Effect of Cooling Rates and Temperatures on Quality and Safety of Quahog Clams (Mercenaria mercenaria)

The model ordinance in the National Shellfish Sanitation Program's Guide for the Control of Molluscan Shellfish was initially established for oysters; however, the clam industry also follows the protocol. Rapid cooling during periods when the growing waters exceed 80°F (26.7°C) results in cold shock, which causes unacceptable mortalities in clams. The clam industry was looking for a procedure to lower the clams to the standard temperature while minimizing shell shock mortalities during the warm summer months. Three tempering treatments were examined, and total aerobic plate counts (APCs) and most-probable-number (MPN) counts of Vibrio, V. parahaemolyticus, and fecal coliforms were enumerated. In treatment 1 (control), clams were harvested, held for 5 h at 90°F (32.2°C), and then moved to 45°F (7.2°C) for storage. In treatment 2, clams were harvested and held for 5 h at 90°F (32.2°C), followed by 12 h at 65°F (18.3°C) and 12 h at 55°F (12.8°C), and then were moved to 45°F (7.2°C) for long-term storage. In ...