Advanced seafood sorting solutions

Optical sorting refers to the use of optical technology to separate a flow of products into different streams based on certain criteria. The technology is an indefatigable and less error-prone replacement for manual unhygienic sorting and it does not take long to cover the cost of the investment.

In the seafood processing industry sorting is often necessary at different junctures; for example, as the raw material enters the production, during processing, and before packaging. The first sorting procedure will ensure that only raw material that meets the specific requirements of the company enters into the production process, while the second round of sorting will filter items that are poorly processed or that are defective and need to be discarded. A last check sorter can also be implemented before packaging for products to be sent to the end customer. The usefulness of this technology has led several companies to develop commercial applications that are used in different fields, apart from food processing; these machines may be found in the mining, and recycling industries, and pharmaceutical industries among others.

Tomra Sorting creates high-tech solutions that efficiently separate good from bad in a flow of products.


Start in reverse vending machines

In Europe one of the prominent manufacturers of sorting equipment is the Norwegian company Tomra. Founded in 1972 in Asker, Norway, the company started with the design, manufacture and sale of reverse vending machines, the devices used in supermarkets to collect empty beverage containers from customers. From the collection of beverage containers the company graduated into material recovery including the pickup, transport and processing of empty beverage containers for beverage producers in the US and Canada. Tomra today has two main business areas: collection solutions, which include the streams reverse vending, material recovery and compaction; and sorting solutions, including recycling, mining, food and specialty products. While collection solutions are the older business line and responsible for the bulk of the company’s revenues, the sorting solutions business area grew from 25% to 35% of the group’s total operating revenue between 2011 and 2012.

Tomra’s sorting solutions that are deployed in the recycling business enable material processing facilities to sort materials such as plastic, metal, household waste and paper rapidly and efficiently, while in the mining industry sorting machines identify and stream precious materials, minerals, or gemstones away from the dross. In the food business Odenberg machines were used to sort large products such as potatoes and carrots, but it was only in 2012 with the acquisition of a Belgian firm, Best, that the company developed a capacity to provide sorting solutions for smaller products like dried fruit and nuts, fruits, vegetables, French fries and chips, and many other products. Best came with a portfolio of proprietary detection mechanisms including special technologies, like Detox™, which is used to detect aflatoxin, a toxic fungus that can infect nuts and dried fruits. Another technology developed by Best is Fluo™ that uses the fluorescent features of products to give a better contrast between items and thereby improve the efficiency of detection.

After the scanning technology has identified a faulty product, a jet of air will shoot it on to a reject belt to be discarded.


Sixty-five types of sorting equipment

The sorting solutions make use of sensor-based technologies to identify, separate, and stream products. A machine is typically constituted of a scanning technology and a machine platform. The latter comprises all the parts of the equipment apart from the scanner. By combining different scanning technologies with different platforms Odenberg and Best, within Tomra Sorting can offer more than 65 varieties of sorting machines. Of course, for each product the company knows which is the most efficient combination of scanning technology and machine platform to be used. In the seafood sorting side of the business the main technologies used are cameras, lasers, and x-rays. The cameras can sort based on colour; differences in colour such as black spots on shrimps, discoloured flesh, anything that deviates from the pre-programmed colour spectrum can be sorted out of the batch. Cameras can also detect unusual shapes, that is, if the product scanned is too big, or too small, too curved or too straight, it can be rejected by the system. While cameras can reliably distinguish external characteristics of the product scanning technologies based on lasers go a step further. A laser too can sense differences in colour, but in addition, it can examine the texture of the product and determine whether it is hard or soft and even measure the moisture content. This ability makes it a useful tool to determine the presence of impurities that are not visible to the camera. The shell of shrimp, for example, is transparent and may not be visible to a camera, or even a human eye for that matter, but because it is hard while the shrimp meat is soft it can be detected by a laser. Poorly peeled shrimp or shell that has inadvertently gotten mixed with the product can thus be identified by a laser and removed from the product flow. This ability makes laser scanning an ideal tool when there is a risk of transparent impurities or contamination of the same colour as the product.

Mussels too can be sorted so that any discoloured or damaged pieces are discarded. The scanning technology is programmed to reject based on criteria keyed in by the operator.

With the increase in the production of warmwater shrimp it was necessary for the sorting equipment to be adapted to this product as well.


Combining different scanning technologies for better results

X-ray scanners are also used by the seafood industry. Like the scanners at airports used for people and luggage x-ray sorting technology is based on the varying extent to which different materials absorb x-rays. Softer materials let x-rays pass through while dense substances absorb them. These differences can be used to detect the presence of impurities such as shell, glass, metal, or stone inside a product such as scallop meat or mussel meat. X-ray scanning poses no health hazards for either the operator or the product, stresses Johan Germeys, Market Unit Manager for seafood. Although it uses high voltages to generate the x-rays, the scanning machine is designed and built to international standards and is completely insulated from its environment. While the x-ray scanning technology is usually a separate piece of equipment, the camera and laser scanning technologies can also be combined into a single machine, called a dual machine or one using dual technology. By combining a camera with a laser, for example, the seafood would be sorted to remove all discoloured or misshapen objects as well as to remove unwanted objects such as shell or by-catch. This makes these applications particularly useful in vessel-based facilities as fishermen want to reduce the amount of unusable material they bring back to shore as it uses up space and increases fuel consumption. If the material is sorted as it comes on board the by-catch can be discarded at once. We are seeing increasing interest in our seafood sorting solutions for on-board purposes, says Mr Germeys. In the South Pacific Ocean sorting solutions have been installed on vessels targeting greenshell mussels and in the South Atlantic Ocean they are used by the scallop fishing and on-board freezing vessels.

Tomra’s sorting solutions for seafood are already commonly used in the shrimp and prawn processing sector, and to sort mussels, scallops and tuna. The company has had to respond and adapt its products to changes in the seafood market which in the case of shrimp, for example, have been marked. Johan Germeys recalls how the machines were first implemented to sort coldwater shrimp (Pandalus borealis) in markets in Canada, Greenland, Iceland, and Scandinavian countries. But with the spread of shrimp farming during the last decade in Asia and Latin America, there was a wave of consolidation among the coldwater shrimp processors and the sorting machines had to be developed to sort warmwater varieties. In addition, while in the past it was typical for a company to process only one kind of shrimp, today processors import shrimp from different parts of the world and they can be different species, so the sorting machinery has to be programmed to deal with different species of shrimp.


Belt vs. free fall

For the seafood sorting solutions there are essentially two machine platforms that can be combined with the scanning technologies. One of them, Genius™, has a horizontal belt on which the product is laid prior to scanning. A belt-fed scanner is used for wet products – peeled shrimp, scallops – as it gives better stability and product handling. Genius™ can combine cameras and lasers to scan different sides of the product in different inspection zones. After being scanned the machine’s software sends a signal to one or more of the high speed precision air ejectors that sends a millisecond blast of air to remove the offending product to the appropriate reject stream. The Genius™ platform is modular and so is easy to adapt precisely to the customer’s requirements. With belt widths that vary from 64 cm to 2 meters and a speed of 3 m/s the sorter can process up to five tonnes of material an hour. The second platform used for seafood is called Helius™ and it differs from Genius™ mainly in that the scanner is not belt fed. Instead the product free falls towards the inspection zone, where it is scanned by multiple lasers from all angles. The ability to scan the product from all sides as well as the sorter’s small footprint are two of the advantages of the Helius™. In other respects it functions like the Genius™.


Infeed systems determine sorting efficiency

Crucial for both Genius™ and Helius™ is the infeed system that distributes the product prior to scanning as uneven distribution can impact the efficiency of the sorting. Tomra Sorting offers its own infeed solutions, usually shakers or vibro-conveyors, which spread the product into a monolayer for optimal sorting. But the sorters can also be integrated into an existing processing line which may already have a spreader. In any event Tomra Sorting can provide a total solution that includes the sorter, the infeed system, and the reject and accept belts. The company also develops the software that runs the machines which includes training the machine to recognise what is to be rejected. Today’s sorters can connect to the internet and in case of problems engineers from the company can log onto the machine and investigate the issue.

These sorting machines have typically an efficiency in the range of 95-97% with low figures for bad in good and good in bad. But the biggest advantage of the machine is that it is quicker, more accurate, and ultimately cheaper than manual sorting. To get an accurate picture of the areas in the world with the most potential for sorting solutions, the company has set up a unit that will analyse the global seafood market to identify future developments.


Focus shifts from product to market

Tomra will continue to refine and develop its sorting solutions, both the hardware and the software, emphasises Mr Germeys, but while in the past the company developed the product and then looked for the market where it could be implemented, the focus today is on finding out from a customer where the problem lies and then working together to develop a solution tailored to that specific issue. Nowadays, every machine that leaves our factory is customised to the individual needs of the client. We have a 100 people working in research and development and so are well equipped to respond to any challenges the market may throw at us.