## 3 Results and Discussion
### Volatile Organic Compositions  
The dynamic headspace of the volatile compounds from the samples were analysed by SPME. It was found that as many as 58 volatile metabolites were detected from freshly cut spearmints (Supplementary Table S1). Of those, the major compound group was terpene hydrocarbons, along with the sesquiterpenes and alcohols. The major volatile compounds representing the specific aroma of spearmints include D-carvone (C51, 31.6%), (-)-beta.-bourbonene (C37, 13.5%), D-limonene (C12, 17%), carophyllene (C42, 9.0%) and.beta.-myrcene (C11, 4.0%). These were comparable to the composition analysed of the essential oil of spearmint in different studies (carvone (40.0-70.0%), limonene (10.0-15.2%) and myrcene (8.93%) [20; 56]), depending on the growing stages and cultivation areas. Factors such as ecotype, phenylases and the environment, including temperature, relative humidity, irradiance and photoperiod, are also crucial for the variation of the aromatic profiles [20; 56]. In our study, volatile organic compounds changed during the storage of spearmint, and a heatmap analysis clustered the samples according to the aromatic profiles to two major groups (Figure 3A). Compounds such as spiro (2.4) heptane, 1,5-dimethyl-6-methylene-/Cyclohexanol, 2-methyl-5-(1-methylphenyl)-, (1.alpha.2,beta.5,alpha. )- (C52), (E)-beta.-Famesene+Humulene (C46), beta-cubebene (C39), 1,6-cyclodextrinadiene, 1-methyl-5-methylene-8-(1-methylallyl)-, [S-(E,E)]- (C49), 1H-cyclodextrinprop[e]azulene, 1a,2,3,4a,5,6,7b-octahydro-1,1,4,7-tetramethyl-, [1 aR-(1a.alpha,4.alpha,4.beta,7b.alpha. )]- (C38), 4-isopryl-1,6-dimethyl-1,2,3,4-tetrahydroonaphthalene (C53), alpha.-cubebene (C34), (+)-eplicyclosesquiphellandrene (C47), 1,6-cyclodextrinadiene, 1-methyl-5-methylene-8-(1-methyl ethyl)-, [S-(E,E)]-beta.-copaene (C41), and caryophyllene (C42) were clearly separated from the rest of the treatments. To have a better picture of the relationship between CO\({}_{2}\) treatments during storage, a principal component analysis (PCA) was utilised. The variables were depicted across PC1 (48.94%) and PC2 (17.58%). The results illustrated three distinguishable clusters, in which the samples at the initial day clustered in one group. Over time, the aroma of the sample stored in air conditions shifted to a different cluster (arrow indicated in Figure 3B), while the treatments of CO\({}_{2}\) treatments, especially those of higher concentrations, were categorised into different groups. A biplot analysis (Figure 3C) elucidated the relationship of these samples with ethanol (C2), cyclohexanone, 2-methyl-5-(1-methylphenyl)- (C43), pulegone (C45), alpha-terpineol (C48), cyclohexene, 3-methyl-6-(1-methylphenyl)-, (3R-trans)- (C50), 2-Cyclohexen-1-ol, 2-methyl-5-(1-methylphenyl)-, and cis (C55). During storage, minimally processed vegetables, including cut spearmints, are prone to quality degradation due to both microbiological spoilage and physiological activities. The primary benefit of lowering O\({}_{2}\) and elevating CO\({}_{2}\) in the CA is the reduction in the respiration/metabolic rate of the commodity, thereby retarding the senescence process [57]. This was, however, not effective in reducing microbiological growth [58]. In fact, the high CO\({}_{2}\) concentrations during the production of fermentative metabolites, viz., ethanol and acetaldehyde, represent the off-odour of the produce [59]. The results of this study, however, showed that the content of acetaldehyde was much lower in the air enriched with 20% CO\({}_{2}\), compared with those of the lower concentration and the CTRL during the initial 5 day storage (Figure 2E). In contrast, the ethanol concentration seemed to peak at day 5, and decreased thereafter. The rest of the treatments were able to maintain the ethanol level throughout (Figure 2F).