Abstract
The aim of the study was to explore the effects of different design variables in the onboard bleeding process of cod on bleeding efficiency and the resulting product quality. A time- and flow-controlled process was used to create variable bleeding conditions for whole gutted cod onboard a wet-fish trawler. Two main design variables influencing the bleeding process are the pump flow recirculation (PFR) and the water replacement ratio (WRR); they were studied in five different combinations (groups). The effects of different bleeding conditions were evaluated by measurements of free fatty acids (FFAs), phospholipids (PLs), and total heme iron (HI) content during freezer storage for up to four months. The results for PL content and the regression model indicate that the enzyme activity in the fish muscle is lower in cases where PFR exerts greater influence in the bleeding process than WRR. The effects of successful blood removal also seem to be most noticeable after one month of freezer storage, rather than in fresh cod after seven days or after four months of simulated frozen food-chain storage. The study indicates that, with the bleeding medium to fish ratio of around 3:1 and enough WRR (over 100% replacement in 20 min), the PFR becomes the limiting design parameter regarding efficient blood removal and should be at least 10% of the tank volume per minute to ensure enough recirculation and flow of water in the bleed-out tanks.
Highlights
An increasing demand for high-quality fresh fish has led fish producers globally to focus on and improve raw material handling and processing
As the storage time became longer, there was a decline in PL content for all groups, except Group E, which showed lower PL values after one month of freezer storage compared to four months
This study aimed to evaluate the effects of these variables at three different storage times based on the free fatty acids (FFAs), PL, and heme iron (HI)
Summary
An increasing demand for high-quality fresh fish has led fish producers globally to focus on and improve raw material handling and processing. Improvements in temperature control and packaging have extended the shelf-life of fish and promoted an increase in fresh fish processing and export [1,2,3,4]. High-end products, like fresh cod loins, require the raw material to be well drained of blood and uniform in color. Bleeding is generally the first process the fish goes through after catching and is aimed to drain most of the blood from the muscle [5]. Insufficient bleeding can affect the shelf-life of products through product taste, odor, visual appearance, and residual blood, which can promote lipid oxidation, provide nourishment for bacteria, and cause increased enzymatic activity [7]
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