Figures (5)  Tables (1)

    • Figure 1. 

      Diagrams of volatile compounds in green tea samples with different fixation temperatures. (a) Diagrams of the total contents of volatile compounds in all green tea samples. (b) Hierarchical cluster analysis heatmap of volatile compounds in all green tea samples. FL: fresh tea leaves; AFs: after fixed tea leaves; TSs: Tea samples.

    • Figure 2. 

      Changes of volatile compounds in green tea fixed with different temperatures. AF190: tea leaves fixed at 190 °C; AF220: tea leaves fixed at 220 °C; AF250: tea leaves fixed at 250 °C; AF280: tea leaves fixed at 280 °C; AF310: tea leaves fixed at 310 °C; AF340: tea leaves fixed at 340 °C. Different lowercase letters indicate significant differences in the contents of compounds at p < 0.05. The temperature range is depicted by a single unit length along the coordinate axis.

    • Figure 3. 

      Changes in the content of key aroma components with various fixation temperatures. AF190: tea leaves fixed at 190 °C; AF220: tea leaves fixed at 220 °C; AF250: tea leaves fixed at 250 °C; AF280: tea leaves fixed at 280 °C; AF310: tea leaves fixed at 310 °C; AF340: tea leaves fixed at 340 °C. Different lowercase letters indicate significant differences in the contents of volatile compounds in green tea samples at p < 0.05.

    • Figure 4. 

      Main synthetic pathways of key aroma components impacted by various fixation temperatures. (a) Aromatic/terpenoid-related volatiles; (b) Lipid-related volatiles; (c) Carotenoid-related volatiles; (d) Shikimate-related volatiles.

    • Figure 5. 

      Aroma characteristics of green tea samples with different fixation temperatures.

    • No. Compound Boiling Point
      (°C)      		 Odor threshold (ng/mL) Content (ng/mL) Odor active value
      AF190 AF220 AF250 AF280 AF310 AF340 AF190 AF220 AF250 AF280 AF310 AF340
      1 Hexanal 129.6 5 25,890.85 19,811.58 20,684.53 23,509.97 15,314.54 7,401.65 5,178.17 3,962.32 4,136.91 4,701.99 3,062.91 1,480.33
      2 (Z)-3-Hexen-1-ol 156.0−157.0 13 4,269.35 3,919.25 1,553.05 1,751.49 1,258.30 1,201.35 328.41 301.48 119.47 134.73 96.79 92.41
      3 2-Butoxy-1-ethanol 168.4 880 0.00 0.00 0.00 0.00 21,575.90 27,864.85 0.00 0.00 0.00 0.00 24.52 31.66
      4 2,3-Octanedione 230.0 − 76.33 80.69 65.47 76.73 98.57 34.60 − − − − − −
      5 (Z)-3-Hexenyl acetate 75.0−76.0 31 86.57 169.63 137.80 192.79 76.12 127.22 2.79 5.47 4.45 6.22 2.46 4.10
      6 (E)-Linalool oxide (furanoid) 201.0–202.0 320 6,524.00 3,662.21 2,017.66 1,465.78 1,130.51 654.76 20.39 11.44 6.31 4.58 3.53 2.05
      7 (Z)-Linalool oxide (furanoid) 188.0−192.0 320 12,185.93 5,925.80 3,710.26 2,560.51 1,455.47 909.18 38.08 18.52 11.59 8.00 4.55 2.84
      8 Linalool 198.0 6 21,743.76 14,360.20 7,148.75 6,189.82 4,248.04 1,876.03 3,623.96 2,393.37 1,191.46 1,031.64 708.01 312.67
      9 Nonanal 195.0 253 423.76 322.79 269.65 270.55 151.59 28.00 1.67 1.28 1.07 1.07 0.60 0.11
      10 (E)-4,8-Dimethylnona-1,3,7-triene 81 (Press: 18 Torr) − 56.69 65.15 72.32 100.38 68.70 41.25 − − − − − −
      11 Phenylethyl Alcohol 218.2 390 7,053.80 2,852.71 1,828.99 1,872.61 216.44 8.52 18.09 7.31 4.69 4.80 0.55 0.02
      12 Methyl salicylate 220.0−224.0 40 612.52 452.55 273.70 297.19 164.79 127.66 15.31 11.31 6.84 7.43 4.12 3.19
      13 (Z)-3-Hexenyl isovalerate 98.0 110 10.64 12.95 71.27 13.59 13.96 18.91 0.10 0.12 0.65 0.12 0.13 0.17
      14 Hexanoic acid, ethenyl ester 168.6 − 123.48 104.38 117.74 128.01 150.15 49.92 − − − − − −
      15 Geraniol 230.0 7.5 777.55 374.60 294.32 834.80 50.34 334.08 103.67 49.95 39.24 111.31 6.71 44.54
      16 3-Hydroxy-2,2,4-trimethylpentyl isobutyrate 255.0−260.0 − 103.81 127.55 205.91 198.24 108.56 153.71 − − − − − −
      17 (Z)-3-Hexenyl hexanoate 115.0 16 56.61 72.30 113.90 112.33 61.05 89.18 3.54 4.52 7.12 7.02 3.82 5.57
      18 (Z)-3-hexen-1-yl-3-methylbutanoate 60.0 − 27.36 33.16 38.42 51.45 24.12 44.00 − − − − − −
      19 Coumarin 301.7 34 91.96 107.95 91.43 138.29 88.31 86.72 2.70 3.17 2.69 4.07 2.60 2.55
      20 (E)-β-Ionone 271.0 0.007 46.35 43.19 49.04 50.49 45.17 55.23 6,621.52 6,169.83 7,006.11 7,212.63 6,452.43 7,889.93
      21 δ-Decalactone 117.0−120.0 1 2,888.92 2,753.56 2,718.35 4,074.61 2,257.06 3,077.52 2,888.92 2,753.56 2,718.35 4,074.61 2,257.06 3,077.52
      The odor thresholds in water were obtained from previous studies[6,12,13]. The boiling points of volatile compounds were cited from www.ncbi.nlm.nih.gov.

      Table 1. 

      Analysis of key aroma components of green tea significantly impacted by different fixation temperatures.