Til innholdet




Prosjektnummer: 900995
Status: Avsluttet
Startdato: 01.05.2014
Sluttdato: 15.06.2016

Pin bone pulling

Results achieved
Project summary from the final reports
The objectives of this project were to investigate whether ultrasound treatment could be used to weaken the pin bones attachments, at least to similar degree as post mortem aging during rigor does. Furthermore to find out whether torque controlled pulling would result in higher success ration of bone removal, compared with pulling at constant speed.

The results show that the ultrasound technology is a promising method for weakening pin bone attachments. With the experimental setup used in this work, HIFU treatment is more effective for decreasing bone attachment in cod than in salmon. For cod, a reduction in pulling force of 50–70 per cent was observed, but care must be taken to avoid overtreatment of bones, which can result in bones breaking during pulling. For salmon, HIFU treatment resulted in a reduction of 30 per cent for peak force and 10 per cent for total pulling work. For some applications, 30 per cent reduction of bone pulling force may be sufficient. However, it is not possible to conclude on the full potential for HIFU treatment of salmon without further development of the Method.

HIFU treatment is not yet fulfilling industrial requirements, particularly regarding treatment time which does not meet requirements on throughput in processing plants. The treatment speed used in the experiment was 1–3 mm/s whereas the typical belt speed in industry is 300–400 mm/s. It may be possible to manufacture custom made transducers with higher power output and thus lower processing time. Further adjustments are also needed to guarantee that the treatment does not cause adverse effects on fillet quality.

Preliminary studies of the torque controlled device indicate that there is yet a considerable risk of breaking bones, although the pulling was less abrupt and the pulling velocity relatively low, compared with traditional Marel technique for removing pin bones. 

In task 3 of the project it was planned to combine physical methods to weaken bone attachments and automatic mechanical approaches to remove the bones from fillets. This test was terminated since the results obtained in task 1 and 2 were not satisfying for conducting an industrial test.
Resultatene er interessante og viser at HIFU kan være en metode for å løsne tykkfiskbein i pre-rigor fiskefilet med en reduksjon i trekkraft på 50–70 % for torsk, og 30 % for laks.

Metoden må imidlertid utvikles videre sammen med en teknologileverandør for å oppfylle fiskeindustriens krav til produksjonshastighet og sikre at behandlingen ikke påvirker kvaliteten i negativ retning.
Automation of pin bone removal is one of the major obstacles that the fish processing industry faces. Different technical approaches have been developed, leading to success in removal of pin bones by pulling in post-rigor salmon, but neither in pre-rigor salmon nor cod. The advantages of removing pin bones by pulling is that the structure of the fillets remains intact and losses of flesh removed with bones are minimal in comparison to cutting. Therefore, larger portion of the fillets can be used for higher value products.

Current needs of the industry:
• pin deboning of both pre- and post-rigor white fish – particularly cod; and
• pre-rigor pin deboning of salmon to enable processing near/at slaughtering site.

Problems related to pin bone removal by pulling:
• high variation in pin bone removal success, due to variation in raw material;
• gripping of bones and pulling without slipping off or breaking the bones;
• differences in anatomy and fillet composition between species, influences gripping and pulling of bones;
• high variation in condition of wild fish in comparison to farmed; size, physical condition, easier to  control handling and processing procedures in farming 
• bone attachments are stronger in pre-rigor fish in comparison to post-rigor fish; and
• access to bone ends, is influenced by rigor status and filleting. The cutting position of pin bones varies and bones may be (partly) removed by the filleting procedure and machines used.
Among challenges with pin deboning of wild cod is high variation in biological condition of the fish, in handling after catch and in processing procedures. In cod and salmon, pulling forces are significantly reduced during rigor mortis, due to biochemical processes and tension results from muscle contraction when the muscle is still attached to the skeleton. 
Weakening of pin bone attachments is a relevant issue in pin bone removal, particularly in pre-rigor fish where the attachments holding the bones are strong and post-mortem ageing is still limited. Procedures that accelerate post-mortem ageing of fish muscle are not fast enough, i.e. do not cause immediate effects, in order to enable pin bone removal when the fish is processed directly after slaughtering.
• to evaluate the effects of physical methods (e.g. ultrasound) for weakening the bone attachments in fish while minimizing adverse effects (e.g. gaping, discoloration etc., due to denaturation);
• to test innovative technical approaches in pin bone pulling, such as torque controlled pulling device.
The goal is to increase success rate and stability of bone removal, for example by reducing the risk of bone breaking or losing grip of the bones during pulling.
Expected project impact
The deliverables of this project will show whether the approaches tested are feasible to be incorporated in automatic systems for pin bone pulling. The prerequisites are that the physical methods will weaken the pin bone attachment sufficiently to enable pin deboning of pre-rigor fish and/or different species. Furthermore, the torque controlled pulling will potentially give better results than standard bone pulling.

Innovative technologies enabling pin bone removal from cod and salmon are being identified as one of the priorities to increase automation, production rates and productivity in fish processing. The advantages of automation are:
• more continuous flow of material through the processing plant;
• opportunities to improve control of temperature during processing;
• stability in production, including yield and quality; and
• increased ratio of fillets used for higher value products.

In processing of farmed salmon, pin bones are removed by cutting in pre-rigor fish and by pulling in post-rigor fish. The development (duration) of rigor mortis takes 2–4 days, depending on several factors such as the condition (e.g. energy reservoir in case of struggling) of the fish when slaughtered, harvesting methods and holding temperature prior to processing. In Norway, this waiting time is often used to transport the fish (either as gutted or fillets) to EU where the pin deboning, portioning and packing into retail units takes place. However, the late deboning can be considered ineffective as compared to doing everything in the one processing plant, and it also prevents selling high value added products from Norway.
Project design and implementation
The feasibility of different approaches for increasing success rate in pin bone removal by pulling will be tested:
1. weakening of bone attachments in pre-rigor salmon and cod by physical methods (e.g. ultrasound). The study will be performed in two stages; first initial tests to identify optimal parameters of treatment applied and then an experiment to document the treatment effect on bone attachment and product quality;
2. automatic mechanical approaches. The effects of torque controlled pulling to reduce risk of bone breaking and losing grip of bone during pulling will be evaluated;
3. combination of physical methods to weaken bone attachments and automatic mechanical approaches to remove the bones from fillets
Project owner is Marel, responsible will be Kristján Hallvarðsson (Marel). Mr Hallvarðsson has extensive experience leading fish automation projects. Dr. Karsten Heia at Nofima, will be the co-ordinator of the project.
Project organization
The project will be carried out at Nofima in Tromsø, Marel in Gardabaer, Iceland and fish processing plants. Nofima has collaboration with the physics department at University of Tromsø with a common instrumental park, for example on ultrasound equipment and will make use of these facilities in this project. Marel be responsible for testing mechanical approaches for gripping and pulling out the pin bones.
Dissemination of project results
The results will be summarised in report and presented at FHF-seminar and meetings with stakeholders from the seafood industry.