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Fluorometric Detection of Active Alkaline Phosphatase and Gamma-Glutamyl Transferase in Fluid Dairy Products from Multiple Species

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Over the past 80 years, a variety of methods have been developed to detect underpasteurized or improperly pasteurized milks used in dairy products. Existing methods are hampered by duration of analysis, poor reproducibility, and in some cases the use of hazardous chemicals. To overcome these issues, two new methods have been developed using fluorogenic substrates for two marker enzymes, alkaline phosphatase and gamma-glutamyl transferase. In 30 min, up to 18 samples can be analyzed in triplicate by both methods on two separate 96-well plates. Sample preparation is not necessary for liquid milks when using these methods. The relative standard deviation for each assay is less than 9%, and the correlation coefficient for results of the two methods is greater than 0.98. Using the new methods, milks from four species and nine commercially available liquid milk products were tested. The new methods were also tested directly against an existing phosphatase method (Fluorophos) in spiked whole milk samples.

Document Type: Research Article


Affiliations: 1: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 5100 Paint Branch Parkway, College Park, Maryland 20740, USA. 2: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 5100 Paint Branch Parkway, College Park, Maryland 20740, USA; Joint Institute for Food Safety and Applied Nutrition, University of Maryland, College Park, 5201 Paint Branch Parkway, College Park, Maryland 20740, USA; Oak Ridge Institute for Science and Education, 1299 Bethel Valley Road, Oak Ridge, Tennessee 37830, USA

Publication date: May 1, 2013

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