EXPERIENCE WITH THE APPLICATION OF GAS CHROMATOGRAPHY-MASS SPECTROMETRY IN COMBINATION WITH SOLID-PHASE MICROEXTRACTION FOR THE STUDY OF THE COMPOSITION OF VOLATILE ORGANIC COMPOUNDS IN MATRICES WITH THE HIGH FAT CONTENT
Current article presents a methodological approach for a comparative study of the composition of volatile organic compounds (VOCs) in a natural product and a nature-identical flavoring substance. The identification of VOCs was performed by gas chromatography-mass spectrometry without reference compounds. The identification was made based on coincidence of the experimental and reference mass spectra and linear retention indices. During the first step, the closest match factor substance was selected based on the library search. During the second step, the result was verified by the means of experimental and reference retention indices data proximity. The reference retention indices were selected considering the identity of the experimental conditions (chromatographic stationary phase, temperature programming mode). The impossibility of identification of aroma components in acetonitrile extract of fragrance was shown due to the overlapping of their peaks with peaks of di- and tri- glycerides of fatty acids. The extraction and concentration of VOCs from vapor were carried out using the head space solid-phase microextraction. The fragrance content investigation revealed 39 volatile organic compounds including propylene glycol and triacetin as the markers of synthetic fragrances. In natural cocoa butter, also 39 volatile organic compounds were identified. All of them were common for the fermented cocoa beans. Pyrazines derivatives, characteristic of cocoa aroma, were presented with the following 7 components: 2,3-dimethylpyrazine; 2,5-dimethylpyrazine; ethylpyrazine; 2-methyl-6-ethylpyrazine; 2,3,5-trimethylpyrazine, 2,5-dimethyl-3-ethylpyrazine; tetramethylpyrazine. In quantitative terms, the isomeric 2,3-butandiols predominate in the head space of natural cocoa butter accounting for 37 percent of total VOC content. The analytical technique used allows investigation of multicomponent objects including the heterogeneous ones.