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United States Department of Agriculture

Agricultural Research Service

Title: Growth of Listeria Monocytogenes in Seafood Salad As Affected by the Ph of Mayonnaise and Storage Temperature

Authors
item HWANG, CHENG-AN
item Tamplin, Mark

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 1, 2004
Publication Date: July 12, 2004
Citation: Hwang, C., Tamplin, M.L. 2004. Growth of Listeria monocytogenes in seafood salad as affected by the pH of mayonnaise and storage temperature. International Food Technologists. Abstract. 99D-32.

Technical Abstract: Seafood salad has been identified as a ready-to-eat food with a relatively high incidence of contamination by Listeria monocytogenes; however, little is known about the behavior of this pathogen in seafood salad as a function of product pH and storage temperature. To produce data towards the development of a predictive growth model, a 6-strain cocktail of L. monocytogenes was inoculated into a mixture of shrimp and crabmeat, mixed with mayonnaise that was previously adjusted with NaOH to pH 3.7, 4.0, 4.4, 4.7 or 5.1, and then stored at 4°, 8° or 12°C under an aerobic atmosphere. With an initial inoculum of 1.5 log cfu/g, L.monocytogenes grew in salad at each combination of storage temperature and mayonnaise pH. At 4°C, the growth rate of L. monocytogenes at pH 3.7, 4.0, 4.4, 4.7, and 5.1 was 0.0107, 0.0112, 0.0113, 0.0103 and 0.0096 log cfu/h, respectively. Levels in the salad increased from 1.5 log cfu/g to 6.0-7.0 log cfu/g after 22 days of storage. At 8°C, the growth rate of L. monocytogenes was 0.0175, 0.0182, 0.0185, 0.0176, and 0.0155 log cfu/h at pH of 3.7, 4.0, 4.4, 4.7, and 5.1,respectively, reaching 7.0 log cfu/g in all samples after 16 days of storage. At 12°C, the growth rate of L. monocytogenes was 0.0283, 0.0222, 0.0220, 0.0235, and 0.0216 log cfu/h at pH of 3.7, 4.0, 4.4, 4.7, and 5.1, respectively, reaching 7.0 log cfu/g in all samples after 12 days of storage. At each storage temperature, the lag phase duration decreased with decreasing mayonnaise pH. These studies demonstrate that seafood salad supports the growth of L. monocytogenes over a wide range of pH values and storage temperatures that are relevant to commercial production practices.

Last Modified: 9/29/2014