Real-time detection of plastic shards in cheese using microwave sensing technique

Abstract: Recently, Lidl had to set a recall action due to dangerous pieces of plastic found in the cheese products. The plastic shards, if swallowed, can cut the oral cavity or obstruct breathing. Current inspection techniques in the cheese industry are for the detection of metals using X-ray that does not offer a complete solution as many foreign bodies can go undetected. This paper demonstrates the use of a portable real-time microwave sensing technique for the non-destructive detection of plastic in cheese. The electromagnetic (EM) patch antenna was designed and tested on five Cheddar cheese samples. Different sizes of plastic shards, 1x10mm; 2x15mm and 5x20mm, were inserted into the samples and measurements were taken with and without the foreign objects. The initial results demonstrated that the patch antenna at 4GHz was able to detect and classify Polyvinyl Chloride (PVC) shards with an R2 = 0.95. The initial results are promising and further investigation will be undertaken to detect different shapes and types of foreign objects in food products.