## 2 Results and Discussion
### Aroma Blueprinting by AI Smelling Based on Sensomics  
As reported by [PERSON] and co-workers in their studies on Darjeeling black tea (infusions and dried leaves) [21; 38], a group of 24 odorants with high flavor dilution (FD) factors was recognized to play a prominent role in defining the characteristic aroma of the final infusion. Within these 24 chemicals, 16 were identified as having a high odor activity value (OAV), i.e., the ratio between the odorant concentration in the food vs. its odor threshold. It is commonly assumed that the higher the OAV value, the higher its contribution to the overall sensory perception. Among the most odor-active compounds revealed by sensomics (16), i.e., those with OAV values \(\geq\) 1 (value recognized to be significant in contributing to the flavor of food [44]), the current method reliably monitors 13 of them with a fully automatized procedure that avoids laborious sample-preparation steps. With IS-SPME-GC-MS, an effective aroma blueprinting method is achieved that supports, or even replaces, sensory panel evaluation in the perspective of quality benchmarking and quality controls. Regarding aroma features, the Strecker aldehydes formed during the fermentation process [1] (2-_methyl butanal_ and _3-methyl butanal_) concur to an intense malty perception, while _phenylacetaldehyde_ evokes a pleasant honey-like note. Responsible for floral notes are _geraniol_ (rose-like) and _\(\beta\)-ionone_ (violet-like), and for fruity notes, _linal_ and _\(\beta\)-damascenone_. An important contribution to the black tea aroma identity is also provided by the green and grassy notes of _hexanal_, _(E)-2-nonenal_, and _(E,E)-2,4-nonadienal_. Fatty perception is modulated by C9 unsaturated aldehydes, while fishy notes are from [_(Z)-4-heptenal_] and fatty/fried by [_(E,E)-2,4-decadienal_]. All these aldehydes are formed from the enzyme-catalyzed oxidation of fatty acids during plant growth and manufacturing processes [42]. The aroma blueprint of the infusions is visualized as spider diagrams based on OAV values in a logarithmic scale (Figure 2). By this visualization for each compound, the concentration is associated with the relative OT in water and the odor descriptor. The spider diagrams show that most tea samples have a specific aroma profile characterized by a good balance of markers; in general, teas from Ceylon, Assam, and Kenya likely have a similar aroma profile, especially for some notes such as fruity (_\(\beta\)-damascenone_), malty (Strecker aldehydes), honey-like (_phenyl acetaldehyde_), and cucumber-like (_(E,Z)-2,6-nonadienal_). On the other hand, Assam infusion is characterized by a lower content of terpene derivates (_geraniol_ and _linalo_) than the other teas, likely resulting in weaker citrus and rose-like notes. The aroma profile confirms the great diversity of samples from Darjeeling. A very important outcome deriving from the calculation of OAVs consists of the explanation of the role played by each specific analyte in the definition of the aroma profile. Although present at very low concentrations (range 0-4 \(\upmu\)g/L), some analytes such as _\(\beta\)-damascenone_, _\(\beta\)-ionone_, _(Z)-4-heptenal_, and _(E,Z)-2,6-nonadienal_ are extremely potent, being characterized by very low OTs (e.g., 0.004 \(\upmu\)g/L for _\(\beta\)-damascenone_); as an example, _\(\beta\)-damascenone_ generates the maximum OAV of 94.8 in Darjeeling Testa Valley tea, where OAVs were higher also for other key volatiles (i.e., _linalo_, _3-methyl butanal_, and _2-methyl  
Figure 2: Spider diagrams with Odor Activity Values (OAVs) illustrating the contribution of each key aroma compound to the aroma perception of selected teas. OAV data are reported on logarithmic scale. Ceylon tea’s aroma profile is reported as average value calculated from four different lots. butanal_).