# Analysis of Volatiles in Food Products
## 3 Methods of Volatile Compounds Separation and Identification  
The second important step of volatiles analysis is their separation and identification. SPME has been broadly employed in a sequence of several analytical techniques: capillary electrophoresis (CE), gas chromatography (GC), inductively coupled plasma MS (ICP-MS), ICP-optical emission spectrometry (ICP-OES), and mass spectrometry (MS) [49; 100]. Not frequently liquid chromatography (LC) was applied to analyze volatile compounds [101]. Moreover, various detectors are applied, e.g., universal flame ionization (FID) or selective detectors, e.g., nitrogen-phosphorus (NPD), flame photometric (FPD), electron capture (ECD) detectors. However, the most frequently used detector in the analysis of volatile compounds is the mass detector (MS) [49]. MS is a powerful tool to identify compounds. By the MS it is possible to maintain screening of volatile compounds and then the comparison of obtained mass spectrums with the literature and/or available databases. For example, [PERSON] et al. [102] optimized the GC-MS technique to aroma evaluation of most popular beverages like wine and coffee. Additionally, [PERSON] et al. [103], who evaluated aroma profiles of food products, based on compounds' molecular masses. In the latest research, [PERSON] et al. [104] presented the usefulness of GC-MS in the determination of aroma-active regions of protein-based products. Research about the aroma of protein-rich products is nowadays an important aspect because a lot of vegan products are not always formulated with high consumer acceptability. Therefore, the knowledge in this area needs a lot of improvement. Moreover, based on GC-MS signals, [PERSON] et al. [105] built the database of the volatile profile, which can be used in the food authenticity. [PERSON] et al. [106] reconstruct the aroma of citrus fruits using chemical standards and then analyzed its profile on GC-MS. Miniaturization is not only proposed in extraction practice but also as it was presented by [PERSON] et al. [107] in the case of analytical devices. [PERSON] et al. [107] constructed portable GC-MS equipment and compare their possibilities with benchtop devices. In their opinion usage of a portable GC-MS was satisfactory and allowed to analyze in any place. The time-consuming methods are replaced with the newer ones. [PERSON] et al. [108] employed Proton Transfer Reaction Mass Spectrometry to do fast screening of volatiles profile of meat from the market and therefore, avoid the spoilage of meat. Instead of a time-consuming method that needs a few days to be performed, they applied a methodology that requires only a few minutes. The volatile profile is a complex mixture, which is why, often, the usage of GC-MS is not enough to unravel the aroma of food products. Therefore, a set of equipment is needed to recognize the active regions responsible for odor. [PERSON] et al. [48] used two-dimensional GC to describe the potent odorants of hazelnuts, whereas [PERSON] et al. [109] prepared the quality fingerprint of virgin olive oil due to its volatiles profile. Interestingly, the GCxGC approach was established by [PERSON] et al. [110] to evaluate the profile of aroma as well as compounds with toxicology properties. Besides the demand for advanced analytical equipment, [PERSON] and [PERSON] [78] highlighted the importance of the statistical analysis of obtained data. An important aspect is also the determination of food odor at the time of its consumption. In this case, the APCI-MS, named as Atmospheric-Pressure Chemical Ionization Mass Spectrometry, is often used. [PERSON] et al. [111] applied APCI-MS to evaluate honey authenticity. Additionally, other techniques of analysis have been adopted to the determination of volatiles profile, e.g., ion mobility spectrometry [112], or infrared spectroscopy [113]. Several approaches have been adopted to establish volatile profiles in quantitative and semi-quantitative terms and, therefore, the results have been expressed in different ways.