Publications (2)3.55 Total impact
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ABSTRACT: Reproducibility of aerobic plate count (APC), coliform and fecal coliform counts in frozen cod was examined by 14 laboratories (3 government, 4 university and 7 industry) using primarily FDA recommended procedures. In order to assure homogeneity of samples, the fish was comminuted and thoroughly mixed. The 35°C and the “room temperature” (26°C) APC on Sample A (a good quality product) were 1.3 × 105/g and 2.6 × 105/g, respectively, and for Sample B (a questionable quality product) the counts were 2.9 × 105/g and 6.4 × 105/g, respectively. Standard deviations among counts (log10 values) were 0.26 and 0.32 for the 35°C counts and 0.24 and 0.40 for the 26°C counts of Sample A and B, respectively. The std. dev. were reduced to 0.19, 0.22, 0.17 and 0.25, respectively, when counts that did not show significant overlap (based on Dur can's New Multiple Range Test) were excluded from the calculations. Coliform counts on Sample A (not inoculated) ranged from <30 to 4.6 × 105/100g. Coliform and fecal coliform counts for Sample B (inoculated at estimated level of 1 × 104/100g) were 5.8 × 103/100g and 5.5 × 103/100g, with a std. dev. of 0.43 and (.37, respectively. The std. dev. for the coliform counts was reduced to 0.30 when counts from one laboratory were excluded, based on Duncan's New Multiple Range Test.
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ABSTRACT: The behavior of two strains of Listeria monocytogenes (147 and ATCC 19111) was evaluated at different stages of salmon processing. At lower temperatures of 2, 7, and 11 degrees C, L. monocytogenes survived on dry wood surfaces for at least 3 days without added nutrients but was unrecoverable after 2 days at 22 degrees C. Moisture or minimal nutrients on the wood surface increased viability of L. monocytogenes at all incubation temperatures. When large amounts of nutrients were provided, the recoveries of L. monocytogenes at low temperatures (< or = 11 degrees C) were essentially unchanged over the 3-day holding period, and rapid growth was observed at room temperature. In the presence of natural microflora, L. monocytogenes died off rapidly in seawater within 36 h at room temperature. When held at < or = 11 degrees C, L. monocytogenes lost viability throughout storage but was still detectable after more than 6 days of incubation. In the absence of natural microflora, both strains of L. monocytogenes were static during the holding period at all temperatures. At 2, 7, and 11 degrees C, L. monocytogenes in nonsterile salmon blood-water remained viable even after 6 days of incubation, whereas in sterile blood-water, growth of L. monocytogenes was observed at 7 and 11 degrees C. In the absence of natural microflora, L. monocytogenes grew better than it did in the presence of natural microflora. L. monocytogenes 147 was more competitive with background organisms than was L. monocytogenes ATCC 19111. No L. monocytogenes could be detected in the digestive tract of salmon 3 days after its introduction. The survival pattern of L. monocytogenes in fish digestive tracts was similar, regardless of whether the fish were feeding or not. A noticeable decline in the pathogen was observed as early as 3 h after introduction.
University of MaineOrono, Minnesota, United States