## 3 Results and Discussion  
### Changes in Basic Indexes During Embryo Rice Storage  
#### 3.1.1 Changes in Oxidation Index During Embryo Rice Storage  
Fatty acid is the hydrolyzed product of fat, which is an important index that reflects the quality of embryo rice. The higher the fatty acid content, the worse the quality of rice [26]. Fatty acid values gradually increased with the extension in storage time (Figure 1A). At the two temperatures, the fatty acid value increased from 6.23 to 56.19 and 35.10 mg/100 g KOH, respectively. The fatty acid value at 25 \({}^{\circ}\)C increased faster than that at 4 \({}^{\circ}\)C. In this study, the fatty acid value (35 mg/100 g KOH) of the sample was set as the limit of shelf life, beyond which it was considered to be stale [27]. Compared with the results of [PERSON] et al. [28], the shelf life of embryo rice was extended at both storage temperatures. The shelf life at 25 \({}^{\circ}\)C was 120 d, which was 240 d at 4 \({}^{\circ}\)C. The increase in fatty acid value was closely related to the lipase activity of the embryo rice [29]. The relative enzyme activity first increased and then decreased, and was relatively slow at 4 \({}^{\circ}\)C (Figure 1B), which was consistent with the results of [PERSON] et al. [30]. Lipase activity increased first and then decreased during storage, mainly due to the activation of endogenous enzymes and the increase in exogenous enzymes produced by microorganisms in the initial stage of storage, and decreased later due to the consumption of substrate fat. At 25 \({}^{\circ}\)C, lipase activity reached a maximum of 158.41% in 180 d and 149.56% in 300 d at 4 \({}^{\circ}\)C. MDA first increased and then decreased (Figure 1C). The increase in MDA content is mainly due to the fact that fatty acids can be produced during the storage process of embryo rice, which degrade to form some small molecules such as MDA, while the subsequent decrease in MDA is due to its volatility and can be released into the air in the form of gas [31]. At the same storage time, the MDA content of embryo rice at 25 \({}^{\circ}\)C was higher than that at 4 \({}^{\circ}\)C. The results indicated that high temperature accelerated the process of fat oxidation and MDA was one of the products of fat oxidation.  
The catalase decreased continuously during storage (Figure 1D), mainly because, during the storage process, rice will breathe and consume nutrients, the ability of CAT synthesis and renewal will decrease, and the decomposition process of enzymes will accelerate, resulting in a decrease in the overall content and activity of CAT [32]. With an  
Figure 1: Changes in (**A**) fatty acid, (**B**) lipase, (**C**) malondialdehydedehyde, (**D**) catalase, (**E**) DPPH, and (**F**) FRAP during embryo rice storage. The values represent the mean \(\pm\) standard deviation. Capital letters indicate significant differences at two temperatures (\(p<0.05\)), and lowercase letters indicate significant differences at storage times of 0–300 d (\(p<0.05\)).  
extension in storage time, DPPH decreased (Figure 1E). This may be because polyphenols in the germ are the main antioxidant components, and with the extension of storage time, fewer polyphenols are retained in the germ [33]. The FRAP value increased first and then decreased with storage time (Figure 1F). The early increase in FRAP may be due to the gradual release or transformation of some potential antioxidant substances in embryo rice in the early storage stage. The late decline in FRAP was mainly due to the gradual decomposition of antioxidant substances during storage, enzymatic hydrolysis, or microbial action, which led to a decrease in reducing capacity.