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Minimising your contamination risks

12 April 2018

Martyn Cotterill discusses the rise in physical contamination in food, and suggests some practical ways to avoid these incidents. 

According to the Food Standard Agency’s Annual Reports of Incidents, the frequency of incidents of physical contamination from foreign bodies in food products has increased by 11.5% since 2013, including contamination from metal, plastic, glass and more.

While the risk of foreign bodies entering the food production process is a huge concern to food processors incidents of physical contamination in food has continued to rise steadily over the past nine years. For example, in 2016/17, the FSA investigated 2,265 incidents, 698 more than in 2013/14.

A robust Hazard Analysis and Critical Control Point Analysis (HACCP) system and thorough identification of critical control points (CCPs) at each stage of the production process will result in the risk of physical contamination being minimised in a variety of ways. For example, the introduction of magnetic separators and detection systems is virtually 100% effective when used correctly.

Physical contamination in the food industry usually refers to the addition of matter that is not directly of biological origin, such as metal plastic and glass. Such contamination can make its way into the food production process in a number of ways - via incoming raw materials; poorly maintained machinery; poorly maintained lighting; storage containers; human error; sabotage; and pests such as insects or rodents.

When it comes to metal contamination, a robust HACCP system can remove the contamination risk by incorporating some of the following measures:

Magnetic separators: Magnetic separators are used to remove ferrous and paramagnetic contamination. Commonly located at goods intake points - both before and after process machinery, or at the end of the process line to attract and remove ferrous contamination - they are suited to use where there is a large throughput of ingredients and where continuous production is critical.

Magnetic separators can be used in most manufacturing processes that involve powders, granulates, liquids, syrups or pastes. For removing primary contaminants or larger fragments such as nuts, bolts and nails; chute magnets, underflow magnets, bullet magnets and drum magnets can be used. They are usually fitted at the raw ingredient inlet or cleaning points on conveyor lines, vibratory feeders or in-line chute sections.

High-intensity magnetic separators can remove secondary contamination - down to minute particles. These include a range of grid magnets which are commonly fitted in-line at each stage of manufacture. House magnetic cartridges for use in pneumatic conveying lines or rotating grids to deal with products prone to ‘caking’ or ‘bridging’ are also available. There are also magnetic filters for liquid processing lines of all viscosities such as pastes, jams, juices and soups.

This method of removing foreign bodies is effective because each magnet only has to remove contaminants between it and the previous magnet. This allows for accurate identification and investigation of the cause of the contamination, and also highlights wear and deterioration in critical machinery. Magnetic separation systems also reduce product wastage as the magnets only remove contamination and do not eject a good product.

Magnetic design and performance has improved significantly over the past 20 years largely due to advances in magnetic materials. The best performing magnetic separators today incorporate rare earth magnetic material, also known as neodymium iron boron. Rare earth magnets are six times more powerful than traditionally used ceramic magnets and last indefinitely if cared for correctly.

Magnetic separators can remove sub-micron size particles. In addition to ferrous contamination they also remove stainless steel fragments. Most process lines are constructed from 316 grade stainless steel, which, in its natural state, is non-magnetic. When stainless steel becomes work-hardened – i.e. sawn, filed, or drilled – the fragmented pieces become magnetic and are removed from the process by the separator.

Although magnetic separators are relatively easy to access and clean, auto-cleaning units are available that are either controlled by PLC, main control room or machinery interface. This ensures regular in-process cleaning and logging of contamination levels.

Metal detectors: Metal detectors are integral to most HACCP plans. Typically, they are available in three configurations - conveyor fed systems for inspecting packaged or solid goods; gravity fed systems for inspecting free-flow materials such as powder and grain; and pipeline systems for liquid processing lines.

They are located at critical control points either to inspect incoming raw materials or to carry out the final check on the finished product. They consist of a search head, control panel, feed or transport system and reject mechanism. When using or selecting a metal detector it is important to assess use and the operating environment.

Metal detection systems are limited in that they can only detect particles from 0.5mm. It is, therefore, important that they are used in conjunction with a magnetic separator.

X-ray machines: X-ray systems are widely used to identify both ferrous and non-ferrous contaminants such as bone, glass and rubber. They are usually positioned at the end of the line as a final check.

Generally their performance is not affected by the same environmental factors that affect a metal detector. However, performance can be limited depending on the density of the product being inspected and items such as hair, thin glass, sub-micron metal particles and paper may go undetected. Different systems are available to suit packaged products, liquids or granules.

Vibratory sieves and screens: Vibratory sieves and screens are used at the start of the production process to verify the integrity of the ingredients, as well as to screen out contamination and oversized product. They are usually used for powders or granules and include one or more mesh screens. Ingredients can be gravity or pneumatically fed through the mesh.

Typically the mesh will remove any contaminants that measure 20 microns or more. To enhance the screening process, sieves can be fitted with a magnetic grid to remove ferrous contaminants from sub-micron size. Although very effective for the primary removal of contaminants, it is important that other methods are also employed to remove smaller particles, as well as matter created in process.

Despite the rise in incidents relating to physical contamination from foreign bodies in food, it is clear that with the correct prevention measures, the problem is avoidable. Food processors face immense scrutiny of their food safety standards, procedures and documentation, therefore it is absolutely imperative that each stage of production must be carefully assessed, and robust contamination prevention measures implemented. Advances in separation and detection technology ensure that the products and expertise necessary are now available to satisfy HACCP and legislative requirements. With commitment and investment in preventative solutions, it is possible for the food industry to reduce the number of incidents reported to the FSA, and ensuring that the food industry is able to honour its responsibility to consumers.

Martyn Cotterill is general sales manager for Foreign Body Removal at Eclipse Magnetics.

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