## 4 E-Nose: Principles and Main Agri-Food Applications
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Category** & **Application** & **Sensor Arrays** & **Chemometrics Approach** & **Classical Methods for Comparison** & **Reference** \\ \hline Identification of early infestation of & & & & \\ _Bactracon dorsal_ in citrus & & MOS & PCA, LDA & & [73] \\ _(Citrus reticulate)_ & & & & \\ \hline Detection of pathogen (Salmonella, & & & & \\ _Erwiniz_, _Streptavidinocucas_ and & & & & \\ _Staphylococcus_) contamination & & MOS & PCA, HCA & HS-GC-MS & [74] \\  & of apples & & & \\ \hline Decay detection of peach & & & & \\ _Prunusersica L. Batsch_) during & & MOS & PISR, LS-SVM, & & \\ storage & & & & \\ _evaluation_ & & & & \\ \hline Detection of diseased blueberry & & & & \\ fruit inoculated with grey mold & & & & \\ _(Botrits cinerea)_, anthracnose & & & & \\ _(Colletotrichum glueosporoides)_ and & & & & \\ Alternaria rot (Alternaria sp.) & & & & \\ \hline Identification of spoiled tomato & & & & \\ (inoculated with _Aspergillus and_ & & & & \\ _Pariicillin_ spp.) & & MOS & PCA & DHS-GC-MS & [77] \\ \hline Classification of damaged and & & & & \\ infested apples (_Malus domestic_) & & & & \\ \hline Early detection of smoke taint in & & & & \\ wine grapes, while not perceivable & & & & \\ by sensory evaluation & & & & \\ \hline Discrimination between fermented & & & & \\ and unfermented musts & & & & \\ \hline Comparison of threshold detection & & & & \\ performance and concentration & & & & \\ quantification with a trained human & & MOS & PCA & Sensory analysis & [81] \\ sensory panel & & & & \\ \hline Monitoring postharvest controlled & & & & \\ partial dehydration & & & & \\ \hline Calibration transfer applied to the & & & & \\ analysis of wine aroma using & & & & \\ synthetic wine prepared from the & & & & \\ most common wine aromas & & & & \\ \hline Classification of Tempranillo wines & & & & \\ according to geographic origin & & & & \\ \hline Identification of geographical origin & & & & \\ of Sauvignon Blanc wines, with & & MOS and MS & & \\ GC-MS that was then used to train & & based & & \\ an LDA & & & & \\ \hline Discrimination of beer and wines & & & & \\ tainted with off-flavors & & & & \\ \hline Five different wines elaborated with & & & & \\ the major varieties from the DO & & & & \\ vinos de Madrid were used for & & MOS & PCA & GC-MS & [87] \\ testing the discrimination capability & & & & \\ of the developed system & & & & \\ \hline Characterization of different wine & & & & \\ fruits (blackberry, cherry, raspberry, & & & \\ blackcurmat, elderberry, cranberry, & & & & \\ apple and peach) based on their & & & & \\ odor profiles & & & & \\ \hline Monitoring of aroma production & & & & \\ during wine must fermentation & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._E-nose finds application in different steps of the agri-food production chain, such as process monitoring, harvesting time evaluation, storage condition and SL evaluation. The latter includes the assessment of freshness or decay degree, microbial contamination and off-flavor formation [90]. The odor constituents of fruits vary greatly during ripening and storage (mainly in terms of terpen, alcohols and esters); therefore, the aromatic composition at a specific moment can provide important information about the maturity level and can be efficiently discriminated through E-nose tools [58; 60; 61]. An important shift in the VOCs profile, indeed, can occur with different storage or processing protocols, such as roasting applied to coffee or cocoa [63; 72] or partial controlled dehydration of grapes [82]. Additionally, food pathogens produce specific off-flavors from their metabolism and often lead to significant decay of the organoleptic features of the products, resulting in economic loss, consumer rejection and risks for consumers' health. Many studies have proved that such VOCs can be studied to assess for an early bacterial and fungi contamination of fresh or minimally processed agri-food products during storage [63].