Bioelectrical Impedance Analysis Measures of Body Composition and Condition, and Its Sensitivity to the Freezing Process

Measuring body composition and condition are integral parameters within seafood quality assurance methods. Bioelectrical impedance analysis (BIA) has been successful in measuring body composition and condition on a variety of fish that have never been frozen, but its applicability on previously frozen fish is unknown. The objectives of this study were to measure albacore tuna (Thunnus alalunga) with BIA prior to and after freezing. Predictions of body composition and measures of condition (measured by phase angle) were compared in fish that were just caught and again after they were frozen and allowed to thaw. Results indicate that BIA works well on fresh fish but not after they were thawed. Correlation scores (r) between predicted and actual values of water, dry mass, fat-free mass, ash, and protein in the fresh fish were > 0.69 and < 0.17 after they were frozen. Phase angles of the fresh fish were similar to other studies (similar to 24 degrees) and approached zero after they were frozen. Reactance values decreased dramatically in the frozen fish, and its usage on frozen fish may be useful to the seafood industry in determining if fish have previously been frozen.