Haemoglobin (Hb) was determined by a modified version of the method by Hornsey (1956) which is based on analysis of the heme group. Four grams of minced fish were vortexed for 30 s with 18 mL of freshly made acidic acetone (with final concentration 80% acetone, 2% hydrochloric acid, 18% water) in a 50 ml plastic tube followed by incubation for 60 min in darkness at 10°C and thereafter filtered through a Whatman filter no 1. In case of unclear filtrate it was filtered twice. The Hb content was determined spectrophotometrically at 640 nm. Standard curve was prepared from bovine Hb and as blank the acidic acetone was used. Hb content was determined on triplicates and results are expressed as µmole Hbequivalents per kilogram minced fish.
Total iron A 0.5 g portion of minced fish was mixed with 3 mL water, 150µL HCl and 750 µL HNO3 in Teflon vials. The samples were then microwave digested (Milestone microwave laboratory system Ethos Plus Sorisole, Italy) as described earlier (Larsson et al., 2007) . The analysis of iron was performed with ion chromatography as described by Fredrikson et al. (2001) . The HPLC system used was from Waters (Milford, MA, USA) with a Triathlon PEEK auto injector and a Waters 626 gradient pump. Iron content was determinate in duplicates and results are expressed as micromole iron per kilogram minced fish.
Total iron A 0.5 g portion of minced fish was mixed with 3 mL water, 150µL HCl and 750 µL HNO3 in Teflon vials. The samples were then microwave digested (Milestone microwave laboratory system Ethos Plus Sorisole, Italy) as described earlier (Larsson et al., 2007) . The analysis of iron was performed with ion chromatography as described by Fredrikson et al. (2001) . The HPLC system used was from Waters (Milford, MA, USA) with a Triathlon PEEK auto injector and a Waters 626 gradient pump. Iron content was determinate in duplicates and results are expressed as micromole iron per kilogram minced fish.