Rapid and non-invasive multivariate approach for the quality control of raw milk from mountain areas based on proton transfer reaction mass spectrometry data

Abstract

Rationale: A rapid and non-invasive method for the control of milk by proton transfer reaction mass spectrometry was developed. The approach has the potential to verify the geographic origin and altitude of dairy farms, provided that the cows have been extensively grazed with forage that reflects the botanical composition of the mountain environment. Methods: Over a 1-month period, a total of 116 samples were analysed by proton transfer reaction mass spectrometry (PTRMS). A multivariate control chart based on the Hotelling T2 statistic was built with PTRMS data and, for comparison, with the chemical parameters obtained by infrared spectroscopy (FTIR, MilkoScan). Results: The headspace analysis of the samples led to characteristic volatile profiles. Farms located in different mountain areas were discriminated by the protonated molecules m/z 45 (acetaldehyde), 59 (acetone), 73 (2-butanone) and 89 (butyric acid, ethyl acetate, pentanol). Milk samples were also discriminated according to the altitude of the farms according to m/z 45, 59, 63 (dimethyl sulfide), 73 (propionic acid, methyl acetate) and 81 (terpenes). Conclusions: A multivariate control chart based on PTRMS data was used for the quality control of milk. Milk samples from farms located at different mountain areas and altitudes were successfully discriminated.