## 3 Results and Discussion
### Changes in VOCs  
Table S3 shows the changes in VOCs in yellowtail muscle stored at different temperatures. In total, 145 compounds were identified in this study. The VOCs were classified into thirty-nine aldehydes, twenty-four alcohols, ten alkanes, five aromatic compounds, eleven acids, one alkyl halide, three esters, five furans, twenty-two ketones, one terpene, two sulfides, and twenty-two unidentified compounds (unknowns). Most of the detected aldehydes, alcohols, and ketones were consistent with previous findings and were derived from the degradation of lipids in fish meat [16; 60]. Figure 4 shows the PCA results for VOCs in the yellowtail muscle during storage at different temperatures. The scores for PC1 and PC2 accounted for 32.5% and 22.5% of the total variation, respectively. In DM, the samples at all storage temperatures moved in the positive direction of the PC2 score with storage, with longer storage periods moving to the left at each storage temperature. For OM, the samples at all storage temperatures moved in the negative direction of the PC1 score and in the positive direction of the PC2 score during storage. The storage periods of the samples with similar scores for both OM and DM were as follows: SC storage > ice storage > refrigeration. These results suggest VOC alterations during storage for both muscle parts at all storage temperatures, and these changes can be suppressed at lower temperatures, that is, SC. These results agree with the above-mentioned results for the VCCs. Figure 3: Heat map visualization and hierarchical clustering based on the dataset of relative bacterial abundance at the genus level from raw yellowtail muscles during storage at different temperatures. OM, dorsal part of ordinary muscle; DM, dark muscle. The class indicates muscle type, storage method (R, refrigerated; I, ice; S, super-chilled), and storage time. Colors indicate the common logarithm of relative abundance. Figure 4. Score scatter plot (A) and loading plot (B) of principal component analysis (PCL and PC2) based on volatiles in raw yellowish muscles during storage at different temperatures. The data were preprocessed using an auto-scale. (A) OM, dorsal part of ordinary muscle. DM, dark muscle. The muscle type (OM and DM), storage method (R, refrigerated; I; ice; S, super-chilled), and storage time (fdd) are indicated. (B) The numbers in the loading plot indicate the peak numbers in Supplementary Table S1. The loading plots showed that in OM, VOCs such as (_E,E_)-2,4-ocatdienal and (_E,E_)-2,4-heptadien with high PC1 factor loadings and VOCs such as (_E,E_)-3,5-ocatdien-2-one and (_E,E_)-2,6-nonadienal with low PC1 factor loadings significantly decreased or increased during storage, respectively. In DM, VOCs, such as unknown compounds with KI (1742) and 1-hexanol with high PC2 factor loadings, increased significantly during storage at all temperatures. In DM, a few VOCs increased significantly during the storage period at all temperatures. Although many VOCs in DM increased during the early stages of storage, they plateaued or decreased during the later stages of storage. This is believed to be the result of lipid oxidation, which leads to an increase in the concentration of VOCs and their subsequent degradation. In DM and OM at all storage temperatures, esters such as ethyl acetate were not detected early in storage but were detected later in storage, with some exceptions. Esters are produced by esterification of alcohols and carboxylic acids in meat via microbial esterase activity [17]. _Pseudomonas_ and _Brochottrix_ are spoil-causing bacteria that are capable of producing esters [17]. Therefore, it is highly probable that esters are produced during bacterial growth. Under all storage conditions, 3-methylbutanol in OM was undetectable before storage and was detected in late storage. The VOC in DM significantly increased during late storage. 2-Methylbutanol in OM was undetectable before storage but was detected during late storage under all storage conditions.