## 3 Results
### Analysis of the VOCs Under Different Storage Temperatures by GC-IMS  
#### 3.4.1 Analysis of Topographic Plots  
In the topographic plots of Figure 3A, each spot represented a volatile substance. The long red line represented the reactive ion peak generated by the hydrated hydrogen ions in the detector. The detected substance captured the positive charge in the hydrated hydrogen ions, allowing it to move in the migration tube. Due to the different migration times of various substances, they can be distinguished. The leftmost plot was measured at 0 d for fresh fruit, while the three right-hand panels were plots of LT, IT, and FT at 42 d. Due to the loss of commercial value after 84 d of storage, the data at 42 d were used for comparison. In the comparative topographic plots of Figure 3B, the blue background plot on the far left represented the volatile compounds at 0 d, and the three white background plots on the right were comparative topographic plots of LT, IT, and FT on 42 d. If the topographic plots of the group at 42 d and 0 d were the same in a specific area, they had the same concentration. The color was red if the group at 42 d had a higher concentration of a certain VOC than at 0 d. Otherwise, the color was blue. The greater the difference in substance content was, the darker the color was. As observed from the comparative topographic plots, there were many dark blue and red areas in the LT group, indicating that this group lost many original VOCs and produced new compounds. In contrast, the FT group had less composition differences compared to 0 d. The IT group had the least number of red and blue spots among all the treatment groups, suggesting that IT largely retained the original flavor and did not produce unpleasant flavors. Although LT storage is the most common storage method, the fruit quality during storage may rapidly decline [34; 35]. This may be attributed to the high level of metabolic activities within the fruit. FT storage slowed down the metabolism by freezing the fruit tissue, but the ice crystals formed during freezing may damage the cellular structure, which can be detrimental to the fruit [35]. The breakage of various plasmalemma in the fruit leads to disruption of the metabolism and direct contact between various substrates and enzymes. Some studies suggested that the formation of ice crystals inside the fruit may also change during the freezing process, thus affecting the internal structure of fruit [36]. IT storage maintained the temperature at the edge of fruit tissue freezing and kept the respiration and metabolism rate low [17], thus allowing the original flavor to be retained. Lipoxygenase-catalyzed unsaturated fatty acids are the main cause of odor [37; 38]. IT storage may decrease lipoxygenase activity [18], which may be another way to explain the lesser unfavorable flavor in the IT group. The results of the TEM analysis also demonstrated that the IT group had the best membrane structure integrity, thus maintaining slow and stable metabolism, slowing down fruit flavor deterioration, and making IT the most effective treatment for preserving the original flavor of the fruit. Through the NIST 2020 RI DB-5 database, 25 volatile substances (monomers and dimers of a substance are counted as one) were identified from the topographic plots (Table 1), including 9 esters, 5 alcohols, 4 ketones, 4 aldehydes, 2 furans, and 1 ether. Esters had the highest percentage of all volatile compounds, up to 36%, while ethers only accounted for 1%. It has been shown that esters are the main VOCs of blue honeysuckle, akin to those reported for other fruits [39; 40].