# Assessment of Soybean Oil Oxidative Stability from Rapid Analysis of its Minor Component Profile
## 2 Results and Discussion
### Characterization of the Commercial Virgin and Refined Soybean Oils
#### 2.1.2 Composition in Minor Components Determined by DI-SPME-GC/MS  
The methodology used here for the determination of minor oil components allows one to compare the amounts and relative proportions of several types of compounds in different oils. Figure 1 shows the abundances of the main minor components that are expected to influence the oxidative stability of soybean oil. These include compounds with attributed antioxidant ability like tocopherols (\(\alpha\)-, \(\beta\)-, \(\gamma\)-, and \(\delta\)-) and other tools, squalene, and sterols [5; 6; 7], but also free fatty acids, which could favor lipid oxidation [2]. It can be observed that, contrary to what might be expected bearing in mind the denomination of the studied oils, the refined one (RSO) exhibits a higher level of tools, among which tocopherols account by far for the highest proportion. Regarding this issue, it should be noticed that lower levels  
Figure 1: Bar graphics representing the abundance, expressed as arbitrary area units of the mass spectrum base peak of each compound (see Table S1, Supplementary Material) extracted from the total ion chromatograms obtained by DI-SPME/GC-MS, divided by \(10^{5}\), in VSO and RSO of: tools (tocopherols and others), sterols, squalene, and free fatty acids. All the figures reported are mean values corresponding to 2 replicates. T: tocopherol; Tm: tocomonoenol; Tt: tocopriend; Camp: campesterol; Stig: stigmasterol; S: sitosterol; Br: brassicasterol; Eqn: ergostanol; Egtn: ergostenol; Stign: stigmastol; Av: avenasterol; Cycl: cycloartenol; A: amyrin; Sq: squalene; Unsat: sum of oleic, linoleic, and linoleic acids. of tools and of other types of compounds with antioxidant ability were found in another virgin soybean oil studied previously in comparison with the refined one [23], and that other authors also reported a higher concentration of tocopherols in commercial refined sunflower oil than in another virgin cold-pressed oil originating from the same plant species [12]. Nonetheless, the tocopherol profile is the same in both cases, with \(\gamma\)-tocopherol being the most abundant, followed by \(\delta\)- and \(\alpha\)-tocopherol, in line with data from other studies [22; 24]. It is worth noticing the presence in both oils of \(\gamma\)-toctrienol, also with an attributed antioxidant ability [6] and not detected in other studies concerning soybean oil [24; 25], as well as of \(\gamma\)- and \(\alpha\)-tocomponoenols; the latter type of compounds might also act as antioxidants taking into account findings relative to the \(\delta\)-isomer [26]. Other phenolic compounds different from tools, considered important antioxidants in other plant-derived foodstuffs, are in low concentration in soybean oil [27]. Therefore, although data about them are not provided, it is not expected that they greatly affect the oxidative stability of this type of oil. Regarding sterol content, which includes desmethylsterols but also less commonly found 4,\(A^{\prime}\)-dimethyl sterols like \(\alpha\)- and \(\beta\)-amyrin, this is also higher in RSO than in VSO, \(\beta\)-sitosterol being the most abundant, in agreement with the findings of other authors [28]. The squalene concentration, instead, is basically the same in both oils. Despite these results appearing somewhat surprising considering that refining of soybean oil depletes the level of certain minor components [8], it must be taken into account that several factors other than the refining process can also affect the minor oil component composition of commercial oils from different suppliers. Thus, as pointed out by [PERSON] and [PERSON] [29], the tocopherol content of soybean oil can also be influenced by the state of the soybeans or the proportion of damaged beans, together with storage conditions and length. In addition, soybean variety and climatic factors can also affect soybean oil composition [30].