The aroma of food is represented by volatile organic compounds (VOCs). Some of them can significantly influence the aroma profile of cheese and due to their specificity also provide a clear unequivocal distinction between them. Their detection is especially important for the determination of food quality. The aroma profile of cheese can be influenced by several factors, e. g. geographical and climatic conditions, milk quality, the technological production process, the ripening conditions of the cheese and also the storage of the cheese. Crucial factors are temperature, time, storage in the dark or in the light and the material in which the cheese is stored. Differences in the content of the individual VOCs result from different transformation of these compounds and from changes in the cheese itself.
Many groups of VOCs are present in cheese, such as fatty acids (FA), ketones, aldehydes, esters, alcohols, hydrocarbons, N-containing compounds and S-containing compounds. They are mainly the products of processes that take place during cheese ripening, such as lipolysis and proteolysis, as well as the metabolism of lactose, lactate and citrate. FA and the metabolism of free amino acids (FAA) are also important processes.
Based on VOCs emissions, the aroma of Mohant semi-soft cheeses from Bohinj was characterized and the influence of cheese storage on the VOCs present was determined. The compounds were identified and quantified using gas chromatography coupled with mass spectrometry. Before real sample measurements, the extraction of analytes and chromatographic method were optimized. Analytes were sampled in two ways - with direct HS sampling and with a combination of HS sampling and solid phase microextraction (HS-SPME). Grey three-phase fiber divinylbenzene-carboxene-polydimethylsiloxane (DVB-CAR-PDMS) was used.
The results of HS sampling were used to investigate the ratio of analytes in cheese as a function of storage time. HS-SPME sampling was used to identify as many compounds as possible. A key factor in the latter extraction is the phase with which the fiber is coated, as it directly affects the binding of the analytes. An entire range of VOCs in Mohant cheese was determined and thus, its specific aroma was characterized. Biogenic amines in the cheese samples were not detected.
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