Characterisation of odorants in roasted stem tea using gas chromatography–mass spectrometry and gas chromatography-olfactometry analysis

Summary The effects of roasting treatment on sensory quality and related compounds in green tea were investigated. The combined application of roasting temperature and time 100 °C for 90 min, 120 °C for 60 min and 140 °C for 30 min achieved the most satisfying sensory quality. The HPLC analysis showed that the contents of cis‐catechins, bitter and umami amino acids reduced with increase in temperature, while the contents of trans‐catechins and soluble sugar increased with the temperature rise. The content of caffeine and sweet amino acids did not change significantly compared with untreated tea sample. The decrease in cis‐catechins, total polyphenols and bitter amino acids reduced the bitterness and astringency of the green tea, while the increase in total soluble sugars improved the sweetness and mellow taste. The sensory evaluation results showed that the sensory quality of the tea was significantly enhanced through roasting treatment.

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“…b). This was consistent with previous study that the content of umami AA decreased gradually during roasting process (Sasaki et al ., ).…”

Section: Resultsmentioning

confidence: 97%

Effects of roasting treatment on non‐volatile compounds and taste of green tea

Mao

Fang

et al. 2018

Int J of Food Sci Tech

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“…After roasting at 200 °C, trans ‐catechins, including GCG, (‐)‐gallocatechin (GC), and (‐)‐catechin gallate (CG), are increased. Furthermore, the level of ( 2S , 3R )‐catechin [(‐)‐catechin] is increased with the corresponding decrease of ( 2R , 3R )‐catechin [(‐)‐epicatechin] (Fiori et al., , Sasaki et al., ). (‐)‐EC may not produce (+)‐catechin after heating.…”

Section: Tea Chemistrymentioning

confidence: 99%

Chemistry and Biological Activities of Processed Camellia sinensis Teas: A Comprehensive Review

Liang

Zhou

et al. 2019

Comp Rev Food Sci Food Safe

346

237

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Tea is a typical processed beverage from the fresh leaves of Camellia sinensis [Camellia sinensis (L.) O. Kuntze] or Camellia assamica [Camellia sinensis var. assamica (Mast.) Kitamura] through different manufacturing techniques. The secondary metabolites of fresh tea leaves are mainly flavan‐3‐ols, phenolic acids, purine alkaloids, condensed tannins, hydrolysable tannins, saponins, flavonols, and their glycoside forms. During the processing, tea leaves go through several steps, such as withering, rolling, fermentation, postfermentation, and roasting (drying) to produce different types of tea. After processing, theaflavins, thearubigins, and flavan‐3‐ols derivatives emerge as the newly formed compounds with a corresponding decrease in concentrations of catechins. Each type of tea has its own critical process and presents unique chemical composition and flavor. The components among different teas also cause significant changes in their biological activities both in vitro and in vivo. In the present review, the progress of tea chemistry and the effects of individual unit operation on components were comprehensively described. The health benefits of tea were also reviewed based on the human epidemiological and clinical studies. Although there have been multiple studies about the tea chemistry and biological activities, most of existing results are related to tea polyphenols, especially (‐)‐epigallocatechin gallate. Other compounds, including the novel compounds, as well as isomers of amino acids and catechins, have not been explored in depth.

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“…Various teas, such as green tea and black tea, are consumed widely 41 . Many researchers have analyzed fragrances of these teas, which contain several unknown compounds 29 , 41 . Since tea is extracted from young leaves (and stems) of C .…”

Section: Resultsmentioning

confidence: 99%

“…Previous studies showed various volatile compounds in teas 29 , 41 ; however, valerianol has not been referred to. Although there are several reports on valerianol, such as exhibiting the antibacterial activity 52 mentioned above and the bioconversion of valerianol by the fungus Mucor plumbeus 53 , it has not been studied intensely on the whole.…”

Section: Discussionmentioning

confidence: 96%

Identification of novel sesquiterpene synthase genes that mediate the biosynthesis of valerianol, which was an unknown ingredient of tea

Hattan

Shindo

Sasaki

et al. 2018

Sci Rep

Self Cite

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Seven cDNA clones encoding terpene synthases (TPSs), their structures closely related to each other, were isolated from the flower of Camellia hiemalis (‘Kantsubaki’). Their putative TPS proteins were phylogenetically positioned in a sole clade with the TPSs of other Camellia species. The obtained Tps genes, one of which was designated ChTps1 (ChTps1a), were introduced into mevalonate-pathway-engineered Escherichia coli, which carried the genes for utilizing acetoacetate as a substrate, and cultured in a medium including lithium acetoacetate. Volatile products generated in the E. coli cells transformed with ChTps1 were purified from the cell suspension culture, and analyzed by NMR. Consequently, the predominant product with ChTPS1 was identified as valerianol, indicating that the ChTps1 gene codes for valerianol synthase. This is the first report on a gene that can mediate the synthesis of valerianol. We next synthesized a Tps ortholog encoding ChTPS1variant R477H (named CsiTPS8), whose sequence had been isolated from a tea tree (Camellia sinensis), carried out similar culture experiment with the E. coli transformant including CsiTps8, and consequently found valerianol production equally. Furthermore, GC-MS analysis of several teas revealed that valerianol had been an unknown ingredient in green tea and black tea.

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Characterisation of odorants in roasted stem tea using gas chromatography–mass spectrometry and gas chromatography-olfactometry analysis

Cited by 61 publications

References 39 publications

Effects of roasting treatment on non‐volatile compounds and taste of green tea

Effects of roasting treatment on non‐volatile compounds and taste of green tea

Chemistry and Biological Activities of Processed Camellia sinensis Teas: A Comprehensive Review

Identification of novel sesquiterpene synthase genes that mediate the biosynthesis of valerianol, which was an unknown ingredient of tea

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