Dietary Protein Level Has Minimal Effect on Flesh Quality of Frozen Stored Sunshine Bass, Morone chrysops × M. saxatilis

Abstract

The storage stability of frozen muscle from sunshine bass, Morone chrysops × M. saxatilis, fed diets containing various levels of protein (29, 36, 42, and 45%) was determined by measuring thiobarbituric acid reactive substances (TBARS), an indicator of lipid oxidation, and changes in shear stress and tensile strength of the muscle during storage. Fish fed a 45% protein diet had a higher (P < 0.05) dressed yield than fish fed diets containing 29 and 36% protein. Percentages of moisture, protein, fat, and ash of fresh fillet were not different (P > 0.05) among all dietary treatments. The n-3 fatty acids composed one-third of thc total fatty acids in muscle, and the n-3/n-6 fatty acid ratio was lower in muscle of fish fed from the 29% protein diet (1.89) than those fed from the higher protein diets (2.70-3.40). Other fatty acids, however, were similar among all muscle samples. Storage at -20°C for 6 months did not cause significant (P > 0.05) increases in lipid oxidation for skin-on fillets, but from month 4 to month 6, skinless fillets exhibited marked increases (P < 0.05) in TBARS. Changes in TBARS were generally not affected by dietary protein levels. Shear stress and tensile stress of muscle tissue showed inconsistent changes during storage and no differences (P > 0.05) due to dietary regimen were observed. The results indicate that physical and chemical characteristics of hybrid striped bass muscle after 6 months of frozen storage were minimally influenced by dietary protein level.