Characterization of surface orientation and tenderness of sous vide processed edible offal and psoas muscle from Dohne Merino sheep

The microstructural orientation and tenderness of edible offal and the psoas minor muscle from Dohne Merino sheep were compared in this study. Following evisceration and cleaning, fresh meat samples were collected from slaughtered lambs and ewes of different age groups and thermally processed to varying degrees of doneness using sous vide apparatus. A scanning electron microscope (SEM) was used for the characterization of the surface orientation and elemental composition. The results for tenderness showed that edible offal with anisotropic orientation had higher Warner-Bratzler shear force (WBSF) values, but those with some degrees of uniformity (isotropicity) in their surface orientation were comparatively tender. The rumen and trachea from the lambs, six-tooth and eight-tooth sheep at 10 - 12, 23 - 36 and 28 - 48 months old at slaughter had the highest WBSF values among all the meat samples. Our findings showed that edible offal from the lambs with isotropic orientation was more tender and richer in protein than those from ewes. Also, processing the psoas minor muscle and edible offal with sous vide at 100 ºC in the shortest cooking time of 30 minutes had the greatest effect on tenderness of the meat samples. In descending order, the psoas minor muscle, liver and tongue from the lambs were found to be inherently more proteinaceous than other meat samples. The differences observed in the tenderness and protein contents of the edible offal and the psoas muscle could be attributed to variations in the microstructural organization of the muscle fibres in Dohne Merino and to their response to thermal processing.Keywords: anisotropy, doneness, isotropy, meat processing, Merino, scanning electron microscopy