## 2 Results and Discussion  
### HS-SPME GC-MS Results  
Solid-phase microextraction (SPME) is a very popular analytical extraction technique used before GC-MS headspace (HS) analysis thanks to its ease-to-use, the possibility of automation, and good sensitivity. SPME utilizes a short, thin, solid rod of fused silica coated with an absorbent/adsorbent polymer. The coated fused silica (the SPME fiber) is attached to a metal rod, and both are protected by a metal sheath that covers the fiber when not in use. SPME is particularly well suited to the analysis of dairy products being capable of extracting a broader range of analytes than most other sample preparation methods [12]. Moreover, thanks to the relatively low temperatures and short times at which headspace SPME extraction is performed, the risks to induce thermal artifacts are extremely low if compared with other techniques such as simultaneous distillation-extraction (SDE) [13]. Methods developed for the analysis of organic compounds from aqueous samples by SPME coupled to GC have been used to analyze VOCs in fresh and ripened dairy productions [8; 14]. A wide range of fibers with varying affinities for specific classes of volatile organic compounds is available. After a preliminary screening of seven different types of SPME fibers (100 \(\upmu\)m PDMS (polydimethylsiloxane), 60 \(\upmu\)m PEG (Carbowax-Polyethylene Glycol), 85 \(\upmu\)m PA (Polyacrylate), 75 \(\upmu\)m CAR/PDMS (Carboxen/Polydimethylsiloxane), 85 \(\upmu\)m CAR/PDMS, 50/30 \(\upmu\)m DVB/CAR/PDMS (Divinylbenzene/Carboxen/Polydimethylsiloxane), and 65 \(\upmu\)m PDMS/DVB (Polydimethylsiloxane/Divinylbenzene)) 75 \(\upmu\)m CAR/PDMS was chosen, because it provides the higher number of extracted volatiles. This fiber has been suggested to work particularly well for the analysis of volatiles in dairy products [12]. Extraction conditions have also been preliminarily explored by checking the effect of different times (10 min up to 4 h) and temperature (40 and 60 \({}^{\circ}\)C). A good compromise between the multiplicity of extracted volatiles and peak intensity was found by headspace exposing the fiber for 60 min at 60 \({}^{\circ}\)C and this experimental condition was selected for the present characterization. A total of 27 compounds belonging to different chemical classes (nine ketones, five alcohols, four acids, three hydrocarbons, two furans, one ester, one lactone, one aldehyde, and one oxime) have been identified. Ketones, which might induce fruity and floral sensory notes, are common constituents of most dairy products [15; 16; 17] and by far the most important class of compounds contributing to the mascarpone cheese aroma. In particular, 5 different ketones (2-heptanone > 2-pentanone > 2-propanone > 2-nonanone \(\approx\) 2-butanone) represent almost 75-80% of the sample headspace. The compounds 2-heptanone and 2-pentanone characterized by odor descriptors including sweet, fruity, orange peel, and herbaceous [15] are the dominating volatile organic compounds in all samples. Several alcohols have been detected, but differently from ketones, are not present in all samples--1-pentanol and 2-ethyl-1-hexanol, both common primary alcohols detected in dairy products [15], are ubiquitous, and ethanol and 1,2 propandiol have been detected only in one sample (Manufacturer B), suggesting a possible technological origin. Other minor compounds, including short- and moderate-chain even-numbered fatty acids (C\({}_{4}\)-C\({}_{12}\)), ethyl acetate, \(\delta\)-hexalactone, toluene, benzaldehyde and methoxyphenyl oxime have been already found in cheese products [16; 18; 19]. The two hydrocarbons 2,4-dimethylheptene and 2,2,4,6,6-pentamethylheptane have been detected only in one sample (Manufacturer A) and the latter has been detected in the volatile fraction of butter [20]. Furfurral and 2-furanmethanol, identified in all mascarpone cheese samples, have been found to contribute to the nutty and roasted aroma of Parmigiano-Reggiano cheese [21].