Superchilling of rested Atlantic salmon: Different chilling strategies and effects on fish and fillet quality

Rested Atlantic salmon was superchilled in seawater slurry (−1.93 ± 0.27 °C). The chilling efficiencies of slurry and crushed ice were compared. The feasibility of using slurry to produce subzero core temperatures before packing was also evaluated. Simulated transport to market, with or without ice after initial superchilling (1 day), was also studied. Fish quality (Quality Index, fillet colour, pH, water content, water-holding capacity, hardness and bacterial loads) was evaluated at arrival to ‘market’ and after keeping the fish ‘in the market’ for 1 week. The results were compared with continuous ice (control) or slurry storage. In terms of quality, pre-chilling in slurry and continuous storage in slurry were evidently not advantageous over traditional ice storage, as evaluated after 4 days. After 11 days, both advantages and disadvantages of continuous superchilling were observed. Notably, subsequent ice storage of superchilled fish resulted in increased bacterial load and inferior fillet hardness.

Research highlights
► Rested Atlantic salmon are superchilled in seawater slurry, or traditionally in ice, immediately after killing.
► Chilling in slurry is more rapid than in ice, although fish quality is nevertheless similar when the fish are presented in the market.
► Superchilling of salmon is not advantageous unless storage time is comparatively long (at least 10 days).
► Superchilling of salmon has both advantages and disadvantages.
► Transfer of salmon from slurry to subsequent storage in ice results in more rapid growth of bacteria and softer texture.