## 3 Results and Discussion
### Effect of Storage Conditions on Character Impact Odorants of Blueberries
#### 3.2.1 AEDA Analysis by GC-MS-O
Previous research reported the importance of methyl 2/3-methylbutanoate and ethyl 2/3-methylbutanoate in 'Bluecrop' and 'Elliott' blueberries, which had high FDs at 128-512 [8], in agreement with our study. Ethyl 2/3-methylbutanoate was not previously identified in 'Snowchaser' blueberries [21], which could be due to the fact that the panelists in the SPME-GC-O study could not perceive the esters due to their low concentrations [8]. In addition, the difference could be due to this study, as SAFE extraction was used to extract, concentrate, and discriminate trace volatiles from the artifacts coupled with enrichment by cold-splitless injection. Aldehydes and Corresponding Alcohols: Lipid Oxidation Products from the Lipoxygenase Pathway  
C6 aldehydes and their corresponding alcohols that contribute characteristic \"green-leaf\" and \"fresh fruity\" notes are derived from linoleic and \(\alpha\)-linolenic acids in the membrane lipids of blueberries [8]. The synthesis of these aldehydes occurs via the oxylipin pathway using multiple enzymatic reactions, such as those catalyzed by lipoxygenases and hydroperoxide lyase. The aldehydes may be converted to their corresponding alcohols by alcohol dehydrogenases [25]. Aldehydes could also be reduced to their corresponding alcohols by aldehyde reductases or oxidized to C6 acids [8]. The results of AEDA confirmed that hexanal, (Z)-3-hexenal, (E)-2-hexenal, (E)-3-hexen-1-ol, and (Z)-3-hexen-1-ol provide fresh berry and green aroma notes to the blueberry samples. Their FDs showed a similar dramatically decreasing trend relative to SC when the blueberries were subjected to the S1 treatment. The odor potential was impressively enhanced in the S2 and S3 treatments for (Z)-3-hexenal (FD = 16,384 and 4096), but hexanal and (E)-2-hexenal did not increase from S1 to S2. This pattern, in terms of an inhibitory impact of S1 on FDs, was also repeated for the alcohol-derived volatiles (E)-3-hexen-1-ol and (Z)-3-hexen-1-ol, with mixed effects on the FDs of S2 and S3. Other important aldehydes with moderate odor potentials were 3-methylbutanal and (E,Z)-2,6-nonadienal, which were previously identified in blueberries [8; 26; 27] and are reported as having malty [28] and green and cucumber notes [8], respectively. 3-methylbutanal was reported to be synthesized by the decomposition of by-products during the biosynthesis of valine, leucine, and isoleucine [28]. Meanwhile, 2,6-nonadienal is generated from polyunsaturated carboxylic acids [8; 29]. Unlike the other aldehydes, both 3-methylbutanal and (E,Z)-2,6-nonadienal increased from SC to S1. For 3-methylbutanal, the FDs continued to increase throughout storage. Conversely, for (E,Z)-2,6-nonadienal, the FDs soared to 16,384 and 1024 in the S1 blueberry samples then decreased in S2 (8192, 64) and S3 (512, 128). The general overall decrease during the initial cold storage in the major aldehydes and alcohols (e.g., (E)-3-hexen-1-ol, and (Z)-3-hexen-1-ol, hexanal, (E)-2-hexenal, (Z)-3-hexenal, and (E,Z)-2,6-nonadienal), which are products of the lipoxygenase pathway (S1), is consistent with previous studies [6; 30]. This has also been observed in peaches, tomatoes, and apples [25; 31; 32]. Chilling could possibly inhibit the C6 aldehyde and alcohol production due to decreases in hydroperoxide lyase and alcohol dehydrogenase activities in the oxylipin pathway [25]. In the same study, it was found that warming tomatoes at 20 \({}^{\circ}\)for up to 4 days after chilling was found to increase the regulation of a group of genes that controlled lipoxygenase activity and slow down the expression of other genes, which may explain the recovery of volatiles at warmer temperatures (S2 and S3 in this study). Terpenes: Products of Terpene Synthase  
Terpenes and their derivatives are generally formed enzymatically from acetyl CoA and pyruvate provided from carbohydrate substrates via the mevalonate pathway in plastids and the cytoplasm of plants [8; 33].