Effects of Onboard Processing on Groundfish Quality

Abstract

The scope of this study is processing onboard fresh fish trawlers, focusing on bleeding and cooling processes and the effects on product quality and shelf-life. In recent years there has been a shift from less valuable frozen products to higher value fresh fish export of fillets and loins from Iceland. This development in the fresh fish fillets markets was made possible by technological improvements in the value chain in the last decade. However, the primary onboard processing has been a weak link in terms of research studies in the value chain of groundfish. This research gap in the value chain and the renewal of the Icelandic fleet led to the current study, in which the objective is to evaluate primary processing onboard fresh fish trawlers focusing on the bleeding and cooling processes. The study evaluation is aimed at the effects of new onboard processes, to provide design criteria for further technical innovation and provide measurement results that producers can use as references regarding shelf-life and quality indicators. This is done with onboard research on time and temperature control, variable bleeding conditions and methods, different cooling and superchilling methods, and on superchilled storage with focus on the effects on shelf-life and product quality. The results of the study show that the waiting time in the reception hold is the main deciding factor regarding fillet colour. As for the method of bleeding and gutting fish, the two-step process of bleeding and gutting showed only marginally better results in terms of fillet colour, compared to direct gutting. Results of bleeding media conditions show the effects of time, temperature, water flow and recirculation on fillet quality, and indicate that pump flow recirculation has more effect on bleeding efficiency than water replacement. Comparison of newly developed onboard primary processing systems to older ones confirms improvements in terms of uniformity of both bleeding and cooling. The study results show that it is not advisable to store whole ungutted cod in onboard RSW for more than 24 hours. The onboard superchilling of whole gutted fish reduces some spoilage factors but superchilled storage after fillet processing was found to be more important for extended shelf-life. Simulation of a superchilled value chain from catch to market indicates that the freshness period and shelf-life can be extended by up to four days, compared to traditional ice cooling of whole fish and storage of fillets at 1 °C. The study outcomes can provide technical developers with premise and requirements for further technical solutions needed to deliver fish of the highest possible quality and with a maximum shelf-life to secondary processing.