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Survey, Detection and Identification of Bacteria causing ropy milk defect in raw and pasteurized milk

Investigators
Jimenez-Flores, Rafael
Institutions
California Polytechnic State University
Start date
2007
End date
2010
Objective
1. Screen and identify the microorganism(s) causing ropy milk defect in samples of raw and pasteurized milk. 2. Determine if there is a correlation between the organisms producing RM in raw and pasteurized milk.
More information
The objective of this study was to identify and classify the current population of bacteria causing ?ropy milk? and help develop better strategies to maintain and improve milk quality. Researchers surveyed a commercial milk supply presenting a ropy milk (RM) defect, isolated bacteria with proven positive RM production, and identified their DNA using API/ID32 and Randomly Amplified Polymorphic DNA (RAPD) methods. They hypothesized that this work would reveal the biological nature of microorganisms producing RM, and it would confirm if the RM organisms in raw and pasteurized milk are related. This study isolated and identified Klebsiella oxitoca and Klebsiella pneumoneae as the main organisms causing ropy milk. Results show severe flaws on assuming that the ?ropy milk test? can predict or correlate the quality of pasteurized milk. The organism(s) responsible for ?ropy milk? production were found in the farm environment; mostly in the cow bedding material. Thermal death curves for these organisms prove they did not survive pasteurization at 65?C (149?F) and 70?C (160?F).
Funding Source
Dairy Research Inst.
Categories
Food Defense and Integrity
Bacterial Pathogens