Effect of roasting conditions on the aroma characteristics of Fenghuang Dancong oolong tea (Yashixiang)

Abstract

Background Roasting is a crucial refining process for Fenghuang Dancong (FHDC) tea, imparts diverse aroma profiles to the final products. Yashixiang (YS) tea is the most popular FHDC variety among consumers. Methods This study identified the aroma-active compounds (AACs) of YS tea under various roasting treatments utilizing SPME coupled with GC×GC-O-TOF MS, and analyze the variations in aroma components among the light-fired(LF), medium-fired (MF), and high-fired (HF) YS samples using multivariate statistical analysis. Results A total of 126 AACs were detected, among which only 38 aroma-active compounds had a relative odor activity value ≥ 1. Partial least squares-discriminant analysis demonstrated significant differences in the aroma compositions of the three samples. In the LF sample, alcohols, aldehydes, ketones, and esters constituted the primary aroma contributors, explicitly ( E,E )-2,4-heptadienal, ( E,Z )-2,6-nonadienal, 3,5-octadien-2-one, 6-methyl-5-hepten-2-one, and ethyl octanoate. In the MF sample, the increases in compounds like γ -caprolactone and 2,3-butanedione endowed the tea with a rich creamy aroma. Conversely, in the HF sample, the contents of heterocyclic compounds closely associated with the Maillard reaction, such as 2-ethyl-5-methylpyrazine, 2,5-dimethyl-3-ethylpyrazine, N -methylpyrrole-2-carboxaldehyde, indole, and 2-pentylfuran, increased significantly. Conclusions The roasting process achieves the aromatic evolution of YS tea from “green, floral, and fruity” to “sweet, woody, roasted, smoky, and medicinal” by dynamically regulating pathways such as fatty acid oxidation, the Maillard reaction, and thermal degradation.