycarbonate guard, a fractured plastic scoop. The policy: register every piece of glass and brittle plastic in the production environment (often called the 'glass and brittle plastic register'), inspect each piece on a defined cadence, document breakages with implicated-product investigation, and replace breakable items with shatter-resistant equivalents where possible. Lights in production zones must be shatter-resistant or protected. A glass and brittle plastic register that hasn't been updated in 12 months is a frequent BRCGS minor.