Abstract |
The main objective of the present study is the development of an analytical
methodology for the determination of the metabolite and lipid profile of white brine
cheeses by combining NMR spectroscopy and chemometrics. This methodology was
then used to examine the authenticity of Protected Designation of Origin feta cheese.
For the purpose of this study, feta cheese was compared to other Greek white brine
cheeses. The white cheese samples that were analyzed originate from cheese
producers that are operating in different regions of Greece. The types of analyzed
white cheeses were feta, white cheese made from sheep’s and goat’s milk and white
cheese made from cow's milk.
NMR spectroscopy was used to detect and quantify the chemical compounds
present inwhite brine cheese. The quantified compounds include amino acids (alanine,
asparagine, valine, glycine, isoleucine, leucine, lysine, methionine, tyramine, tyrosyni,
phenylalanine), organic acids (lactic, succinic, citric, butyric, gamma-aminobutyric,
formate, acetate, 3-hydroxybutyrate), sugars (lactose, galactose, glucose), fatty acids
(linoleic, linolenic, diglycerides, triglycerides, butyrate, caproleic, cholesterol) and
other compounds (glycerol, choline, uracil).
Two sequential sample pretreatment experimental protocols, using solvents of
different polarity, were followed in order to perform the separate analysis of polar and
apolar fraction of white cheese. Water was used as a solvent for the isolation of amino
acids, organic acids, sugars and other low molecular weight organic compounds,while
chloroform was used for the isolation of fatty acids and lipid profiling of cheese.
The quantitative metabolic profile and the 1Η NMR spectra of the white
cheese samples, in combination with appropriate multivariate statistical analysis
methods were used as effective tools for the development of metabolomics models
which can separate feta samples from other white cheeses according to the type of
milk (sheep - cow) and the type of cheese (feta cheese - white cheese). With the use of
the aforementioned models, additionally, the metabolites and the NMR spectral
regions that are more effective in successful separating white brine cheese samples
according to milk type and production type were obtained.
|