| To study the differences of volatile flavor compounds in different walnut varieties and the distinguishing methods of walnut varieties, five walnut varieties were selected as study subjects, and gas chromatography-ion mobility spectrometry (GC-IMS) and electronic nose (E-nose) technology with the combination of PCA, LDA and cluster analysis were used to study the composition of volatile flavor compounds and variety differences of walnuts. The results showed that GC-IMS combined with cluster analysis and E-nose technology combined with LDA could effectively distinguish walnut varieties. In addition, a total of 73 volatile compounds were separated by GC-IMS from the five walnut varieties, and 19 substances were identified, mainly including alcohols, ketones, aldehydes and esters. Moreover, key substances to distinguish walnut varieties were determined as follows: ethanol, 2-methyl-1-propanol, 1-pentanol, 3-methyl-3-butene-1-ol, n-hexyl alcohol, 2-heptanone, pentanal, hexanal, heptanal, nonanal, benzaldehyde and ethyl acetate. The results of E-nose analysis showed that W3C, W5C, W1C and W6S sensors had a greater contribution to the differentiation of walnut varieties, and LDA was more obvious than PCA in the differentiation of walnut varieties due to the consideration of inter-group differences. Compared with the two flavor analysis techniques, GC-IMS could conduct qualitative and quantitative detection of volatile substances. E-nose couldn’t identify the specific types of volatile substances, but the sample processing was simple and could realize the rapid differentiation of varieties. |
