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From: Food Quality & Safety magazine, August/September 2012

Strategies for Maintaining Product Purity During Food Processing

by Jeff Kaveney

Eriez® Metal Detector Conveyor System inspecting pizza

The food industry faces unique challenges as it tries to protect product purity while handling materials in the most efficient, economical, and sanitary way during processing. With the food industry’s high purity standards, even the most minute particles must be completely extracted.

When materials are intended for human consumption, particles that would be allowable in end products for other uses can create a potential crisis if they are not detected and removed. To maintain product purity, effective strategies often include a combination of magnetic separation, metal detection, and/or X-ray inspection equipment.

When used properly, magnetic separation equipment can virtually eliminate ferrous metal contamination from dry and liquid products. In many cases, high-intensity permanent or electromagnets can remove 300 series stainless steel that has been abraded from equipment.

Magnetic separators are available in an extensive variety of designs to meet manufacturers’ precise needs. For optimum extraction results, the right equipment must be chosen for the job. Selecting the proper magnetic separator requires a thorough understanding of magnetic properties, the process application, and environmental elements that exist in the installation. Equipment should be chosen based on the materials being processed and the many application considerations.

Eriez® E-Z Tec® DSP Metal Detector
Eriez® E-Z Tec® DSP Metal Detector

Metal Detection

Investing in a metal detector can safeguard against machinery damage, production downtime, and loss of product quality. In many operations, metal detectors are the last line of defense for contaminant detection.

With today’s advanced metal detection technology, it is possible to consider incorporating detection at several stages in a process, not just at the output. Metal detectors should be used anywhere and everywhere there is the chance that metal particles may contaminate a product stream.

Detection is especially critical in the food industry, as well as any other application where the product is one that may be consumed by humans or animals. When product purity is a safety consideration or when contaminant particles may be of a size and type that could damage downstream processing equipment, detection takes on a more crucial role.

Metal detection at the input point of a process is appropriate—and vital if the raw materials could be contaminated. Even if contamination would not damage downstream process equipment, contaminated materials result in a product that would eventually be rejected by detectors on the output side. Whole batches of product, along with the money spent to produce it, can be wasted as a result of undetected contaminated materials.

Detection and rejection of contaminated raw materials come at a small cost when compared with rejection of finished product. This principle applies equally to intermediate steps in the processing of a product—if the output of an expensive process step is susceptible to rejection for metal contamination, metal detectors should monitor both the input and the output of that step.

In situations where it is not an option to stop the process to deal with contaminated product, a state-of-the-art metal detector is equipped with an automatic reject device. The detector can also keep detailed logs for accurate and comprehensive record keeping.

Eriez® Standard Metal Detector Conveyor System
Eriez® Standard Metal Detector Conveyor System

X-Ray Inspection

X-ray technology complements metal detection and plays an important role in detecting metal contaminants and other foreign objects. This type of equipment is most often used in the food, pharmaceutical, chemical, packaging, and other sanitation-related industries.

For manufacturers utilizing foil packaging, metal detectors are not the ideal inspection solution. X-ray systems offer an effective method for inspecting these types of finished products. X-ray inspection systems can also ensure product and package integrity by reliably scanning for missing or broken products or pills, detecting metal contaminants and packing voids, confirming fill levels, and controlling product and package mass.

Many factors that have traditionally negatively affected metal detectors, such as ground loops, conductive products, and ambient noise, do not affect X-ray machines.

The U.S. government issues strict guidelines for the operation of X-ray machinery in an industrial environment. Manufacturers are required to certify that their products meet FDA guidelines for the radiation safety performance standard for X-ray systems. When used properly, X-ray inspection systems will not degrade or irradiate products.

Metal detection technology has become vital to ensuring product quality in the food industry as highly sensitive, compact metal detector systems meet strict FDA standards and accommodate space-restricted areas.

Evolution of Inspection

Recent advances in magnetic separation technology have resulted in a variety of separators specifically developed for the treatment of fine, high-purity materials. The technology necessary to produce the highest quality, purest, and safest products for the food industry is improving every day.

Metal detection technology has advanced tremendously and has become vital to ensuring product quality in a variety of diverse industries worldwide—particularly in the food industry. Highly sensitive, compact metal detector systems meet strict FDA standards and accommodate space-restricted areas. There are systems tailored to the specific needs of practically any industry.

Contemporary metal detectors have inherited all the reliability, ruggedness, accuracy, and flexibility of digital electronics and computer technology. They can solve many formerly intractable problems, such as the detection and rejection of very fine ferrous and nonferrous materials in free-falling products, interference from nearby moving metallic equipment, and metal identification.

Eriez® E-Z Tec® XR-Bulk X-Ray Inspection System
Eriez® E-Z Tec® XR-Bulk X-Ray Inspection System
Pistachio X-Ray with Stone Detected

Modern metal detectors operate consistently for long periods of time, often in adverse environments, with little attention or maintenance. They can be configured for minimal intrusion with established process flow. The power required to operate both the detector and the reject device—if any—is minimal, even if a special conveyor is needed to pass the product through the metal detector. Metal detectors can routinely be configured to reject the contaminated product automatically, even if the possible rejection point is some distance from the detector. The detector can also keep detailed records of detected metal, including estimated size and type. Therefore, suspicious product can be isolated after the fact, based on time of processing.

The latest generation of X-ray inspection systems uses advanced linear array technology for superior sensitivity, speed, and sophistication, for both loose product flow and packaged inspection. These cutting edge X-ray systems provide immediate and automatic analysis, detection, and rejection of process and packaged foods, pharmaceuticals, and other goods that require the highest levels of product integrity.

Products are inspected using a high-performance computer image analysis system, which enables the detection of small statistical variations in the product that signal contamination or deviation from accepted specifications.

The main safety features of a cabinet X-ray include a light tower, emergency stop buttons, key lock, curtains, and tunnel covers with dual interlocks. The FDA requires these features on such machines.

Eriez® Plate Magnet
Eriez® Plate Magnet
Eriez® E-Z Tec® XR-Bulk X-Ray Inspection System
Eriez® Grate Magnet
Eriez® E-Z Tec® XR-Bulk X-Ray Inspection System
Eriez® Super B Ferrous Trap

Examine All Options

With so many advances in the area of magnetic separators, metal detectors, and X-ray machines, food manufacturers have an array of equipment options to help them reliably detect contamination and protect and maintain the purity of their products. Before the selection process can begin, it’s imperative to understand options and needs. Selecting the proper equipment is crucial to success.

A good starting point in selecting magnetic separators, metal detection, and X-ray inspection equipment is a complete plant survey and appraisal of plant operations. This survey, which should be performed by an experienced professional, is a great way to find out if current installations are providing the best possible protection. It is also an opportunity to learn what the equipment can and cannot do, and to discover the advantages of the newer technologies.

For maximum extraction results in magnetic separation, the right equipment, at the right strength, must be chosen for a particular application. Equipment should be chosen based on the types of material being processed, how the material is introduced to the magnetic separator (i.e., flood vs. metered feed), and other environmental factors.

Proper metal detector selection depends at least as much on the product and the process as on the metal to be detected. Sometimes the existing form of the product—or, more frequently the process—leads to a very difficult, expensive, or “impossible” metal detection problem. Consult with an expert to select the most effective metal detector. Many suppliers offer free plant audits to help users identify the appropriate metal detector for their particular application and space constraints.

X-ray systems are being used everywhere, from the smallest operations to the largest corporations. Some major retailers are now encouraging or even requiring their suppliers to utilize X-ray systems. To determine whether or not an X-ray system is right for your application, you must first understand the technology’s capabilities and limitations.

To decide if X-ray technology is right for you, consider product testing, which some manufacturers offer at no charge. Testing is the best way to adequately evaluate all the variables involved in your particular application. By supplying the X-ray manufacturer with samples of your products, you can find out what the machines can actually do for you. Most importantly, find a manufacturer you trust. Your manufacturer should work with you to find a unit that meets your needs effectively, without the extra expense of unnecessary features.

The manufacturer you choose should help determine what products are right for you, now and in the future. The company should also keep you up to date on emerging technologies and support you with continued customer service.


Jeff Kaveney is manager of product marketing and administration for Eriez, based in Erie, Pa.

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