## 3 Discussion  
### GC \(\times\) GC/HR-TOF/MS Analysis  
The alcohols, aldehydes and ketones, produced by lipid oxidation and Strecker degradation of amino acids [9], remarkably contributed to the truffle flavor. For instance, 1-octen-3-ol (along with other C8 volatiles) was a potential signal molecule produced by both truffle mycelium and fruiting bodies [20,21], which had been found in most truffles. 1-Pentanol was once detected in both _T. borchii_ and _T. melanogaster_[6]. 2-Methyl-1-butanol has previously been reported as a volatile compound in _T. magnatum_. Phenylethyl alcohol has also been identified in some kinds of truffle species, such as _T. aestivum_[22] and _T. mesentericum_[23]. A series of short chain aldehydes, such as hexanal, heptanal, (_Z_)-2-heptenal, nonanal, 5-ethylcyclopent-1-encarboxaldehyde, _E_-2-octenal, benzaldehyde, benzeneacetaldehyde, 2/4-decadienal and \(\alpha\)-ethylidene-benzeneacetaldehyde, were identified in both samples, and all of them were found in various species of truffle [6,10]. Acetoin, previously discovered in _T. melanosporum_ (Soria) [10] and _T. indicum_[6], has a bland, woody, yogurt odor and a strong buttery and creamy aroma when diluted to 1.0%. According to the published literature, acids detected in truffle volatile components seemed fewer. Though identified, there were only a small number of acids, such as acetic acid, 2-propenoic acid and 2-methylhexanoic acid [10,23]. A total of twelve acid compounds were identified in this research, which dominated the aroma profile of both samples with the maximum proportion (67.5% in BT, 53.9% in WT) based on concentrations. Meanwhile, eight acids were detected in both of the samples: 2-methylpropanoic acid, 3-methyl-butanoic acid, hexanoic acid, heptanoic acid, octanoic acid, (_E_)-2-octenoic acid and benzeneacetic acid. All of the \"extraction systems\" have different performances linked to their different chemical and physical characteristics. In terms of the different reported methods applied to extract truffle volatiles, the widely-used methods, SPME and SBSE, are very efficient via divinylbenzene/carboxen/polydimethylsiloxane fiber (DVB/CAR/PDMS; thickness: 50/30 \(\upmu\)m). Besides, SPME is a powerful technique for the analysis of volatile organic sulfur compounds in truffle aromas [24]. DSE can extract most of the components in the samples, including volatile and nonvolatile compounds based on the theory of \"like dissolves like\". When combined with SAFE, this method allows the fast and careful isolation of volatiles from solvent extracts of food [25] and is able to remove any nonvolatile materials. The method DSE-SAFE has been used in many aspects of volatile compounds in food, such as fruit [26], milk [27], sauces [28], meat [29], wines [30], and so on. However, the method acts as a new technique in the detection of volatiles in truffles. Considering furans and furanones detected in the samples, 2-pentylfuran has been detected in _T. excavation, T. aestivum_[23] and _T. aestivum, T. melanosporum_[10] via SPME. It has an odor of fruity, green and earthy beany with a vegetable-like nuance. Both dihydro-5-pentyl-2(3\(H\)) furanone (coconut, creamy, waxy, sweet, buttery and oily) and 2(5\(H\)) furanone (buttery) had been found in _T. melanosporum_[6] by SBSE. Both aroma profiles and the amount of volatile compounds from truffles varied in species [31]. According to Table 1, in addition to the identical composition with various concentrations, the difference between the two samples was also reflected in the types of compounds identified, while 24 of them were only detected in BT samples and 13 of them only in WT samples. Among the 30-60 volatiles produced by a single truffle, only a small amount of them contributes to the aroma profile [32]. Besides, sulfur-containing compounds were essential compositions, for they acted as truffle aromas that humans perceived. In this study, more sulfur-containing compounds were detected in white truffles in terms of both amounts and contents.