Soft flesh problem in freshwater rainbow trout investigated by magnetic resonance imaging and histology

To investigate the soft flesh problem in rainbow trout, the dynamics of water in postmortem white muscle were studied by magnetic resonance imaging, histology, and rigor index (theta(r)) measurements. At 24-h postmortem, the trout identified as having the soft flesh problem (theta(r) greater than or equal to 40 degrees) differed from the others (0 degrees less than or equal to theta(r) less than or equal to 20 degrees) by longer transverse relaxation time (T2 greater than or equal to 45 ms) and smaller diffusion anisotropy (DA less than or equal to 1.3), which proved to be the most relevant nuclear magnetic resonance parameter for an early diagnosis of the soft flesh problem. To interpret these results, we hypothesized an early and exacerbated tenderization phenomenon because of protein denaturation, inducing important modifications in fine connections that anchor the 3-dimensional structure of the tissue. The incidence of 3 slaughtering procedures on rigor were tested, and no differences were detected for trout presenting the soft flesh problem.