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.

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