The biggest reason for buying packaged food by any consumer is ‘to have safe experience’ and if something comes which is not expected in a pack, increases the risk of consumer dissatisfaction, regulatory risk and in the end, it may damage the Brand Image, write eminent food safety specialists Anurag Mishra and Nuno F Soares.


The biggest reason for buying packaged food by any consumer is ‘to have safe experience’ and if something comes which is not expected in a pack, increases the risk of consumer dissatisfaction, regulatory risk and in the end, it may damage the Brand Image.

This may lead to the recall of the product and there are many examples available in the market. Food recalls can happen due to a variety of reasons, including the detection of foreign bodies in food products.

A total of 42 extraneous material recalls were issued in the U.S. in 2017, with metal and plastic contamination topping the list in this category. Each accounted for 12 and 11 total recalls, respectively. Almost all of these recalls were for various meat products, including one issued by poultry giant Perdue Foods.

More than 132,000 pounds of chicken nuggets were recalled last year after Tyson Foods found out they might have bits of hard plastic inside the nuggets. The USDA fielded complaints from naive nugget consumers who said they’d found strips of plastic up to 21 millimeters long inside their chicken. Tyson said it normally runs its chicken nuggets through a metal detector – who knew? – But that it didn’t catch the plastic pieces.

To avoid the above issues, manufacturers must deploy a suitable mechanism to detect and eliminate any possible foreign object in the finished goods. The selection of the mechanism must be based out of basis risk assessment and type of possible foreign object in the entire process.

Developments in modern technology have given some robust options to detect and eliminate foreign objects from the finished / semi-finished goods. In recent years these options seem to be very effective and used across the globe. Some of the available and effective options are:

Metal Detectors

Metal detectors are the most common and widely used method to detect foreign bodies in the food industry, but as the examples above demonstrated they cannot control a large spectrum of non-metal materials. When using this type of equipment, metal objects within a food product produce an unbalance in a balanced radio frequency or magnetic field. This typically generates an electrical signal alarming the equipment operator of the situation.

This method can detect very thin metallic objects such as metal rust and aluminum foil. However, certain factors can affect the sensitivity of metal detectors. The type, shape, and orientation of metal play a role in the effectiveness of detection. The equipment’s operating frequency also affects sensitivity. Other factors like the position of the metal in the aperture, type of product scanned, packaging material and environmental conditions such as vibration are often referred to as limitations to appropriate detection. Also, non-metallic contaminants, such as rubber and glass, are not detectable since they do not affect the magnetic field.

Metal detectors are easy to operate, typically have low maintenance costs and are cheaper than other alternatives like X-ray detection. This permits that they can be used almost anywhere in food industry facilities. A metal detector placed at the end of a production line, as the last barrier to guarantee that metal contaminants do not reach the consumer, is an obvious move. Nevertheless, food safety professionals should also consider that if that detector (or a second one) is placed at the beginning of the line it could have extra benefits:

Metal detectors

Metal detectors are the most widely used method to detect foreign bodies in the food industry, they can detect very thin metallic objects such as metal rust and aluminum foil.

X-ray

In the case of X-ray detection, the equipment produces an image of the food product that can be analyzed for contamination. Due to their high energy, X-rays can penetrate solid bodies. When going through the inspected product X-rays are more or less attenuated according to the density of matter present. If an object is present with a different density from that of the food product, it will be represented in the image (picture below, on the left and middle). The ability to spot different densities adds another feature to the equipment – the capacity to identify product defects like missing products in packages (picture below, on the right), products without filling or incorrect shape.

X-ray systems can detect several foreign bodies such as metals, non-ferrous metals, stones, glass, PVC plastic, bones, ceramic, Teflon plastic, sugar or flavor clumps. On the other hand, X-ray machines cannot detect some contaminants such as paper, cardboard, wood, hair, insects, thin glass, low-density plastics, and low-density stones. One interesting application is in the seafood industry to detect fish bones. There is equipment available based on this technology that prepared to detect needles (injected fish products) and calcified bones (according to the manufacturer “commonly achieves a 99% detection rate on calcified bones larger than 0,7 mm, in their smallest dimension, with false positives at or below 3%”).

Ultrasound

Ultrasound-based measurement is a promising method to detect foreign bodies because it has the ability to differentiate discontinuities in acoustic impedance between different regions within a given volume. These discontinuities would represent something that differs from its surroundings, such as a foreign body. This technique, although already used widely in the food industry in liquid level detection or suspended solids concentration (among other applications), is still not well known as an option for foreign body detention. Despite of that, for instance, a patent has been conceded in 2004 for an ultrasound transmitter that detects foreign material in heterogeneous process streams, like bones in a slurry of chicken meat. In the case where pulse and echo mode is used for measurements, the transducer transmits impulse ultrasound signals to the food product and the ultrasound velocity is calculated by the echo’s round-trip and time elapsed. Flaws and particles in the food product are detected by examining either the reflected signal amplitude or arrival time due to impedance discontinuity. Several advantages are linked with the ultrasound technique, since it has large applicability, most materials can be detected, and the equipment is low-cost and performs truly non-destructive tests.

By using the above options we may eliminate the foreign objects in their products so that consumer gets the best the experience and value for money.