Application of gas chromatography-mass spectrometry and chemometrics methods for assessing volatile profiles of Pu-erh tea with different processing methods and ageing years

Abstract

25Volatile changes and the post-fermentation ageing process of tea remain largely unknown. Additionally, 26 the understanding of the ageing and storage processes of tea mostly rely on sensory experience and 27 lack the support of scientific and accurate data. In this paper, a development method based on the 28 head-space solid phase microextraction/gas chromatography-mass spectrometer (HS-SPME/ GC-MS) 29 combined with multivariate statistical methods was used to assess volatile profiles in different type 30 Pu-erh teas, including raw, ripe and aged Pu-erh teas. A total of 122 aroma components were identified 31 in 57 Pu-erh teas. Differences in the manufacturing type and storage years of Pu-erh teas resulted in 32 different compositions and contents of volatile components. The characteristic volatiles in aged teas 33 were hexadecanoic acid, dihydroactinidiolide, caffeine, linalool, 6,10,14-trimethyl-2-pentadecanone, 34 β-ionone, cedrol, and phytol; the characteristic volatiles in raw teas were linalool, tridecane, caffeine, 35 dihydroactinidiolide, β-ionone, 6,10,14-trimethyl-2-pentadecanone, dodecane, etc.; and the 36 characteristic volatiles in ripe teas were 1,2,3-trimethoxybenzene, hexadecanoic acid, 37

Comparison of Volatiles in Different Jasmine Tea Grade Samples Using Electronic Nose and Automatic Thermal Desorption-Gas Chromatography-Mass Spectrometry Followed by Multivariate Statistical Analysis

“…The 6-methyl-5-heptane-2-one was described as sweet, fruity, with orange odor notes, and previous studies confirmed that the compound showed an increasing trend in the processing of Oolong tea [9,38]. Regarding acetophenone, it was identified in Oolong tea [39], green tea [40], Pu'er tea [41] and Jasmine tea [27], but had little effect on the tea aroma. Moreover, there was a negative correlation between the relative content of 6-methyl-5-hapten-2-one and the quality grade.…”

Comparative analysis of volatiles difference of Yunnan sun-dried Pu-erh green tea from different tea mountains: Jingmai and Wuliang mountain by chemical fingerprint similarity combined with principal component analysis and cluster analysis

“…The volatile compounds were identified by comparing their mass spectra with those of the mass spectra libraries NIST 08 and Wiley 7. Additionally, a series of n-alkanes (C 8 –C 40 ) were run under the same chromatographic conditions to calculate the RIs of detected compounds by comparing them with the RIs provided by the NIST Chemistry Web Book ( http://webbook.nist.gov/chemistry/ ) and in previous literature [ 31 – 36 ].…”

Exploration of a Method of Distinguishing Different Nongxiang Tieguanyin Tea Grades Based on Aroma Determined by GC-MS Combined with Chemometrics

“…Furthermore, it can extract relevant information and discover patterns in large series of data [16]. The most frequently used chemometric methods, including PCA [17], PLS-DA [13], and HCA [17], have been confirmed to be efficient and rapid methods to highlight differences among tea samples [18][19][20]. PCA is based on the concept of dimensionality reduction to transform multiple indicators into a few comprehensive ones, thereby simplifying the analysis process [21][22][23].…”