Ultrasound velocity measurement to determine lipid content in salmon muscle; the effects of myosepta

Abstract

Currently, there are no reliable and inexpensive non-destructive techniques available to measure the composition of fish during processing. In this paper, ultrasound pulse transit time measurement techniques are applied to aquaculture to measure the intramuscular fat in salmon fillets. Measurements on samples of salmon white muscle are described and the results of velocity measurements on a group of samples of varying fat content are reported. Differences from theory are considered in the light of the muscle structure. Results suggest that it is possible to group the velocities into “high fat”, “medium fat” and “low fat” categories but not to predict fat content with great accuracy because of inhomogeneity in the structure of the muscle. Ray-tracing techniques were used to model the propagation velocity of a wavefront travelling through a single salmon sample. The model provided an insight into how variations in fat content, myoseptum thickness and myosepta configuration affect measured velocity.