## 2 Results and Discussion
### PTR-ToF-MS Results and Comparison with HS-SPME GC-MS Findings  
As other Direct-Injection Mass Spectrometric (DIMS) technologies, PTR-MS finds application in many sectors, from environmental sciences to food chemistry, and from biological studies to medical applications. With this regard, we recently described a tailored system, that found application in this \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & **Claimed Characteristics** & **Manufacturer** \\ \hline
**M1** & \multicolumn{1}{c}{Mascarpone} & A \\ \cline{2-3}
**M2** & \multicolumn{1}{c}{Mascarpone} & B \\ \cline{2-3}
**M3** & \multicolumn{1}{c}{Mascarpone} & C \\ \cline{2-3}
**M4** & \multicolumn{1}{c}{Mascarpone} & B \\ \cline{2-3}
**M5** & \multicolumn{1}{c}{Mascarpone} & C \\ \cline{2-3}
**M6** & \multicolumn{1}{c}{Mascarpone} & C \\ \cline{2-3}
**M7** & \multicolumn{1}{c}{Mascarpone} & M \\ \cline{2-3}
**M8** & \multicolumn{1}{c}{Mascarpone} & M \\ \cline{2-3}
**M9** & \multicolumn{1}{c}{Mascarpone without lactose} & M \\ \cline{2-3}
**M10** & \multicolumn{1}{c}{Mascarpone without lactose} & M \\ \cline{2-3}
**M11** & \multicolumn{1}{c}{Mascarpone without lactose} & C \\ \cline{2-3}
**M12** & \multicolumn{1}{c}{Mascarpone without lactose} & C \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of commercial ‘Mascarpone’ samples analyzed in the present study. All samples (M1–M12) were investigated by PTR-ToF-MS analysis. Underlined samples (M1–M3) were evaluated also by HS-SPME GC-MS.  
Figure 1: Principal Component Analysis (PCA) biplot of the 3 different commercial samples of mascarpone (M1, M2, and M3). For each sample, the mean (n = 4) is represented by the sample name. Score plot was given by the Volatile Organic Compound (VOC) content for each sample and loading plot of the single volatile organic compounds. The codes correspond to the samples indicated in Table 1.  
study, achieved connecting PTR-ToF-MS with an automated sampler, and associated custom-made data analysis applications that improve the versatility of the analytical approach in the determination of VOCs in association with i) huge numbers of samples, ii) bioprocesses monitoring, and iii) high numbers of variables to be considered [11]. PTR-MS has been already exploited to study VOCs associated to dairy products such as mozzarella cheese [22], Grana Padano, Parmigiano Reggiano, and Grana Trentino cheeses [23], liquid whey [24], butter and butter oils (by means of quadrupole-based PTR-MS analyses, sensory analyses and classical chemical analyses) [25], milk and whey powders [26], anhydrous milk fat [26], and fermented milk-based beverages (yogurt and kefir) [27; 28]. All samples included in this study have been analyzed by PTR-ToF-MS. A total of 411 mass peaks were detected and extracted. Upon comparison with the blanks, 92 peaks were kept that are significantly different between various manufacturers (\(p<0.01\) with Bonferroni correction) and tentatively identified on the basis of exact mass, isotopic ration, and literature [29]. PTR-MS allowed the detection and characterization of a larger number of VOCs/VOC fragments, which was larger than the number of volatiles identified by GC. For the PTR analysis, all vials were incubated alternatively at 40 \({}^{\circ}\)C or at 60 \({}^{\circ}\)C (data not shown) for 30 min before PTR-MS analysis. The last one was the temperature at which good results were obtained by HS-SPME GC-MS. However, with PTR, even at 40 \({}^{\circ}\)C, the analysis was successfully performed and results were reliable. For this reason, we report the data performed at 40 \({}^{\circ}\)C, a temperature closer to the real mascarpone cheese testing conditions. One-way ANOVA followed by Tukey HSD test was carried out to compare and underline significant differences among the assessed mascarpone samples. For each peak, we obtained the concentration of the corresponding VOC ion in the headspace of all explored samples. Boxplots reported in Figure 2 illustrate the observed trends for 6 ions among the tested samples, as illustrative cases.