Comparative Investigation\nof Aroma-Active Volatiles\nin (“Ruixue”, “Liangzhi”, “Crystal\nFuji,” and “Guifei”) Apples by Application of\nGas Chromatography–Mass Spectrometry–Olfactometry (GC–MS–O)\nand Two-Dimensional Gas Chromatography-Quadrupole Ma

Aroma dramatically impacts the overall flavor profiles\nand consumer\nacceptance; therefore, it is necessary to conduct a comprehensive\nanalysis of the aroma characteristics of apples. In this study, the\naroma differences among four popular apple varieties (“Ruixue”,\n“Liangzhi”, “Crystal Fuji,” and “Guifei”)\nwere compared using two extraction methods (headspace-solid phase\nmicroextraction, and solvent-assisted flavor evaporation) coupled\nwith gas chromatography–mass spectrometry–olfactometry\n(GC–MS–O) and two-dimensional gas chromatography-quadrupole\nmass spectrometry (GC × GC-qMS). A total of 82 odorants were\nidentified via GC–MS–O, and 143 volatiles were identified\nby GC× GC-qMS. Among them, 41 key aroma-active compounds (butanal,\nethyl acetate, 3-methylbutanal, methyl butanoate, 2-methylpropyl acetate,\nethyl 2-methylbutanoate, ethyl 3-methylbutanoate, butyl acetate, hexanal,\n2-methylbutyl acetate, 1-butanol, 2-methylpropyl butanoate, 3-methylbutyl\nacetate, (<i>E</i>)-2-hexenal, butyl butanoate, butyl 2-methylbutanoate,\nhexyl acetate, hexyl butanoate, hexyl, 2-methylbutanoate, 1-octen-3-ol,\n3-methylthiopropanol, 1,3-octanediol, linalyl acetate, and so on)\nwith high odor activity values (OAVs) and AI value (odor activity\nvalues ≥1 or aroma intensity ≥3) were identified. Partial\nleast-squares-discriminant\nanalysis showed that Ruixue exhibited a high “fruity”\nnote, Guifei and Crystal Fuji had the greatest “wood,”\n“floral,” and “sweet” notes, while Liangzhi\npresented a significant “green” note. This study provided\nflavor chemistry support for the apple quality control and production.