# Domestic Use Simulation and Secondary Shelf Life Assessment of Industrial _Pesto alla genovese_
## 3 Results and Discussion
### Colour Measurement
Overall, the lightness value of the two pesto sauces underwent only slight modifications in a few samples, which however were perceived as acceptable by the sensory panel, hence not influencing the suitability for consumption of the products. The parameter a* represents the red-green axis of the CIEL*a*b* colour system, in which negative values indicate the greenness colour intensity [19]. This value was used as a quality parameter to evaluate the colour changes of fresh pesto [24] and in the shelf life assessment of pesto [20]. Values of a* of P1 and P2 during storage after opening are reported in Table 4.  
Significant changes (\(p\) < 0.05) were found during domestic storage after opening only in sample C for S1P1 and in samples B and D for S2P1. Anyway, by considering altogether the values of the samples from the five domestic environments and of both scenarios, the a* parameter of P1 was not significantly different during household storage (\(p\) = 0.08). A significant difference during time after opening was observed for S1P2 in samples A, B, C, and D and for S2P2 in samples A, C, and D. In general, changes in a* occurring in P2 highlight a slight decrease (i.e, a slight increase of greenness) during the first 5 days, followed by stabilization. A comparison between a* values from the two scenarios highlighted no significant differences at each sampling time (\(p\) = 0.46). [PERSON] and [PERSON] [20] studied the variation of greenness in fresh pesto, finding that the a* values increased during the primary shelf life. The difference with our findings may be due to the different products since the authors focused on a refrigerated, minimally processed pesto. On the other side, the pesto sauces used in this study had undergone a more intense thermal treatment (allowing shelf-stability) with subsequent degradation of chlorophyll and colour modification: as described by [PERSON] and [PERSON] [24], indeed, the thermal treatment causes an increase of the a* value of pesto. Often, derived colour indexes have proved to be more useful to assess colour changes compared to primary parameters; for this reason, the overall colour variation (\(\Delta\)E) and the browning index (BI) were calculated and the trend throughout storage has been reported in Figure 2. For both P1 and P2, the \(\Delta\)E values did not differ significantly between the two scenarios (\(p\) = 0.29 and 0.16, respectively), whereby the \(\Delta\)E values of both scenarios of the same pesto sauce have been condensed and shown in a single broken line, each for one type of pesto. Statistical analysis revealed differences throughout the period after opening only for P1, however, mean values at 5 and 20 d were not significantly different. In general, it can be inferred that \(\Delta\)E for both pesto sauces remained stable during refrigerated storage after opening. BI can reveal a possible browning of the product, which in pesto sauce is a consequence of a nonenzymatic process, due to the reaction between proteins and oxidized lipids [20]. In P1, no significant difference of BI values between S1 and S2 was observed (\(p\) = 0.27), as well as during the period after opening (\(p\) = 0.32). On the other hand, the BI of P2 was found to change significantly during the first 5 days of storage after opening (\(p\) < 0.05). Similarly to P1, no significant difference (\(p\) = 0.13) was observed between the scenarios. The difference in BI between the two types of pesto may be due to their different \(\mathrm{a_{w}}\) value, which is considerably lower in P1 (0.9046) as compared with P2 (0.9554): indeed, as suggested by [PERSON] et al. [26], nonenzymatic browning is strictly related to \(\mathrm{a_{w}}\) values. Overall, results suggest that the primary and derived colour parameters of both shelf-stable pesto brands after opening were not influenced by the level of domestic use. Moreover, colour changes are hardly noticeable throughout the period after opening, and for this reason, they were not perceived by the sensory panel.