# Domestic Use Simulation and Secondary Shelf Life Assessment of Industrial _Pesto alla genovese_
## 3 Results and Discussion
### Volatile Organic Compounds Profiling  
_Pesto alla genovese_ is appreciated for its flavour, which results from its specific formulation based on basil, hard cheese, garlic, and nuts. The sensory perception of Pesto might change after opening due to loss of key odorants, and oxidation reactions of volatiles and/or fatty components. The sensory assessment of pesto samples during the period after opening did not reveal significant changes perceived by tasters. A further investigation on the volatile fraction was aimed at confirming the stability of pesto during the time after opening and at determining possible changes which are not detected by sensory assessment. Hence, the volatile profiles of P1 and P2 sampled at the time of first opening were compared with those of samples stored refrigerated for 20 d after first opening, managed under scenario S2, which implied a more intensive level of use (worst case). Figure 4 shows typical chromatograms of pesto (Figure 4a for P1 and Figure 4b for P2, respectively). Overall, more than 70 peaks were identified, mostly related with basil volatile composition. Slight differences occurring in the volatile profile of P1 and P2 result from the differences in formulation (as reported in the Materials and Methods section). Among the major peaks, linalool, estragole (or methyl clavicol, only in P1), eugenol, eucalypt, _trans_-\(\alpha\)-bergamotene, _trans_-\(\beta\)-ocimene, \(\beta\)-myrcene arise from basil [28; 29],  
Figure 3: Trend of pH values for Pesto samples (P1: triangle; P2: circle) during household storage after first opening. Each line reports the mean value of samples from the five households and managed under the two scenarios. Different letters within each line indicate significant differences (\(p\) < 0.05). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Pesto Brand (Code)** & **pH** & **a\({}_{\text{w}}\)** & **Indication of SSL (d)** \\ \hline P1 & 5.64 \(\pm\) 0.07 \({}^{\text{a}}\) & 0.9046 \(\pm\) 0.0004 \({}^{\text{g}}\) & 5 \\ P2 & 4.18 \(\pm\) 0.05 \({}^{\text{f}}\) & 0.9554 \(\pm\) 0.0010 \({}^{\text{b}}\) & 5 \\ P3 & 4.00 \(\pm\) 0.01 \({}^{\text{g}}\) & 0.9579 \(\pm\) 0.0006 \({}^{\text{b}}\) & 7 \\ P4 & 4.51 \(\pm\) 0.03 \({}^{\text{e}}\) & 0.9358 \(\pm\) 0.0008 \({}^{\text{d}}\) & 14 \\ P5 & 4.47 \(\pm\) 0.04 \({}^{\text{e}}\) & 0.9293 \(\pm\) 0.0006 \({}^{\text{e}}\) & few days \\ P6 & 5.45 \(\pm\) 0.02 \({}^{\text{b}}\) & 0.9574 \(\pm\) 0.0012 \({}^{\text{b}}\) & 3–4 \\ P7 & 4.72 \(\pm\) 0.04 \({}^{\text{d}}\) & 0.9207 \(\pm\) 0.0015 \({}^{\text{f}}\) & 5 \\ P8 & 4.43 \(\pm\) 0.02 \({}^{\text{e}}\) & 0.9508 \(\pm\) 0.0008 \({}^{\text{c}}\) & 4 \\ P9 & 4.44 \(\pm\) 0.02 \({}^{\text{e}}\) & 0.9667 \(\pm\) 0.0013 \({}^{\text{a}}\) & 3 \\ P10 & 4.91 \(\pm\) 0.02 \({}^{\text{c}}\) & 0.8447 \(\pm\) 0.0008 \({}^{\text{h}}\) & 10 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: a\({}_{\text{w}}\) and pH values of ten types of commercial shelf-stable pesto sauces. Values are given as mean \(\pm\) SD (\(n\) = 3). Different letters within each column indicate significant differences (\(p\) < 0.05). P1 and P2 were used in this study for the secondary shelf life assessment. as the major ingredient in pesto formulation, representing about 72-83% of the overall chromatographic area. The most representative volatile compounds, contributing about 86-90% of total chromatographic area, were selected for comparison between the reference (just-opened)  
Figure 4: Typical chromatogram of the volatile fraction of pesto (**a**) P1 and (**b**) P2 as obtained by SPME-GC/MS. sample and aged (20 d from first opening) sample for P1 (Figure 5a) and P2 (Figure 5b). As it can be inferred, the relative abundance of dominant compounds for aged samples basically reflects the profile of just-opened samples, thus confirming the substantial stability assessed through the sensory evaluation. For P1, the relative abundance of the key volatile compounds determined at the time of opening and after 20 d did not show significant difference (\(p<0.05\)).