# Effect of Seasoning Addition on Volatile Composition and Sensory Properties of Steved Pork
## 3 Results and Discussion
### Volatile Compounds Profiling in the Fresh and Stewed Pork

Table 1: The comparison of kinds and content ratios of volatile compounds by gas chromatography-mass spectrometry/olfactometry (GC-MS/O) and two-dimensional gas chromatographic combined with time-of-light mass spectrometry (GC \(\times\) GC-TOFMS). processing of pork products plays a crucial role in the formation of aldehydes [23]. It can be also found that 15 compounds, namely, nine saturated aldehydes (butanal, pentanal, hexanal, heptanal, octanal, nonanal, decanal, pentadecanal and (_E_)-octadec-9-enal), four olefin aldehydes ((_E_)-oct-2-enal, (_E_)-non-2-enal, (_Z_)-dec-4-enal and (_E_)-dec-2-enal), as well as two aromatic aldehydes (benzaldehyde and benzeneacetaldehyde) were simultaneously identified in all stewed pork samples. The saturated and olefin aldehydes could be produced from the degradation of fatty acids [28] and the aromatic aldehydes were usually generated from Strecker reaction [29]. Among them, except for pentanal and benzeneacetaldehyde, the contents of other 13 compounds were significantly higher (_p_ < 0.001) in SP\({}_{1}\) and SP\({}_{2}\) than those in SP\({}_{3}\), SP\({}_{4}\), SP\({}_{5}\), and SP\({}_{6}\). Moreover, (_Z_)-hept-2-enal, 2-butyloct-2-enal, and tertadecanal were detected only in SP\({}_{1}\) and SP\({}_{2}\). It was shown that the spices, soy sauce, sugar, and cooking wine may have an inhibitory effect on the production of some aldehydes in stewed pork. Moreover, 4-(1-methylethyl)-benzaldehyde, p-anisaldehyde and cinnamaldehyde, with mint and sweet aroma [20], could be generated from the Chinese different spices, including fennel, anise, and cinnamon, respectively. Alcohols, with pleasant fruity and floral notes [18], are mainly derived from spices [30] and the oxidative decomposition of lipid [31]. For the identified alcohols, 1,8-cineole, pentan-1-ol, hexan-1-ol, oct-1-en-3-ol, heptan-1-ol, 2-ethylexan-1-ol, octan-1-ol and (_E_)-oct-2-en-1-ol could be detected in all pork samples. Among them, the linear alcohols (pentan-1-ol, hexan-1-ol, heptan-1-ol, octan-1-ol and (_E_)-oct-2-en-1-ol) and branched alcohols (oct-1-en-3-ol and 2-ethylexan-1-ol) were the main lipid oxidation products. Meanwhile, the contents of these compounds were significantly higher (_p_ < 0.01) in SP\({}_{1}\) and SP\({}_{2}\) than those in FP, SP\({}_{3}\), SP\({}_{4}\), SP\({}_{5}\) and SP\({}_{6}\). The 1,8-cineole, linalool, terpinen-4-ol, terpineol, (4R,6R)-2-undecen-1-ol and cis-geraniol increased significantly (_p_ < 0.001) in SP\({}_{3}\) as the spices were added in the stewed pork and greatly reduced in SP\({}_{4}\), SP\({}_{5}\) and SP\({}_{6}\). This result shows that these above compounds were mainly formed from aged brine (spices, soy sauce, sugar and cooking wine). Ketones are often considered to have a great influence on the aroma of meat and meat products since they are presented in large amounts and exhibited specific aroma in food [32]. As shown in Table 2, 7 ketones such as 6-methylhept-5-en-2-one, 4-isopropyl-2-cyclohexenone, piperitone, carvone, 4-phenylbutan-2-one, 4-methoxyphenylacetone and xanthoxylin were detected in the spice, soy sauce, sugar and cooking wine processed samples (SP\({}_{3}\), SP\({}_{4}\), SP\({}_{5}\) and SP\({}_{6}\)), and they were not detected in fresh pork (FP), stewed pork with water or salt (SP\({}_{1}\) or SP\({}_{2}\)). It indicated that more ketone compounds were formed due to the addition of food seasoning, which provided a richer fruity and nutty aroma [25] for the overall pork flavour. [PERSON] et al. [33] reported that the methyl ketones were considered as the precursors to the fatty aromas related to cooked meat, which could be formed by the oxidative degradation of fatty acids [34]. In this study, the methyl ketones (e.g., heptan-2-one, octan-2-one, pentane-2,3-dione, octane-2,3-dione, 3-octen-2-one, (_E_,_E_)-3,5-octalen-2-one, 6-methyl-3,5-heptadiene-2-one and acetophenone) were originated from the oxidation of lipids during heating.