A great deal can go wrong when processing food products for mass consumption. The smallest oversight in a processing plant can be magnified many times over as a potentially tainted product is shipped out to be eaten by hundreds of thousands of customers. As a result, hygiene and sanitation standards for food plants are some of the most rigorous in the world.

The gradual process of automation in the food production industry holds great potential for improved food safety as there is less chance for human error. However, automating production lines with industrial conveyor belts and elevators is hardly the perfect system, and instances of accidental food contamination are still relatively commonplace.

A recent example is a US Food and Drug Administration (FDA) warning to global food giant Kellogg concerning the company’s cookie plant in Augusta, Georgia. Although the Keebler and Famous Amos cookie brands produced at the plant were found to be uncontaminated, traces of listeria monocytogenes (the bacteria that causes listeriosis, a potentially fatal form of food poisoning) were found on and around the production line’s conveyor belts.

“Conveyor belts for the food industry are often created using tungsten inert gas (TIG) welding.”

An extract of the FDA’s letter reprinted in the Los Angeles Times reads: "We note that although your finished product cookies may not support the growth of L monocytogenes, the positive environmental swabs are indicators of insanitary conditions in your facility and demonstrate a failure of cleaning and sanitation operations that may allow for contamination of foods with filth or pathogens."

The warning, presented to Kellogg on 7 June this year, demonstrates that exacting standards have to be upheld in food plants to ensure that automated processes meet the requirements set by national bodies.

Here we round up some of the technologies that are helping to make food conveyor belts part of the solution rather than part of the problem.

Sanitation and cleaning: conveyors for the food industry

Although conveyor belts are commonly used in almost all industries, those used in the food industry must adhere to a number of requirements unique to this application. In terms of basic construction materials, conveyor belts for the food industry are often created using tungsten inert gas (TIG) welding, a complex process that takes longer than standard welding, but ensures greater strength and protection from contamination.

Food-contact conveyor belts must also be designed with hygiene in mind. US conveyor automation specialist Dorner’s AquaPruf 7400 series has several design features intended to maximise the belt’s sanitary qualities. The conveyor’s TIG welded frame features no horizontal surfaces so that water or bacteria have no place to settle and proliferate. Its stainless steel rounded cross members minimise internal surfaces that could prove difficult to clean effectively, and wear strips are removable without tools so that every inch of the conveyor’s frame can be accessed during cleaning. On top of this, the company claims the 7400 series belts can be fully disassembled in less than two minutes without tools, making for a quicker cleaning process.

“Key to food hygiene on a conveyor belt is maintaining the surface integrity of the top layer of the belt.”

These design concepts led to Dorner’s 7400 conveyors being recertified in December 2010 by the US Department of Agriculture as the only modular conveyor on its list of certified equipment for the hygiene-intensive meat and poultry industry. "Sanitation is such an important topic to food processors, and will remain so for the foreseeable future," said Dorner’s marketing director John Kuhnz on the 7400’s recertification. "When it comes to manufacturing food and moving it throughout a plant, you can’t do better than our Ultimate series – which represents the highest level of sanitation in a modular belt conveyor on the market today."

Ideal belt properties

As well as effective design and construction of a food conveyor’s frame, the right materials and techniques have to be utilised for the belt itself to be appropriate for HACCP (hazard analysis and critical control points) applications. Key to sustained food hygiene on a conveyor belt is maintaining the surface integrity of the top layer of the belt. Different materials are used for different food industry applications to make sure that cuts and damage to the belt – which can harbour pathogens – are limited.

German conveyor belt manufacturer Forbo Siegling employs different synthetic HACCP belt materials for different sectors of the food processing industry. Different synthetic materials like polypropylene, polyethylene and polyacetal have various properties that increase or reduce their effectiveness for sectors like meat and poultry, baked goods and dairy products.

These materials can also be made incision-resistant so that portions can be cut on the production line without compromising the surface, as well as dehesive so that stickier foods slide off low-friction surfaces for increased efficiency and easier cleaning. A common problem for food plants is that, over time, conveyor belts suffer wear and tear (hydrolytic decomposition) from regular cleaning with hot water and disinfectants. According to Forbo Siegling, its range of synthetic belt materials are far more resistant to this cumulative damage, meaning that belts can go through more cleaning cycles before starting to show the strain.

“The system identifies objects of the incorrect colour and removes them with a precise air knife.”

Smart technologies

To further combat contamination of food production lines by pathogens and foreign objects, the industry is beginning to see new, innovative applications of camera and sensor-based technologies to monitor food conveyor systems.

For example, camera technology has now advanced to meet the scope and precision required to have an impact on the industrial food production process. At the International Food Machinery and Technology Exhibition held in Tokyo, Japan on 7-10 June 2011, Hitachi Zosen showed off a new debris removal system designed to remove foreign objects from production lines.

The system works using a set of cameras that monitor food as it is transported down the conveyor belt (dried cabbage was used for the demonstration), identifying objects of the incorrect colour and removing them with a precise air knife. According to the company, the system was made possible by the development of camera technology; where before such systems could only differentiate within a width of around 150mm, this area has now been increased to around 600mm, meaning that Hitachi Zosen’s new system can process around 300kg-400kg of food per hour. In the future, the company plans to develop technology to detect abnormalities in shape as well as colour, allowing for an even more precise debris removal process.