UVM Theses and Dissertations
Format:
Print
Author:
Lynch, Daniel Peter
Dept./Program:
Nutritional and Food Sciences
Year:
2012
Degree:
MS
Abstract:
With increasing consumer demand for raw milk in the U.S., debate is growing over food safety guidelines and public policies regarding its consumption. This study was conducted to assess the microbiological quality and shelf life of retail raw milk samples obtained in three New England states (Maine, New Hampshire and Connecticut). New England states permitting retail raw milk sales have differing microbiological criteria for, producers and varying testing requirements for raw milk safety surveillance. Microbial surveillance was performed to obtain baseline data on quality indicators and pathogen incidence in retail raw milk, and to determine whether values differed by state. Shelf life was examined to determine the microbiological quality of raw milk prior to stated sell-by date. Over a six-month period, raw milk samples (n=98) were purchased at retail locations in Maine, N.H., and Conn. Samples were analyzed for standard plate count (SPC), coliform count (CC), and somatic cell count (SCC).
Pathogen incidence was assessed using qualitative and quantitative screening methods for Campylobacter jejuni, E. coli O157:H7, Salmonella sp. and Listeria monocytogenes. L. monocytogenes was detected in 2.0% of all samples (2/98). Overall SPC ranged from a low of 40 CFU/ml to a high of 6.1x10⁷ CFU/ml. The average (mean) overall SPC was 1.7x10⁶ CFU/ml with a geomean of 2.2x10⁵. Overall CC ranged from a low of <1CFU/ml to a high 2.1xl0⁴ CFU/ml. The average overall CC was 517 CFU/ml with a geomean of 2 CFU/ml. Samples were analyzed for compliance with the 10 coliform/ml regulatory standard for pasteurized milk. A total of 94.4% of milk samples obtained from Conn. had CC of less than or equal to 10 CFU/ml, versus 51.3% and 36.4% of samples obtained from Maine and N.H., respectively. This difference was statistically significant as determined by Chi square analysis (p=.001). This may be due to more stringent Conn. production guidelines which require pathogen testing for retail raw milk producers.
Pathogen incidence was assessed using qualitative and quantitative screening methods for Campylobacter jejuni, E. coli O157:H7, Salmonella sp. and Listeria monocytogenes. L. monocytogenes was detected in 2.0% of all samples (2/98). Overall SPC ranged from a low of 40 CFU/ml to a high of 6.1x10⁷ CFU/ml. The average (mean) overall SPC was 1.7x10⁶ CFU/ml with a geomean of 2.2x10⁵. Overall CC ranged from a low of <1CFU/ml to a high 2.1xl0⁴ CFU/ml. The average overall CC was 517 CFU/ml with a geomean of 2 CFU/ml. Samples were analyzed for compliance with the 10 coliform/ml regulatory standard for pasteurized milk. A total of 94.4% of milk samples obtained from Conn. had CC of less than or equal to 10 CFU/ml, versus 51.3% and 36.4% of samples obtained from Maine and N.H., respectively. This difference was statistically significant as determined by Chi square analysis (p=.001). This may be due to more stringent Conn. production guidelines which require pathogen testing for retail raw milk producers.