Figures (6)  Tables (2)

    • Figure 1. 

      The integration of programmable logic control (PLC) into the green tea rolling process. The height of the lid descent on the rolling machine barrel is controlled by the PLC and affects the rolling pressure. After basic rolling for 130 min (Stage A, in total eight turns down, 16 cm below, 130 min), three rolling pressures were further developed over the same period (50 min): low rolling pressure (LRP, Stage A + B, in total ten turns down, 20 cm below), medium rolling pressure (MRP, Stage A + C, in total 12 turns down, 24 cm below), and high rolling pressure (HRP, Stage A + D, in total 14 turns down, 28 cm below). YS, green tea processed by YS cultivar; YH, green tea processed by YH cultivar; LJ, green tea processed by LJ cultivar.

    • Figure 2. 

      Lid pressures detected by PLC sensor under static and rotational conditions. YS, green tea processed by YS cultivar; YH, green tea processed by YH cultivar; LJ, green tea processed by LJ cultivar. LRP, green tea processed with low rolling pressure; MRP, green tea processed with medium rolling pressure; HRP, green tea processed with high rolling pressure.

    • Figure 3. 

      Sensory evaluation and chromatic analysis of green tea samples with different rolling pressure treatments. (a) Taste attributes of green tea samples. (b) Chromatic difference analysis of green tea samples. * p < 0.05 and ** p < 0.01 indicate that significant differences were observed between groups within each cultivar. YS, green tea processed by YS cultivar; YH, green tea processed by YH cultivar; LJ, green tea processed by LJ cultivar. LRP, green tea processed with low rolling pressure; MRP, green tea processed with medium rolling pressure; HRP, green tea processed with high rolling pressure.

    • Figure 4. 

      Contents of basic compounds in green tea samples. * p < 0.05 and ** p < 0.01 indicate that significant differences were observed between groups within each cultivar. YS, green tea processed by YS cultivar; YH, green tea processed by YH cultivar; LJ, green tea processed by LJ cultivar. LRP, green tea processed with low rolling pressure; MRP, green tea processed with medium rolling pressure; HRP, green tea processed with high rolling pressure.

    • Figure 5. 

      Levels of catechin monomers in green tea samples. * p < 0.05 and ** p < 0.01 indicate that significant differences were observed between groups within each cultivar. YS, green tea processed by YS cultivar; YH, green tea processed by YH cultivar; LJ, green tea processed by LJ cultivar. LRP, green tea processed with low rolling pressure; MRP, green tea processed with medium rolling pressure; HRP, green tea processed with high rolling pressure.

    • Figure 6. 

      Non-target metabolomics analysis of green tea samples by different rolling pressures. (a) PLS-DA score plots of metabolites in green tea samples. (b) Heatmap of dynamic changes of key metabolites in YS and LJ. (c) Correlation analysis between top 10 characterized metabolites with taste attributes. YS, green tea processed by YS cultivar; YH, green tea processed by YH cultivar; LJ, green tea processed by LJ cultivar. LRP, green tea processed with low rolling pressure; MRP, green tea processed with medium rolling pressure; HRP, green tea processed with high rolling pressure.

    • No. Metabolites m/z RT/ min p VIP Fragmentation score
      Amino acids and derivatives
      1 L-Histidine trimethylbetaineb 198.1236 0.69 < 0.01 1.5 36.1
      2 S-Prenyl-L-cysteineb 377.1541 11.71 < 0.01 4.8 49.8
      3 N-Feruloylglycyl-L-phenylalanineb 435.094 5.07 < 0.01 1.7 54
      Flavonoids
      4 3,3',4',7-Tetrahydroxyflavanb 293.1017 10.38 < 0.01 3.7 31.2
      5 Kaempferol 7-(6''-galloylglucoside)b 601.1185 4.31 < 0.01 3.4 79.2
      6 Isoorientin 2''-[p-coumaroyl-(->6)-glucoside]b 757.1963 5.11 < 0.01 1.7 66.7
      7 Isowertin 2''-rhamnosideb 593.1863 5.75 < 0.01 2.3 76.5
      8 Flavoxateb 433.2154 12.57 < 0.01 3.0 32.6
      9 Liquiritina 419.1334 10.38 < 0.01 4.0 30.2
      10 Isomargariteneb 637.178 5.75 < 0.05 1.9 44.4
      11 3,3',5-Trihydroxy-4',7-dimethoxyflavanoneb 331.0823 11.54 < 0.01 2.9 36.8
      12 Kaempferol 3-neohesperidoside-7-(2''-p-coumaryllaminaribioside)b 531.1431 4.94 < 0.01 2.2 40.3
      13 Nevadensina 343.0824 13.47 < 0.01 2.7 79.3
      14 Dihydroprudomeninb 1033.283 5.55 < 0.01 1.2 34
      Lipids and lipid-like molecules
      15 Lubiminolb 277.1772 7.30 < 0.01 1.5 47.5
      16 Lippioside IIb 587.1964 5.18 < 0.01 1.2 52.3
      17 Clerosterol 3-glucosideb 616.4628 11.22 < 0.01 2.7 43.3
      18 Sugeonolb 298.1799 12.70 < 0.01 1.9 69.7
      19 Cucurbitacin Db 549.3469 12.95 < 0.01 1.7 51.2
      20 Beta-Cubebeneb 243.149 13.73 < 0.01 4.3 49.6
      21 22-Hydroxydocosanoic acidb 374.3625 13.14 < 0.01 1.0 86.2
      22 Momordicoside Bb 1012.546 11.59 < 0.01 1.9 54.3
      23 (9S,10E,12Z)-9-Hydroperoxy-10,12-octadecadienoateb 353.2584 11.33 < 0.01 2.6 48.7
      24 Geranyl Acetatea 215.164 5.28 < 0.01 1.8 42.4
      25 Cucurbic acidb 213.1483 4.81 < 0.01 1.7 57.3
      26 (R)-1-Octen-3-olb 129.1261 2.68 < 0.01 3.9 36.4
      27 Heptanoic acidb 113.095 2.68 < 0.01 3.6 33.3
      28 (3S,7E,9S)-9-Hydroxy-4,7-megastigmadien-3-one 9-glucosideb 388.2327 2.56 < 0.01 1.5 59.4
      29 2-(3-Hydroxy-4-methylphenyl)-5-methyl-4-hexen-3-oneb 282.1448 1.44 < 0.01 2.0 30.1
      30 Ligustrosideb 523.1825 5.77 < 0.01 3.8 70.5
      31 (1S,2S,4R,8R)-p-Menthane-1,2,8,9-tetrolb 203.1282 5.09 < 0.01 1.4 39.1
      32 Hexyl glucosideb 245.1392 5.09 < 0.01 1.1 71.3
      33 4-Isopropylbenzoic acidb 209.0813 8.79 < 0.01 2.0 44.6
      34 Obacunoneb 499.1979 8.82 < 0.01 2.0 51.2
      35 25-Acetylvulgarosideb 523.2916 10.75 < 0.01 1.2 76.2
      36 Gamma-Linolenic acidb 313.1923 12.94 < 0.01 4.9 56.8
      37 Sativoside B1b 710.3165 11.85 < 0.01 2.4 31.7
      38 Capsicoside Ab 710.3166 11.01 < 0.01 2.2 73.1
      39 5,9-Epidioxy-3-hydroxyergost-7-en-6-oneb 479.2929 10.53 < 0.01 1.3 57
      Benzenoids
      40 1-Methoxy-4-[5-(4-methoxyphenoxy)-3-penten-1-ynyl]benzeneb 327.1588 4.96 < 0.01 1.7 50.2
      41 4R,5R,6S-Trihydroxy-2-hydroxymethyl-2-cyclohexen-1-one 6-(2-hydroxy-6-methylbenzoate)b 309.0966 6.11 < 0.01 1.5 84
      42 Etoxazolea 360.1766 13.69 < 0.01 1.7 85
      43 5-(12-Heptadecenyl)-1,3-benzenediolb 385.2481 12.81 < 0.01 1.7 45.3
      44 N,N-Diethylbenzeneacetamideb 192.1384 8.38 < 0.01 3.5 58.9
      45 3-Methylbenzaldehydeb 121.065 5.80 < 0.01 3.0 44.4
      46 Benzaldehydeb 107.0494 4.58 < 0.01 1.0 30.4
      47 3-Methoxytyramineb 150.0913 3.67 < 0.01 1.9 55.8
      48 Lawsoneb 393.0621 7.49 < 0.05 1.3 76.2
      a and b indicate that the metabolite identification confidence levels correspond to Level 1 and Level 2 based on the Metabolomics Standards Initiative (MSI).

      Table 1. 

      Detailed information of 48 key differential metabolites among YS green tea samples treated by different rolling pressures.

    • No. Metabolites m/z RT/ min p VIP Fragmentation score
      Amino acids and derivatives
      1 N-Jasmonoylisoleucineb 324.2167 9.54 < 0.01 3.9 51.9
      2 L-Norleucineb 132.1019 1.09 < 0.01 1.3 63
      Flavonoids
      3 Sakuranetinb 305.1017 8.78 < 0.01 1.8 41.8
      4 2-(3,4-Dihydroxyphenyl)-5,6-dihydroxy-7-methoxy-4H-1-benzopyran-4-oneb 358.0946 12.99 < 0.01 1.9 35.6
      5 Limocitrol 3-glucosideb 559.1095 2.95 < 0.01 1.7 48.1
      6 Kaempferola 285.0406 6.96 < 0.01 1.5 90.1
      7 Apigenina 269.0457 6.76 < 0.01 1.5 86.9
      8 Narirutinb 561.1614 5.68 < 0.01 2.3 88.4
      9 Kaempferol 3-(6-acetylgalactoside)b 489.1038 5.03 < 0.01 1.8 83.5
      Lipids and lipid-like molecules
      10 (S)-Nerolidol 3-O-[a-L-rhamnopyranosyl-(1->2)-b-D-glucopyranoside]b 553.2981 10.94 < 0.01 1.4 77.7
      11 Kanokoside Db 625.2656 13.59 < 0.01 3.2 60.4
      12 Oleuropeinb 579.1498 4.38 < 0.01 1.4 66.9
      13 Ineketoneb 351.2526 10.72 < 0.01 1.5 49.6
      14 Methyl (3x,10R)-dihydroxy-11-dodecene-6,8-diynoate 10-glucosideb 421.1465 7.06 < 0.01 1.6 50.6
      15 Gibberellin A8-cataboliteb 345.1329 6.24 < 0.01 3.6 72.2
      16 Traumatic acidb 227.1284 7.91 < 0.01 3.4 54.5
      17 Sebacic Acida 201.1125 5.84 < 0.01 1.8 86.6
      18 Xi-3-Hydroxy-5-phenylpentanoic acid O-beta-D-Glucopyranosideb 391.119 8.41 < 0.01 2 32.5
      19 4-Isopropylbenzoic acidb 209.0813 8.79 < 0.01 2.4 44.6
      20 Obacunoneb 499.1979 8.82 < 0.01 2.1 51.2
      21 Methyl epijasmonateb 245.118 12.52 < 0.01 2.3 49.9
      22 5b-Dihydrotestosteroneb 335.2229 14.52 < 0.01 5.6 39.8
      23 Decylubiquinoneb 321.207 14.24 < 0.01 5.5 43
      24 Aflatoxin P1b 343.0462 7.10 < 0.01 2.5 59.8
      25 2beta,9xi-Dihydroxy-8-oxo-1(10),4,11(13)-germacratrien-12,6alpha-olideb 277.1058 7.05 < 0.01 2.7 52.6
      26 (1S,4R)-10-Hydroxyfenchone glucosideb 389.1818 5.79 < 0.01 2.4 48.6
      Benzenoids
      27 Aloe-Emodina 271.0598 6.75 < 0.01 1.9 71.4
      28 N,N-Diethylbenzeneacetamideb 192.1384 8.38 < 0.05 1.4 58.9
      a and b indicate that the metabolite identification confidence levels correspond to Level 1 and Level 2 based on the Metabolomics Standards Initiative (MSI).

      Table 2. 

      The detailed information of 28 key differential metabolites among LJ green tea samples treated by different rolling pressures.