Characterization of the key odorant compounds in ‘Qinguan’ apples (Malus × domestica)

'Qinguan' apple is native to China with the outstanding qualities of disease resistance and long storage time. In this study, gas chromatography-mass spectrometry (GC-MS) was used to identify the volatile compounds in peel and flesh of post-harvest 'Qinguan' apples. Ninety-four and seventy volatile compounds were identified in 'Qinguan' peel and flesh, respectively. Esters and alcohols were predominant in 'Qinguan' peel, while alcohols were identified as the main volatiles in 'Qinguan' flesh. Odor-active compounds and the sensory profile of 'Qinguan' apples were investigated by aroma extract dilution analysis-gas chromatography-olfactometry (AEDA-GC-O) and sensory description analyses. The sensory profile of 'Qinguan' apples was mainly characterized by aroma descriptors of fruity and green categories. Among the 15 odor-active compounds with flavor dilution factor (FD) ranging from 3 to 81, hexyl acetate, α-farnesene, hexanol, and hexanal (with FD = 81) were shown to be the most potent odor-active compounds in 'Qinguan' apples. Based on the results obtained from GC-MS, AEDA-GC-O, and omission tests, hexyl acetate as the most abundant ester in peel was suggested to be one of the characteristic aroma compounds of 'Qinguan' apple, contributing to its strong fruity aroma note, while the other characteristic aroma compound, α-farnesene, was responsible for the green note.