Microstructure of Cuts Through the Connective Tissue Framework of Meal

Abstract

The connective tissue framework (endomysium and perimysium) of raw meat samples was stained with silver in frozen sections for the light microscope. In bovine sternomandibularis samples which had been slowly and incompletely cut with a sharp blade parallel to the longitudinal axes of the muscle fibers, two major zones of connective tissue deformation were found. In advance of the blade the endomysium was compressed while to the rear of the cutting edge endomysium was stretched. Perimysial septa were pushed into a syncline in advance of the blade and spread tension through the sample by pulling on adjacent endomysium. In samples of porcine longissimus dorsi muscles, the mean numbers of connective tissue boundaries located along pairs of perpendicular transects were correlated with mean muscle fiber cross sectional areas, r=— 0.83, P<0.005. However, endomysial sheaths were often slightly flattened in one direction while perimysial septa were sometimes approximately parallel. In transects through such regions more connective tissue boundaries were crossed in one of a pair of perpendicular transects. Thus, when the meat was transected in only one direction, the correlation between the number of connective tissue boundaries transected and mean muscle fiber cross sectional area was reduced, r=—0.54, P<0.005. This directional effect at the microstructural level was thought to be related to the phenomenon of transverse anisotropy in meat samples during shearing. In bovine sternomandibularis samples cut perpendicularly to the longitudinal axes of muscle fibers, muscles fibers and their endomysial sheaths were compressed in advance of the blade and stretched to the rear of the cutting edge. In samples cut perpendicularly both muscle fibers and endomysial sheaths were severed whereas in samples cut in a parallel manner only connective tissues were severed and most muscle fibers were left intact. In transverse sections of samples from the porcine longissimus dorsi muscle, samples from the anterior half-length of the muscle had more (P<0.01) muscle fibers and endomysial sheaths per unit area than samples from the posterior half-length of the muscle.