– average yield increase of 34% for mussels, 23% for lobsterclaws and 5% for white and brown crab meat
Full scale trials have just been completed which show that High Pressure Processing (HPP) has practical and commercial benefits in enhancing peeling and picking yields from seafood products, however the high cost of the equipment could be a limiting factor.
The trials were conducted by the Campden BRI, using both pilot and commercial scale equipment. The project was jointly funded by FIFG, Norconserv and Seafish under a Seafish Industry Project Fund.
Overall high pressure processing trials were carried out on 11 species of fish including nephrops, mussels, oysters, crab, cold water prawns, warm water prawns, lobster, unsmoked salmon, squid, mackerel and cod with some positive results.
The main benefit from HPP treatment of mussels and oysters was the ‘automatic’ shucking that was achievable, along with an increase in meat weight after processing. Mussels were completely released from the shell at almost all conditions tested, with average increase in yield of 34%.
Oysters still had some loose attachment to the shell but could probably be separated by a simple vibrating belt. To prevent liquor loss it would be necessary to manually seal the product shut, in the USA this is done by banding. The effects of HPP on sensory quality appear to be favourable with samples generally perceived to be plump, attractive and less chewy than controls.
In the commercial scale crab trials, large yield increases were observed. Brown meat yield was 23% in the HPP treated sample, compared with 18% in the control. Similarly, white meat yield was 12.9% compared with 8.3% in the control. However excessive water uptake did affect product quality but it was felt this could be controlled. Yield on lobster claws was up to 23% higher and in many instances HPP treated lobster was considered to be higher sensory quality than the control.
Commercial trials on Nephrops resulted in a 1% yield increase. This may be too small to be of commercial interest, but could potentially be improved with optimisation or by using unfrozen tails. Commercial scale trials on warm water prawns gave a significant yield increase of 4.7% compared with the untreated samples. It was observed that in pressure treated prawns a greater proportion of the prawn could be removed intact.
“The results are very clear. For certain species HPP can be used to successfully increase yield and even slow microbiological spoilage. It also has the potential for new product development and to simplify or mechanise labour intensive shucking operations,” said Richard Watson, Seafish Project Manager.
“The drawback is that HPP equipment does represent a significant capital investment. Commercial sized equipment able to process 150kg and 1500kg of seafood per hour, currently costs around €0.5 and €1 million respectively. Processing costs are around 4p – 12p per kilo including the recovery of capital costs, with the larger machines offering a lower cost per kilo,” he said.
