| Keemun black tea(KBT)is one of the four famous teas in the world.As a popular drink,KBT has a unique taste and is of great benefit to human health.Compared to green tea or other types of tea,black tea has the strongest aroma and is the most popular.Deuterium-depleted water(DDW),also called light water,the deuterium content of which is lower than that in water in nature.With different ratios of deuterium and hydrogen,the physico-chemical properties of water will also change.Numerous studies showed that DDW can inhibit the growth and reproduction of cancer cells.The interaction between DDW and KBT was studied for the first time.In this study,stir bar adsorption extraction(SBSE)was used to extract aroma components of KBT brewed in three types of water(deuterium content was 40 ppm,70ppm and 150 ppm,among which the water with deuterium content of 15 oppm was distilled water for control).Combined with gas chromatography-mass spectrometry(GC-MS)and gas chromatography-olfaction(GC-O),important aroma compounds were screened,qualitatively and quantitatively determined.The GC-O results showed that a total of 43 aroma compounds contributed to the overall aroma,and 20 compounds(OAVs ≥ 1)were identified as important compounds by OAV calculation,among which 8 key compounds(OAVs ≥ 10)were: hexanal,β-myrcene,1-hexanol,linalool,geraniol,benzyl alcohol and phenylethyl alcohol.By analyzing the quantitative standard curves of 20 important aroma substances in KBT,it was found that the standard substances of 14 substances were promoted in water with40 ppm deuterium content,while the trend of aroma release was inhibited in water with70 ppm deuterium content.The standard curve of the two substances showed the opposite effect of the above compounds,which inhibited the aroma release in the water with 40 ppm deuterium content and promoted the aroma release in the water with 70 ppm deuterium content.The remaining aroma substances showed the same trend in general,and the aroma release was promoted in both types of DDW,indicating that the DDW did affect the release effect of aroma substances.The DDW with 40 ppm mainly promoted the release effect,while the water with 70 ppm deuterium inhibited the release effect of aroma substances.In this study,the effects of taste substance(-)-epigallocatechin gallate(EGCG)and key aroma components of KBT were studied.The aroma profile of KBT after adding EGCG was studied by fingerprint radar atlas of electronic nose,and the influence of taste substance on aroma substance was preliminarily determined.It was found that the effects of EGCG were most pronounced in water containing 70 ppm deuterium,so this water was used as the substrate for subsequent studies.Then,nine important aroma substances were selected to interact with different concentrations of EGCG.The effects of EGCG were further verified by sensory experiments.The results showed that the release effects of linalool and geraniol were inhibited in each concentration of EGCG solution,and the aroma release levels of hexanal,methyl salicylate and β-ionone was strongest in EGCG at 0.02g/L,0.05g/L and 0.05g/L concentration respectively.The research of this subject can provide data support for the application of DDW in the field of tea,and it is expected to further improve the flavor of KBT and make more healthy and popular tea drinks. |
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