Stir bar sorptive extraction (SBSE) combined with gas chromatography-mass spectrometry (GC-MS) was used to detect the volatile composition of 20 Anjibaicha samples, and gas chromatography-olfactometry-mass spectrometry (GC-O-MS) combined with relative odor activity value (ROAV) was utilized to identify its key aroma-active compounds. Results showed that 109 volatile compounds were detected in the tea samples. Among them, geraniol, diisobutyl phthalate, phytol, methyl salicylate, cis-jasmone, linolenic acid, and linalool were the most abundant components. It was found that the contents of volatile components in different grades of Anjibaicha varied greatly. Moreover, a total of 34 common characteristic peaks were selected to establish a fingerprint of the volatile components of Anjibaicha. Sixteen compounds were identified as key aroma-active compounds of Anjibaicha, including trans-β-ionone, geraniol, linalool, hexanal, heptanal, (E)-2-heptenal, α-ionone, and (Z)-3-hexenyl hexanoate.

In order to explore the protective effect of Yongchun Foshou tea extracts on ulcerative colitis (UC) and the key bioactive compounds involved, we established a mouse model of UC induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS) and intragastrically the mice with the water extracts of clean-aroma, strong-aroma and aged-aroma Yongchun Foshou oolong tea (200 mg/(kg·d)). We evaluated the effects of these three tea extracts on body mass, colon mass per unit length and pathological colon tissue as well as the serum levels of interleukin (IL)-6, IL-10, IL-1β, and tumor necrosis factor α (TNF-α) in mice with ulcerative colitis. Compared with the model group, body mass, colon mass per unit length, and pathological colon tissue were improved in the mice treated with each of the three tea extracts. There was no significant difference in body mass in the mice treated with the water extracts of strong-aroma and aged-aroma oolong tea for 5-7 days after UC induction compared with those before UC induction (P > 0.05). The mice treated with clean-aroma and strongaroma tea extracts showed a significant reduction in colon mass per unit length (P < 0.05 and P < 0.01). Each of these tea extracts reduced the degree of inflammation in mouse colon tissue, significantly increasing the concentrations of the antiinflammatory cytokine IL-10 (P < 0.05 and P < 0.001). The concentrations of the pro-inflammatory cytokines IL-1β and IL-6 were significantly decreased in the mice treated with strong-aroma tea extract (P < 0.05). The correlation analysis of the major compounds in the tea extracts and inflammatory cytokines revealed that flavone glycosides and N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSF) were negatively correlated with three pro-inflammatory cytokines (IL-6, IL-1β, and TNF-α). On the other hand, theanine, catechins, and flavone glycosides were significantly positively correlated with IL-10 (P < 0.05). In conclusion, the water extracts of the three aroma types of Yongchun Foshou oolong tea have an ameliorative effect on acute ulcerative colitis. Strong-aroma tea extract is the most effective among these extracts, and the polyphenols in the extract may play an important role.

In order to explore the relationship between altitude and the major quality components of tea, the contents of the major non-volatile chemical components tea polyphenols and amino acids, as well as the composition and content of aroma components in baked green tea samples made from tea plants from different altitudes were analyzed. Then, the key components that significantly differed among tea samples were identified by multivariate statistical analysis, and their correlation with altitude was evaluated. Results showed that there was a statistical significant difference in the total amount of free amino acids among tea samples (P < 0.05), and that the contents of theanine, glutamine, threonine, serine and arginine in the high-altitude group (650–1102 m) were significantly higher than in the low-altitude group (400–600 m). A total of 298 aroma components were identified from all samples, including aldehydes, alcohols, alkenes, alkanes, ketones, aromatic hydrocarbons, organic acids, esters, lactones, phenols, alkynes, amines, ethers, oxygen heterocyclic compounds, nitrogen compounds and sulphur compounds, with aldehydes and alkanes being the most abundant ones. The results of partial least squares discriminant analysis (PLS-DA), cluster analysis and correlation analysis indicated that the contents of quality components significantly differed (P < 0.05) between the low- and high-altitude groups, and 26 differential aroma compounds such as 3-methylbutanenitrile, α-phellandrene and indole were identified. It was also shown that the contents of total free amino acids, theanine, glutamine, threonine, serine and arginine as well as 3-methylbutanenitrile were higher in the high-altitude group than in the low-altitude group, while the opposite was observed for the contents of 25 aroma compounds such as α-phellandrene and indole. Furthermore, correlation analysis indicated that the contents of theanine, serine, threonine and total free amino acids had a significantly positive correlation with sensory taste scores. Nine aroma compounds including (Z)-2-heptenal, 3-penten-2-one, 4-methyloctane, 3-ethyl-heptane, 1-octen-3-one, α-phellandrene, (E,E)-2,4-heptadienal, 3,4-dimethylfuran-2,5-dione and 4-methylindan had a significantly negative correlation with altitude. It was speculated that the formation and accumulation of aroma precursors may be related to altitude.

Green tea was made from one bud with two leaves from the tea cultivar Longjing 43 by stir frying, roasting, steaming or sun drying. Stir bar sorptive extraction (SBSE) combined with gas chromatography-olfactometry-mass spectrometry (GC-O-MS) was applied to analyze the influence of different manufacturing processes on the key aromaactive compounds of green tea. The results showed that 31, 27, 25 and 30 key aroma-active compounds were respectively identified from stir-fried green tea, roasted green tea, steamed green tea and sun-dried green tea, which all had floral, fruity and green flavors. Totally, 13 key aroma-active compounds were common to these 4 types of green tea, including β-ionone, naphthalene, linalool, linalool oxide I, geraniol, 1-octene-3-ol, 2-heptanone, heptanal, hexanal, (Z)-3-hexenyl acetate, (E,E)-2,4-decadienal, α-ionone, and phenylethyl alcohol. It was found that β-ocimene and (Z)-hex-3-enyl 2-methylbutyrate contributed greatly to the aroma characteristics of stir-fried green tea; 2-pentylfuran, phenylacetaldehyde and α-terpineol contributed greatly to the aroma characteristics of roasted green tea; and geranylacetone, γ-terpinene and α-citral contributed greatly to the aroma characteristics of sun-dried green tea. The results obtained from this study will help to understand the formation mechanism of green tea aroma quality and to develop directional processing and regulation technologies for green tea aroma quality.

In this study, the volatile components and key aroma-active compounds of 13 representative Huiming tea samples were analyzed using stir bar sorptive extraction (SBSE) combined with gas chromatography-olfactometry-mass spectrometry (GC-O-MS). Results showed that a total of 120 volatile components were identified, mainly including 26 alcohols, 26 esters, and 14 ketones. Among them, the contents of the aroma compounds geraniol, 2,2,4-trimethyl-3-hydroxypentyl isobutyrate, indole, (Z)-jasmone, and 1-octen-3-ol were the highest. Moreover, a total of 42 key aroma-active compounds were identified by GC-O analysis, including 2-ethyl-3,5-dimethylpyrazine, 6-methyl-5-heptene-2-one, linalool, (Z)-3-hexenyl butanoate, 3,5-octadiene-2-one, and (E)-β-ionone, which played an important role in the formation of the fresh and floral aromas of Huiming tea. The results of this study will contribute to revealing the chemical basis of the aroma quality of Huiming tea, and provide a theoretical basis for improving the aroma quality of Huiming tea.