# Internet of Food (IoF), Tailor-Made Metal Oxide Gas Sensors to Support Tea Supply Chain
## 3 Results
### GC-MS Results
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Compound** & **TGO** & **SPG** & **SGL** & **SGM** \\ \hline Cyanoacetic acid & \(1.685\times 10^{5}\) & \(1.165\times 10^{5}\) & \(5.677\times 10^{4}\) & \(6.301\times 10^{4}\) \\ Hexanal & \(7.22\times 10^{5}\) & \(5.751\times 10^{5}\) & \(2.889\times 10^{4}\) & \(3.529\times 10^{5}\) \\ Limonene & \(1.378\times 10^{7}\) & \(1.976\times 10^{5}\) & \(2.602\times 10^{8}\) & \(2.011\times 10^{5}\) \\
6-metile 5-epten-2-one & \(6.233\times 10^{5}\) & \(3.789\times 10^{5}\) & \(2.731\times 10^{5}\) & \(3.617\times 10^{5}\) \\ Nonanal & \(5.81\times 10^{5}\) & \(1.133\times 10^{5}\) & \(9.298\times 10^{4}\) & \(1.462\times 10^{5}\) \\ \(\alpha\)-terpineol & \(1.098\times 10^{6}\) & \(3.145\times 10^{6}\) & \(8.024\times 10^{6}\) & \(7.628\times 10^{5}\) \\
5,6,7,7a-tetrahydro, & & & & \\
4,4,4,7a- Trimethyl 2 & 3.448 \(\times\) 10\({}^{5}\) & \(4.843\times 10^{5}\) & \(4.819\times 10^{5}\) & \(2.836\times 10^{5}\) \\ (4H)—benzofuranone & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Common compounds between the analyzed green teas. the presence of nitrogen and air. It occurs naturally in lemongrass and sweet grass oil [33]. On the other hand and regarding the GC-MS results from the black tea samples, it is possible to say that there were seven black teas subjected to GC-MS analysis, with different flavors and belonging to different origins and composition. The results obtained showed that there are four VOCs in common to all the samples (Table 4). * Nonanal: (C\({}_{9}\)H\({}_{18}\)O) is an aldehyde. It has a strong and greasy odor which develops notes of orange and rose when diluted. The fat recalls the flavor of citrus fruits. It is synthesized by the catalytic oxidation of the corresponding alcohol or by the reduction of the respective acid. In nature, we find it in orange, mandarin, lemon, and lime oils. It is also found in more than 200 foods and drinks including apples, tomatoes, rum, wine, plum, coconut, cardamom, avocado, corn oil, broccoli, milk, egg, tea, and others [34]. * Ammonium acetate: (C\({}_{2}\)H\({}_{7}\)NO\({}_{2}\)) is an ammonium salt obtained from the reaction between ammonia and acetic acid. It is used to regulate acidity in food, even though the EU decided to ban its use as a food additive [33]. * Phenylethyl alcohol: (C\({}_{8}\)H\({}_{10}\)O) is an alcohol. It has a characteristic rose odor and initially a slight bitter taste. The dessert is reminiscent of peaches. It is synthesized from toluene, benzene, or styrene. It is found in esterified form in rose concentrate or distilled rose water. It is present in the essential oil of lily, narcissus, and tea leaves but not only because it has been found in more than 200 foods and drinks including peaches, grapes, coffee, tea, mushrooms, mango, kiwi, rum, whiskey, milk, butter, cheese, and more [33,34]. * 5,6,7,7a-Tetrahydro, 4,4,7a- trimethyl1 2 (4H)--benzofuranone: (C\({}_{11}\)H\({}_{16}\)O) is a heterocyclic compound. It has a coumarin and musky smell. This compound is formed from the photo-oxidation of caroten. The flavor is linked to the fruit and in particular to their point of ripeness. It is obtained from the degradation process of \(\beta\)-carotene in the presence of nitrogen and air. It occurs naturally in lemongrass and sweet grass oil [33].