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

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 nondestructive detection of plastic in cheese. The electromagnetic (EM) patch antenna was designed and tested on five Cheddar cheese samples. Different sizes of plastic shards, 1 × 10 mm, 2 × 15 mm and 5 × 20 mm, were inserted into the samples, and measurements were taken with and without 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.