A Scanning Electron Microscopy Study of Effects of Processing on Crustacean Muscle

Abstract

Scanning electron microscopy (SEM) was employed to evaluate structural damage to blue crab (Cullinectes supidus) muscle resulting from thermal processing combined with freezing preservation in the course of developing the methodology for applying SEM to the study of processinglpreservation effects on muscle tissue. Specimens dissected from thermally processed, fast and slow frozen, conventionally frozen stored crabmeat were glutaraldehyde-fixed, solvent exchanged, freeze fractured, critical point dried, gold coated and examined and photographed with an Etec "Autoscan" microscope. Gross structural damage to the thermally processed tissue due to ice crystal formation and growth was clearly observable in low magnification (ca. 150x) micrographs of freeze-fractured transverse surfaces. Ice crystal formation and growth followed the well documented patterns associated with fast and slow frozen native (i.e., raw) muscle tissue studied in thin section by means of transmission microscopic techniques following conventional freezer storage. It was determined that the low magnification images best depicted gross structural damage to intact fibers or fiber bundles while high magnifications (ca. > 1000x) depicted ultrastructural organization and damage quite satisfactorily. An accelerating voltage of 10 Kev was adequate for the former whereas 20 Kev proved superior in the latter case, although the risk of 'charging' was increased at the higher voltage. An osmium post-fix was found to be unnecessary, gluteraldehyde being adequate. Freeze fracturing was essential for revealing 'intracellular' damage especially, and critical point drying appeared to be superior to freeze drying prior to gold coating. Crustacean muscle is especially well suited to SEM study.

Nondependence of diffusion-controlled peak dispersion on diffusion coefficient and ionic mobility in capillary zone electrophoresis without electroosmotic flow

“…It can be concluded from this equation, that the ratio u/D, occurring in the expression for the plate number, must have a distinct, constant value. This relation was mentioned by Giddings (4) and is experimentally evaluated here.…”

“…The ratio u/D (eq 6), only depending on the charge number, is substituted in eq 3 for the plate height or in eq 4 for the plate number, thus obtaining the following expressions (4,8,9):…”

Relationship of Freezing Preservation Parameters to Texture-Related Structural Damage to Thermally Processed Crustacean Muscle

“…Wired shrimp and crab cores were immersed together with several others in cheesecloth bags which were held submerged until freezant temperature was reached a s indicated by the recorder. At zero time (immediately after freezing) and after 1, 3, 6, and, in some cases 9 months of frozen storage duplicate specimens of each variable were prepared for and examined by SEM for texture-related structural damage due to ice crystal formation and growth, employing procedures described in Giddings and Hill (1976). Results are in the form of electron photomicrographs, visual comparison of which reveals differences resulting from the different freezing and frozen storage methods.…”

“…In an earlier research note (Giddings and Hill 1976) the feasibility of employing scanning electron microscopy (SEM) to study thermal processinglfreezing preservation-connected structural damage to muscle food was demonstrated on cooked-frozen blue crab muscle. Light microscopy and, to some extent transmission electron microscopy have proven useful in following the effects of ice crystal formation and growth in frozen raw fish tissue (Mills 1975).…”

Stationary-phase phenomena in capillary supercritical fluid chromatography

“…Although only limited data on the solute diffusivities in polymeric stationary phases have been published (20-22,18), a recent study by Cramers et al (18) on Dh values in GC failed to find any measurable differences between mechanically coated and chemically immobilized (cross-linked) siloxane polymers. According to molecular kinetic theory (23,24), several factors may influence solute diffusivity in the liquid phase: temperature, viscosity, and its "molecular enviroment"…”