## 3 Results and Discussion
### Effect of Refrigerated Storage
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Processing** & **VID** & **Identity** & **RI** \\ \hline \multirow{3}{*}{Thermal (72 \({}^{\circ}\)C for 15 s)} & \(-\)0.954 & 3-methyl-2-buten-1-yl acetate & 919 \\  & \(-\)0.951 & pentyl acetate & 911 \\  & \(-\)0.948 & 2-methylpropyl butanoate & 943 \\ \hline \multirow{3}{*}{HPP (600 MPa for 3 min)} & \(-\)0.971 & butyl propanoate & 906 \\  & \(-\)0.970 & pentyl acetate & 911 \\  & \(-\)0.938 & ethyl 2-methylbutanoate & 896 \\  & \(-\)0.920 & hexyl acetate & 1010 \\  & \(-\)0.841 & (_E_)-2-hexenal & 851 \\ \hline \multirow{3}{*}{PEF (15.5 kV/cm)} & \(-\)0.939 & butyl propanoate & 906 \\  & \(-\)0.878 & ethyl 2-methylbutanoate & 896 \\ \cline{1-1}  & \(-\)0.858 & hexyl acetate & 1010 \\ \cline{1-1}  & \(-\)0.831 & hexanal & 797 \\ \hline \hline \end{tabular} These discriminant markers are listed in increasing order of VID coefficient. Positive VID coefficients signify an increase in concentration during storage while negative coefficients denote a decrease. Their retention index (RI) is also listed.  
\end{table} 
Table 2: Volatiles selected by the VID procedure as markers significantly changing as a function of shelf life, in thermal, HPP and PEF pasteurized apple juices. Figure 2: PLS-DA biplots showing the change in the volatile fraction of thermally (72 \({}^{\circ}\)C for 15 s) (**a**), HPP (600 MPa for 3 min) (**b**) and PEF (15.5 kV/cm and specific energy of 158 kJ/L) (**c**) pasteurized apple juice during refrigerated storage (from week 0, 1, 2, 3, 4  to 4 ). The volatile compounds are represented with open circles. Volatiles clearly changing as a function of shelf life (which are discriminant markers) are named. In the next step, to increase insight into the evolution of the changes of these compounds up on storage in the differently pasteurized apple juices, the GC-MS data was plotted as a function of time. As an example, the changes of hexyl acetate, butyl propanoate and (_E_)-2-hexenal are presented in Figure 3.  
Immediately after processing, these volatile compounds were detected at higher levels in PEF and HPP pasteurized samples compared to thermally pasteurized samples. This observation is comparable with the discussion in the previous section that conventional thermal processing seems to have a negative impact on these aroma-relevant volatile compounds immediately after processing. During storage, these compounds have decreased in a similar fashion in all processed samples. Hence, the present work demonstrated that process impact comparison should be performed not only immediately after processing but also during storage. These observations are in line with research results previously reported by [PERSON] et al. (2019). Moreover, it is noteworthy that the amount of these selected volatile compounds appears to be slightly higher in PEF and HPP pasteurized apple juices in comparison to their conventional counterparts by the end of storage (Figure 3). It is unsure whether the observed differences would be perceived by humans. However, since most of these volatiles are reported to be contributing to apple juice aroma, mild pasteurization by PEF or HPP could provide better aroma retention during storage.