Variation in texture of farmed atlantic salmon (salmo salar l). relevance of muscle fiber cross-sectional area

Mechanical properties were studied between and within fillets of 80 conventionally farmed Atlantic salmon (3.5 kg) using a Warner-Bratzler blade (WB) and a 12.5-mm flat-ended cylinder. The relationship between the muscle fiber cross-sectional area versus mechanical response variables was examined. The average muscle fiber area differed significantly between salmon of similar size. Mechanical properties also varied substantially among individuals and between locations within fillets, showing firmer texture in the posterior fillet part on average. Shear force (WB) was 2-2.4 times higher with a wider range for analyses performed perpendicular than parallel to the muscle fibers. Raw fillets with low fiber cross-sectional area (<12.500 μm² on average) had significantly firmer texture compared with fillets with larger fibers. However, correlation analyses of individual data showed relatively low overall influence of muscle fiber size on the texture properties (r [less-than or equal to] 0.35). Thus, the texture of salmon fillets is clearly multifactorial where muscle fiber size is not a major determinant. Soft salmon flesh reduces consumer acceptability and causes quality downgrading in the salmon processing industry. Therefore, it is important to elucidate antemortem and postmortem factors influencing fillet firmness, including knowledge about intrapopulation variations of conventionally farmed salmon. The present study showed pronounced variation between individuals and between sections of the same fillet. It is suggested that sectioning of salmon fillets for different products or markets may improve utilization of intrinsic texture qualities. Furthermore, development of invasive online methods for sorting fillets according to firmness would be beneficial for the industry. Variations in muscle fiber size explained less than 12% of the overall texture variations. However, the indicated relationship between small muscle fibers and texture firmness implies that better understanding of the underlying basis for muscle growth pattern (rate of fiber recruitment versus volume growth of existing fiber) is needed.