## 3 Results
### Product Shelf-Life  
Figure 6 shows the evolution of O\({}_{2}\) and CO\({}_{2}\) in the packages' headspaces during storage for all the samples, both in PET and PP. As expected, due to the respiration of the apple tissues, accumulation of CO\({}_{2}\) and consumption of O\({}_{2}\) were observed. The decrease in O\({}_{2}\) was faster for apples in the PET packaging, due to the higher thickness and lower permeability of this kind of material. Indeed, after only three days, the O\({}_{2}\) was totally consumed. However, no significant difference in CO\({}_{2}\) and O\({}_{2}\) content were found between treated (P5, P10) and control samples (C) for both packaging materials, confirming the results obtained by the permeability measurements. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **Food Simulant** & **Overall Migration (mg/dm\({}^{2}\))** \\ \hline  & & **PP** & **PET** \\ C & Acetic acid (3\%) & \textless{1} & \textless{1} \\ C & Distilled water & \textless{1} & \textless{1} \\ P5 & Acetic acid (3\%) & \textless{1} & \textless{1} \\ P5 & Distilled water & \textless{1} & \textless{1} \\ P10 & Acetic acid (3\%) & \textless{1} & \textless{1} \\ P10 & Distilled water & \textless{1} & \textless{1} \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Overall migration (mg/dm\({}^{2}\)) related to the PP and PET samples. Figure 6: O\({}_{2}\) (dotted lines) and CO\({}_{2}\) (solid lines) concentration in the headspaces of PP (**A**) and PET (**B**) packages of fresh-cut apples subjected to 5 (P5) and 10 (P10) min of plasma exposure compared with the untreated ones. Different lowercase and uppercase letters indicate significant differences (\(p<0.05\)) among O\({}_{2}\) and CO\({}_{2}\) values, respectively. The color data, expressed in L (lightness) and a* (redness) of the CIE-Lab color scale, are reported in Table S1. After exposure of the packages to CAP, and during the 9 days of storage, the values remained fairly constant, with no significant differences. Titrable acidity (TA) of apple samples and firmness values (N), measured in the apple samples during storage, are reported in Table 6.  
TA showed an increase during storage in all apple samples packaged in PE; this could be related to the production of carbonic acid from CO\({}_{2}\), present in higher concentration in PET packages compared with PP ones. However, this difference was related to the type of material, while the exposure to CAP in both cases did not lead to any significant difference among samples. In addition, for sample hardness data (Table S2) measured by penetration tests, results were not influenced by exposure to CAP. Cell loads of total bacterial count, _Lactobacillus_ spp., yeasts, and molds of packaged apples samples are shown in Table 7. These microbial groups were chosen because they are the main spoilage agents of minimally processed fruits and vegetables and, consequently, are able to affect the product shelf-life [23]. Although the dominance of spoilage depends on many factors, the raw material initial microbiota, the package atmosphere gas composition, and the gas permeability of packaging materials are pivotal to the determination of the relative ratios among the different microbial groups and their cell loads during storage. Otherwise, aerobic mesophilic bacteria, yeasts, lactic acid bacteria, and Enterobacteriaceae are generally used as microbial spoilage indicators of fruits to model the shelf-life of minimally processed fruits and vegetables in relation to process and storage variables [23; 24; 25]. No significant differences (\(p<0.05\)) were observed among control and treated samples for both packaging materials used during storage at 8 \({}^{\circ}\)C. All considered microbial groups considered showed a similar trend in the samples, independent of the CAP treatment applied. Total mesophilic bacteria played the main role in the spoilage of packaged apples, followed by lactobacilli and yeasts, independent of the packaging material considered.