The butcher trade has a clear advantage over the fish industry. Carcasses of cattle and pigs have always been cleanly divided into individual parts and the different cuts then traded at appropriate prices. Which piece of meat comes from which part of an animal’s body and how it can be best used requires a fair amount of experience from the consumer, but decades of persistence in this field paid off in the end. Almost all meat eaters have at least some understanding of terms such as fillet, topside, knuckle, neck and the like. The fish industry has spared itself this trouble and has no comparable traditions. Perhaps it also lacked the necessary imagination, because for centuries fish was simply just fish. But in these animals, too, there are also differences in meat quality – as the Japanese have demonstrated at the latest with their elaborate system of toro, otoro, chutoro and akamai cuts of tuna. Knowledgeable sushi eaters are entirely familiar with these terms. And fish processors are now slowly beginning to realize that fillets and cheeks don’t have to be the only products that can be cut from fish. The number of special cuts from fish has grown rapidly in recent years. Of course, every cut has its own special characteristics, qualities, prices and preferred uses. The international fish business is now buzzing with so many new terms that even experienced fish experts are sometimes overwhelmed, to say nothing of the plight of helpless consumers. Although the complicated cuts confuse rather than guide consumers in their choice, the system is currently even being further perfected, because artful cutting and deboning of a fish already opens up more value adding options.
More or less everyone is in the meantime familiar with terms such as fillets, steaks or loins. And the meaning of butterfly, centre or tail cuts is probably understood from the literal sense, but supreme, darne, pavé, tronçon, paupiette, cravatte and escalopes, delice and goujon are most likely known by only very few. But such cuts are currently gaining importance at the same rate as trade with high-end convenience and online shopping increases. Anyone who knows exactly what he is ordering will perhaps be spared some unpleasant surprises.
However, the growing number of cuts does not only pose an ever increasing challenge to fishmongers and consumers: processing plants, too, must react to these new developments. With the exception of portion fishes such as trout, sea bass and sea bream, fillets were long considered the non plus ultra of fish processing. It was a work process that could be carried out quite perfectly by machine in many fish species and with an acceptable yield of meat, too. Whether herring, cod or salmon – the difference between hand- and machine-filleted fish is probably hardly noticed by an end customer. Even trimming, that delicate process which is decisive for the quality and convenience of the fillet can in the meantime be carried out very well using machines for some species of fish. Software packages with image recognition, electronic controls, and cutting systems that can be accurately guided along set contours enable the production of almost perfectly trimmed fillets, which hardly require any manual adjustments.
Mechanical solutions revolutionize fish processing
Although hand filleting usually enables a few per cent higher yields than machine filleting, when it comes to portioning, "intelligent" technology is far superior to what a person can achieve. The television commercial, in which a customer repeatedly orders rather "odd" amounts at the service counter and the well-trained salesperson slices off the requested amount to a gram every time is only a joke. What a person might succeed in doing in exceptional cases is routine for high-precision cutting machines. "Portion control" is the method that makes it possible even in the case of irregularly shaped natural products such as fish fillets to cut precise portion pieces with a predetermined weight or a certain size. Only with this technology were the conditions created that enable supermarkets and discounters today to offer fresh fish – whatever the shape – in the store’s self-service section as portions of a fixed weight packed under modified atmosphere.
The technical effort to cut exactly portioned 300 gram pieces repeatedly from a fillet is enormous. And portion cutters do not only work quickly and accurately, but also make the cuts so skillfully that there is hardly any wastage. In most cases the fillets pass through a tunnel at the beginning of the process in which they are scanned in three dimensions by laser beams in order to calculate the optimum cutting layers according to the required specification. The Marel Portion Cutting system can also be combined with the intelligent production software Innova. This provides easy to use remote programming, enables real-time monitoring of the processes, and provides reports on the actual performance and system capacity utilization. Portion cutters are available in several sizes, with different outputs, fittings and extras. Already the small I-Cut 11 operates with high precision, can be programmed via touch screen for a particular portion weight or a desired portion size and easily integrated into processing lines. This also applies to the I-Cut 36 which with up to 1,000 cuts per minute not only works extremely fast, but is at the same time also very accurate. And this machine is also very flexible and allows a cutting angle of 45°, which at constant portion weight makes for a larger and more natural-looking product. Even more ease of operation and greater output is possible with the I-Cut 130 Portion Cutter which due to its enormous throughput quantities is particularly suited to large processing companies. Special (optional) features of the 130 are the active product holders which stabilize the fillet on the belt during cutting and the "TrimSort" system, which removes trim parts efficiently.
The B35 portion cutter for fish from Norfo cuts portion pieces at angles between 45 and 90° at a speed of up to 450 cuts per minute. More than 80 different cutting programs can be stored in the automatic machine controls. For pre-cooked ready meals, which only need to be reheated before consumption, it is advisable to portion the fish before cooking in accordance with the declared product weight. Cooked fish is sensitive, soon falls apart and so is difficult to cut. If the above portioning is not technologically feasible or reasonable, the fish should be cooled thoroughly before cutting in order to achieve acceptable results.
Norfo also offers fully automatic sawing lines that accurately cut 7.5 kg frozen blocks into portions of varying sizes from fish finger format to 240 x 30 x 127 mm plates. In such processing lines the blocks mostly pass through several saws in succession and thereby gradually assume the shape of the final product. Using the Norfo system the process starts, for example, with the automatic single band saw ABS, which cuts the initial block into elongated bricks of the desired width. These are then cut into plates by the multiple band saw MBS and then divided into portions with the APS portion saw. This line can process up to 5,500 kg frozen blocks per hour. About 6% of the initial weight is lost as "sawdust".
The 3D Intelligence Portion Cutter Type F from the Japanese manufacturer NIKKO enables particularly demanding cuts. It cuts frozen salmon fillets into Kirimi portions, all of them with the same weight, the same length and the same width. To achieve this amazing portioning feat the cutter is equipped with sufficient computing power and a high-performance 3D sensor that measures each fillet precisely and sets the angle of the two cutting blades precisely for this Japanese-style diagonal portion cutting. As a rule, the fillets are cut into 10 Kirimi portions, and up to 3,000 cuts per hour are possible.
Bones are a major obstacle to fish marketing
But even the most accurately processed fillets and portions wouldn’t stand a chance in many markets if they were not free of bones. Although the filleting problem has been largely solved for some fish species there are still the annoying pinbones to contend with. Pinbones are found in the front area of the fillet closely above the centre bone. They can be pulled out by hand with pliers or tweezers or mechanically removed with small hand-held or large automatic devices. The goal is always the same: to remove the pinbones as completely as possible without damaging the structure of the fillet and so not to decrease the yield and ultimately to increase the value of the boneless product. Pulling out the pinbones by hand using pliers or tweezers is simple and thorough but also time-consuming and therefore recommended only for the domestic kitchen or small catering establishments. Once large amounts of fillets have to be freed of pinbones, it will hardly be possible to get around investment in a viable hand device. The range of available products is broad, but the principle on which they function is almost always the same. Most devices have counter-rotating rollers or discs, which clamp the ends of the pinbones protruding from the lean meat and pull them more or less gently out with the rotary movement. Important for their function is above all to pull out the bones accurately in the direction in which they lie to avoid gaping of the flesh. In addition, the action must be as uniform as possible so that the pinbones don’t break or crack leaving the lower part still in the fillet.
The hand-held STEEN ST590 / 100E pinbone remover stands out, for example, according to the manufacturer for a particularly gentle operation that allows virtually undamaged fillets. To remove the pinbones, the device must be held just above the critical area of the fillets. The working speed can be adjusted via the control box. Unlike most pinbone removers of this kind the hand-held STEEN does not need a compressor or compressed air connections. The FTC Eco Flex handheld Pinbone Puller from TRIO pulls pinbones out of both fresh and thawed or smoked fillets. According to the company brochure, the system has been used for several fish species, including salmon, trout, whitefishes, cod, hake and haddock, and up to six fillets per minute can be rendered free of bones. The manufacturer of the hand-held electric EXOS pinbone removers emphasizes their long experience in this field: they have produced such devices for more than 20 years and have improved them continuously over this long period. The current models were fast, extremely reliable and particularly easy to operate. The ergonomic device is lightweight and sits comfortably in the hand, which prevents premature tiring of the operator. Since the device was driven by an electric motor, it was ready for use immediately when needed, less prone to faults, and largely maintenance-free.
Although the biological and technological fundamentals of pinbone removal would seem to be largely clarified, scientific institutions are still working on the subject. The University of Alaska recently presented a mechanical pinbone remover which is about the size of a circular saw bench. This device can remove the pinbones of both wild caught and farmed salmon and trout. The fillets are simply pushed over the work table of the device with the interior side down and the device detects the ends of the pinbones and removes them with almost no damage to the flesh. According to information from the developer the UA-Pinbone Remover can pull 85 to 95% of the pin bones, a respectable value for this step, but subsequent manual finishing is still necessary.
Large processing plants mostly use single or multi-lane automatic pinbone removers for this sensitive process anyway, which can be directly integrated into the processing lines, have a high throughput, and also work very thoroughly and cleanly. The single-lane Uni-Food 350 is regarded as a kind of basic device that can be considered for use in smaller farms. It removes about 95% of the pinbones from 10 to 20 fillets per minute, and has now also been technically upgraded and is available as the 350-NK SIX. In this model, six sets of knives and rollers provide a significantly higher performance (40-50 fillets / min) and a better result. According to the manufacturer the pinbones are usually completely removed, only in isolated cases does a maximum of three bones remain in the fillet. In the case of the Carnitech 2615 the company brochure additionally emphasizes the device’s clean and hygienic operation because after their removal the pinbones are immediately sucked away by vacuum via a tube, so that after their passage through the machine the fillets lie largely "waste-free" on the belt. The specialists for pinbone removal also include the Danish company Kaj Olesen which, with its EASY-MATIC series offers pinbone removers for various species of fish and different capacity requirements. The machines are available in designs between a one- and an eight-lane version and as TWIN models that are even more thorough and efficient. Fresh fish is kept clean during processing by a water spray system, smoked fish using an air blower. The EASY-MATIC 102 is equipped for example with two remover heads and can process 700 to 1,200 kg salmon fillets per hour. That corresponds to 16 to 22 fillets per minute, depending on the type, size and condition of the salmon. Olesen states that the EASY-MATIC remover removes between 90 and 95% of the pinbones. The machines achieve the best results in fishes after rigor mortis has already passed.
New technical approaches to pinbone removal
All technology suppliers and fish processors face this problem because the pinbones cannot be removed cleanly from freshly slaughtered salmon and other species, and certainly not without damaging the flesh. They are joined by connective tissue tendons to the lean meat (especially on the front at the tip) and can therefore only be pulled out at this stage with brute force, which causes considerable damage to the fillets. Not until three to five days after slaughter when rigor mortis has subsided and the fish "matured" can the pinbones be removed properly. In some species of fish, including white fish species such as cod, pollock or haddock, pulling the pinbones causes considerable problems even then. In the past, processors working with these species usually resorted to cutting out the fillet area generously with a V-cut which cut away the pinbone strip as a whole, along with the adjacent flesh. However, this reduces the usefulness of the fillet, which mostly then gaped at the front and looked ugly, and also leads to yield losses, because 3 to 7% of the fillet was lost with this cut.
Now however there are new ideas and approaches that can perhaps soon solve this problem elegantly. SINTEF, an independent Norwegian research organization and Trio have developed a camera-based system that detects the positions of pinbones in the fillet so that a long slender knife may be pushed into the muscle meat at the apex of the pin-bones from the front parallel to the outer skin. It severs the tendons at the top of the pinbones, thereby making it possible to pull these bones out one to two hours after slaughter.
A different approach, which SINTEF developed together with Marel in the project APRICOT ("Automatic Pinbone Removal In COd and whiTefish") relies on X-ray technology and a water jet cutting mechanism. The individual bones are localized in the flesh by X-rays and then cut out with high precision by means of an ultra-fine water jet. In a press release the developers emphasize in particular the speed and thoroughness of the system. It works regardless of the size of the fish to be processed, allows high yields because hardly any waste is produced, and the fillets are guaranteed free of bones. A prototype of the new filleting and deboning machine is now to be tested in practice. If it proves itself, the system could possibly be ready for serial production already this year, but at the latest next year.