The present study proposed a method for the determination of 12 glycosidic aroma precursors (benzyl β-D-glucopyranoside, benzyl β-primeveroside, 2-phenylethyl β-D-glucopyranoside, 2-phenylethyl β-primeveroside, geranyl β-D-glucopyranoside, geranyl β-primeveroside, linalyl β-D-glucopyranoside, linalyl β-primeveroside, nerolidyl β-D-glucopyranoside-1, nerolidyl β-D-glucopyranoside-2, nerolidyl β-primeveroside-1, and nerolidyl β-primeveroside-2) in tea using high performance liquid chromatography-triple quadrupole-mass spectrometry (HPLC-TQ-MS), and applied it to evaluate the compositional characteristics of glycosidic aroma precursors in five types of tea from Fujian province of China. Samples were extracted with methanol, purified by the QuEChERS method, and separated on a ACQUITY UPLC BEH C18 column using a mobile phase composed of water and acetonitrile with 5 mmol/L ammonia as a regulator. The separation was completed within 10 minutes. The limit of detection (LOD) and the limit of quantification (LOQ) of the proposed method ranged from 0.21 to 4.39 ng/mL and from 0.69 to 14.64 ng/mL, respectively, and the average recoveries were in the range of 81.34%–114.72%, with relative standard deviations (RSDs) of 0.40%–8.98%. Partial least squares-discriminant analysis (PLS-DA) was performed to distinguish the differences in glycosidic aroma precursors among Dahongpao tea, Shuixian tea, Tieguanyin tea, Tanyang Gongfu tea, and Baimudan tea. It was found that the compositional characteristics of glycosidic aroma precursors in tea were significantly affected by both tea variety and making process. Benzyl β-primeveroside, 2-phenylethyl β-primeveroside, geranyl β-primeveroside, and geranyl β-primeveroside were the key differential compounds. The conclusion of this study has a positive significance for optimizing the tea-making process and regulating tea quality.
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This study aimed to explore the origin discrimination technology for White Peony tea from small regions based on aroma characterization, so as to provide the technical support for tea origin traceability and brand building.
The aroma composition of White Peony tea from the main production areas (Zhenghe, Songxi, and Fu'an) was analyzed using the gas chromatography-mass spectrometry (GC-MS) with a headspace solid-phase microextraction method. A model for identifying the origin of White Peony tea was constructed by integrating mathematical and statistical methods to screen for characteristic compounds.
The aroma compounds in White Peony tea were comprised with aldehydes (24), ketones (23), alcohols (22), esters (14), acids (8), and other compounds (alkanes, alkenes, furans, ethers, anhydrides, phenols, amines, naphthalenes, etc.). The average aroma content in the tea samples was (3 487.93±1 014.04) μg·kg-1. The average aroma content in samples from Zhenghe County was significantly higher than that in samples from Songxi County and Fu'an City (P<0.01). For samples from Songxi and Fu'an, there was no significant difference. The total content of alcohols and acids in samples were not significantly different across the three regions (P>0.05), while the total content of ketones, aldehydes, and esters in samples from Zhenghe were significantly higher than those in samples from Fu'an and Songxi (P<0.01). Furthermore, 58 aromatic compounds, including hexanol, 1-octen-3-ol, and benzyl alcohol, showed no significant differences among the three regions (P>0.05). The PLS-DA and OPLS-DA models were well-validated with prediction indices of 0.732 and 0.728, respectively, and the discrimination accuracy of them was 98.89% and 96.67%, respectively. Based on two models, 38 and 46 characteristic aroma substances were identified with VIP values ≥1. The stepwise discriminant analysis also proved stable and reliable, screening 20 characteristic aroma compounds with 100% accuracy in both initial and cross-validation. Using combined OPLS-DA, PLS-DA, and stepwise discriminant analysis, 1H-Pyrrole-2-carboxaldehyde, 1-ethyl-, Geranial, Undec-8-enal <cis->, Benzyl alcohol, Cyclohexanol, 2,6-dimethyl-, Hept-5-en-2-one <6-methyl->, Trans-3-Nonen-2-one, Cyclodecanone, Nonanoic acid, Ethyl ester, and Benzyl acetate were identified as the main characteristic aroma compounds in samples from Zhenghe County. Ionone <(E)-, beta-> was the main characteristic aroma compound for samples from Songxi County. The characteristic aroma compounds in samples from Fu'an City were Enanthaldehyde, Hexanol <n->, Nerol, 3-Nonen-5-one, Nonanoic acid, ethyl ester, and Geranyl acetate.
A method for discriminating the origin of White Peony tea from small regions based on aroma characteristics was developed.
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