# Internet of Food (IoF), Tailor-Made Metal Oxide Gas Sensors to Support Tea Supply Chain
## 3 Results  
### GC-MS Results  
After closure, vials were placed in the autosampler HT280T (HTA s.r.l., Brescia, Italy) to proceed with vial conditioning and volatile organic compound (VOC) extraction. Regarding the data extracted from the GC-MS-SPME analysis, the volatile fingerprints for each tea were identified, and the tables are presented at the end of the article in Appendix A (Tables A1-A11). It was possible to identify the common compounds between the green tea samples that are presented in Table 3.  
In total, an average of 100 volatile compounds were found for each sample analyzed, of which only seven in common to all samples. * Cyanoacetic acid: (C\({}_{3}\)H\({}_{3}\)NO\({}_{2}\)) is an organic compound that has two functional groups: COOH typical of carboxylic acids and NC with triple bond typical of nitriles. It is obtained from the treatment of chloroacetate with sodium cyanide followed by acidification or electrolysis by cathodic reduction of carbon dioxide or the anodic oxidation of acetonitrile. It is a precursor of synthetic caffeine by theophylline [33]. * Hexanal: (C\({}_{6}\)H\({}_{10}\)O) is an aldehyde. In the cell, it is contained in the cytoplasm. It has a sweet almond and honey flavor and is found in several foods including soy, cucumber, black elderberry, and black current [33]. * Limonene: (C\({}_{10}\)H\({}_{16}\)) is the most widespread and most important monoterrene. It has a lemon smell and turpentine-like notes. It is obtained by steam distillation of citrus peel and pulp obtained from the production of juice [33]. It should be specified that it is present as two isomers: R-LIMONENE and D-LIMONENE. In particular, it is R-LIMONENE in the SGP, while in the others, it is D-LIMONENE, and both isomers are present in the SGM. * 6-methyl, 5-hepten-2-one: (C\({}_{8}\)H\({}_{14}\)O) is an unsaturated ketone called sulcatone. It has a strong, greasy, green, citrus smell and tastes reminiscent of pear. It is obtained from citronella or citral oil by mixing for 12 h in aqueous solution with K2 CO3 and subsequent distillation and fractionation under vacuum. It was originally identified in lemongrass; later, it was also discovered in the essential oils of lemons and geraiums. We also find this ketone in grapes, melon, peaches, avocados, cognac, mangoes, rice, olives, blueberries, and more [33]. * 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 beverages including apples, tomatoes, rum, wine, plum, coconut, cardamom, avocado, corn oil, broccoli, milk, eggs, tea, and others [34]. * \(\alpha\)-Terpineol: (C\({}_{10}\)H\({}_{18}\)O) is a monoterpenic alcohol. It has a characteristic smell of lilac with a sweet flavor reminiscent of peach. It is obtained from the hydration of the terpene or from the pentane tricarboxylic acid by cyclization or from the isoprene and methyl-vinyl-ketone. It is present in more than 150 derivatives of herbs, leaves, and flowers. Form D is found in cardamom, star anise, sage, and marjoram oil. The L form is present in lavernder, lime, and cinnamon leaves. The racemic form is the eucalyptus [33; 34]. * 5,6,7,7a-Tetrahydro, 4,4,7a-Trimethyl-2(4H)-benzofuranone: (C\({}_{11}\)H\({}_{16}\)O\({}_{2}\)) 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