Characterization and Evaluation of Volatile Compounds in Different Types of Protected Peach Fruits

The volatile compounds of 18 protected peach fruits (5 types) were analyzed by headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), and the characteristic volatile components in different peach fruits were screened and evaluated. A total of 197 volatile compounds were detected, among which 22 common typical volatile compounds were found in all samples. The composition (57-99 types) and contents (2.860-7.018 mg/kg) between different samples showed significant differences. Esters were the predominant type of volatile compounds, among which two important esters, hexyl acetate (0.624-2.851 mg/kg) and (E)-2-hexenyl acetate (0.487-1.850 mg/kg) accounted for more than 50% of the total contents and played a crucial role in the formation of peach aroma. Lactones were largely connected with the “peach-like” odor, and were at a high level in flat peaches (nectarine type). δ-and γ-decalactone were the two lactones with high contents. C₁₃-norisoprenoids were found to existe only in common peaches (white-fleshed peaches), which indicated that the existence of C₁₃-norisoprenoids obviously associated with fruit types of white-fleshed and yellow-fleshed peaches. Research showed that the esters, lactones and terpenoids were extremely susceptible to the alteration of planting locations. By multivariate discriminant analysis, the main contributing volatile components were screened out, and samples of different fruit types could be differentiated based on the potential important differential volatile compounds. Moreover, the VIP value combined with variable coefficient played an important role in screening characteristic volatile compounds to distinguish the protected peach samples belonging to different fruit types.