MALDI-TOF-MS Platform for Integrated Proteomic and Peptidomic Profiling of Milk Samples Allows Rapid Detection of Food Adulterations

Adulteration
of ovine, caprine, and buffalo milks with more common
bovine material occurs for economic reasons and seasonal availability.
Frauds are also associated with the use of powdered milk instead of
declared, fresh material. In this context, various analytical methods
have been adapted to dairy science applications with the aim to evaluate
adulteration of milk samples, although time-consuming, suitable only
for speciation or thermal treatment analysis, or useful for a specific
fraud type. An integrated MALDI-TOF-MS platform for the combined peptidomic
and proteomic profiling of milk samples is here presented, which allows
rapid detection of illegal adulterations due to the addition of either
nondeclared bovine material to water buffalo, goat, and ovine milks
or of powdered bovine milk to the fresh counterpart. Peptide and protein
markers of each animal milk were identified after direct analysis
of a large number of diluted skimmed and/or enriched diluted skimmed
filtrate samples. In parallel, markers of thermal treatment were characterized
in different types of commercial milks. Principal components scores
of ad hoc prepared species- or thermal treatment-associated adulterated
milk samples were subjected to partial least-squares regression, permitting
a fast accurate estimate of the fraud extents in test samples at either
protein and peptide level. With respect to previous reports on MALDI-TOF-MS
protein profiling methodologies for milk speciation, this study extends
that approach to the analysis of the thermal treatment and introduces
an independent, complementary peptide profiling measurement, which
integrates protein data with additional information on peptides, validating
final results and ultimately broadening the method applicability.