Food Engineering

Metal detector for discerning cheeses

April 1, 2011
Finding metal shards in cheese is one thing, but to do it in the presence of RFID tags is a real challenge. 

Specialty Blue Stilton cheese for Marks & Spencer passes through the Loma IQ3 metal detector. The detector can compensate for RFID tags as they pass through with the cheese. Source: Loma Systems.



Anthony Rowcliffe and Son, Ltd., cheese and specialty chilled food suppliers in the UK, supplies more than 1,000 different products, including its own Clemency Hall brand. Established 42 years ago in London, it offers same-day delivery to a variety of major supermarkets, delis, farm shops, butchers and upscale retailers such as Marks & Spencer-for which it provides 11 artisan cheeses. A combination of product integrity and a skilled staff has enabled the processor to achieve an annual turnover of more than $62 million.

Because Anthony Rowcliffe cheeses are individually hand-cut with wire, it was vital to have a metal detection system sensitive enough to identify the smallest metal contaminants. For this reason, the processor chose the IQ3 metal detector from Loma Systems. According to Jason Fisher, Anthony Rowcliffe head of operations, “We chose Loma Systems due to the whole package they offered: their knowledge, testing, product and price.”

Because the processor inspects products in trays, Loma specified a carriage track reject conveyor. It pushes reject trays down a separate conveyor system to ensure trays with contaminated product are kept separate from trays that have been inspected and found to be safe.

An industry-standard RFID tracking system requires products be tracked throughout the delivery process using identifiable metal tags to guarantee they arrive at specific locations. These metal RFID tags emit a signal, causing significant problems with some metal detectors and resulting in erroneous reports of metal contaminants, which can lead to false rejects. Loma’s variable frequency detector provided the solution to this problem. Because the machine is able to learn the signal emitted by the metal RFID tags, it can eliminate that signal and find contaminants that are actually in the products.

Because cheeses vary in moisture levels, salt content, density and size, signal levels at different frequencies vary greatly. The metal detector responds by automatically calibrating to the variety of cheeses on six cutting lines. With its product memory, it offers space for 200 different products and various signal levels between 31 and 882 kHz. The system’s automatic product-learn function ensures maximum sensitivity and accuracy without constant operator adjustment, making it possible to purchase only one machine that can handle six lines, thus avoiding the significant expense of purchasing multiple machines to cope with different products.

“The machine is excellent, and the variable frequency metal detector is invaluable,” Fisher states.

The metal detector comes standard with a tough search head rated to IP69K environmental protection. Operators find it easy to use, making it simpler to achieve maximum functionality.

“Operating the IQ3 metal detector on a daily basis has proved effortless,” says Kathy Pattenden, cutting room supervisor. “Having met our standards and adhered to our customers’ strict code of practice, the IQ3 metal detector has recognizably increased production efficiency.”