A Portable Chemiluminescence Assay of Alkaline Phosphatase Activity To Monitor Pasteurization of Milk Products
2019
Sarver, Ronald | Higbee, Cayley | Biswas, Preetha | Zhang, Lei | Banner, Nate | Rice, Jennifer | Mozola, Mark | Tollakson, Zachari | Hardrath, Luci | Bulthaus, Mary | Zangl, Justin
A chemiluminescence assay using a handheld luminometer to measure the activity of alkaline phosphatase was developed that can detect 0.002% or more of unpasteurized milk in various milk products. Evaluation of the assay followed an National Conference on Interstate Milk Shipments (NCIMS)–approved protocol in which aliquots of pasteurized milk products were spiked with raw milk at various levels. Milk products evaluated included skim white milk, 1 and 2% fat content white milk, whole white milk, strawberry-flavored 1% fat content milk, chocolate-flavored 1% fat content milk, half-and-half, and heavy cream. Split samples were prepared, and alkaline phosphatase activities were determined in triplicate on 4 days by three NCIMS-accredited laboratories by the chemiluminescent method and NCIMS-approved reference methods. Equivalence of the chemiluminescent method to the approved reference methods was demonstrated for all eight products evaluated over a range of raw milk concentration from 0 to 0.5%, using criteria established by NCIMS, in which mean results obtained by the three laboratories by the chemiluminescent method were within 1 standard deviation of the mean results obtained by the NCIMS-approved reference methods at each alkaline phosphatase concentration. Procedures for measurement of microbial and reactivated alkaline phosphatase were also established for the method.
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