# Photo-Stimulated Luminescence Approach for Effective Identification of Irradiated Fruit
## 3 Results and Discussion  
### Preliminary Tests  
Table 2 reports the results obtained in the preliminary tests carried out on 10 types of fruit. As expected, all the non-irradiated samples gave negative PSL responses, very close to each other, ranging from 183 to 501 total counts. On the contrary, the irradiated samples showed very different PSL responses, ranging from a few hundred counts to hundreds of thousands of counts, depending on the fruit. Among the fresh fruits (Table 2a), kiwi and orange samples showed good PSL sensitivity to radiation, giving total counts of tens of thousands, well above the positive T\({}_{2}\) threshold. Mango peel samples showed lower sensitivity, but they were still adequate for identifying irradiated samples, with total counts all above the positive threshold T\({}_{2}\). A test carried out on mango stem provided higher counts, but further investigations on different \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{3}{c}{(a)} \\ \hline
**Fruit** & **0 kGy** & **0.5 kGy** & **1 kGy** \\ \hline kiwi & \(\begin{array}{c}396\pm 54\\ 357\pm 54\end{array}\) & \(\begin{array}{c}35,483\pm 195\\ 55,697\pm 241\end{array}\) & \(\begin{array}{c}15,121\pm 133\\ 30,808\pm 182\end{array}\) \\ \hline lemon & \(\begin{array}{c}397\pm 54\\ 435\pm 55\end{array}\) & \(\begin{array}{c}3005\pm 74\\ 2473\pm 71\end{array}\) & \(\begin{array}{c}3691\pm 79\\ 2221\pm 69\end{array}\) \\ \hline mango peel & \(\begin{array}{c}258\pm 53\\ 489\pm 55\end{array}\) & \(\begin{array}{c}7378\pm 100\\ 7918\pm 102\end{array}\) & \(\begin{array}{c}17,802\pm 143\\ 82,463\pm 292\end{array}\) \\ \hline mango stem & & & & 269,364\pm 521\) \\ \hline orange & \(\begin{array}{c}478\pm 55\\ 491\pm 55\end{array}\) & \(\begin{array}{c}31,536\pm 185\\ 27,947\pm 175\end{array}\) & \(\begin{array}{c}25,453\pm 167\\ 75,104\pm 288\end{array}\) \\ \hline papaya & \(\begin{array}{c}249\pm 53\\ 232\pm 53\end{array}\) & \(\begin{array}{c}1327\pm 62\\ 4532\pm 84\end{array}\) & \(\begin{array}{c}4265\pm 83\\ 3261\pm 76\end{array}\) \\ \hline pineapple peel & \(\begin{array}{c}370\pm 54\\ 286\pm 53\end{array}\) & \(\begin{array}{c}780\pm 58\\ 754\pm 57\end{array}\) & \(\begin{array}{c}712\pm 57\\ 558\pm 56\end{array}\) \\ \hline pineapple leave & \(\begin{array}{c}401\pm 54\\ 388\pm 54\end{array}\) & \(\begin{array}{c}545\pm 56\\ 541\pm 56\end{array}\) & \(\begin{array}{c}1069\pm 60\\ 802\pm 58\end{array}\) \\ \hline tangerine & \(\begin{array}{c}375\pm 54\\ 343\pm 54\end{array}\) & \(\begin{array}{c}3235\pm 76\\ 465\pm 55\end{array}\) & \(\begin{array}{c}1138\pm 61\\ 2985\pm 74\end{array}\) \\ \hline \hline \multicolumn{3}{c}{(b)} \\ \hline
**Fruit** & **0 kGy** & **0.5 kGy** & **1 kGy** \\ \hline dried date & \(\begin{array}{c}456\pm 55\\ 183\pm 52\end{array}\) & \(\begin{array}{c}3988\pm 81\\ 5737\pm 91\end{array}\) & \(\begin{array}{c}15,827\pm 136\\ 7280\pm 99\end{array}\) \\ \hline dried prune & \(\begin{array}{c}494\pm 55\\ 366\pm 54\end{array}\) & \(\begin{array}{c}857\pm 58\\ 1152\pm 61\end{array}\) & \(\begin{array}{c}1774\pm 66\\ 3618\pm 78\end{array}\) \\ \hline raisin & \(\begin{array}{c}501\pm 55\\ 442\pm 55\end{array}\) & \(\begin{array}{c}538,058\pm 735\\ 725,344\pm 853\end{array}\) & \(\begin{array}{c}878,725\pm 939\\ 839,301\pm 917\end{array}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: PSL results of the preliminary tests: (a) fresh fruit; (b) dried fruit. parts of the stem are necessary to verify this result. All the other fresh fruits showed lower PSL sensitivity to radiation and gave non-positive results, mostly intermediate. Among them, pineapple samples gave the worst results, providing total counts close to and even below the negative T\({}_{1}\) threshold. The tests performed on pineapple leaves did not give better results either. Regarding dried fruit (Table 2b), raisins showed the highest PSL sensitivity to radiation of all the fruit tested in this preliminary work, giving hundreds of thousands of counts for the irradiated samples.