## 3 Results and Discussion
### Odorants in Dried Shititake Mushrooms
#### 3.2.2 Odorants Identified by DSE-SAFE
In the dried shitake mushrooms, there were 22 predominant odorants, of which ethyl acetate (218.34 \(\pm\) 16.35 \(\mu\)g/g) had the highest concentration, followed by acetic acid (177.54 \(\pm\) 2.78 \(\mu\)g/g), phenylethyl alcohol (9.20 \(\pm\) 2.10 \(\mu\)g/g) and isovaleric acid (7.06 \(\pm\) 0.28 \(\mu\)g/g). Phenylethyl alcohol and isovaleric acid were only reported to show higher contents in the dry _Flammulina velutiples_[47]. Lenthionine had the highest OAV of 14713 and was considered as the most important contributor, followed by 1-octen-3-one (1989) and phenylacetaldehyde (422). This illustrated that whatever the fresh or dried shitiake mushrooms, lenthionine and 1-octen-3-one contributed the main flavor to the overall aroma. In addition, there was some inconsistency between DF determined by DFA, FD determined by AEDA and OAV. In the fresh shitiake mushrooms, benzaldehyde and (E)-2-octen-1-ol had the highest DF factors (DF = 8), and isovaleric acid and octanoic acid had relatively high FD factors (FD = 27), but they all had lower OAVs (OAVs!). Similarly, 2-ethyl-1-hexanol, benzaldehyde and (E)-2-octen-1-ol had the highest DF factors (DF = 8), and 1-hexanol and 3-(methyl-thio)-1-propanol had relatively high FD factors (FD = 27), but they all had lower OAVs (OAVs!) in the dried shitiake mushrooms. This might be due to DFA and AEDA were carried out on the extracts of shitiake mushrooms, which eliminated the influence of food matrix. However, OAV took into account the effect of the food matrix [31]. This inconsistency indicated that the food matrix affected the contribution of volatile components to the aroma. Moreover, ethyl acetate, acetic acid, phenylethyl alcohol and 3-hydroxy-4,5-dimethyl-2(5H)-furanone were identified as predominant odorants in dried shitiake mushrooms by AEDA and their OAVs were greater than or equal to 1, but DFA showed they were non-essential. 1-Octen-3-ol had relatively high OAV and DF factor, but it was not identified as predominant odorants by AEDA in the fresh samples. This might be due to the fact that DFA and AEDA were based on different extraction methods, HS-SPME and DSE-SAFE. HS-SPME specializes in extracting highly volatile compounds and DSE-SAFE extracted semi-volatile and volatile compounds [21]. Thus, the combination of DFA and AEDA could more comprehensively identify the odorants of shitiake mushrooms. On the basis of OAV \(\geq\) 1, 3-methyl-butanol (chocolate), octanal (citrus-like), (E)-2-octenal (fatty, nutty), phenylacetaldehyde (floral), _trans_-4,5-epoxy-(E)-2-decenal (metallic), 3-octanone (mushroom), 1-octen-3-one (mushroom), 3-(methyl-thio)-1-propanol (cooked potato-like), 3-(methyl-thio)-1-propanol (cabbage), lenthionine (sulfury, burnt), 1-octen-3-ol (mushroom), phenylethyl alcohol (honey) and 3-hydroxy-4,5-dimethyl-2(5H)-furanone (seasoning-like) were considered to be the key contributors to the aroma of fresh shitiake mushrooms, and ethyl acetate (pineapple), 3-methyl-butanal (chocolate), phenylacetaldehyde (floral), 2,3-butanedione (sweet, creamy), 1-octen-3-one (mushroom), dimethyl trisulfide (sulfury), 3-(methyl-thio)-1-propanol (cooked potato-like), lenthionine (sulfury, burnt), 1-octen-3-ol (mushroom), acetic acid (vinegar-like), isovaleric acid (sweaty), phenylethyll alcohol (honey), 3-hydroxy-4,5-dimethyl-2(5H)-furanone (seasoning-like) and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel) were detected as the key contributing odorants in the dried shitiake mushrooms.