Foreign bodies entering the food processing chain and passing undetected through to consumers is clearly a major concern for the food industry. Examples of foreign bodies include metal, wood, ceramic, glass, rubbers and plastics and, due to the varying nature of these, often different detection techniques are necessary to target each. One of the most difficult categories to detect is rubbers and plastics (grouped together as polymers) due mainly to their comparative low density (similar to many foods) and non-conductive/non-magnetic nature. Polymers are used extensively throughout food production lines and hence being able to detect foreign body fragments of them is an important consideration.

Early revisions of ‘detectable’ polymers relied purely on visual detection to prevent foreign body contamination. Polymer products were (and commonly still are) coloured blue to render them easier to detect on a food line due to the lack of naturally occurring blue in food products. 

More recent enhancements lead to the introduction of metal detectable polymers, detectable by conventional metal detection systems. This remains probably the most common format of detectable polymer.