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 treatment 3, clams were harvested and held for 5 h at 90 °F (32.2 °C), followed by 24 h at 55 °F (12.8 °C) before being moved to 45 °F (7.2 °C) for long-term storage. Three replicate trials were performed with triplicate analyses during late June through early to mid-August. The current National Shellfish Sanitation Program standard is treatment 1; it contained statistically (P ≤ 0.05) higher total APCs than treatments 2 and 3 throughout the 21-day storage period. APCs ranged from 2.3 × 10(4) immediately after harvest to 2.7 × 10(6), 1.6 × 10(5), and 4.8 × 10(5) for treatments 1, 2, and 3, respectively, after 14 days of storage. A statistical analysis showed that treatments 2 and 3 had significantly lower total MPN per gram Vibrio than treatment 1 on day 7 but were equal to treatment 1 on days 1 and 14. MPN per gram for V. parahaemolyticus was statistically lower in treatments 2 and 3 than in treatment 1 on storage days 1 and 7. However, on day 14, treatment 3 was significantly lower than treatments 1 and 2. There was no statistical difference for fecal coliforms. The greatest mortality occurred in treatment 1 (87.4%), followed by treatment 2 (83.3%) and treatment 3 (66.0%). The outcome of this research clearly shows that treatments 2 and 3 can cool clams to a temperature of 45 °F (7.2 °C) without compromising quality or safety and can reduce the number of dead clams introduced into the marketplace.

Analysis of Campylobacter jejuni , Campylobacter coli , Salmonella , Klebsiella pneumoniae , and Escherichia coli O157:H7 in Fresh Hand-Picked Blue Crab ( Callinectes sapidus ) Meat †.

This study was conducted to determine the levels of Campylobacter jejuni , Campylobacter coli , Salmonella , Klebsiella pneumoniae , and Escherichia coli O157:H7 in fresh hand-picked blue crab ( Callinectes sapidus ) meat. An attempt was made to correlate these selected pathogens and general microbial quality to processors' sanitation practices and facility size. Hand-picked crabmeat samples from 12 blue-crab-processing facilities in the Chesapeake Bay region were collected and analyzed. Twenty samples from each of the different facilities were collected on different processing days. Facilities were chosen on the basis of production levels and Virginia Department of Health inspection scores as an indicator of sanitation practices (excellent, ≥94.5, acceptable, <94.5). All samples were tested between 16 h and 36 h after collection. Campylobacter jejuni was isolated from 36 (15%) of the 240 samples and Campylobacter coli was isolated from 14 (5.8%). Quantitative levels in all case were below limits of detection (<0.30 MPN/g). Klebsiella pneumoniae was isolated from a total of 51 (21%) samples. Counts ranged from less than 0.30 to 4.3 MPN/g. Aerobic plate counts ranged from 7.4 × 103 to 4.6 × 108 CFU/g with coliform counts ranging from <0.3 to 32.8 MPN/g. Fecal coliform levels were <0.3 to 2.26 MPN/g and Escherichia coli from <0.3 to 0.77 MPN/g. Salmonella spp. and Escherichia coli O157:H7 were not detected in any of the 240 samples analyzed. No significant differences (P < 0.05) between size and inspection scores were observed for general microbial quality or the presence of Klebsiella pneumoniae or Campylobacter species.