Mix-and-read method for assessment of milk pasteurization using a smartphone or a common digital camera

Alkaline phosphatase (ALP) is the most widely used marker of the adequacy of milk pasteurization since it is inactivated at temperatures slightly higher than those required for elimination of pathogens. The cutoff level is 350 mU/L. The approved colorimetric, fluorometric, and chemiluminometric meth...

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Bibliographic Details
Published in:Analytical and bioanalytical chemistry 2020-09, Vol.412 (23), p.5663-5669
Main Authors: Sevastou, Areti, Tragoulias, Sotirios S., Kalogianni, Despina P., Christopoulos, Theodore K.
Format: Article
Language:English
Subjects:
Adequacy
Alkaline phosphatase
Alkaline Phosphatase - metabolism
Analytical Chemistry
Animals
Assessments
Biochemistry
Calibration
Cameras
Cattle
Characterization and Evaluation of Materials
Chemiluminescence
Chemistry
Chemistry and Materials Science
Coefficient of variation
Colorimetry
Cost analysis
Cow's milk
Dairy industry
Detectors
Digital cameras
Digital imaging
Electronic cameras
Food Science
Image acquisition
Laboratory Medicine
Methods
Milk
Milk - chemistry
Milk - enzymology
Monitoring/Environmental Analysis
Pasteurization
Phenolphthalein
Phosphatases
Photography - instrumentation
Photomultiplier tubes
Pretreatment
Research Paper
Sheep
Smart phones
Smartphone
Smartphones
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Summary:Alkaline phosphatase (ALP) is the most widely used marker of the adequacy of milk pasteurization since it is inactivated at temperatures slightly higher than those required for elimination of pathogens. The cutoff level is 350 mU/L. The approved colorimetric, fluorometric, and chemiluminometric methods require specialized readers with photomultipliers as detectors, and the samples are usually analyzed one-by-one. We developed a low-cost mix-and-read method that exploited a smartphone or a common digital camera as detectors for the chemiluminometric determination of ALP in milk. As samples, we used pasteurized cow and sheep milk spiked with ALP, as well as mixtures of pasteurized and raw (non-pasteurized) milk. Chemiluminescence images acquired by the smartphone or the digital camera were analyzed by the ImageJ software. The limits of detection (LODs), for images captured by the smartphone, were 4.4 mU/L and 11.1 mU/L for cow milk and sheep milk, respectively, while with the digital camera, the respective LODs were 6.2 mU/L and 6.7 mU/L, respectively. The coefficients of variation (CVs) at the cutoff level of 350 mU/L were 8% and 8.5% for the cow and sheep milk, respectively. For images by the digital camera, the CVs were 5.8% and 5% for cow and sheep milk, respectively. The performance of the method is similar to methods that use a microtiter plate and a luminometer for chemiluminescence measurements. Sample pretreatment is not necessary. The microtiter well format combined with detection by a smartphone enables the analysis of multiple samples simultaneously. It is anticipated that the method will prove useful for the rapid assessment of milk pasteurization efficiency in dairy industries, especially in remote areas where expensive instruments are not available. Graphical abstract
ISSN:1618-2642
1618-2650
DOI:10.1007/s00216-020-02786-3