Microbiological Evaluation of Shrimp (Pandalus borealis) Processing

Abstract

Line samples from three different shrimp processing plants (brine-cooked shell-on, hand-peeled raw, and machine-peeled cooked) in Maine were examined for microbiological quality. Aerobic plate count (APC) of freshly caught shrimp (Pandalus borealis) was found to be about 530/g (Plate Count Agar at 35 C) while salt-requiring (SR) organisms were at significantly higher concentration (1.11 ×105/g; Salt Water Medium at 21 C). Some increase in psychrotrophic-mesophilic flora of shrimp delivered to the plant was observed. Cooking in-plant or on board the boat drastically reduced the SR flora, which was subsequently observed to increase after culling and inspection in the brine-cooked shell-on process. No such significant fluctuation due to processing was detected in APC. Shrimp sampled from steel barrels before a hand-peeled raw operation exhibited relatively high APC (7.2 × 104/g) and SR microflora (2.78 × 106/g). Heading and hand-peeling reduced the APC and SR bacterial loads by 71 and 95%, respectively. Subsequent processing and holding at room temperature resulted in a product with an APC and SR load of about 4 × 104/g. Similarly, high APC (1.66 × 105/g) and SR bacterial loads (1.84 × 105/g) were detected in samples obtained from a storage hopper of the machine-peeled cooking process. Although significant reduction in bacterial load was detected on line samples of this process (fluming, preheating, and cooking), the total bacterial load reached about 4 × 104/g before the canning step. Low levels of contamination with coliform and/or coagulase-positive staphylococci were detected in the three processes studied.