## 3 Results
### Volatile Organic Compounds  
Volatile organic compounds (VOCs) identified in the Provolone del Monaco cheese samples were divided into 6 families, including organic acids, alcohols, ketones, aldehydes, esters, and other compounds (Table 3). Organic acids were the most abundant VOCs detected. In particular, acetic acid (ranging from 18.25 to 2503.02 ug/kg), butanoic acid (ranging from 186.02 to 11,469.36 ug/kg), and hexanoic acid (ranging from 203.99 to 5022.33 ug/kg) were found. These molecules are typical of dairy products and come from the oxidative decarboxylation of \(\alpha\)-keto acids, which originate from branched amino acids released during proteolysis [34]. Organic acids (and relative quantities) are the main responsibles for the Provolone del Monaco PDO cheese aroma, giving it its pungent, sour, cheesy, and buttery odors [35; 36; 37; 38]. Alcohols and ketones are the second and third most abundant families detected, respectively, and arise from \(\beta\)-oxidation and decarboxylation of free fatty acids released during lipolysis [34]. Most likely, for this reason, no alcohols were revealed at the beginning of ripening. Among the alcohols, ethanol (ranging from 9.49 to 56.73 ug/kg), 1-butanol (ranging from 6.38 to 79.81 ug/kg), and 2-ethyl-1-hexanol (ranging from 8.20 to 80.20 ug/kg), mostly contribute to the Provolone del Monaco aroma, with characteristic alcoholic, fruity, and spicy aromas, respectively. Among ketones, acetoin (3-hydroxy-2-butanone, ranging from 3.77 to 61.91 ug/kg), which is a characteristic dairy product volatile compound, can be found only in the first days of ripening. Aldehydes (hexanal and nonanal) were found in small amounts during ripening. These compounds are produced from \(\alpha\)-keto acids by decarboxylation [34] and can be quickly converted into alcohols or their respective acids [39] during ripening. This could explain why hexanal (ranging from 26.60 to 63.66 ug/kg) was found only at time 0 in the cheese samples. Esters were the less abundant family detected. Two molecules were identified, ethyl hexanoate (ranging from 35.24 to 123.33 ug/kg) and butyl butanoate (ranging from 33.92 to 47.24 ug/kg). Their origin could be attributed to the reaction between free fatty acids and alcohols [34]. An integrated and multidisciplinary system of analysis is becoming a valuable tool to analyze and study food, taking into account the various aspects of food quality and composition by employing innovative and emerging technologies with statistical analysis. Such a multi-technique approach to food research enables utilizing all the resources of quality, safety, and traceability in food systems. The joined approach of multidisciplinary analysis techniques of food matrices with the multivariate statistical approach enlarges the possibilities to exploit a wide range of food traits and aspects. The \"Integrated Approach\" is the key to modern food research and the innovative challenge for analyzing and modelling agro-food systems in their totality [40; 41; 42; 43]. To better understand the VOC distribution during ripening, a Principal Components Analysis (PCA) was carried out using the recorded dataset, which is shown in Figure 2.  
The PCA illustrates which families are characteristic at different ripening times. The F1 and F2 factors explain 97.8% of the total variability. In particular, the factor F1 explains 74.7%. The main contribution to F1 comes from alcohols (21.3%). The factor F2 explains 23.1% of the variability, with the main contribution given from esters (39.0%), followed by aldehydes (38.7%). As expected, the majority of molecules were found in the last months of ripening. In particular, after 90 and 180 days, cheese samples showed a large amount of organic acids and alcohols. Furthermore, cheese at the 270-day timepoint was characterized mainly by esters, ketones, and other compounds. \begin{table}