Analysis of Cheese Small Molecules by UPLC–QToF-MS and Multivariate Statistical Methods Using Several Extraction Procedures

Abstract

Lyophylized (L) and nonlyophylized (NL) samples of two cheeses from different batches were extracted with either methanol:water (8:2, v/v) or isopropanol:water (7:3, v/v), and the extracts were analyzed by ultraperformance liquid chromatography coupled with electrospray ionization/quadruple-time-of-flight mass spectrometry (UPLC–ESI–QToF-MS) in both positive and negative modes. Chromatographic and mass spectrometric data were further compared for different samples by paired t test and principal component analysis (PCA). Mass spectra at different elution times were manually checked and major peaks tentatively identified according to their m/z values by search in available databases. A number of gangliosides and polyglycosilated ceramides were found to be the most abundant components. PCA showed samples could be clustered according to extraction procedure and cheese, and paired t test comparison also showed significant (p < 0.05) differences between L and NL samples extracted with methanol:water. L and NL samples could only be distinguished in PCA when data from the whole chromatographic range were used. Results are discussed based on extraction solvent polarity and feasibility of PCA for comparison of cheese chemical composition after untargeted UPLC–MS analysis.