A Portable Chemiluminescence Assay of Alkaline Phosphatase Activity to Monitor Pasteurization of Milk Products

Abstract

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. HIGHLIGHTS

Polyacrylic Acid-Ca2+(Ce3+) Nanoclusters as Fluorescent “Off–On–Off” Probes for Quantitative Detection of Pyrophosphate and Alkaline Phosphatase

“…Hitherto, a variety of methods have been applied in the quantitative detection of PPi, including fluorescence, , colorimetry, , and chemiluminescence . On the other hand, fluorescent strategies, , colorimetric methods, , electrochemistry, , chemiluminescence, , and surface-enhanced Raman scattering have also been developed for qualitative and quantitative detection of ALP. Compared to colorimetric methods with weak anti-interference capability and high detection limits, and electrochemical analysis methods with relatively weak signals and low sensitivity, fluorescence methods feature low sample requirements and strong resistance to interference.…”