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Journal of Food Science and Technology logoLink to Journal of Food Science and Technology
. 2019 Jul 8;56(10):4632–4647. doi: 10.1007/s13197-019-03911-6

The impacts of brewing in glass tumblers and thermos vacuum mugs on the aromas of green tea (Camellia sinensis)

Qianying Dai 1,2,✉,#, Yurong Jiang 1,2,#, Sitong Liu 1,2, Jing Gao 1,2, Huozhu Jin 1,2, Huiqiang Wang 1,2, Mingji Xiao 1,2, Zhengzhu Zhang 1,2, Daxiang Li 1,3,✉
PMCID: PMC6801281  PMID: 31686695

Abstract

This study investigated the effect of brewing apparatus on the aromatic feature of tea infusion. Huangshan Maofeng tea infusion was brewed under glass tumblers (GT) or thermos vacuum mugs (TVM) for up to 180 min. Tea infusion sensory attributes were evaluated using quantitative descriptive analysis and the composition of volatiles were analyzed using headspace solid phase microextraction coupled with gas chromatography-mass spectrometry. Results showed that GT tea infusion at each brewing duration possessed stronger ‘Pure’, ‘Fresh’ and ‘Grassy’ attributes than TVM tea infusion, whereas TVM tea infusion showed a higher intensity on ‘Steamed’ aroma. A total of 74 volatiles were detected in tea infusion, and aldehydes and alcohols appeared to be the major volatiles. Total aldehydes concentration percentage decreased in tea infusion with brewing process, whereas an increase on total alcohol percentage was found. Principal component analysis indicated that brewing duration and apparatus played vital roles in altering the volatile composition in tea infusion, whereas orthogonal partial least squares discriminant analysis (OPLS-DA) revealed that GT tea infusion samples were separated from TVM tea infusion samples. OPLS-DA also screened 20 volatiles that significantly contributed to the differentiation of GT and TVM tea infusion.

Keywords: Green tea, Volatile compounds, GC–MS, Quantitative descriptive analysis, Principal component analysis, Orthogonal partial least squares discriminant analysis

Introduction

Green tea is one of the most popular beverages in the world, especially in Asia like China and Japan (Baba and Kumazawa 2014). Tea leaves (Camellia sinensis L. O. Kuntze) after harvest are normally dehydrated through a heating process to preserve the quality. During the heating process, the endogenous enzymes in tea leaves are inactivated, which could prevent tea leaves from oxidation and darkening (Ananingsih et al. 2013). It has been confirmed that consumption of green tea could benefit human heathy (Huang et al. 2014). For example, green tea contains high amounts of polyphenols and other nutrients, and these compounds have been confirmed to significantly lower the occurrence of cancer, cardiovascular diseases, inflammation, and other chronic diseases (Chacko et al. 2010; Michele et al. 2007; Setozaki et al. 2016; Shigeki et al. 2011) Additionally, the green tea consumption could be beneficial for intestinal microecology and contribute to host health (Sun et al. 2018).

Green tea in the Asian regions is prepared in a different way as the western countries. Basically, green tea in Asia is made through brewing the whole dried tea leaves with hot water in a tea apparatus. Brewing temperature and steeping duration play significant roles in the determination of green tea quality. For example, hot water and brewing duration could facilitate the extraction of sensory and functional components from tea leaves to green tea infusion (Guo et al. 2010; Wang et al. 2017). However, water with extremely high temperature during the tea steeping process might result in massive amounts of bitter and astringent compounds like catechins to be incorporated into green tea, which could increase the bitterness and astringency of green tea (Xu et al. 2018). Meanwhile, brewing green tea in a long duration also result in green tea with a much bitter and more astringent mouthfeel (Lee et al. 2013).

Tea apparatus also exerts a vital role in the quality of green tea since different apparatuses possess different features on holding the water temperature during green tea brewing process. In China, glass tumblers and porcelains are the main apparatuses to green tea steeping. Recently, vacuum mugs have gained much attention as a new apparatus to brewing green tea. Compared to glass tumblers and porcelains, vacuum mugs could maintain the water temperature in a long period of time, which could affect the release kinetics of sensory components from green tea leaves. In the meantime, anoxic condition in vacuum mugs might inhibit the evolution of sensory compounds in green tea, which might further alter the sensory attributes of green tea.

In the present study, we selected Huangshan Maofeng green tea, one of the greatest teas in China, and brewed the tea in glass tumblers (GT) or thermos vacuum mugs (TVM) for up to 3 h. The sensory attributes of these tea samples were compared using quantitative descriptive analysis (Stone et al. 2004). The aromatic compounds in two apparatus brewed tea infusion samples were extracted using headspace solid phase microextraction (HS-SPME) and further analyzed using gas chromatography-mass spectrometry (GC–MS) (Sheibani et al. 2016; Wang et al. 2008). The composition of aromatic compounds in these tea samples were compared. Additionally, multivariate statistical methods were further applied to screen the key aromatic compounds that led to the differentiation on these tea samples with different tea brewing apparatuses. The findings from this study could provide a useful information on quality control of tea brewing and further unveil the role of tea aromatic compounds in the tea sensory attributes.

Materials and methods

Tea brewing

Huangshan Maofeng tea leaves were purchased at a local market in Huangshan, Anhui, China in 2017. The tea leaves were presented as one bud and one leaf. The tea samples were immediately transported back to our lab and stored at 4 °C prior to the analysis. Glass tumblers (GT) and thermos vacuum mugs (TVM), used as the tea brewing apparatuses, were purchased from a grocery store in Hefei, Anhui, China (Fig. 1). Three grams of the tea was placed in either GT or TVM, and then 150 mL Milli-Q water at 100 °C was added to the tea. The green tea brewing was conducted for 5, 30, 60, 120, and 180 min, respectively. Subsequently, the tea infusion was separated from the brewed tea leaves through mesh filters. Each tea brewing process was carried out in triplicate.

Fig. 1.

Fig. 1

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Glass tumblers and thermos vacuum mugs used for brewing tea

Quantitative description analysis

The sensory attributes of these tea infusion samples were carried out on a professional panel using (QDA) quantitative descriptive analysis (Owusu et al. 2013). This panel consisted of 7 well-trained panelists, including 3 males and 4 females with a 20-40 age range. These panelists were the graduate students majoring in food science and had basic knowledge on sensory evaluation. Before the panel, these panelists had already trained several times on evaluating the aromatic feature and intensity of tea infusion. Six sensory attributes, including ‘Pure’, ‘Strong’, ‘Fresh’, ‘Grassy’, ‘Steamed’ and ‘Metallic’, were included in the quantitative descriptive analysis to investigate the overall aroma of tea infusion. The panel was conducted in a standard sensory evaluation laboratory at 25 °C. Each panelist was given a 20-mL tea infusion sample each time and asked to rate the intensity of each sensory attribute using a five-point scale (point 0 to 5 indicated “not perceptible” to “very strong”). A 10-min break was provided to the panelists between these samples.

Volatile compounds

Volatile compounds in these tea infusion samples were extracted using headspace solid phase microextraction (HS-SPME) according to a published method with minor modifications (Liu et al. 2018). In brief, 50 mL of the tea infusion sample was mixed with 4 g analytical grade potassium chloride (Sigma-Aldrich) in a 100-mL vial containing a magnetic stirrer. The vial was tightly capped with tetrafluoroethylene and then placed in a water bath at 70 °C for 5 min under an agitation for sample equilibration. A 50/30 µm CAR/PDMS/DVB SPME fiber (Supelco Inc, Bellefonte, PA, USA) was inserted to the headspace of the vial for 50 min at 70 °C under the same agitation to adsorb volatile compounds. Afterwards, the fiber was removed from the vial headspace and immediately inserted to the GC injection port for 5 min to release the volatiles at 250 °C.

An Agilent 7870A gas chromatography coupled with an Agilent 5975 mass spectrometer (Agilent Technologies, Santa Clara, CA, USA) was used to analyze the volatile compounds in these tea infusion samples. A 60 m × 0.25 mm × 0.25 µm DB-5MS capillary column (Agilent Technologies, Santa Clara, CA, USA) was used to separate these volatile compounds under a flow rate of carrier gas (helium) at 1 mL/min. The oven temperature gradient was conducted as follows: held at 40 °C for 3 min, increased to 80 °C under a 5 °C/min rate and held at 80 °C for 2 min, increased to 170 °C under a 3 °C/min rate and held at 170 °C for 2 min, and finally increased to 250 °C under a 3 °C/min and held at 250 °C for 5 min. The interface of the mass spectrometer was set at 250 °C with a 70-eV electron impact mode. A selective ion mode was used under a mass scan range of m/z 30 to 400. A C6–C25 n-alkane series (Supelco, Bellefonte, PA, USA) under the same chromatographic condition was used to determine the retention indices. The volatile compounds were identified by comparing their mass spectrum with the retention indices and the NIST11 library.

Statistical analysis

Data were expressed as the mean ± standard deviation of three replicate tests. Analysis of variance was carried out to evaluate the mean difference of the quantitative descriptive analysis data using t test under a significant level of 0.05 on SPSS Statistics 20.0 (IBM Corp., Armonk, NY, USA). Radar plots were drafted using Origin 2016 Software (Origin Lab Corp., Northampton, MA, USA). Multivariate analyses, including principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA), were performed using the detected volatile compounds as variables on SIMCA-P software 14.1 (Umetrics, Umea, Sweden).

Results and discussion

Quantitative descriptive analysis

Figure 2 shows the difference on the sensory attributes of the tea infusion samples using quantitative descriptive analysis. The main attributes evaluated in this analysis included ‘Pure’, ‘Strong’, ‘Fresh’, ‘Grassy’, ‘Steamed’ and ‘Metallic’, and the rating of each attribute was given by a professional taste panel. It was clearly observed that the extension of the brewing duration significantly reduced the intensity of the ‘Pure’, ‘Fresh’ and ‘Grassy’ attributes. However, the ‘Steamed’ aromatic attribute in the tea infusion was significantly enhanced along with the increase of the brewing duration. These indicated that extremely long brewing duration might play a negative effect on the sensory attributes of tea infusion.

Fig. 2.

Fig. 2

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Aromatic profile in tea infusion brewed by glass tumblers and thermos vacuum mugs during brewing process. * and ** in each attribute represent significant difference at a significant level of 0.05 and 0.01, respectively

In comparison of the tea infusion brewed in different apparatuses at each brewing time, it was found that the tea infusion steeped in the thermos vacuum mugs (TVM) exhibited a significant weaker intensity on the ‘Pure’, ‘Fresh’ and ‘Grassy’ attributes than that brewed under the glass tumblers (GT). However, a much stronger intensity on the ‘Strong’, ‘Steamed’ and ‘Metallic’ aromas was found in the TVM brewed tea infusion compared to the GT tea infusion (Fig. 2). For instance, the GT tea infusion was received a better rating on the ‘Pure’ attribute than the TVM tea infusion after the tea samples were brewed for 5 min. Such a significant discrimination on the ‘Pure’ attribute became much greater in these tea infusion samples after 180 min brewing duration. Similarly, the ‘Fresh’ aroma displayed a significant difference in the GT and TVM tea infusion samples, and extension of the brewing duration resulted in this aroma difference in a greater level. Regarding the ‘Grassy’ attribute, the tea infusion brewed in the GT exhibited a higher rating than the TVM tea infusion at the brewing duration of 5, 30, 60, 120 and 180 min. It should be noted that similar ratings on ‘Strong’ aroma were found in these tea infusion samples at 5- and 30-min brewing duration. However, the TVM tea infusion at the brewing duration of 60, 120 or 180 min showed a much higher rating on the ‘Strong’ aroma compared to the GT tea infusion. Similarly, the TVM tea infusion was given a higher rating on the ‘Steamed’ feature than the GT tea infusion at each brewing duration.

It has been known that the sensory attributes of tea infusion were essentially determined by the composition of volatile compounds in tea infusion (Wang et al. 2017). The differences on these attributes between the GT and TVM tea infusion samples indicated that the tea brewing apparatus might play an important role in altering the composition of volatile compounds in tea infusion through altering the volatile compounds extraction and/or affecting the further evolution of volatile compounds in tea infusion. Therefore, we further investigated the composition of volatile compounds in these tea infusion samples.

Volatiles percentage in tea infusion

The aromatic compounds in each sample were analyzed using HS-SPME combined with GC–MS, and these volatile compounds were further identified through comparing their mass spectrum with the retention indices and the NIST11 library. A total of 74 volatile compounds were detected in these tea infusion samples, including 15 alcohols, 18 aldehydes, 6 ketones, 8 esters, 19 hydrocarbons and 8 other volatiles (Table 1). Due to the lack of the volatile compound standards in the present study, the relative concentration percentage was used to estimate the evolution of each volatile compound in the tea infusion (Lucero et al. 2010; Lv et al. 2012). The relative concentration percentage of each volatile was calculated through the peak area of each volatile over the sum of all the volatile peak areas.

Table 1.

Retention time, retention index, identification and relative amount percent (RA %) of volatile compounds in tea infusion brewed by glass tumblers and thermos vacuum mugs during brewing process

No. RT (min) Compounds RI Identificationa 5 min 30 min
GT TVM GT TVM
1 6.170 Butanal, 3-methyl- 607 RI, MS 0.06 ± 0.01 0.56 ± 0.12 ND ND
2 7.636 Pentanal 678 RI, MS 0.06 ± 0.01 ND ND ND
3 8.042 Acetaldehyde 698 RI, MS 1.50 ± 0.33 3.17 ± 0.07 2.32 ± 0.37 1.79 ± 0.26
4 10.709 Hexanal 785 RI, MS 7.31 ± 1.00 4.81 ± 0.52 4.68 ± 0.28 1.88 ± 0.23
5 13.361 p-xylene 855 RI, MS 0.90 ± 0.03 0.62 ± 0.09 0.97 ± 0.12 0.65 ± 0.17
6 14.612 Heptanal 886 RI, MS 3.29 ± 0.58 3.49 ± 0.19 2.10 ± 0.14 4.95 ± 0.27
7 17.340 Benzaldehyde 954 RI, MS 0.58 ± 0.04 1.48 ± 0.37 0.61 ± 0.10 0.87 ± 0.11
8 18.030 1-hepten-6-one, 2-methyl- 971 RI, MS 1.02 ± 0.19 1.19 ± 0.02 1.27 ± 0.11 1.22 ± 0.03
9 18.230 Furan, 2-pentyl- 975 RI, MS 3.85 ± 0.47 4.26 ± 0.19 4.10 ± 0.38 5.22 ± 0.23
10 18.536 Mesitylene 983 RI, MS 0.46 ± 0.03 0.92 ± 0.25 0.64 ± 0.02 0.99 ± 0.15
11 18.766 Octanal 989 RI, MS 4.25 ± 0.22 4.19 ± 0.07 2.11 ± 0.10 2.19 ± 0.16
12 19.391 (E, E)-2,4-heptadienal 1004 RI, MS 0.37 ± 0.12 0.19 ± 0.20 ND ND
13 19.406 4-carene 1005 RI, MS ND 0.07 ± 0.02 0.28 ± 0.03 0.23 ± 0.05
14 19.692 p-cymene 1012 RI, MS 0.13 ± 0.02 0.27 ± 0.07 0.18 ± 0.04 0.53 ± 0.05
15 19.877 Limonene 1017 RI, MS 0.40 ± 0.07 0.44 ± 0.07 0.47 ± 0.07 0.57 ± 0.12
16 19.982 β-terpinene 1020 RI, MS 0.61 ± 0.04 ND 0.67 ± 0.14 ND
17 20.002 β-ocimene 1021 RI, MS 0.59 ± 0.04 0.51 ± 0.03 0.82 ± 0.11 0.49 ± 0.10
18 20.137 2,2,6-trimethyl-cyclohexanone 1024 RI, MS 0.48 ± 0.09 0.48 ± 0.01 0.54 ± 0.07 0.63 ± 0.12
19 20.422 (Z)-β-ocimene 1032 RI, MS ND 0.60 ± 0.09 ND 0.72 ± 0.06
20 20.532 Benzeneacetaldehyde 1035 RI, MS 0.46 ± 0.10 0.51 ± 0.02 0.26 ± 0.05 0.25 ± 0.05
21 20.948 γ-terpinene 1046 RI, MS ND ND ND ND
22 21.458 Linalool oxideI 1060 RI, MS 0.8 ± 0.04 0.81 ± 0.08 1.02 ± 0.15 0.51 ± 0.15
23 21.974 Terpinolene 1074 RI, MS ND ND ND 0.08 ± 0.14
24 22.054 Linalool oxideII 1076 RI, MS 1.08 ± 0.15 0.77 ± 0.10 1.39 ± 0.07 0.98 ± 0.23
25 22.404 Linalool 1085 RI, MS 8.21 ± 0.67 7.96 ± 0.52 11.83 ± 0.46 14.85 ± 0.33
26 22.574 Nonanal 1090 RI, MS 20.71 ± 1.93 20.93 ± 0.39 12.19 ± 0.73 15.44 ± 0.12
27 23.240 Hotrienol 1108 RI, MS ND 0.25 ± 0.02 ND 0.32 ± 0.03
28 23.855 2-isopropyl-5-methylhex-2-enal 1127 RI, MS 1.00 ± 0.08 ND 1.09 ± 0.05 ND
29 24.336 Cis-sabinol 1141 RI, MS 0.37 ± 0.06 ND 0.28 ± 0.05 0.31 ± 0.03
30 25.266 (Z)-butanoic acid, 3-hexenyl ester 1169 RI, MS 0.90 ± 0.09 1.20 ± 0.20 1.21 ± 0.12 3.67 ± 0.67
31 25.382 Terpinen-4-ol 1172 RI, MS ND ND 0.08 ± 0.01 ND
32 25.476 1-Dodecene 1175 RI, MS ND ND 0.81 ± 0.10 ND
33 25.487 (E)-2-nonenal 1176 RI, MS 0.60 ± 0.09 0.97 ± 0.20 0.39 ± 0.06 0.82 ± 0.14
34 25.662 Naphthalene 1181 RI, MS 0.19 ± 0.04 0.72 ± 0.02 0.28 ± 0.03 0.62 ± 0.14
35 25.772 Methyl salicylate 1184 RI, MS 0.84 ± 0.21 1.43 ± 0.20 0.99 ± 0.06 0.49 ± 0.21
36 25.827 α-terpineol 1186 RI, MS ND ND ND 0.74 ± 0.33
37 25.992 Decanal 1191 RI, MS 12.83 ± 2.29 7.94 ± 0.38 11.71 ± 0.28 5.92 ± 0.56
38 26.613 β-cyclocitral 1210 RI, MS 1.15 ± 0.05 1.25 ± 0.11 1.25 ± 0.02 1.29 ± 0.15
39 26.873 Cis-3-hexenyl isovalerate 1219 RI, MS 0.4 ± 0.02 0.36 ± 0.01 0.51 ± 0.09 0.40 ± 0.05
40 27.108 Benzothiazole 1226 RI, MS ND ND 0.90 ± 0.18 0.36 ± 0.52
41 27.503 Pinanediol 1239 RI, MS ND ND ND ND
42 27.773 (E)-2-decenal 1248 RI, MS 0.85 ± 0.17 ND ND ND
43 27.979 α-citral 1255 RI, MS 0.20 ± 0.10 0.47 ± 0.12 0.49 ± 0.06 0.18 ± 0.02
44 27.979 β-citral 1255 RI, MS ND ND ND ND
45 28.229 Trans-myrtanol 1263 RI, MS ND ND ND ND
46 28.329 Linalyl acetate 1267 RI, MS 0.26 ± 0.09 0.32 ± 0.16 0.90 ± 0.04 0.26 ± 0.03
47 28.484 Geraniol 1272 RI, MS 0.22 ± 0.09 0.30 ± 0.08 0.33 ± 0.10 0.33 ± 0.08
48 28.830 Limonene dioxide 1283 RI, MS 0.22 ± 0.09 0.16 ± 0.04 0.14 ± 0.04 0.07 ± 0.02
49 29.105 Undecanal 1292 RI, MS 1.35 ± 0.17 1.24 ± 0.16 1.26 ± 0.18 1.35 ± 0.12
50 29.485 Methylgeranate 1305 RI, MS 0.32 ± 0.05 0.26 ± 0.04 0.31 ± 0.01 0.31 ± 0.04
51 29.585 Theaspirane 1309 RI, MS 0.24 ± 0.07 0.36 ± 0.06 1.81 ± 0.4 0.43 ± 0.05
52 30.426 α-cubebene 1339 RI, MS 1.06 ± 0.10 1.16 ± 0.17 1.71 ± 0.09 1.24 ± 0.08
53 31.092 (Z)-hexanoic acid, 3-hexenyl ester 1362 RI, MS 1.25 ± 0.06 2.01 ± 0.14 1.18 ± 0.06 1.61 ± 0.25
54 31.712 Cis-jasmone 1385 RI, MS 0.60 ± 0.18 0.60 ± 0.12 0.78 ± 0.17 0.61 ± 0.18
55 31.957 Dodecanal 1393 RI, MS 0.94 ± 0.20 0.57 ± 0.05 0.84 ± 0.10 0.37 ± 0.09
56 32.463 α-ionone 1412 RI, MS 0.32 ± 0.05 0.29 ± 0.05 0.32 ± 0.04 0.35 ± 0.04
57 32.978 Geranyl acetone 1432 RI, MS 4.36 ± 0.76 3.40 ± 0.40 4.30 ± 0.53 3.25 ± 0.33
58 33.344 Germacrene 1446 RI, MS 0.24 ± 0.03 0.32 ± 0.02 0.33 ± 0.03 0.40 ± 0.15
59 33.889 δ-cadinene 1467 RI, MS 3.29 ± 0.49 0.60 ± 0.07 5.40 ± 0.45 7.83 ± 0.34
60 33.964 β-ionone 1470 RI, MS 1.82 ± 0.14 3.25 ± 0.13 2.23 ± 0.22 2.70 ± 0.36
61 34.484 α-muurolene 1490 RI, MS ND ND ND ND
62 34.489 3,5-bis(1,1-dimethylethyl)phenol 1490 RI, MS 1.40 ± 0.24 ND 1.37 ± 0.18 ND
63 35.015 β-cadinene 1510 RI, MS 0.55 ± 0.15 4.78 ± 0.30 0.81 ± 0.05 1.01 ± 0.21
64 35.150 Calamenene 1516 RI, MS 1.22 ± 0.27 2.72 ± 0.31 1.65 ± 0.28 2.81 ± 0.17
65 35.425 Cadine-1,4-diene 1527 RI, MS 0.47 ± 0.36 1.22 ± 0.22 1.36 ± 0.07 1.51 ± 0.13
66 35.681 α-calacorene 1538 RI, MS 0.80 ± 0.12 0.68 ± 0.10 0.35 ± 0.07 0.80 ± 0.32
67 35.906 Nerolidol 1547 RI, MS 0.31 ± 0.09 0.26 ± 0.07 0.57 ± 0.06 0.48 ± 0.1
68 35.916 Caryophyllene oxide 1547 RI, MS ND 0.51 ± 0.17 ND 0.34 ± 0.28
69 37.577 Cedrol 1614 RI, MS ND 0.14 ± 0.07 ND 0.14 ± 0.02
70 37.827 Cubenol 1624 RI, MS 0.59 ± 0.04 ND 0.94 ± 0.02 ND
71 38.223 τ-cadinol 1639 RI, MS 0.95 ± 0.22 1.99 ± 0.10 1.23 ± 0.24 1.65 ± 0.26
72 38.598 τ-muurolol 1653 RI, MS ND ND ND ND
73 42.211 2-ethylhexyl salicylate 1794 RI, MS 0.17 ± 0.05 ND ND ND
74 42.411 Isopropyl myristate 1803 RI, MS 0.58 ± 0.08 ND 1.44 ± 0.40 ND
No. RT (min) Compounds 60 min 120 min 180 min
GT TVM GT TVM GT TVM
1 6.170 Butanal, 3-methyl- 0.18 ± 0.07 ND ND ND ND ND
2 7.636 Pentanal ND ND ND ND ND ND
3 8.042 Acetaldehyde 4.97 ± 0.78 1.46 ± 0.16 5.72 ± 0.96 5.22 ± 0.70 3.59 ± 0.37 1.75 ± 0.66
4 10.709 Hexanal 1.27 ± 0.28 1.24 ± 0.25 1.16 ± 0.37 ND 3.56 ± 0.54 ND
5 13.361 p-xylene 1.11 ± 0.05 0.65 ± 0.18 1.16 ± 0.16 0.56 ± 0.08 0.90 ± 0.31 0.69 ± 0.20
6 14.612 Heptanal 1.95 ± 0.32 4.91 ± 0.59 1.84 ± 0.14 2.54 ± 0.13 1.97 ± 0.07 2.40 ± 0.13
7 17.340 Benzaldehyde 0.52 ± 0.24 0.78 ± 0.14 0.71 ± 0.11 0.91 ± 0.14 0.48 ± 0.08 1.28 ± 0.09
8 18.030 1-Hepten-6-one, 2-methyl- 1.43 ± 0.25 1.40 ± 0.12 1.27 ± 0.13 1.16 ± 0.05 1.70 ± 0.10 1.63 ± 0.12
9 18.230 Furan, 2-pentyl- 5.01 ± 0.30 6.52 ± 0.45 5.57 ± 0.21 6.41 ± 0.24 9.07 ± 1.18 7.27 ± 0.30
10 18.536 Mesitylene 0.40 ± 0.04 0.14 ± 0.02 ND 0.12 ± 0.03 ND 0.15 ± 0.02
11 18.766 Octanal 2.02 ± 0.20 1.47 ± 0.08 1.86 ± 0.40 0.88 ± 0.11 1.32 ± 0.17 0.78 ± 0.11
12 19.391 (E, E)-2,4-heptadienal ND ND ND ND ND ND
13 19.406 4-Carene 0.25 ± 0.03 0.29 ± 0.01 ND 0.32 ± 0.03 ND 0.38 ± 0.05
14 19.692 p-Cymene 0.20 ± 0.04 0.34 ± 0.04 0.25 ± 0.03 0.29 ± 0.03 0.28 ± 0.03 0.37 ± 0.03
15 19.877 Limonene 0.59 ± 0.05 0.82 ± 0.14 0.60 ± 0.05 0.84 ± 0.04 0.65 ± 0.18 1.04 ± 0.16
16 19.982 β-Terpinene 0.83 ± 0.11 ND 0.80 ± 0.01 ND 0.68 ± 0.27 ND
17 20.002 β-Ocimene 0.96 ± 0.09 0.72 ± 0.21 1.03 ± 0.08 1.02 ± 0.04 1.04 ± 0.12 0.83 ± 0.17
18 20.137 2,2,6-Trimethyl-cyclohexanone 0.63 ± 0.12 0.47 ± 0.09 0.53 ± 0.07 0.57 ± 0.03 0.57 ± 0.07 0.44 ± 0.06
19 20.422 (Z)-β-ocimene ND 1.12 ± 0.21 ND 1.12 ± 0.08 ND 1.34 ± 0.02
20 20.532 Benzeneacetaldehyde 0.36 ± 0.06 0.25 ± 0.14 0.41 ± 0.07 0.32 ± 0.09 0.28 ± 0.05 0.45 ± 0.08
21 20.948 γ-Terpinene ND 0.30 ± 0.05 0.41 ± 0.12 0.28 ± 0.08 0.10 ± 0.04 0.32 ± 0.05
22 21.458 Linalool oxideI 1.16 ± 0.12 0.68 ± 0.03 1.15 ± 0.11 0.78 ± 0.05 1.00 ± 0.11 0.99 ± 0.10
23 21.974 Terpinolene ND ND ND ND ND 0.50 ± 0.12
24 22.054 Linalool oxideII 1.52 ± 0.07 1.45 ± 0.15 2.23 ± 0.46 1.81 ± 0.26 1.98 ± 0.23 1.60 ± 0.34
25 22.404 Linalool 16.23 ± 0.24 21.57 ± 0.35 17.53 ± 0.1 27.22 ± 0.11 18.56 ± 0.64 31.78 ± 1.27
26 22.574 Nonanal 9.29 ± 2.21 12.38 ± 0.56 7.02 ± 0.33 6.78 ± 0.67 5.69 ± 0.77 5.76 ± 0.73
27 23.240 Hotrienol ND 0.30 ± 0.08 ND 0.28 ± 0.09 ND 0.37 ± 0.07
28 23.855 2-Isopropyl-5-methylhex-2-enal 1.19 ± 0.18 ND 1.23 ± 0.08 1.21 ± 0.09 1.36 ± 0.07 1.40 ± 0.10
29 24.336 Cis-sabinol 0.30 ± 0.09 0.40 ± 0.03 0.29 ± 0.04 0.45 ± 0.10 0.34 ± 0.03 0.91 ± 0.17
30 25.266 (Z)-butanoic acid, 3-hexenyl ester 1.36 ± 0.10 0.93 ± 0.07 1.45 ± 0.10 0.84 ± 0.13 0.87 ± 0.05 0.68 ± 0.03
31 25.382 Terpinen-4-ol 0.29 ± 0.09 0.19 ± 0.06 0.18 ± 0.04 0.21 ± 0.04 0.13 ± 0.06 0.33 ± 0.10
32 25.476 1-Dodecene ND ND ND 1.16 ± 0.29 ND ND
33 25.487 (E)-2-nonenal 1.03 ± 0.18 0.29 ± 0.09 2.14 ± 0.78 1.12 ± 0.35 0.98 ± 0.13 0.49 ± 0.16
34 25.662 Naphthalene 0.36 ± 0.12 0.54 ± 0.03 0.31 ± 0.08 0.58 ± 0.13 0.36 ± 0.12 0.65 ± 0.23
35 25.772 Methyl salicylate 1.15 ± 0.22 0.72 ± 0.24 1.46 ± 0.25 2.34 ± 0.19 ND ND
36 25.827 α-Terpineol ND 1.87 ± 0.12 1.46 ± 0.25 2.34 ± 0.19 ND 2.53 ± 0.29
37 25.992 Decanal 9.71 ± 0.85 3.52 ± 0.65 5.32 ± 0.27 3.79 ± 0.37 5.26 ± 0.32 4.40 ± 0.36
38 26.613 β-Cyclocitral 1.39 ± 0.11 1.58 ± 0.18 1.28 ± 0.25 1.43 ± 0.03 1.41 ± 0.07 1.64 ± 0.09
39 26.873 Cis-3-hexenyl isovalerate 0.51 ± 0.08 0.63 ± 0.17 0.52 ± 0.12 0.34 ± 0.08 ND 0.43 ± 0.12
40 27.108 Benzothiazole 0.22 ± 0.10 0.47 ± 0.09 1.24 ± 0.42 0.37 ± 0.15 ND ND
41 27.503 Pinanediol ND ND 0.20 ± 0.02 ND 0.24 ± 0.17 ND
42 27.773 (E)-2-decenal ND ND ND ND ND ND
43 27.979 α-Citral 0.15 ± 0.07 0.72 ± 0.16 0.27 ± 0.08 ND 0.33 ± 0.15 ND
44 27.979 β-Citral ND ND ND 0.23 ± 0.01 ND 0.14 ± 0.04
45 28.229 Trans-myrtanol ND ND ND ND ND 0.73 ± 0.21
46 28.329 Linalyl acetate 0.46 ± 0.16 0.28 ± 0.07 0.49 ± 0.07 0.51 ± 0.07 0.39 ± 0.01 0.52 ± 0.09
47 28.484 Geraniol 0.20 ± 0.07 0.31 ± 0.08 0.36 ± 0.06 0.53 ± 0.06 0.26 ± 0.05 0.15 ± 0.02
48 28.830 Limonene dioxide 0.12 ± 0.01 0.35 ± 0.16 0.22 ± 0.02 0.29 ± 0.24 0.25 ± 0.04 0.15 ± 0.04
49 29.105 Undecanal 1.03 ± 0.28 0.76 ± 0.08 0.79 ± 0.06 0.97 ± 0.12 ND ND
50 29.485 Methylgeranate 0.25 ± 0.07 0.32 ± 0.01 0.31 ± 0.12 0.27 ± 0.08 0.27 ± 0.03 0.29 ± 0.07
51 29.585 Theaspirane 0.16 ± 0.06 0.59 ± 0.12 0.29 ± 0.04 0.61 ± 0.13 0.32 ± 0.05 1.02 ± 0.16
52 30.426 α-Cubebene 2.13 ± 0.15 1.11 ± 0.25 2.17 ± 0.48 0.75 ± 0.15 2.61 ± 0.26 0.81 ± 0.13
53 31.092 (Z)-hexanoic acid, 3-hexenyl ester 0.99 ± 0.13 1.34 ± 0.35 0.69 ± 0.26 1.20 ± 0.33 0.77 ± 0.05 0.67 ± 0.20
54 31.712 Cis-jasmone 0.87 ± 0.25 0.63 ± 0.14 0.82 ± 0.15 0.77 ± 0.17 0.41 ± 0.15 0.68 ± 0.12
55 31.957 Dodecanal 0.75 ± 0.17 0.25 ± 0.05 0.48 ± 0.10 0.32 ± 0.06 0.42 ± 0.01 0.33 ± 0.01
56 32.463 α-Ionone 0.34 ± 0.03 0.41 ± 0.07 0.43 ± 0.04 0.39 ± 0.04 0.42 ± 0.03 0.49 ± 0.02
57 32.978 Geranyl acetone 2.84 ± 0.88 1.91 ± 0.30 2.42 ± 0.28 1.87 ± 0.21 2.99 ± 0.28 2.05 ± 0.24
58 33.344 Germacrene 0.38 ± 0.02 0.31 ± 0.04 0.40 ± 0.08 0.30 ± 0.02 0.41 ± 0.11 0.36 ± 0.11
59 33.889 δ-Cadinene 6.77 ± 0.31 7.07 ± 0.24 7.80 ± 0.38 4.72 ± 0.47 8.97 ± 0.51 4.39 ± 0.61
60 33.964 β-Ionone 2.22 ± 0.07 3.31 ± 0.30 2.63 ± 0.01 2.87 ± 0.15 2.19 ± 0.14 3.38 ± 0.17
61 34.484 α-Muurolene ND ND ND ND 1.74 ± 0.26 ND
62 34.489 3,5-Bis(1,1-dimethylethyl)phenol 1.52 ± 0.16 ND ND ND ND ND
63 35.015 β-Cadinene 1.09 ± 0.07 1.28 ± 0.13 0.98 ± 0.32 0.78 ± 0.11 1.32 ± 0.15 0.79 ± 0.21
64 35.150 Calamenene 2.22 ± 0.14 2.69 ± 0.35 2.50 ± 0.19 1.87 ± 0.22 3.42 ± 0.37 1.91 ± 0.19
65 35.425 Cadine-1,4-diene 1.72 ± 0.09 1.37 ± 0.23 1.85 ± 0.25 1.10 ± 0.09 1.95 ± 0.49 1.14 ± 0.11
66 35.681 α-Calacorene 0.42 ± 0.10 0.65 ± 0.08 0.28 ± 0.08 0.44 ± 0.04 0.49 ± 0.05 0.57 ± 0.03
67 35.906 Nerolidol 0.44 ± 0.15 0.83 ± 0.11 0.46 ± 0.15 0.72 ± 0.27 0.68 ± 0.17 ND
68 35.916 Caryophyllene oxide 1.00 ± 0.24 0.70 ± 0.26 1.52 ± 0.34 0.30 ± 0.02 ND 0.57 ± 0.05
69 37.577 Cedrol ND 0.15 ± 0.00 ND 0.11 ± 0.03 0.17 ± 0.09 0.17 ± 0.08
70 37.827 Cubenol 1.21 ± 0.15 ND 1.24 ± 0.23 ND 1.65 ± 0.29 ND
71 38.223 τ-Cadinol 2.33 ± 0.18 2.25 ± 0.55 2.28 ± 0.24 2.15 ± 0.23 3.19 ± 0.26 2.73 ± 0.17
72 38.598 τ-Muurolol ND ND ND 0.32 ± 0.17 ND 0.39 ± 0.08
73 42.211 2-Ethylhexyl salicylate ND ND ND ND ND ND
74 42.411 Isopropyl myristate ND ND ND ND ND ND
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RT retention time, RI retention index calculated in the experiment, ND not detected

aMethod of identification: MS, mass spectrum comparison using NIST11 library; RI, retention index was checked through the websites of www.flavornet.org and www.webbooknist.gov

The main constituents in tea infusion were hexanal, heptanal, benzaldehyde, octanal, limonene, methyl salicylate, nonanal, geraniol, decanal, geranyl acetone, β-ionone, nerolidol, linalool and linalool oxides. Our results were similar as the other green tea reports (Baba and Kumazawa 2014; Qin et al. 2013). Among these volatile compounds, aldehydes appeared to be the dominant volatiles present in these tea infusion samples (Fig. 3). It was observed that extending the brewing duration resulted in a decrease on the percentage of the total aldehydes in the tea infusion brewed under the GT and TVM. Additionally, the GT brewed tea infusion exhibited a higher total aldehyde percentage than the tea infusion brewed with the TVM. For example, the total aldehydes represented for 56.01% of the total volatile concentration in the GT tea infusion at the 5-min brewing duration, whereas the TVM tea infusion at the same brewing duration only contained 48.60% total aldehydes compared to the total volatile concentration. Although the relative content percentage of the total aldehydes was dropped in both tea infusions with the brewing time, the GT tea infusion remained the higher percentage of aldehydes level (23.06%) than the TVM tea infusion (19.07%) after brewing the tea for 180 min. We speculated that the thermos vacuum mug, compared to the glass tumbler, could remain tea infusion at a stable high temperature condition, which could accelerate the degradation of aldehydes. It has been reported that aldehydes are the major flavor contributor in tea infusion, and they could contribute to the tea with the green, freshly mown grass, green plants, citrusy, fatty, and sweets scents (Zhu et al. 2015). Therefore, the decrease on the total aldehydes in these tea infusion samples might lower the ‘Fresh’ aromatic intensity. This was in accordance with the quantitative descriptive analysis in the present study (Fig. 2).

Fig. 3.

Fig. 3

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Evolution of different volatile groups in tea infusion brewed by glass tumblers and thermos vacuum mugs during brewing process

Alcohols were found to be one of the major volatile compounds in the tea infusion samples (Fig. 3). The percentage of the total alcohols appeared to enhance in these tea infusion samples along with the tea brewing duration. The total alcohols percentage increase with the brewing duration might result from the extraction of alcohols from tea leaves (Yang et al. 2013). It should be worth noting that the total alcohol relative concentration percentage in the tea infusion brewed with the TVM was much higher than that in the GT tea infusion at each brewing duration point. For example, after 180-min brewing the GT tea infusion only contain the total alcohol concentration at 26.96% of the total volatile content, whereas the total alcohol percentage was 40.09% of the total volatile concentration in the TVM tea infusion. It has been reported that hot water played a vital role in extracting alcoholic volatiles (Schuh and Schieberle 2006). In the present study, the thermos vacuum mugs could effectively remain the temperature of the hot water than the glass tumblers. This could facilitate the extraction of the alcoholic volatiles from tea leaves into the tea infusion. More importantly, the anoxic condition in the TVM could prevent these alcoholic volatiles from further oxidation, which might result in the lower level of aldehydes in the TVM tea infusion.

The other volatiles were observed in these tea infusion samples with a high percentage besides aldehydes and alcohols, and these volatiles mainly consisted of heterocyclic compounds such as furan, pyrrole, and their corresponding derivatives (Fig. 3). It was found that the tea infusion sample brewed in the GT and TVM showed a continuous increase on the total others percentage along with the brewing process. Additionally, the concentration percentage of the total others in the GT tea infusion was accumulated in a much faster rate than that in the TVM tea infusion during the brewing process. The percentage of the total others in the GT tea infusion was higher than that in the TVM tea infusion at the 120- and 180-min brewing duration. It has been reported that the other volatiles, like heterocyclic compounds, could bring the roast, woody, and nutty flavor notes to tea production, which might play a negative role in the tea aromatic quality (Joshi and Gulati 2015).

Regarding the total esters, a relatively stable total esters percentage was found in both tea infusion during the brewing process from 5 min to 120 min. Both tea infusion samples exhibited a low percentage on the total esters at 180 min of brewing duration. Meanwhile, both glass tumblers and thermos vacuum mugs did not significantly affect the percentage of the total esters since no percentage difference was observed between two tea infusion samples at each brewing duration. Similarly, the total ketones percentage also remained quality stable during the whole brewing process in these tea apparatuses, and no total ketones percentage differences were found in the tea infusion brewed under the GT and TVM. The percentage of the total hydrocarbon concentration increased in the GT tea infusion with the brewing process, whereas an increase and then a decrease on the total hydrocarbon concentration percentage was found in the TVM tea infusion. The tea infusion brewed under the GT had a higher percentage of the total hydrocarbon than the TVM tea infusion at 120- and 180-min brewing duration.

Multivariate statistical analysis

Principal component analysis (PCA) was used to investigate the similarity of these tea infusion samples during the whole brewing process under different tea apparatuses (Fig. 4a) using the volatile compounds as the variables. The first and second principal component (PC1 and PC2) represented 26.3% and 18.9% of the total variance, respectively. Furthermore, the PCA model quality was judged by the degree of agreement between the established model and data (R2) and the model predictive ability (Q2) (Yamamoto et al. 2012). A perfectly accurate model is considered as the value of R2 and Q2 are at 1. The R2 and Q2 from this PCA model were found to be 0.772 and 0.420, respectively. These indicated that the PCA model was in a good fitness with these variable data. It was observed that brewing duration exerted a significant role in altering the composition of volatile compounds in these tea infusion samples. For example, the tea infusion samples at the 5-min brewing duration was placed at the positive scale of the PC1 and extending the brewing duration resulted in a shift of the tea infusion samples towards negative position of the PC1. This indicated that the composition of the volatile compounds was altered in these tea infusion samples under different brewing duration period. In addition, different tea brewing apparatuses indeed resulted in the differentiation on the volatile compounds profile, and such the differentiation was more relied on the PC2 component. For example, the tea infusion samples brewed with the GT were almost positioned at the positive scale of the PC2, whereas the TVM tea infusion samples were on the negative section of the PC2.

Fig. 4.

Fig. 4

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Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) using volatiles as variables. a PCA score plot; b OPLS-DA score plot; c OPLS-DA model permutation test; and d S-plot of GT and TVM tea infusion under OPLS-DA model

In the orthogonal partial least squares-discriminant analysis (OPLS-DA) (Fig. 4b), the first two components accounted for 18.4% and 44.4% of the total variance, respectively. Regarding the model quality, its R2 and Q2 were 0.987 and 0.976, respectively. These indicated that the OPLS-DA model established exhibited a good fitness and validity. In the score plot of OPLS-DA model, the tea infusion samples brewed under the GT were aggregated on the left section, whereas the TVM tea infusion samples were positioned at the right side of the plot. All the GT tea samples were separated from the TVM samples (Fig. 4b). Furthermore, the OPLS-DA model was validated through a permutation method where a “Y-scrambling’’ validation was applied. In the permutation method, the Y variable values were randomly shuffled, and the models were re-built and re-analyzed (Fang et al. 2013). The permutation test (n = 200) indicated that the model exhibited a high predictability (Fig. 4c) without over-fitting data (Bylesjö et al. 2010). Meanwhile, the model was valid due to the intercept of the Q2 below 0.05 in the OPLS-DA model. An “S” plot was generated to screen out the key volatile compounds that significantly differentiated the tea infusion samples under the different brewing apparatuses (Fig. 4d). Variable in projection value (VIP) is a vital parameter to determine the key variables that could provide the significant contribution to the model construction. It has been accepted that a volatile with its VIP value above 1 could be the most relevant for explaining the response variable. In the present study, a total of 20 volatile compounds appeared to possess their VIP above 1, indicating that these volatiles played a vital contribution in the differentiation of the GT and TVM tea infusion (highlighted as red on Fig. 4d). These volatile compounds included decanal, linalool, cubenol, heptanal, hexanal, (Z)-β-ocimene, β-ionone, α-terpineol, β-terpinene, α-cubebene, 3,5-bis(1,1-dimethylethyl)phenol, geranyl acetone, δ-cadinene, 2-isopropyl-5-methylhex-2-enal, benzaldehyde, hotrienol, β-cadinene, p-xylene, naphthalene, acetaldehyde (Table 2).

Table 2.

Key individual volatile compounds in tea infusion brewed by glass tumblers and thermos vacuum mugs with their aromatic description and variable importance in projection (VIP)

No.a Compounds Aroma descriptionb VIP valuec
37 Decanal Green, peppermint, herbal, fatty 3.259
25 Linalool Floral 3.213
70 Cubenol –d 2.040
6 Heptanal Hay-like, green 1.982
4 Hexanal Green, grassy 1.956
19 (Z)-β-ocimene Citrus, herb, flower 1.932
60 β-ionone Floral, fruity, woody 1.798
36 α-terpineol Woody 1.757
16 β-terpinene – 1.673
52 α-cubebene Waxy, earthy 1.637
62 3,5-bis(1,1-dimethylethyl)phenol – 1.589
57 Geranyl acetone Green, peppermint, fruity, sweet 1.382
59 δ-cadinene Waxy, pungent 1.338
28 2-isopropyl-5-methylhex-2-enal – 1.289
7 Benzaldehyde Floral, almond 1.199
27 Hotrienol Floral, grass 1.100
63 β-cadinene – 1.086
5 p-xylene – 1.083
34 Naphthalene Tar, camphoric, greasy 1.046
3 Acetaldehyde – 1.009
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aNumbers in Table 2 were consistent with numbers Table 1

bAroma description referred from literatures and website of www.flavornet.org

cVIP, Variable importance in the projection, which was analyzed by OPLS-DA

dNo related odor description found in literatures

Key individual volatile compounds

Figure 5 shows the evolution of the volatile compounds with their VIP above 1 in these tea infusion samples during the brewing process. Decanal and linalool were two main volatile compounds that differentiated the GT and TVM tea infusion samples due to their high VIP value (3.259 and 3.251, respectively). Meanwhile, these two volatile compounds also represented a large percentage of the total volatile concentration. A continuous decrease on the decanal concentration percentage was found in the GT tea infusion with the brewing process, whereas the TVM tea infusion sample exhibited an initial decrease and then an increase on its percentage. At each brewing duration, the decanal concentration percentage was much higher in the GT tea infusion that the TVM tea infusion. Both the GT and TVM tea infusion samples showed a continuous increase on the linalool percentage with the brewing process, and the TVM tea infusion at each brewing duration contained much higher linalool percentage than the GT tea infusion. It should be noted that cubenol, β-terpinene, and 3,5-bis(1,1-dimethylethyl)phenol were only found in the GT tea infusion during the brewing process, whereas the volatiles only found in the TVM tea infusion included (Z)-β-ocimene and hotrienol. Additionally, the GT tea infusion contained higher concentration percentage of hexanal, β-terpinene, α-cubebene, geranyl acetone, and p-xylene. heptanal, (Z)-β-ocimene, β-ionone, α-terpineol, δ-cadinene, 2-isopropyl-5-methylhex-2-enal, benzaldehyde and naphthalene appeared to possess a higher concentration percentage in the TVM tea infusion than the GT tea infusion at each brewing duration.

Fig. 5.

Fig. 5

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Evolution of key individual volatile compounds in tea infusion brewed by glass tumblers and thermos vacuum mugs with variable importance in projection (VIP)

Regarding the flavor notes of these volatile compounds (Table 2), hexanal, heptanal and decanal are normally formed through the metabolism of fatty acids, and these compounds are described as the green, grassy, and peppermint notes (Chambers and Koppel 2013). It’s reported that hexanal is sensitive to high temperature and easily degraded (Jihee et al. 2009; Ho et al. 2015). This could explain why the TVM tea infusion had a faster decrease on the ‘fresh’ aroma with the brewing proceeded. Geranyl acetone was also considered to possess the green and magnolia flavor (Xiao et al. 2017). A percentage decrease occurred to geranyl acetone in both tea infusion during the brewing process. However, its percentage remained much higher in the GT tea infusion at each brewing duration. Linalool, α-terpineol and β-ionone are the main products from the carotenoids’ degradation (Ravichandran 2002). These compounds are easily oxidized under high temperature condition to decrease their content in tea infusion conversions (Ho et al. 2015). These volatile compounds have been reported to bring fresh scents, like floral and sweet notes, to tea (Gong et al. 2017). In the present study, their percentage in the TVM tea infusion at each brewing duration was higher than that in the GT tea infusion. Moreover, α-cubebene and naphthalene were reported to provide the uncomfortable odor to tea. α-cubebene was reported to be associated with the ‘waxy, earthy’ attribute and naphthalene was reported to bring ‘tar, camphoric, greasy’ to the tea (Zhu et al. 2018). The concentration percentage of naphthalene was higher in the TVM tea infusion than the GT tea infusion at each brewing duration. It should be noted that α-cubebene appeared to increase its concentration percentage in the GT tea infusion, whereas its percentage decreased in the TVM tea infusion during the brewing process. Its percentage at each duration was higher in the GT than the TVM tea infusion.

Conclusion

In conclusion, a total of 74 volatile compounds were detected in these Huangshan Maofeng tea infusion samples during brewing process, and alcohols, aldehydes and hydrocarbons were found to be the dominant volatile components. Tea infusion brewed under glass tumblers exhibited a higher intensity on the ‘Pure’, ‘Fresh’ and ‘Grassy’ sensory attributes than the thermos vacuum mugs brewed tea infusion. Principal component analysis indicated that brewing duration and apparatus exerted important roles in affecting the volatiles composition in tea infusion samples. Orthogonal partial least squares discriminant analysis further revealed that the aromatic profile in tea infusion brewed by glass tumblers was different as that in thermos vacuum mugs. Twenty volatile compounds were screened as the key components to differentiate tea infusion brewed under glass tumblers and thermos vacuum mugs.

Acknowledgements

This study was finically supported by the National Key Research and Development Program (2017YFD0400805), National Nature Science Foundation of China (331772057) and National Modern Agriculture Technology System (CARS-19). We thanked Dr. Liwei Gu at the Food Science and Human Nutrition Department at the University of Florida for the assistance on principal component analysis and orthogonal projection on latent structure-discriminant analysis. Our sincere acknowledge also gave to Dr. Zheng Li in the Food Science and Human Nutrition Department at the University of Florida for his help on proofreading the manuscript.

Author contributions

Q Dai, Z Zhang, D Li and Y Jiang conceived and designed the study. Q Dai and Y Jiang drafted the manuscript. Y Jiang, S Liu, J Gao performed the experiment. Y Jiang, S Liu, H Jin, H Wang, and M Xiao analyzed the data. All authors have read and approved the final manuscript.

Compliance with ethical standards

Conflict of interest

All authors declared that they have no conflict of interests.

Footnotes

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Authors Qianying Dai and Yurong Jiang have equally contributed to this work.

Contributor Information

Qianying Dai, Phone: +86-551-65786469, Email: daiqianying117@163.com.

Daxiang Li, Phone: +86-551-65786031, Email: dxli@ahau.edu.cn.

References

  1. Ananingsih VK, Sharma A, Zhou W. Green tea catechins during food processing and storage: a review on stability and detection. Food Res Int. 2013;50:469–479. doi: 10.1016/j.foodres.2011.03.004. [DOI] [Google Scholar]
  2. Baba R, Kumazawa K. Characterization of the potent odorants contributing to the characteristic aroma of Chinese green tea infusions by aroma extract dilution analysis. J Agric Food Chem. 2014;62:8308–8313. doi: 10.1021/jf502308a. [DOI] [PubMed] [Google Scholar]
  3. Bylesjö M, Rantalainen M, Cloarec O, Nicholson JK, Holmes E, Trygg J. OPLS discriminant analysis: combining the strengths of PLS-DA and SIMCA classification. J Chemometr. 2010;20:341–351. doi: 10.1002/cem.1006. [DOI] [Google Scholar]
  4. Chacko SM, Thambi PT, Kuttan R, Nishigaki I. Beneficial effects of green tea: A literature review. Chin Med. 2010 doi: 10.1186/1749-8546-5-13. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Chambers E, Koppel K. Associations of volatile compounds with sensory aroma and flavor: the complex nature of flavor. Molecules. 2013;18:4887. doi: 10.3390/molecules18054887. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Fang G, Goh JY, Tay M, Lau HF, Li SF. Characterization of oils and fats by 1 H NMR and GC/MS fingerprinting: classification, prediction and detection of adulteration. Food Chem. 2013;138:1461–1469. doi: 10.1016/j.foodchem.2012.09.136. [DOI] [PubMed] [Google Scholar]
  7. Gong X, et al. Identification of the aroma-active compounds in Longjing tea characterized by odor activity value, gas chromatography- olfactometry, and aroma recombination. Int J Food Prop. 2017 doi: 10.1080/10942912.2017.1336719. [DOI] [Google Scholar]
  8. Guo GY, Hong-Zhou HE, Zhao WJ, Ming-Chao YU, Zhao-Hong LI. Influence on organoleptic evaluation of Xinyang Maojian tea of brewing temperature, brewing time and ratio of tea and water. Food Sci Technol. 2010;35:120–123. [Google Scholar]
  9. Ho CT, Zheng X, Li S. Tea aroma formation. Food Sci Hum Wellness. 2015;4:9–27. doi: 10.1016/j.fshw.2015.04.001. [DOI] [Google Scholar]
  10. Huang J, Wang Y, Xie Z, Zhou Y, Zhang Y, Wan X. The anti-obesity effects of green tea in human intervention and basic molecular studies. Eur J Clin Nutr. 2014;68:1075–1087. doi: 10.1038/ejcn.2014.143. [DOI] [PubMed] [Google Scholar]
  11. Jihee P, Jungmin L, Yongjin C, Chongtai K, Chuljin K, Kichang N, Seungcheol L. Effect of far-infrared heater on the physicochemical characteristics of green tea during processing. J Food Biochem. 2009;33:149–162. doi: 10.1111/j.1745-4514.2008.00203.x. [DOI] [Google Scholar]
  12. Joshi R, Gulati A. Fractionation and identification of minor and aroma-active constituents in Kangra orthodox black tea. Food Chem. 2015;167:290–298. doi: 10.1016/j.foodchem.2014.06.112. [DOI] [PubMed] [Google Scholar]
  13. Lee J, Chambers D, Chambers E. Sensory and instrumental flavor changes in green tea brewed multiple times. Foods. 2013;2:554. doi: 10.3390/foods2040554. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Liu PP, Yin JF, Chen GS, Wang F, Xu YQ. Flavor characteristics and chemical compositions of oolong tea processed using different semi-fermentation times. J Food Sci Tech. 2018;55:1185. doi: 10.1007/s13197-018-3034-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Lucero M, Estell R, Tellez M, Fredrickson E. A retention index calculator simplifies identification of plant volatile organic compounds. Phytochem Anal. 2010;20:378–384. doi: 10.1002/pca.1137. [DOI] [PubMed] [Google Scholar]
  16. Lv HP, Zhong QS, Lin Z, Wang L, Tan JF, Guo L. Aroma characterisation of Pu-erh tea using headspace-solid phase microextraction combined with GC/MS and GC–olfactometry. Food Chem. 2012;130:1074–1081. doi: 10.1016/j.foodchem.2011.07.135. [DOI] [Google Scholar]
  17. Michele A, et al. Prevention of hypertension, cardiovascular damage and endothelial dysfunction with green tea extracts. Am J Hypertens. 2007;20:1321–1328. doi: 10.1016/j.amjhyper.2007.08.006. [DOI] [PubMed] [Google Scholar]
  18. Owusu M, Petersen MA, Heimdal H. Relationship of sensory and instrumental aroma measurements of dark chocolate as influenced by fermentation method, roasting and conching conditions. J Food Sci Tech. 2013;50:909–917. doi: 10.1007/s13197-011-0420-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Qin Z, Pang X, Dong C, Cheng H, Hu X, Wu Lt J. Evaluation of Chinese tea by the electronic nose and gas chromatography–mass spectrometry: correlation with sensory properties and classification according to grade level. Food Res Int. 2013;53:864–874. doi: 10.1016/j.foodres.2013.02.005. [DOI] [Google Scholar]
  20. Ravichandran R. Carotenoid composition, distribution and degradation to flavour volatiles during black tea manufacture and the effect of carotenoid supplementation on tea quality and aroma. Food Chem. 2002;78:23–28. doi: 10.1016/S0308-8146(01)00303-X. [DOI] [Google Scholar]
  21. Schuh C, Schieberle P. Characterization of the key aroma compounds in the beverage prepared from Darjeeling black tea: quantitative differences between tea leaves and infusion. J Agric Food Chem. 2006;54:916–924. doi: 10.1021/jf052495n. [DOI] [PubMed] [Google Scholar]
  22. Setozaki S, et al. Prevention of abdominal aortic aneurysm progression by oral administration of green tea polyphenol in a rat model. J Vasc Surg. 2016;65:1803. doi: 10.1016/j.jvs.2016.06.003. [DOI] [PubMed] [Google Scholar]
  23. Sheibani E, Duncan SE, Kuhn DD, Dietrich AM, O’Keefe SF. SDE and SPME analysis of flavor compounds in Jin Xuan oolong tea. J Food Sci. 2016;81:C348. doi: 10.1111/1750-3841.13203. [DOI] [PubMed] [Google Scholar]
  24. Shigeki Y, Kazuaki M, Akira M, Manabu M, Suong-Hyu H, Tadashi I, Ryuzo S. Oral pretreatment with a green tea polyphenol for cardioprotection against ischemia-reperfusion injury in an isolated rat heart model. J Thorac Cardiov Surg. 2011;141:511–517. doi: 10.1016/j.jtcvs.2010.04.016. [DOI] [PubMed] [Google Scholar]
  25. Stone H, Sidel J, Oliver S, Woolsey A, Singleton RC. Sensory evaluation by quantitative descriptive analysis. Descr Sens Anal Pract. 2004;2004:23–34. doi: 10.1002/9780470385036.ch1c. [DOI] [Google Scholar]
  26. Sun H, Chen Y, Cheng M, Zhang X, Zheng X, Zhang Z. The modulatory effect of polyphenols from green tea, oolong tea and black tea on human intestinal microbiota in vitro. J Food Sci Tech. 2018;55:399–407. doi: 10.1007/s13197-017-2951-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Wang LF, Jooyeon L, Jinoh C, Joohyun B, Sung S, Seungkook P. Discrimination of teas with different degrees of fermentation by SPME-GC analysis of the characteristic volatile flavour compounds. Food Chem. 2008;109:196–206. doi: 10.1016/j.foodchem.2007.12.054. [DOI] [PubMed] [Google Scholar]
  28. Wang YC, Yuan HB, Jia LI, Dong CW, Hua JJ, Jiang YW. Evaluation of taste of Yichang Congou black tea based on different brewing conditions. Sci Technol Food Ind. 2017;12:65–76. [Google Scholar]
  29. Xiao Z, Wang H, Niu Y, Liu Q, Zhu J, Chen H, Ma N. Characterization of aroma compositions in different Chinese congou black teas using GC–MS and GC–O combined with partial least squares regression. Flavour Fragr J. 2017;32(4):265–276. doi: 10.1002/ffj.3378. [DOI] [Google Scholar]
  30. Xu YQ, Zhang YN, Chen JX, Wang F, Du QZ, Yin JF. Quantitative analyses of the bitterness and astringency of catechins from green tea. Food Chem. 2018;258:16–24. doi: 10.1016/j.foodchem.2018.03.042. [DOI] [PubMed] [Google Scholar]
  31. Yamamoto S, Bamba T, Sano A, Kodama Y, Imamura M, Obata A, Fukusaki E. Metabolite profiling of soy sauce using gas chromatography with time-of-flight mass spectrometry and analysis of correlation with quantitative descriptive analysis. J Biosci Bioeng. 2012;114:170–175. doi: 10.1016/j.jbiosc.2012.03.023. [DOI] [PubMed] [Google Scholar]
  32. Yang Z, Baldermann S, Watanabe N. Recent studies of the volatile compounds in tea. Food Res Int. 2013;53:585–599. doi: 10.1016/j.foodres.2013.02.011. [DOI] [Google Scholar]
  33. Zhu JC, et al. Comparison of aroma-active volatiles in oolong tea infusions using GC–olfactometry, GC–FPD, and GC–MS. J Agric Food Chem. 2015;63:7499–7510. doi: 10.1021/acs.jafc.5b02358. [DOI] [PubMed] [Google Scholar]
  34. Zhu Y, et al. Identification of key odorants responsible for chestnut-like aroma quality of green teas. Food Res Int. 2018;108:74–82. doi: 10.1016/j.foodres.2018.03.026. [DOI] [PubMed] [Google Scholar]

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