Rapid Turbidimetric Detection of Milk Powder Adulteration with Plant Proteins

Development
of assays to screen milk for economically motivated adulteration with
foreign proteins has been stalled since 2008 due to strong international
reactions to the melamine poisoning incident in China and the surveillance
emphasis placed on low molecular weight nitrogen-rich adulterants.
New screening assays are still needed to detect high molecular weight
foreign protein adulterants and characterize this understudied potential
risk. A rapid turbidimetric method was developed to screen milk powder
for adulteration with insoluble plant proteins. Milk powder samples
spiked with 0.03–3% by weight of soy, pea, rice, and wheat
protein isolates were extracted in 96-well plates, and resuspended
pellet solution absorbance was measured. Limits of detection ranged
from 100 to 200 μg, or 0.1–0.2% of the sample weight,
and adulterant pellets were visually apparent even at ∼0.1%.
Extraction recoveries ranged from 25 to 100%. Assay sensitivity and
simplicity indicate that it would be ideally suitable to rapidly screen
milk samples in resource poor environments where adulteration with
plant protein is suspected.