Figures (4)  Tables (2)

    • Figure 1. 

      Non-targeted metabolomics analysis of EST and ESO. (a) Volcano plot displaying metabolite abundance variations. Each point represents an individual metabolite, with point size scaled according to its variable importance in projection (VIP) score. Red and blue markers denote significantly upregulated and downregulated metabolites, respectively (VIP > 1, p < 0.05). (b) Principal component analysis (PCA) of all metabolites identified from EST and ESO. (c) Heatmap of top 50 differential metabolites between EST and ESO. (d) Phytochemical classification of the top 50 differential metabolites between EST and ESO and their species quantity ratio. EST and ESO represent the tender leaf and older leaf of E'se tea, respectively.

    • Figure 2. 

      Phenolic and amino acids compounds in EST and ESO. (a) The contents of phenolic compounds in EST and ESO. (b) The contents of alanine, cystine and serine in EST and ESO. * indicates p < 0.05. ** indicates p < 0.01. EST and ESO represent the tender leaf and older leaf of E'se tea, respectively.

    • Figure 3. 

      Volatile compounds in EST and ESO. (a) The chromatograms of volatile compounds in EST and ESO. (b) The percentages of various types of volatile compounds present in EST and ESO. (c) The concentrations of key volatile compounds in EST and ESO. * indicates p < 0.05. ** indicates p < 0.01. EST and ESO represent the tender leaf and older leaf of E'se tea, respectively.

    • Figure 4. 

      Sensory taste and color assessment of EST and ESO. (a) Images of leaves and liquor color of EST and ESO. (b) Rader map of liquor color of EST and ESO, ΔL* corresponds to the level of brightness (+) and darkness (−), Δa* indicates the intensity of redness (+) and greenness (−), and Δb* signifies the intensity of yellowness (+) and blueness (−). (c) Rader map of taste attributes of EST and ESO. (d) Correlation analysis of sensory quality and non-volatile compounds. Blue and red color indicate negative and positive correlations, respectively. EST and ESO represent the tender leaf and older leaf of E'se tea, respectively.

    • Compound class EST ESO
      Free amino acids 39.06 ± 1.41 14.06 ± 0.13**
      Polyphenols 175.49 ± 10.50 151.98 ± 2.40*
      Soluble proteins 68.94 ± 1.42 64.42 ± 2.66
      Reducing sugars 58.25 ± 3.90 60.86 ± 1.41
      * indicates p < 0.05. ** indicates p < 0.01. EST and ESO represent the tender leaf and older leaf of E'se tea, respectively.

      Table 1. 

      The contents of major non-volatile compounds of EST and ESO (mg/g).

    • Classification Sequence Compound name CAS Formula RIa RIb RIc Contents (μg/g) VIP value
      EST ESO
      Aldehydes 1 Butanal, 2-methyl- 96-17-3 C5H10O 663.83 658.81 659 39.73 ± 22.88 N.D.* 1.02
      2 Pentanal 110-62-3 C5H10O 699.24 699.07 699 27.77 ± 13.36 N.D.* 1.04
      3 Hexanal 66-25-1 C6H12O 801.06 800.76 802 202.84 ± 45.50 124.08 ± 48.10 0.95
      4 2-Hexenal, (E)- 6728-26-3 C6H10O 858.57 850.21 854 143.52 ± 51.39 707.80 ± 306.43* 1.02
      5 Heptanal 111-71-7 C7H14O 901.73 901.37 903 34.00 ± 6.11 32.04 ± 11.10 0.72
      6 Benzaldehyde 100-52-7 C7H6O 962.46 957.41 957 1535.05 ± 206.71 416.20 ± 186.34** 1.10
      7 Octanal 124-13-0 C8H16O 1,002.61 1,002.21 1,004 44.72 ± 7.63 50.70 ± 16.89 0.75
      8 2,4-Heptadienal, (E,E)- 4313-03-5 C7H10O 1,010.36 1,008.97 1,011 153.91 ± 32.61 216.59 ± 86.91 0.83
      9 Benzeneacetaldehyde 122-78-1 C8H8O 1,043.45 1,039.58 1,041 108.45 ± 20.08 26.33 ± 12.11** 1.09
      10 Benzaldehyde, 4-methyl- 104-87-0 C8H8O 1,067.53 1,064.10 − 9.36 ± 0.94 N.D.** 1.01
      11 Nonanal 124-19-6 C9H18O 1,104.13 1,103.70 1,105 194.04 ± 31.29 210.46 ± 82.07 0.72
      12 1,3-Cyclohexadiene-1-carboxaldehyde, 2,6,6-trimethyl- 116-26-7 C10H14O 1,194.33 1,193.73 1,195 104.27 ± 12.27 35.72 ± 16.94** 1.09
      13 1-Cyclohexene-1-carboxaldehyde, 2,6,6-trimethyl- 432-25-7 C10H16O 1,215.01 1,213.91 1,222 127.58 ± 17.37 66.52 ± 31.60* 1.01
      14 Pentamethylbenzaldehyde 17432-38-1 C12H16O 1,409.73 1,409.20 − 46.87 ± 10.35 N.D.** 1.11
      Esters 1 Hexanoic acid, methyl ester 106-70-7 C7H14O2 926.63 922.59 922 74.19 ± 12.81 N.D.** 1.11
      2 2-Hexenoic acid, methyl ester 2396-77-2 C7H12O2 967.90 963.09 − 50.40 ± 8.28 N.D.** 1.12
      3 Pentanoic acid,
      2-methyl-, anhydride      		 63169-61-9 C12H22O3 987.03 984.51 − 67.50 ± 11.41 42.25 ± 19.33 0.94
      4 3-Hexen-1-ol, acetate, (Z)- 3681-71-8 C8H14O2 1,005.16 1,004.44 − 35.02 ± 5.41 31.28 ± 9.67 0.75
      5 2(3H)-Furanone, 5-ethyldihydro- 695-06-7 C6H10O2 1,051.99 1,048.05 − 44.69 ± 29.18 34.01 ± 17.74 0.74
      6 Formic acid, octyl ester 112-32-3 C9H18O2 1,073.33 1,070.22 − 61.31 ± 10.57 60.23 ± 23.38 0.71
      7 Methyl salicylate 119-36-8 C8H8O3 1,187.60 1,186.30 1,187 244.17 ± 39.33 81.14 ± 35.00** 1.08
      8 2(3H)-Furanone, dihydro-5-pentyl- 104-61-0 C9H16O2 1,355.93 1,354.07 1,356 32.00 ± 2.65 72.90 ± 35.48 0.94
      9 2(3H)-Furanone, 5-hexyldihydro- 706-14-9 C10H18O2 1,461.12 1,459.61 1,461 50.77 ± 10.07 31.71 ± 10.18 0.97
      10 2-Propenoic acid, 3-phenyl-,
      ethyl ester      		 103-36-6 C11H12O2 1,462.92 1,461.52 − 49.76 ± 17.18 173.87 ± 119.76 0.92
      11 Phthalic acid,
      hept-4-yl isobutyl ester      		 1000356-78-3 C19H28O4 1,860.30 1,859.57 − 35.14 ± 7.03 46.66 ± 14.42 0.85
      12 Hexadecanoic acid, methyl ester 112-39-0 C17H34O2 1,926.78 1,926.42 1,959 37.45 ± 7.61 N.D.** 1.11
      13 Dibutyl phthalate 84-74-2 C16H22O4 1,951.26 1,950.86 1,951 37.90 ± 7.96 47.41 ± 13.80 0.81
      14 Hexadecanoic acid, ethyl ester 628-97-7 C18H36O2 1,993.27 1,993.06 1,993 145.83 ± 28.04 86.18 ± 30.90 0.98
      15 9,12,15-Octadecatrienoic acid, ethyl ester, (Z,Z,Z)- 1191-41-9 C20H34O2 2,165.00 2,164.77 − 41.80 ± 11.28 N.D.* 1.10
      Alcohols 1 1-Penten-3-ol 616-25-1 C5H10O 682.97 679.69 − 70.28 ± 29.24 N.D.* 1.06
      2 1-Octen-3-ol 3391-86-4 C8H16O 982.03 978.76 980 136.67 ± 20.08 77.23 ± 36.63 0.98
      3 Benzyl alcohol 100-51-6 C7H8O 1,035.95 1,032.34 1,037 148.49 ± 11.40 98.17 ± 52.48 0.90
      4 Phenylethyl alcohol 60-12-8 C8H10O 1,109.06 1,108.13 1,110 136.22 ± 8.91 50.54 ± 25.53** 1.09
      5 Phytol 150-86-7 C20H40O 2,106.76 2,106.59 2,114 30.29 ± 5.97 N.D.** 1.11
      Ketones 1 1-Penten-3-one 1629-58-9 C5H8O 684.47 681.49 685 N.D. 31.22 ± 19.43 1.00
      2 5-Hepten-2-one, 6-methyl- 110-93-0 C8H14O 985.79 983.01 986 105.83 ± 14.24 52.51 ± 20.88* 1.05
      3 Cyclohexanone, 2,2,6-trimethyl- 2408-37-9 C9H16O 1,034.38 1,030.89 1,036 162.51 ± 24.52 45.36 ± 23.28** 1.09
      4 Isophorone 78-59-1 C9H14O 1,058.47 1,054.61 1,117 102.99 ± 14.88 43.41 ± 21.29* 1.06
      5 Acetophenone 98-86-2 C8H8O 1,064.14 1,060.46 1,061 516.27 ± 102.90 146.12 ± 43.68** 1.09
      6 3,5-Octadien-2-one 38284-27-4 C8H12O 1,070.34 1,067.00 1,063 116.26 ± 19.42 56.08 ± 26.68* 1.02
      7 Ethanone, 1-(2-hydroxy-5-methylphenyl)- 1450-72-2 C9H10O2 1,303.94 1,303.68 − 39.28 ± 1.19 N.D.** 1.13
      8 2-Cyclopenten-1-one, 3-methyl-2-(2-pentenyl)-, (Z)- 488-10-8 C11H16O 1,390.18 1,389.47 1,395 643.02 ± 73.72 257.02 ± 104.84** 1.08
      9 3-Buten-2-one, 4-(2,6,6-trimethyl-1-cyclohexen-1-yl)- 14901-07-6 C13H20O 1,474.31 1,473.09 1,474 715.00 ± 125.99 557.37 ± 278.34 0.79
      10 3-Buten-2-one, 4-(2,2,6-trimethyl-7-oxabicyclo[4.1.0]hept-1-yl)- 23267-57-4 C13H20O2 1,476.97 1,475.89 − 182.11 ± 12.51 143.07 ± 63.12 0.82
      Hydrocarbons 1 Toluene 108-88-3 C7H8 766.16 759.73 752 56.73 ± 8.68 156.03 ± 87.15 0.94
      2 Oxime-, methoxy-phenyl- 1000222-86-6 C8H9NO2 913.62 911.19 892 916.26 ± 223.44 559.84 ± 450.15 0.84
      3 2-Hexene, 3,5,5-trimethyl- 26456-76-8 C9H18 975.48 971.38 975 64.21 ± 9.54 31.61 ± 15.70* 1.02
      4 Decane 124-18-5 C10H22 999.59 999.51 1000 33.17 ± 4.39 N.D.** 1.12
      5 Nonane, 4,5-dimethyl- 17302-23-7 C11H24 1,062.77 1,059.06 1,056 60.96 ± 14.18 25.60 ± 11.07* 1.04
      6 Ethanone, 1-(2-methyl-1-cyclopenten-1-yl)- 3168-90-9 C8H12O 1,100.12 1,100.10 1,182 59.36 ± 6.66 N.D.* 1.12
      7 Naphthalene 91-20-3 C10H8 1,178.43 1,176.41 1,171 81.16 ± 14.01 33.84 ± 16.21* 1.05
      8 Dodecane 112-40-3 C12H26 1,199.40 1,199.36 1,202 36.40 ± 6.21 28.62 ± 15.23 0.78
      9 Pentadecane 629-62-9 C15H32 1,275.42 1,273.68 − 244.89 ± 57.07 95.73 ± 45.34* 1.04
      10 Dodecane, 4,6-dimethyl- 61141-72-8 C14H30 1,288.32 1,287.35 1,276 44.23 ± 7.09 N.D.** 1.12
      11 Tridecane 629-50-5 C13H28 1,299.29 1,299.21 1,301 44.47 ± 9.72 N.D.** 1.11
      12 Hexadecane, 2,6,11,15-tetramethyl- 504-44-9 C20H42 1,321.26 1,320.04 − 116.06 ± 28.06 49.78 ± 20.75* 1.03
      13 Acenaphthylene 208-96-8 C12H8 1,438.07 1,436.62 − 37.03 ± 6.73 N.D.* 1.11
      14 Octadecane 593-45-3 C18H38 1,495.82 1,495.56 − 46.81 ± 13.45 N.D.* 1.09
      15 Hexadecane, 2,6,10,14-tetramethyl- 638-36-8 C20H42 1,739.86 1,748.07 − 47.36 ± 7.86 31.84 ± 2.93* 1.03
      Others 1 Furan, 2-ethyl- 3208-16-0 C6H8O 700.49 700.37 703 N.D. 41.32 ± 20.95* 1.04
      2 Furan, 2-methoxy- 25414-22-6 C5H6O2 796.81 795.82 − 55.39 ± 13.18 N.D.* 1.10
      3 1-Pentanone, 1-(2-furanyl)- 1192-62-7 C6H6O2 907.38 905.95 − 96.44 ± 15.84 N.D.** 1.12
      4 Eugenol 97-53-0 C10H12O2 1,348.24 1,346.39 1,364 37.68 ± 3.15 N.D.** 1.12
      * indicates p < 0.05. ** indicates p < 0.01. N.D. indicates that the substance has not been detected. EST and ESO represent the tender leaf and older leaf of E'se tea, respectively. RIa: The retention index was determined in this study. RIb: The retention index, sourced from the NIST library. RIc: Reference retention index of compounds[7,48,49].

      Table 2. 

      The contents of volatile substances of EST and ESO (µg/g).