## 3 Results and Discussion
### Analysis of Volatile Compounds of Embryo Rice During Storage
#### 3.2.2 Analysis of HS-SPME-GC-MS of Embryo Rice During Storage  
The key characteristic that defines the aroma of food after storage is volatility, which is a key point in determining whether the food is spoiled [41]. Spoiled food produces unpleasant odors that can have a significant impact on consumer preferences. To assess the alterations in embryo rice stored at two different temperatures over a period of 300 d, HS-SPME-GC-MS was employed to analyze the key volatile compounds present in the samples. The distribution of the content of volatile compounds in embryo rice during storage is shown in Figure 4A,B. The relative content of hydrocarbons was the highest before 180 d, the aldehydes showed an increasing trend, and alcohol compounds increased significantly overall at 240-300 d, which indicated that the types and contents of volatile compounds varied greatly after storage for 180 d. The fluctuation trend at different temperatures was clear, indicating that both temperature and storage time can affect the stability of the compounds. A total of 72 volatile compounds were categorized for the embryo rice samples during storage (Table S2). With reference to the relative content of each volatile compound, heat maps were drawn to visualize the volatile composition of the embryo rice at both temperatures more lucidly and straightforwardly (Figure 4C). A total of 10 aldehydes were found in this study, and their relative contents increased with the prolongation of storage time. There were three types of aldehydes at 0 d. Z-3-Phenyltyralaldehyde is a fragrance with a spicy cinnamon aroma. Trans-cinnamaldehyde has a sweet, spice, candy aroma [42]. 2-Hexena has a sweet almond flavor. The relative content of three aldehydes increased the most during storage, but also increased the most at 4 \({}^{\circ}\)C. 5,6-Dihydro-2H-pyran-2-carbaldehyde and isovanillin appeared at two temperatures on day 60. 5,6-Dihydro-2H-pyran-2-carbaldehyde has an aldehyde aroma. Isovanillin has an olive-like aroma and a strong milky aroma, which can vary with changes in ambient temperature. Benzaldehyde, nonanal, and trans-2-nonenal appeared in late storage. Benzaldehyde is mainly derived from linoleic acid and rises continuously during storage [43]. Nonanal has a cured meat aroma and trans-2-nonenal has a fat aroma. The appearance of the three in the later stage indicated that  
Figure 3: (**A**) Radar map and (**B**) PCA of embryo rice at two temperatures. the odor of the embryo rice had deteriorated. 2,5-dimethylbenzaldehyde and decanal are present only at 25 \({}^{\circ}\)C, indicating that higher temperatures produce more aldehydes. Hydrocarbons are the main volatile components in embryo rice storage, with the highest variety and content. There are 42 types of hydrocarbons during storage, among which there are 6 types of alkanes, most of which do not produce an aroma and have a limited contribution to the whole aroma of embryo rice. Although 1-methylbicyclo [3.2.1] octane, 2-n-butyladamantane, and 1-ethyl-3-methylenedyclobutane appeared at 0 d, it contributed little to the aroma of embryo rice during storage. Barring alkanes, most olefins play a negligible role in shaping the overall aroma [44]. During storage, 11 olefins appeared, and cyclo-pentene had a foul odor at 25 \({}^{\circ}\)C, which can easily cause deterioration and produce unpleasant odors. Styrene appeared at two temperatures for 0-180 d and has a fragrant floral aroma, so it decreased. Alpha-calacorene appeared at two temperatures in earlier storage, with a woody odor. 5-methyl-3-hexen-2-one has a sweet, berry, cheese aroma that appeared at 4 \({}^{\circ}\)C for 60-120 d. Within 300 d of storage, a total of 24 aromatic hydrocarbon compounds were detected. In fact, aromatic compounds were the main  
Figure 4: Analysis of volatile compounds during embryo rice storage: relative content at (**A**) 25 and (**B**) 4 \({}^{\circ}\)C; (**C**) heat maps; and (**D**) ROAV correlation analysis.