# Domestic Use Simulation and Secondary Shelf Life Assessment of Industrial _Pesto alla genovese_
## 3 Results and Discussion
### Microbiological Analyses  
For the sake of conciseness, results of microbiological analyses have been condensed in Table 3, which shows the highest counts for total aerobic mesophilic bacteria (TMB) and Clostridia, expressed as CFU/g, observed in the five home environments on each sampling day. The microbial counts in the table are shown based on the scenario, type of pesto (conditions S1P1, S2P1, S1P2, S2P2), and category of microorganisms (total aerobic mesophilic bacteria and Clostridia). Since the shelf-stability of commercial pesto sauce results from a sterilizing heat process able to destroy all vegetative forms of microorganisms, the product remains commercially sterile until the first opening. For this reason, the degree of contamination  
Figure 1: Temperatures (\({}^{\circ}\)C) recorded in the five domestic refrigerators (A to E) during one week. Values on the right are given as mean \(\pm\) SD (\(n\) = 168). Faded lines represent the temperature profiles (data recorded at 1-h intervals), while the bold horizontal lines indicate the mean values measured for each household. Different superscript letters in the legend indicate significant differences (\(p<0.05\)) among mean values. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Time after Opening (d)**} & \multicolumn{4}{c}{**TMB (CFU/g \(\times\) 10\({}^{\text{1}}\))**} & \multicolumn{4}{c}{**Cl (CFU/g)**} \\ \cline{2-9}  & **S1 P1** & **S2 P1** & **S1 P2** & **S2 P2** & **S1 P1** & **S2 P1** & **S1 P2** & **S2 P2** \\ \hline
5 & 96.4 \(\pm\) 16.6 \({}^{\text{a}}\) & 7.7 \(\pm\) 7.0 \({}^{\text{b}}\) & 10.4 \(\pm\) 1.9 \({}^{\text{b}}\) & 31.5 \(\pm\) 1.3 \({}^{\text{a}}\) & n.d. & 5.0 \(\pm\) 7.1 & n.d. & n.d. \\
11 & 2.7 \(\pm\) 1.3 \({}^{\text{b}}\) & 96.4 \(\pm\) 3.8 \({}^{\text{a}}\) & 1.8 \(\pm\) 0.0 \({}^{\text{b}}\) & 79.3 \(\pm\) 14.0 \({}^{\text{a}}\) & n.d. & 20.0 \(\pm\) 0.0 & n.d. & n.d. \\
16 & 3.2 \(\pm\) 1.9 \({}^{\text{b}}\) & 13.5 \(\pm\) 5.1 \({}^{\text{a}}\) & 4.1 \(\pm\) 0.6 \({}^{\text{b}}\) & 1.8 \(\pm\) 0.0 \({}^{\text{b}}\) & n.d. & 55.0 \(\pm\) 21.2 \({}^{\text{a}}\) & n.d. & 5.0 \(\pm\) 7.1 \({}^{\text{b}}\) \\
20 & 2.3 \(\pm\) 1.9 \({}^{\text{b}}\) & 3.6 \(\pm\) 0.0 \({}^{\text{b}}\) & 0.9 \(\pm\) 0.0 \({}^{\text{b}}\) & 8.1 \(\pm\) 0.0 \({}^{\text{a}}\) & 5.0 \(\pm\) 7.1 & n.d. & n.d. & n.d. \\ \hline \hline \end{tabular} Values are given as mean \(\pm\) SD (\(n\) = 2). Different letters in the same line indicate significant differences (\(p<0.05\)). If letters are not provided, no significant difference was observed. n.d.: not detected.  
\end{table} 
Table 3: Maximum observed counts for total aerobic mesophilic bacteria (TMB) and Clostridia (Cl) amongst the five domestic environments, for each day of sampling, scenario, and pesto. S: Scenario (1, 2); P: Pesto brand (1, 2). of the samples depends on the contamination of the domestic environments in which the opening took place, while the storage temperature could influence the growth rate of microorganisms. As it can be inferred, the maximum TMB count found within S1P1 was 964 CFU/g for sample C at 5 days after opening. For the same pesto and scenario (S1P1), on the following days, TMB counts did not exceed 32 CFU/g. This behaviour, in which the growth of microorganisms was not increasing throughout the storage time, was noticed more than once in this study. Probably, it could be due to the utilization of a different jar of pesto for each day of sampling, although they were opened at the same time, and treated and stored in the same conditions. In the second scenario of P1, the maximum TMB count (964 CFU/g) was recorded on the 11 th day of household storage on sample E. It is worth recalling that each sample was analysed only once, and that at each sampling time a different jar was taken.