关键词: 核桃；挥发性化合物；电子鼻；指纹图谱；偏最小二乘判别分析

Abstract: To clarify the pattern of flavor evolution and the mechanism underlying the dynamic changes in key flavor substances of walnuts during ambient storage, we combined an electronic nose, gas chromatography-mass spectrometry (GC-MS), and gas chromatography-ion mobility spectrometry (GC-IMS) with chemometric methods including principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) to systematically analyze the volatile compounds in walnuts stored at room temperature for up to 220 days. The results showed that the electronic nose rapidly discriminated walnuts stored for different periods. PCA indicated that the first two principal components accounted for 91.9% of the variance, effectively separating samples from different storage stages. GC-MS identified 83 volatile organic compounds (VOCs), and the total VOC concentration exhibited an increase-decrease-increase dynamic trend. Based on odor activity value (OAV), 25 key aromaactive compounds were identified, among which aldehydes such as trans-2-octenal and (E,E)-2,4-nonadienal were the primary contributors to the offflavors of samples at the late stage of storage, originating from lipid oxidation and the Maillard reactions. A fingerprint map based on 67 GC-IMS signals visualized flavor differences across storage periods. Furthermore, using the PLS-DA models established for the early (days 5–50), mid (days 85–150) and late (days 180–220) storage stages, 34 key differential compounds (variable importance in projection (VIP) scores > 1) were identified, including 2,5-dimethylpyrazine. These findings provide a theoretical basis for optimizing the storage of walnuts.

Key words: walnuts; volatile compounds; electronic nose; fingerprint; partial least squares-discriminant analysis