Changes in Flavor Substances of Lightly-pickled Cucumbers during Storage Based on Electronic Nose Combined with GC-IMS

In order to investigate changes in flavor substances of lightly-pickled cucumbers during storage, volatile compounds were analyzed by electronic nose and gas chromatography-ion mobility spectrometry (GC-IMS). The results showed that flavor characteristics of lightly-pickled cucumbers changed obviously during storage. A total of 56 volatile organic compounds (VOCs) were detected by GC-IMS, including 10 alcohols, 30 aldehydes, 8 ketones, 5 esters, 1 furan, 1 acid, and 1 alkane. With the extension of storage period, the relative contents of aldehydes, alcohols and ketones decreased significantly, while the contents of esters increased significantly (P<0.05). Based on relative odor activity value (ROAV≥1), 9 key flavor compounds were found. The key flavor compounds were performed by PLS-DA and 6 differential markers were screened (VIP>1), including cis-6-nonenal, nonenal, 1-penten-3-one, isobutyraldehyde, trans-2,cis-6-nonadienal, and trans-2-octenal. Among them, trans-2-octenal increased with the relative extension of storage time, which might be the main off-flavor compound for flavor deterioration. This study can provide a theoretical basis for flavor quality evaluation of lightly-pickled cucumbers during storage.