Occurrence and growth of Listeria monocytogenes in packaged raw milk

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http://hdl.handle.net/10138/309477

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Castro , H , Ruusunen , M & Lindström , M 2017 , ' Occurrence and growth of Listeria monocytogenes in packaged raw milk ' , International Journal of Food Microbiology , vol. 261 , pp. 1-10 . https://doi.org/10.1016/j.ijfoodmicro.2017.08.017

Title: Occurrence and growth of Listeria monocytogenes in packaged raw milk
Author: Castro, Hanna; Ruusunen, Marjo; Lindström, Miia
Contributor: University of Helsinki, Departments of Faculty of Veterinary Medicine
University of Helsinki, Departments of Faculty of Veterinary Medicine
University of Helsinki, Departments of Faculty of Veterinary Medicine
Date: 2017-11-16
Language: eng
Number of pages: 10
Belongs to series: International Journal of Food Microbiology
ISSN: 0168-1605
URI: http://hdl.handle.net/10138/309477
Abstract: The increased availability of packaged raw drinking milk necessitates the investigation of the occurrence and growth of Listeria monocytogenes in raw milk during distribution and storage. The occurrence of L. monocytogenes in 105 retailed raw milk bottles, 115 bulk tank milk samples, 23 in-line milk filter socks and in 50 environmental samples collected from an on-farm dairy establishment were investigated. Growth of inoculated low-level L. monocytogenes contamination was also investigated in two types of raw milk packaging, namely in 1-litre plastic bottles and 3-litre bag-in-boxes, both stored at three different storage temperatures of 6, 8 and 10 degrees C. The occurrence of L. monocytogenes was higher (4.8%) in bottled raw milk stored until the use-by-date of the package compared to fresh bulk tank milk (1.7%). L. monocytogenes counts were 5 13 CFU/ml in bottled raw milk and 5 1 CFU/ml in bulk tank milk. L. monocytogenes was not detected in the packaging facility, but occurred very frequently (39%) in the milk filter socks. Subtyping of L. monocytogenes isolates using pulsed -field gel-electrophoresis revealed seven pulsotypes, of which two occurred in multiple samples. Targeted inoculum levels of 1-2 CFU/ml yielded L. monocytogenes counts 100 CFU/ml within seven days of storage in 22% of the raw milk packages stored at 6 degrees C, and in all of the raw milk packages stored at 8 degrees C. The frequent occurrence of L. monocytogenes in raw milk and the ability of a low-level L. monocytogenes contamination to grow at refrigeration temperatures highlight the importance of consumer education regarding the appropriate raw milk storage and handling.
Subject: Unpasteurized milk
Ready-to-eat food
Shelf-life
Growth modelling
Growth rate
Lag time
Refrigeration
Food safety
BULK TANK MILK
FIELD GEL-ELECTROPHORESIS
PATHOGENIC BACTERIA
DAIRY FARM
REFRIGERATION TEMPERATURES
MULTIPLEX PCR
UNITED-STATES
RISK-FACTORS
PREVALENCE
CONSUMPTION
416 Food Science
1183 Plant biology, microbiology, virology
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