Metal poses a potential risk in a variety of food products, but this threat can be significantly mitigated by employing suitable equipment and implementing an effective program to manage stray metal particles.
While conscientious food producers have long recognized the importance of controlling metal contamination in food, the adoption of quality control inspections has now reached unprecedented levels. The growing awareness of potential physical metal hazards in food products has spurred an increased demand for more advanced detection strategies, a demand reinforced by regulatory agencies.
Metal contamination typically arises from four sources: raw materials (such as metal tags or screen wire in powder), personal effects (like paper clips or jewelry), maintenance activities (including welding swarf or shavings), and in-plant processing (resulting from small parts or shavings from mills, blenders, slicers, etc.).
A metal detection loop comprises three crucial components: product transfer, the metal detection system, and the reject system. Modern metal detection systems must meet the minimum requirement of rejecting contaminated products from the production line while accurately confirming the rejection. Achieving this relies on precise timing and speed control mechanisms, particularly on high-speed production lines.
To maximize the effectiveness of metal detection, the detector should be positioned as close as possible to the finished product fill station, or all sealed packages should pass through a detector. The integration of inverter controls into the main power supply of the metal detector ensures diligence, enabling the detector to automatically determine reject timing, even when adjusting line speeds remotely or manually.
However, relying solely on a metal detector is insufficient to ensure the detection and removal of all metal. For optimal results, the metal detector should be part of a product-specific quality assurance program. This program requires constant calibrated checks by qualified quality control staff, including regular sensitivity tests scheduled by the metal detector.
The fundamental principle of metal detection revolves around the transmission and reception of electrical impulses, similar to radio waves. All metals possess characteristics that alter the transmitted signal due to their conductivity and magnetic properties.
Quality assurance involves sensitivity checks using samples of various magnetic, non-magnetic, and stainless metals. The testing program undergoes verification, with the metal detector confirming that the test samples match the correct metal type, dimensions, and electromagnetic conductivity required for the specific product under inspection.
Metal Detection Best Practices
