## 3 Results and Discussion
### Effect of High CO2 in CA on Phytochemical Attributes  
Mints are rich sources of phenolics, especially phenolic acid and flavonoids, with a long list of biological activities, including those that have antioxidant potential [43; 44]. In horticulture produce, antioxidants have been used as key quality characteristics to determine the freshness of produce [45]. It was found that the content of phenolics in minimally processed herbs was maintained during the first 3 days at the refrigerated temperature and, in some cases, such as that of freshly cut celery, the content did not change significantly during 28 days of storage at 0 \({}^{\circ}\)C [20; 46]. Our results, nonetheless, exhibited significant drops in the total phenolic content in all cases, while the highest CO2 treatment showed substantial changes (Figure 2A). It was evident that CO2 treatments did not improve total phenolic content; however, the DPPH antioxidant potential was maintained at least during the first 5 days of storage for the CTRL and slightly improved with CO2 treatments. This is possibly due to the ability of the CO2 to inhibit cellular free radical accumulation through the activation of the activity of the antioxidative enzymes SOD, CAT and POX, which are normally present during catabolic respiratory processes [47; 48]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Quality Attributes** & \multicolumn{3}{c}{**Factor Effects**} \\ \hline  & **Treatment** & **Storage Time** & **Treatment * Storage Time** \\ \hline Physiological attribute & & & \\ \hline Weight loss (\%) & ** & ** & NS \\ Farmness (N) & ** & ** & ** \\ Colour & & & ** \\ Lightness (L) & ** & ** & ** \\ a* & ** & ** & ** \\ b* & ** & ** & ** \\ Delta E & ** & ** & ** \\ \hline \multicolumn{4}{c}{Phyctochemical attributes} \\ \hline Total phenolic content (mg gallic acid equivalent 100 g FW\({}^{-1}\)) & ** & ** & NS \\ Antioxidant capacity (DPPH) (mg trolox equivalent 100 g FW\({}^{-1}\)) & NS & ** & * \\ Total ascorbic acid (mg 100 g FW\({}^{-1}\)) & ** & ** & NS \\ \hline Off flavour attributes & & & \\ \hline Ammonia content (mg g\({}^{-1}\)) & ** & ** & ** \\ Ethanol (umol g\({}^{-1}\)) & ** & ** & NS \\ Acetaldehyde (umol g\({}^{-1}\)) & ** & ** & ** \\ \hline \hline \end{tabular} The effect of each main factor and of their interactions is significantly different for \(p\leq\) 0.05 (*); \(p\leq\) 0.01 (**); \(p\leq\) 0.01 (**); \(p\leq\) 0.01 (**); or not significant (NS).  
\end{table} 
Table 1: Effects of the main factors (high CO2 treatments, time of storage and their interaction) on the quality attributes of cut spearmint stored at 5 \({}^{\circ}\)C for 14 days. Additionally, the modified atmosphere is possibly able to minimise the use of antioxidants to scavenge free radicals [48]. Figure 2: Effect of CO\({}_{2}\) concentrations in the control atmosphere (CA) of cut spearmint on total phenolic content (mg GAE 100 g\({}^{-1}\), (**A**)) and DPPH activity (mg TE 100 g\({}^{-1}\), (**B**)), ammonia content (ug g\({}^{-1}\) sample, (**C**)), total ascorbic acid D (mg/100 g\({}^{-1}\) sample, (**D**)), acetaldehyde (umol. g\({}^{-1}\) sample, (E)) and ethanol (umoL g\({}^{-1}\) sample, (**F**)). Vertical bars represent standard error (\(n=3\)). The accumulation of ammonia protein catabolism is used to determine the toxicity of the subcellular structures of leafy produce in CA [34; 49; 50]. During the storage, the toxicity of cell structures increased and was significantly higher in all CO\({}_{2}\) treatments (Figure 2C). [PERSON] et al. [6] and [PERSON] et al. [51] suggested that freshly cut produce is less tolerant at high CO\({}_{2}\) concentrations in CA and it should be avoided to prevent the development of off-flavours and the potential stimulation of pathogen growth. In nature, ascorbic acids are very sensitive, and therefore are used to determine the freshness of produce [52; 53]. Along with other antioxidants, they are known for their activity against free radicals.