Analysis of Key Aroma Compounds in Three Varieties of Rucheng White Tea by Comprehensive Two-Dimensional Gas Chromatography-Quadrupole Time-of-Flight Mass Spectrometry

Abstract

Tea shoots consisting of one bud and two leaves from three tea strains/varieties in Hunan Province, Rucheng Baimao 1 (RT1), Rucheng Baimao 2 (RT2), and Rucheng Baimao Quntizhong (group variety, QT3) were picked and separately processed into white tea using the same procedure involving withering and drying, whose aroma characteristics and volatile components were evaluated by quantitative descriptive analysis (QDA) and analyzed qualitatively and quantitatively by headspace-solid phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography-quadrupole time-of-flight mass spectrometry (GC × GC-QTOF-MS), respectively. Partial least squares-discriminant analysis (PLS-DA) and relative odor activity value (ROAV) were combined to identify the key aroma components of Rucheng Baimao white tea and to explore the impacts of different tea tree varieties on the aroma of white tea. The results showed that the sensory aroma characteristics of the three varieties of Rucheng Baimao white tea differed from one another. Both RT1 and QT3 exhibited floral aromas; RT1 had a pronounced fresh aroma, while QT3 had a prominent tip aroma. RT2 exhibited a minty aroma. Multivariate statistical analysis showed that using variable importance in the projection (VIP) score > 1 with a P value 1.00 as the cutoff, 10 aroma components were identified as contributors to the differences in aroma among the three varieties of white tea. Benzaldehyde played a key role in the fresh aroma of all white tea samples. Hexanal was the key to the fresh aroma of RT1. Benzaldehyde, linalool oxide II, and linalool oxide I significantly contributed to the minty aroma of RT2. 1-Octen-3-ol, citral, and (Z)-4-heptenal were crucial for the tip aroma of QT3. This study provides a theoretical reference for the diversification of aroma types of Rucheng white tea and for understanding the material basis for the key aroma compounds in Rucheng white tea produced from different tea strains/varieties.

Keywords

• white tea; tea strains/varieties; comprehensive two-dimensional gas chromatography-quadrupole time-of-flight mass spectrometry; aroma; multivariate statistical analysis