# Headspace Solid-Phase Microextraction Analysis of Volatile Components in Peanut Oil
## 2 Results and Discussion
### Differences in Volatile Components of Peanut Oil Made from Different Varieties  
Eight types of aldehydes, three types of alcohols, one type of furan, six types of hydrocarbons, two types of ketones, five types of phenols, 15 types of pyrazines, one type of pyridine, and two types of hekei oils roasted at 120 \({}^{\circ}\)C and 140 \({}^{\circ}\)C were identified. Other compounds, including 12 types of aldehydes, one type of alcohol, two types of furans, six types of hydrocarbons, three types of ketones, five types of phenols, 14 types of pyrazines, and one unknown compound, were identified in the No. 9 oil of Tainan selected roasted at 120 \({}^{\circ}\)C and 140 \({}^{\circ}\)C. The types of pyridines and the other compound are listed in Table 1.  
Figure 5: Classification of volatile compounds in Tainan S. No. 16 peanut oils using HS-SPME. **(a)** Tainan S. No. 16 with peanut shell peanut oil at different roasting temperatures. **(b)** Tainan S. No. 16 peanut oil at different roasting temperatures.  
The primary components of the two varieties at different roasting temperatures are shown in Figure 6. At 120 \({}^{\circ}\)C, the heke oil was rich in 2-ethyl-3,6-dimethylpyrazine and 2-ethyl-6-methylpyrazine, while 5-dimethylpyrazine, 2-ethyl-3-methylpyrazine, hexanal, and (_E_)-2-heptenal were only identified in No. 9 oil. At 140 \({}^{\circ}\)C, hekei oil contained greater amounts of 2-ethyl-3,5-dimethylpyrazine, 2,5-dimethylpyrazine, 2-ethyl-3-methylpyrazine, and hexanal, while benzaldehyde was only identified in this sample. The primary components of the No. 9 oil selected in Tainan were _p_-vinylphenol, 5-methylfurfural, and furfural.  
When the roasting temperature was low, the No. 9 oil contained more aldehydes. Among them, hexanal, heptanal, and nonanal are the products of fatty-acid oxidation and can produce peculiar smells that affect the oil flavor [29]. In a study by [PERSON] et al. [30], it was determined that the fatty-acid composition of different varieties of cashew nuts is  
Figure 6: The main volatile compounds of different varieties of peanut oil: (**a**) peanut oil roasted at 120 \({}^{\circ}\)C; (**b**) peanut oil roasted at 140 \({}^{\circ}\)C.  
different, and the oxidation of the oil is affected by the fatty-acid composition of the oil and the processing methodology, while the concentrations of oxygen and free fatty acids are affected by factors such as the interaction of these factors on the oxidation of oil [31]. Therefore, this phenomenon may have been caused by the different fatty-acid compositions and processing temperatures of Tainan S. No. 9 and Tainan S. No. 16 peanuts.  
At higher roasting temperatures of No. 9 oil, the Maillard reaction induced the formation of furfural and 5-methylfurfural [32]. It is speculated that these two compounds do not react with amino acids. The reaction resulted in a lower content of pyrazines in this sample, and no furfural was identified in the hekei oil. It may be that, in this sample, furfural underwent downstream reactions, and the difference in the reaction path may have been due to the different amino-acid contents present in the different varieties.