Source: U.S. Air Force photo/Airman 1st Class Larissa GreatwoodSource: U.S. Air Force photo/Airman 1st Class Larissa GreatwoodIdentifying and sorting out defective packaged food products is critical for protecting the consumer as well as the integrity of your brand. Both metal detectors and X-ray inspection are used to inspect packaged food products and detect the presence of foreign objects, but which technology is ideally suited for your intended application?

A Quick Breakdown

The first line of defense for the consumer and integrity of the brand is to identify the presence of foreign contaminants in food products well before they leave the processing plant. Raw foods and ingredients originate in a natural environment where foreign objects may end up commingled and transported into the processing plant. Manufacturing processing and handling systems are also a source of possible contamination as well as the possibility that bone fragments, pits or shells removed during processing could find their way into the final product.

Inspection equipment needs to be selected in a manner that it is the most suitable for the intended application. It needs to be deployed in such a manner that it exhibits a high level of sensitivity, is easy-to-use, fully automatic, robust, reliable and cost-effective.

Just as important as it is to detect the presence of foreign material, false positives also need to be eliminated. Otherwise, your facility will suffer from loss of product and reduced productivity. To correctly implement an inspection system, facilities should follow HACCP (Hazard Analysis and Critical Control Points) methodologies by identifying which contaminants are most likely to occur and identify the ideal critical control point for a given inspection system.

Metal Detectors

Metal detectors provide a reliable and cost-effective means of detecting even the smallest metal contaminants found in food production anywhere in the process. They excel when inspecting bulk conveyed materials, piped product or gravity flow applications. They are also better suited to handle smaller packages.

The sensitivity of metal detectors is a function of the aperture height through which the product passes as well as the ratio between the aperture size and product size. Moisture content negatively impacts the sensitivity of a metal detector as well as salt content. They are best suited for dry, free-flowing bulk materials through apertures up to 10 inches in height. Larger apertures are possible at the expense of sensitivity. Some models are specifically designed to detect ferrous objects within foil packaging. The added value of implementing metal detectors at a strategic location in a food processing facility cannot be undermined.

X-Ray Inspection Systems

X-ray inspection systems are capable of detecting a wider range of contaminants and are even used to detect foreign glass objects within glass containers. They produce grayscale images that correspond to density gradients. X-ray systems are also used to inspect a product by its shape or the number of objects contained, or may be used to estimate weight.

The scanning rate of X-ray systems is one limitation as they are used to produce and analyze images. They are also more susceptible to operating conditions and exhibit a decreased life expectancy when exposed to harsh environments. They are best suited for controlled environments where product travels at a constant speed. They also may possess a limited speed range.

The sensitivity of an X-ray inspection system is also dependent on product size, although they are still preferred when dealing with larger products. They are also more commonly used when dealing with metalized film packaging.


The performance of the inspection system is determined by detectable contaminant types, minimum contaminant size and probability of detection. Ideally, the goal is to find problems early in the process in order to avoid loss of product. Selecting the ideal detection point and the corresponding system that is best suited varies throughout the process. While raw material feeds and gravity flows are best handled by a metal detector, there has been a growing trend for X-ray inspection systems closer to the end of the process cycle, when the risk of contamination is high for non-metallic materials or when dealing with larger packages. Packaging material trends have also increased the role of X-ray inspection systems in the food and beverage industry.


What Food Processors Should Know: Metal Detection vs. X-ray Inspection

Guide to Metal Detection