Freezing has also been considered as a meth- 

 od of preservation. Since it achieves inacti- 

 vation of bacterial spoilage without a heat 

 treatment, it has a theoretical advantage com- 

 pared with pasteurization. However, the com- 

 mercial production of frozen blue crab meat is 

 minor since its storage life at 0° F is considered 

 to be less than 1 month (U.S. General Services 

 Administration, 1956). If blue crab meat is 

 frozen by conventional techniques (plate freez- 

 er, air-blast freezer, etc.), the meat tends to 

 become spongy and fibrous in texture and it 

 will lose the delicate flavor of fresh meat after 

 a few weeks at 0° F (Dassow, Pottinger, and 

 Holston, 1956). Although this deterioration 

 is probably related to protein and lipid trans- 

 formations in situ, its cause is not clear. Sim- 

 ilar phenomena are believed to limit the frozen 

 storage life of other crustaceans although the 

 rate of this deterioration is dependent on the 

 species used and whether the picked meat or 

 meat-in-the-shell is frozen. 



It is well known that the storage stability of 

 frozen seafoods, in general, can be influenced 

 by the following factors: method (rate) of 

 freezing, method of packaging, and storage tem- 

 perature and its duration. For example, it is 

 known that techniques such as cryogenic freez- 

 ing (vs. plate, air blast, or brine immersion 

 freezing), vacuum packaging (vs. a loose-fit- 

 ting package containing air) and storage below 

 0° F (vs. storage at 0° F or above) may pro- 

 long the storage life of seafoods. In the case 

 of blue crab meat or meat from other crusta- 

 ceans, the relative importance of these tech- 

 niques in determining frozen storage stability 

 has received very little attention. Consequently, 

 the objective of the present investigation is to 

 compare each of these techniques in various 

 combinations with other preservation tech- 

 niques in order to discover which procedures 

 are required to preserve blue crab meat for 

 2 to 8 months without any significant loss in 

 the desirable qualities of freshly picked meat. 



MATERIALS AND METHODS 



Types of Blue Crab Meat 



Most of the experimental i^rogram was per- 

 formed with "regular" blue crab meat obtained 

 from low-salinity waters in the Chesapeake Bay 



and supplied by the J. M. Clayton Company, 

 Cambridge, Md. Regular meat is a trade des- 

 ignation for meat which is picked from crab 

 bodies or cores. Because it contains mostly 

 flake meat with a much smaller quantity of 

 lump meat, it is called "flake" meat in this 

 report. For comparison purposes, hand-picked 

 lump meat and claw meat from the same source 

 were used in smaller quantities. For other 

 comparison tests, regular and lump meat were 

 obtained from the high-salinity waters oflF the 

 Virginia coast and supplied by George 0. 

 Spence and Sons Co., Quinby, Va. The freshly 

 picked samples were shipped in ice to the Na- 

 tional Marine Fisheries Service Laboratory in 

 College Park, Md., and immediately frozen as 

 described below. Each sample in these tests 

 contained appi'oximately 95 g of crab meat. 

 After completing the preservation treatments, 

 the samples were shipped to FMC Central En- 

 gineering Laboratories in insulated styrofoam 

 containers using dry ice for the frozen samples 

 or wet ice for the freshly picked control samples. 



Freezing of Blue Crab Meat 



Two cryogenic liquids, Freon 12- and nitro- 

 gen, were used to freeze individual pieces of 

 meat before packaging. These cryogenic meth- 

 ods were not used on prepackaged meat for two 

 basic reasons. We were aware that prepack- 

 aging the meat would increase the cost of freez- 

 ing per unit of meat frozen since it would 

 lengthen the time needed to freeze all the pieces 

 of meat in that package. Also, there was no 

 evident advantage from a technological view- 

 point for the blue crab industry to freeze pre- 

 packaged meat. Indeed, preliminary experi- 

 mental results have indicated that the quality 

 of individually frozen pieces of blue crab meat 

 is superior to the quality of prepackaged frozen 

 blue crab meat even when the package is kept 

 14,-inch thick during freezing. 



Freezing by immersion in food grade 

 Freon 1 2. — The arrangement of the equipment 

 is shown in Figure I-l. Dewar I (capacity 2 

 liters) was used to cool the Freon coming from 



' Trade names are used to facilitate description; 

 no endorsement of product is implied. The chemical 

 name for Freon 12 is dichlorodifluoromethane. 



