Abstract: In order to investigate the differences in volatile components and major aroma characteristics between tea made from tender and mature leaves of Eucommia ulmoides pre-treated by steam explosion (SE), an electronic nose (E-nose) and headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS) were applied to analyze the effect of SE on the volatile components in tea made from tender and mature leaves of the Eucommia ulmoides cultivar ‘Huazhong 8’. The results showed that the principal component analysis (PCA) and linear discriminant analysis (LDA) models fitted well the E-nose data, which suggested that the aroma characteristics of both tender and mature leaf tea were significantly different between with and without SE pretreatment. Altogether, 177 volatile components were identified by HS-SPME-GC-MS, among which 24 were selected as aroma active substances by orthogonal partial least squares discriminant analysis (variable importance in the projection (VIP) value ≥ 1) and Kruskal-Wallis H test (P < 0.05). The key aroma substance of tender leaf tea without SE was dihydroactinidiolide. The key aroma substances of tender leaf tea with SE were dihydroactinidiolide, nonanal, benzaldehyde and phenylacetaldehyde, contributing to citrus-like, flowery, caramelic, bitter almond-like, nutty, rose-like and chocolate-like aromas. No key aroma substances were found in mature leaf tea without SE, while dihydroactinidiolide and nonanal were identified the key aroma substances in mature leaf tea with SE, contributing to sweet peach-like, woody, citrus-like, flowery and caramelic aromas. The results of this study can provide a reference for the development of beverage products based on Eucommia ulmoides leaves.

Key words: Eucommia ulmoides ‘Huazhong 8’; aroma composition; steam explosion; Eucommia ulmoides tea