Quality of on-board cryogenically frozen sea scallops (Placopecten Magellanicus)

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Virginia Tech


Scallops have traditionally been blast or sharp frozen. This study compared the quality of at-sea cryogenically frozen scallops with fresh and mechanically frozen scallops. A liquid CO₂ batch freezer was installed on-board the scallop boat. Samples were analyzed for microbiological, physical, chemical and sensory qualities. Sample types included fresh scallops, mechanically frozen scallops and 4 hr and 24 hr (on ice) cryogenically frozen scallops.

The thaw loss mean of 4 hr cryogenically frozen scallops was 2.41 percent compared to means of 4.21 percent for 24 hr (on ice) cryogenically frozen scallops and mechanically frozen scallops, P < 0.0001. Cook loss for the 4 hr cryogenic frozen scallop was also reduced (P < 0.01) by 27 percent when baked. Cook method did not affect cook loss. Color measurements on the CIE L* a* b* scale did not differ significantly for raw or baked scallops. Instron peak force measurements had a very high standard error and therefore were not be analyzed statistically. The 4 hr cryogenically frozen scallops met the French Moisture/Protein ratio test standard of 5 (P > 0.02) but higher ratios were observed for 24 hr (on ice) cryogenically frozen scallops and mechanically frozen scallops. Scallops meeting this standard have greater export potential and the ability to attract high value markets. Variations observed in proximate composition were minor and may be due to biological factors. Sensory panelists found a significant difference (P < 0.01 to P < 0.05) among the randomly presented pairs of scallops. Over a 5 month storage period, the sensory characteristics of odor and taste of the cryogenically frozen scallops diminished and the mechanically frozen scallops were consistently scored higher. Mechanically frozen scallops had significantly lower cfu/gm for aerobic, psychrotrophic and coliform counts compared to fresh and cryogenically frozen scallops.

The 4 hr cryogenically frozen scallop had lower thaw and cook loss which could have a significant economic and nutritional significance. Mechanically frozen scallops had a lower microbiological population and frozen storage for 8 months did not affect its taste or odor. Improved Sanitation and process control could establish cryogenically frozen scallops as a premium product.