# Application of Sorbent-Based Extraction Techniques in Food Analysis
## 4 SPME in Food Analysis--Main Fields of Applications
### Volatile Compounds
The partition coefficient of compounds presented in a sample depends on the physiological properties of the substances, type of matrix and isolation conditions. Based on SPME-GC data, many plants or generally food products have been successfully discriminated. SPME coupled directly with MS and multivariate analysis was applied to predict the shelf life of pasteurized milk. SPME-MS was shown to be a more accurate technique than microbiological plating methods (a technique previously reported in this kind of research) [100]. CAR/PDMS fiber was used in those studies and it proved to have advantages over static headspace or dynamic headspace techniques, such as no need for specialized equipment. It was also more efficient at extracting volatile fatty acids from milk. The described system shows a strong potential application for routine work in the dairy industry [100]. [PERSON] et al. [101] characterized aroma compounds in Camembert cheese by SPME-GC-MS. The obtained results were used in a subsequent experiment, which consisted of the direct introduction of extracted compounds into the ionization chamber of MS without chromatographic separation. The results were processed and proved to be a valuable tool in qualitative classification [102]. The SPME-MS approach, followed by statistical analysis--principal component analysis and linear discriminant analysis--was successfully applied as a rapid technique for the biological origin determination of raw spirits [103]. The presented analytical tool enabled determining the origin of samples, depending on the raw material they were produced from. Lack of chromatographic separation and fast 2 min extraction provided results after an extremely short time, which is especially important in laboratory routines [103]. The technique was also used for profiling VOCs in blackcurrant varieties depending on growth latitudes and environmental factors. The study showed the changes in the volatile fraction depending on the growth environment on the composition and quality of analyzed fruits [104]. Another field of interest regarding the implementation of SPME is research on food authenticity. The adulteration of juices has become a significant issue in the beverage industry. SPME and GC with a flame ionization detector (FID) were used in the study by [PERSON] et al. [105], who assessed the adulteration of juices as a tool for enantiomeric purity evaluation. The enantiomeric composition of certain chiral terpenes was investigated to determine the origin of aromas as well as their addition to fruit beverages. The authors concluded that the enantiomeric distribution of chiral terpenes can be a valuable tool in the detection of aromas in addition to fruit beverages. Alteration in enantiomeric distribution may also be an indicator of falsification [105]. The next food product, the authenticity of which is extensively investigated due to many sophisticated adulteration techniques is honey. Two principal techniques are involved in honey falsification: addition to water and extension with sugar/syrups and feeding bees with sugar or syrup labelled as those kinds of honey with the fake floral or geographical origin [106]. VOCs in honey samples contribute to its flavor, and also to the differentiation of honey with floral origin and method of handling [107]. Evaluation of meat and dairy VOCs is of increasing concern, mostly due to the development of sensors informing consumers if meat is spoiled or not. To create this kind of sensor, numerous studies have to be conducted to decide which compounds are indicators of meat spoilage. SPME meets expectations essential for the technique used for this purpose. So far, it has been widely applied in research focused on VOCs occurring in spoilage of food. Recent studies reported the production of VOCs by bacteria isolated from different foods.