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. 2017 May 17;13:145–161. doi: 10.1016/j.dib.2017.05.027

Data on coffee composition and mass spectrometry analysis of mixtures of coffee related carbohydrates, phenolic compounds and peptides

Ana SP Moreira a, Fernando M Nunes b, Cristiana Simões b, Elisabete Maciel a,c, Pedro Domingues a, M Rosário M Domingues a, Manuel A Coimbra a,⁎
PMCID: PMC5451187  PMID: 28603760

Abstract

The data presented here are related to the research paper entitled “Transglycosylation reactions, a main mechanism of phenolics incorporation in coffee melanoidins: inhibition by Maillard reaction” (Moreira et al., 2017) [1]. Methanolysis was applied in coffee fractions to quantify glycosidically-linked phenolics in melanoidins. Moreover, model mixtures mimicking coffee beans composition were roasted and analyzed using mass spectrometry-based approaches to disclose the regulatory role of proteins in transglycosylation reactions extension. This article reports the detailed chemical composition of coffee beans and derived fractions. In addition, it provides gas chromatography–mass spectrometry (GC–MS) chromatograms and respective GC–MS spectra of silylated methanolysis products obtained from phenolic compounds standards, as well as the detailed identification of all compounds observed by electrospray mass spectrometry (ESI-MS) analysis of roasted model mixtures, paving the way for the identification of the same type of compounds in other samples.

Keywords: Coffee, Carbohydrates, Polysaccharides, Phenolics, Mass spectrometry, Melanoidins

Specifications Table

Subject area Chemistry
More specific subject area Composition of coffee and mass spectrometry analyses of coffee related carbohydrates, phenolic compounds and peptides
Type of data Tables and figures
How data was acquired Methanolysis products were analyzed by GC–MS (Trace-GC with Polaris Q MS, Thermo-Finnnigan, San Jose, CA)
Content of chlorogenic acids, caffeine, adsorbed phenolics, and phenolics released by alkaline saponification and alkaline fusion was obtained by HPLC (Dionex Ultimate 3000, Thermo, Waltham, MA);
Content of sucrose, glucose and fructose was determined by anion exchange chromatography (ICS 3000, Dionex);
Total sugars were determined by GC-FID (Trace GC, Thermo-Finnigan);
Protein content was determined using a carbon-nitrogen/protein analyzer (PRIMACS, Skalar Analytical B.V., Breda, The Netherlands);
Roasted coffee powder colors were measured with a CR-300 Minolta chroma meter (Tokyo, Japan);
HPLC-ESI-MS analysis used a Waters Alliance 2690 HPLC system (Milford, MA) coupled to the LXQ linear ion trap (LIT) mass spectrometer (Thermo Fisher Scientific Inc., Waltham, MA);
Direct ESI-MS analyses were also performed using LIT mass spectrometer;
High resolution and high mass accuracy measurements were performed on a LTQ-Orbitrap XL mass spectrometer (ThermoFisher Scientific, Germany).
Data format Analyzed
Experimental factors Roasted model mixtures and coffee beans
Experimental features Chemical characterization and identification of the changes induced by roasting
Data source location Robusta coffee beans from India
Arabica coffee beans from Honduras
Commercial standards of carbohydrates, phenolic compounds and peptides
Data accessibility Data is provided with this article
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Value of the data

  • •

    Detailed chemical characterization of Arabica and Robusta coffee beans and derived fractions is able to be compared with data from other authors when profiling the phenolic compounds incorporated in melanoidins.

  • •

    GC–MS data of methanolysis products of phenolic compounds standards provide information on the efficiency and linkages cleaved by methanolysis and are the basis for their identification in real samples.

  • •

    Mass spectrometry data on the roasting-induced compounds formed from model mixtures mimicking coffee bean composition are valuable for the identification of the same type of compounds in roasted coffee, but also other complex roasted carbohydrate-rich matrices.

1. Data

The data presented in Section 1.1 include gas chromatography-mass spectrometry (GC–MS) chromatograms and respective GC–MS spectra of silylated methanolysis products obtained from phenolic compounds standards such as 4-hydroxycinnamic, ferulic and veratric acids (Fig. 1), 5-O-caffeoylquinic acid (Fig. 2), hesperidin (Fig. 3), naringin (Fig. 4), and ellagic acid (Fig. 5).

Fig. 1.

Fig. 1

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Structures and GC–MS spectra obtained from standards after silylation of the respective products released by methanolysis: A) quinic acid derivative; B) p-coumaric acid (4-hydroxycinnamic acid) derivative; and C) ferulic acid derivative. D) caffeic acid derivative; and E) veratric acid derivative.

Fig. 2.

Fig. 2

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GC–MS chromatograms of A) 5-O-caffeoylquinic acid after silylation with the respective mass spectrum of the peak at the retention time 54.70 min, and B) products of 5-O-caffeoylquinic acid methanolysis after silylation.

Fig. 3.

Fig. 3

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GC–MS chromatograms of A) products of hesperidin methanolysis after silylation and B) hesperetin after silylation with the respective mass spectrum of the peak at the retention time 52.55 min.

Fig. 4.

Fig. 4

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GC–MS chromatograms of A) products of naringin methanolysis after silylation and B) naringenin after silylation with the respective mass spectrum of the peak at the retention time 54.63 min.

Fig. 5.

Fig. 5

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GC–MS chromatogram of products of ellagic acid methanolysis after silylation with the respective mass spectrum of the peak at the retention time 56.39 min.

In Section 1.2 are presented data on the chemical composition of Arabica and Robusta coffee beans, including chlorogenic acid composition (Table 1), simple sugars, caffeine, and protein contents (Table 2) and total sugar composition (Table 3), but also the chromatic properties of respective coffee powders (Table 4). Moreover, data on the chemical composition of high molecular weight materials (HMWMs) isolated from roasted Arabica and Robusta coffee infusions are presented in Subsection 1.2 in Table 5, Table 6. The latter includes the phenolic compounds and quinic acid released by methanolysis from coffee HMWMs.

Table 1.

Chlorogenic acid (CGA) composition (g/100 g of green or roasted coffee).

CGA Green coffees
 Roasted coffees
Arabica Robusta Arabica Robusta
3-O-caffeoylquinic acid (3-CQA) 0.501±0.034 0.666±0.025 0.079±0.007 0.090±0.000
1-O-feruloylquinic acid (1-FQA) 0.059±0.000 0.059±0.000 0.018±0.000 0.043±0.000
3-O-coumaroylquinic acid (3-CoQA) – – 0.073±0.000 0.080±0.000
5-O-caffeoylquinic acid (5-CQA) 4.353±0.253 5.061±0.295 1.492±0.143 1.517±0.095
3-O-feruloylquinic acid (3-FQA) 0.061±0.007 0.072±0.006 0.654±0.002 0.661±0.038
4-O-caffeoylquinic acid (4-CQA) 0.657±0.001 0.932±0.031 0.029±0.005 0.014±0.001
5-O-coumaroylquinic acid (5-CoQA) 0.098±0.004 0.070±0.004 0.182±0.000 0.185±0.000
5-O-feruloylquinic acid (5-FQA) 0.369±0.000 0.843±0.000 – –
4-O-feruloylquinic acid (4-FQA) 0.060±0.008 0.059±0.008 – –
4-O-coumaroylquinic acid (4-CoQA) 0.069±0.005 0.070±0.005 – –
3,4-di-O-caffeoylquinic acid (3,4-diCQA) 0.284±0.036 0.760±0.025 0.054±0.000 0.060±0.000
3,5-di-O-caffeoylquinic acid (3,5-diCQA) 0.459±0.088 0.798±0.020 0.201±0.029 0.379±0.005
Total (CGA) 6.972±0.140 9.397±0.346 2.781±0.209 3.029±0.192
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Table 2.

Simple sugars, caffeine, and protein contents (g/100 g of green or roasted coffee).

Coffee samples Simple sugars
 Caffeine Proteina
Sucrose Glucose Fructose Total
Green coffees
Arabica 7.14±0.53 0.02±0.00 0.03±0.01 7.19±0.53 1.05±0.05 11.68±0.92
Robusta 4.49±0.00 0.07±0.01 0.12±0.01 4.67±0.02 2.57±0.02 12.97±0.83
Roasted coffees
Arabica 0.14±0.00 0.05±0.00 0.01±0.00 0.20±0.00 0.88±0.05 13.34±0.98
Robusta 0.04±0.00 0.02±0.00 0.01±0.00 0.07±0.00 1.59±0.17 16.08±1.18
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a

(Ntotal – Ncaffeine) × 6.25

Table 3.

Total sugar composition (g/100 g of green or roasted coffee).

Coffee samples Sugars
 Total TotalPolymericb
Rhamnose Arabinose Galactose Mannose Glucose GlcPolymerica
Green coffees
Arabica 0.04±0.0 2.00±0.24 7.82±0.31 16.2±0.9 9.76±0.20 6.17 35.8±1.6 32.2
Robusta 0.06±0.0 1.98±0.06 9.96±0.30 15.0±1.2 9.00±1.1 6.69 36.0±2.7 33.7
Roasted coffees
Arabica 0.02±0.0 1.15±0.16 6.25±1.07 16.9±2.5 6.11±1.01 5.99 30.5±4.7 30.4
Robusta 0.06±0.0 1.53±0.11 8.96±0.26 15.5±0.1 6.12±0.36 6.08 32.2±0.3 32.2
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a

GlcPolymeric – polymeric glucose, determined by subtracting to the total glucose content the contribution of glucose present as free glucose and sucrose;

b

TotalPolymeric – polymeric sugars, determined by subtracting to the total sugar content the contribution of glucose present as free glucose and sucrose.

Table 4.

Chromatic properties of roasted coffee powders.a

Coffee samples L* a* b* C* h*
Arabica 37.628±0.742 9.966±0.113a 15.746±0.328 18.635±0.330 56.669
Robusta 40.406±0.210 9.864±0.112a 18.984±0.571 21.394±0.554 62.544
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a

Identical letters in the same column indicate no statistically significant differences.

Table 5.

Yield, chemical composition and spectroscopic properties of the high molecular weight material (HMWM) isolated from roasted Arabica and Robusta coffee infusions.a

Arabica Robusta
Yield (g /100 g coffee) 5.69 7.63
Rhamnose (Rha) 0.21±0.02 0.77±0.05
Arabinose (Ara) 3.47±0.07 4.67±0.25
Galactose (Gal) 28.2±1.3 32.7±3.8
Mannose (Man) 4.51±0.46 7.62±0.94
Glucose (Glc) 0.82±0.10 0.53±0.03
Total sugars 37.2±0.6a 46.2±5.1b
Protein 11.3±0.4a 12.3±1.0a
Kmix 280 nm 6.49±0.52a 7.49±0.46a
Kmix 325 nm 5.34±0.38a 6.30±0.37b
Kmix 405 nm 2.72±0.22a 2.87±0.18a
Melanoidin brown index (MBI) 5.28 6.93
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a

For each chemical component, identical letters in the same row indicate no statistically significant differences (t-Student test, p<0.05); Kmix – specific extinction coefficient.

Table 6.

Phenolic compounds and quinic acid (mmol/100 g) released from HMWM isolated from roasted Arabica and Robusta coffee infusions.a

Arabica Robusta
Adsorbed
3-O-caffeoylquinic acid (3-CQA) 0.011±0.002 0.010±0.004
3-O-coumaroylquinic acid (3-CoQA) 0.005±0.001 0.011±0.006
5-O-caffeoylquinic acid (5-CQA) 0.015±0.002 0.017±0.004
3-O-feruloylquinic acid (3-FQA) 0.022±0.001 0.050±0.002
5-O-coumaroylquinic acid (5-CoQA) 0.012±0.001 0.006±0.001
3,4-di-O-caffeoylquinic acid (3,4-diCQA) 0.008±0.001 0.006±0.001
3,5-di-O-caffeoylquinic acid (3,5-diCQA) 0.005±0.001 0.007±0.001
Total (adsorbed phenolics) 0.078±0.002§.a 0.107±0.011§.a
Saponification
Caffeic acid 1.74±0.02 2.89±0.078
4-Hydroxycinnamic acid 0.030±0.001 0.029±0.000
Ferulic acid 0.161±0.000 0.407±0.029
Total (phenolics released by saponification) 1.93±0.11§.a 3.33±0.02§.a
Methanolysis
Caffeic acid 11.6±2.5 17.1±1.6
4-Hydroxycinnamic acid n.d n.d
Ferulic acid 2.0±0.3 2.1±0.3
Total (phenolics released by methanolysis) 13.6±4.1§ 19.2±1.3§
Quinic acid 4.8±0.3 11.8±1.5
Alkaline fusion
Gallic acid 0.200±0.006 0.305±0.056
Hydroquinone 1.80±0.27 3.23±0.37
3,4-Dihydroxybenzoic acid 10.6±4.2 19.0±0.3
4-Hydroxybenzoic acid 9.30±4.85 17.0±3.6
3,5-Dihydroxybenzoic acid 5.46±0.88 3.86±0.20
2,3-Dihydroxybenzoic acid 0.928±0.055 1.21±0.05
Benzoic acid 2.18±0.09 0.965±0.389
Salicylic acid 1.77±0.17 3.68±2.84
Total (phenolics released by alkaline fusion) 32.3±2.3 49.3±3.5
ANOVA %Variation
Interaction p<0.0001 (4) 3.9
Coffee variety p<0.0001 (1) 3.2
Phenolic method p<0.0001 (4) 91.8
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a

Rows with the same symbol (§) and columns with the same letter indicate no statistically significant differences (p<0.05). Tuckey post-hoc test.

The data presented in Section 1.3 include the mass losses observed after roasting of model mixtures prepared using commercial standards of coffee related carbohydrates, phenolic compounds and peptides (Table 7). The commercial standards used as models of coffee bean components were as follow: (β1→4)-d-mannotriose (Man3), an oligosaccharide structurally related to the backbone of coffee galactomannans; 5-O-caffeoylquinic acid (5-CQA), the most abundant phenolic compound in green coffee beans; and dipeptides composed by tyrosine (Y) and leucine (L), used as models of coffee proteins. Additionally, malic acid (MalA) and citric acid (CitA), the most abundant aliphatic acids present in green coffee beans, were also used. In Subsection 1.3 are also presented electrospray mass spectrometry (ESI-MS) data obtained from the model mixtures, either by direct infusion of the sample into the mass spectrometer, or online coupling to liquid chromatography (LC). Fig. 6 shows LC-MS reconstructed ion chromatograms (RICs) acquired from the roasted mixture Man3-CQA-YL. Table 8 contains the detailed identification of all the ions observed by LC-MS analysis of roasted Man3 and mixtures Man3-CQA-YL, Man3-CQA, Man3-YL, and Man3-LY. In Table 9 are presented the accurate masses obtained from high resolution and high mass accuracy measurements using a LTQ-Orbitrap mass spectrometer for the ions identified after roasting of the mixture Man3-CQA. Table 10, Table 11 summarize the ions identified by ESI-MS analysis of the roasted mixtures Man3-MalA and Man3-CitA, respectively. In Table 12 the accurate masses found by LTQ-Orbitrap for the ions identified after roasting of the mixture Man3-YL are presented. Table 13 provides data on the LC-MS2 fragmentation of roasting-induced compounds formed from the mixture Man3-YL.

Table 7.

Total mass loss (%) and mass loss between 150–175 °C (%) during thermal processing of Man3 and mixtures Man3-CQA-YL, Man3-CQA, Man3-MalA, Man3-CitA, Man3-YL, and Man3-LY, and, and color of the corresponding resulting material.

Sample Total mass loss Mass loss between 150–175 °C Color of the resulting material
Man3 7.1 – White
Man3-CQA-YL 12.7 4.3 Dark brown
Man3-CQA 10.7 2.2 Brown
Man3-MalA 7.6 3.1 Light brown
Man3-CitA 12.4 3.6 Light brown
Man3-YL 14.9 5.2 Dark brown
Man3-LY 14.5 6.5 Dark brown
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Fig. 6.

Fig. 6

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LC-MS reconstructed ion chromatograms (RICs) of the [M+H]+ ions of A) HexYL (m/z 457) and B) Hex2YL (m/z 619), acquired from the roasted Man3-CQA-YL mixture, and C) HexLY (m/z 457), acquired from the roasted Man3-LY mixture.

Table 8.

Summary of [M+Na]+ and [M+H]+ ions identified by LC-MS analysis after roasting (T1) of the Man3 and mixtures Man3-CQA-YL, Man3-CQA, Man3-YL, and Man3-LY, with the indication of the m/z values and the proposed assignments.

Proposed assignment Number of hexose (Hex) units (n)
1 2 3 4 5 6 7 8 9
Roasted Man3
[Hexn+Na]+ 365 527 689
Roasted Man3-CQA-YLa
[Hexn+Na]+ 365 527 689
[Hexn-H2O+Na]+ 347 509
[Hexn-2H2O+Na]+ 329 491
[Hexn-3H2O+Na]+ 311 473
[YLn+H]+ 295
[YLn-H2O+H]+ 277
[YLn-NH3+O+H]+ 294
[(CQA)n+Na]+ 377
[YLn(CQA)+H]+ 631
[HexnYL+H]+ 457 619 781 943 1105
[HexnYL-H2O+H]+ 439 601 763 925 1087
[HexnYL-2H2O+H]+ 421 583 745 907 1069
[HexnYL-3H2O+H]+ 403 565 727 889
[HexnYL-4H2O+H]+ 385 547 709 871
[Hexn(YL)2+H]+ 733 895 1057
[HexnCQAYL+H]+ 793 955 1117
Roasted Man3-CQAa
[Hexn+Na]+ 365 527 689 851 1013 1175 1337 1499
[Hexn-H2O+Na]+ †347 †509 671 833 995 1157 1319
[Hexn-2H2O+Na]+ 329 491 653
[Hexn-3H2O+Na]+ 311 473 635
[(CQA)n+Na]+ 377† 713
[(CQA)nCA+Na]+ 539‡
[(CQA)nCA-H2O+Na]+ 521‡
[HexnCQA+Na]+ 539‡ 701† 863 1025 1187 1349
[HexnCQA-H2O+Na]+ 521‡ 683†
[HexnCQA-3H2O+Na]+ 485 647
[Hexn(CQA)2+Na]+ 875
[HexnQA+Na]+ 377† 539‡ 701†
[HexnQA-H2O+Na]+ 521‡ 683†
[HexnCA-H2O+Na]+ †347 †509
Roasted Man3-YLa
[Hexn+Na]+ 203 365 527 689 851 1013
[Hexn-H2O+Na]+ 347 509
[Hexn-2H2O+Na]+ 329 491
[Hexn-3H2O+Na]+ 311 473
[(YL)n+H]+ 295
[(YL)n-H2O+H]+ 277
[(YL)n-NH3+O+H]+ 294
[HexnYL+H]+ 457 619 781 943 1105 1267
[HexnYL-H2O+H]+ 439 601 763 925 1087 1249
[HexnYL-2H2O+H]+ 421 583 745 907
[HexnYL-3H2O+H]+ 403 565 727 889
[HexnYL-4H2O+H]+ 385 547 709 871
[Hexn(YL)2+H]+ 733 895 1057
Roasted Man3-LY
[Hexn+Na]+ 203 365 527 689 851
[Hexn-H2O+Na]+ 347 509 671 833
[Hexn-2H2O+Na]+ 329 491
[Hexn-3H2O+Na]+ 311 473
[(LY)n+H]+ 295
[(LY)n-H2O+H]+ 277
[(LY)n-NH3+O+H]+ 294
[HexnLY+H]+ 457 619 781 943 1105 1267
[HexnLY-H2O+H]+ 439 601 763 925 1087 1249
[HexnLY-2H2O+H]+ 421 583 745 907 1069
[HexnLY-3H2O+H]+ 403 565 727 889
[HexnLY-4H2O+H]+ 385 547 709 871
[Hexn(LY)2+H]+ 733 895 1057
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a

Ion assignment supported by accurate masses found by LTQ-Orbitrap for roasted mixtures Man3-CQA and Man3-YL. The ions marked with the symbol † or ‡ were attributed to different isobaric compounds: † for two and ‡ for three possible compounds. For roasted Man3-CQA-YL, the ion assignment was made considering the most abundant isobaric compounds identified in the roasted mixture Man3-CQA. However, the presence of isobars in roasted Man3-CQA-YL cannot be excluded.

Table 9.

Accurate masses found by LTQ-Orbitrap for the ions identified after roasting of the mixture Man3-CQA. The theoretical mass and the difference between the theoretical and experimental masses for each predicted formula were obtained from Xcalibur software.

Experimental mass (m/z) Theoretical mass (m/z) Mass error (ppm) RDB equiv. Composition Proposed assignment
323.0757 323.0761 −1.28 8.5 C15H15O8 [HexCA-H2O-H]−
323.097 323.0973 −0.94 3.5 C12H19O10 [Hex2-H2O-H]−
341.1074 341.1078 −1.17 2.5 C12H21O11 [Hex2-H]-
353.0862 353.0867 −1.41 8.5 C16H17O9 [CQA-H]−
353.1072 353.1078 −1.75 3.5 C13H21O11 [HexQA-H]−
461.1071 461.1078 −1.51 12.5 C22H21O11 [HexCQA-3H2O-H]−
497.1071 497.1078 −1.46 15.5 C25H21O11 [(CQA)CA-H2O-H]−
497.1281 497.129 −1.76 10.5 C22H25O13 [HexCQA-H2O-H]−
497.1492 497.1501 −1.86 5.5 C19H29O15 [Hex2QA-H2O-H]−
503.1599 503.1607 −1.61 3.5 C18H31O16 [Hex3-H]−
515.1182 515.1184 −0.37 14.5 C25H23O12 [(CQA)CA-H]−
515.1385 515.1395 −1.96 9.5 C22H27O14 [HexCQA-H]−
515.1596 515.1607 −2.02 4.5 C19H31O16 [Hex2QA-H]−
623.1594 623.1607 −2.02 13.5 C28H31O16 [Hex2CQA-3H2O-H]−
659.1805 659.1818 −1.97 11.5 C28H35O18 [Hex2CQA-H2O-H]−
659.2029 659.2029 −0.09 6.5 C25H39O20 [Hex3QA-H2O-H]−
677.1908 677.1924 −2.3 10.5 C28H37O19 [Hex2CQA-H]−
677.2121 677.2135 −1.97 5.5 C25H41O21 [Hex3QA-H]−
689.1703 689.1712 −1.4 16.5 C32H33O17 [(CQA)2-H]−
839.2433 839.2452 −2.29 11.5 C34H47O24 [Hex3CQA-H]−
851.222 851.224 −2.41 17.5 C38H43O22 [Hex(CQA)2-H]−
1001.2961 1001.298 −1.9 12.5 C40H57O29 [Hex4CQA-H]−
1163.3479 1163.3508 −2.51 13.5 C46H67O34 [Hex5CQA-H]−
1325.3998 1325.4036 −2.92 14.5 C52H77O39 [Hex6CQA-H]−
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Table 10.

Summary of [M+Na]+ ions identified by ESI-MS analysis after roasting of the mixture Man3-MalA, with the indication of the m/z values and the proposed assignments.

Proposed assignment Number of hexose (Hex) units (n)
1 2 3 4 5 6 7 8 9
[Hexn+Na]+ 203 365 527 689 851 1013 1175 1337 1499
[Hexn-H2O+Na]+ 185 347 509 671 833 995 1157 1319 1481
[(MalA)n+Na]+ 157
[HexnMalA+Na]+ 319 481 643 805 967 1129 1291 1453
[HexnMalA-H2O+Na]+ 301 463 625 787 949 1111 1273 1435
[Hexn(MalA)2+Na]+ 435 597 759 921 1083 1245 1407
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Table 11.

Summary of [M+Na]+ ions identified by ESI-MS analysis after roasting of the mixture Man3-CitA, with the indication of the m/z values and the proposed assignments.

Proposed assignment Number of hexose (Hex) units (n)
1 2 3 4 5 6 7 8 9
[Hexn+Na]+ 203 365 527 689 851 1013 1175 1337 1499
[Hexn-H2O+Na]+ 185 347 509 671 833 995 1157 1319 1481
[(CitA)n+Na]+ 215
[HexnCitA+Na]+ 377 539 701 863 1025 1187 1349
[HexnCitA-H2O+Na]+ 359 521 683 845 1007 1169 1331
[Hexn(CitA)2+Na]+ 551 713 875 1037 1199 1361
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Table 12.

Accurate masses found by LTQ-Orbitrap for the ions identified after roasting of the mixture Man3-YL. The theoretical mass and the difference between the theoretical and experimental masses for each predicted formula were obtained from Xcalibur software.

Experimental mass (m/z) Theoretical mass (m/z) Mass error (ppm) RDB equiv. Composition Proposed assignment
275.1393 275.139 0.91 7.5 C15H19O3N2 [YL-H2O-H]−
292.1184 292.1179 1.58 7.5 C15H18O5N [YL-NH3+O-H]−
293.15 293.1496 1.32 6.5 C15H21O4N2 [YL-H]−
341.1082 341.1078 1.18 2.5 C12H21O11 [Hex2-H]−
383.1606 383.1601 1.15 11.5 C21H23O5N2 [HexYL-4H2O-H]−
401.171 401.1707 0.69 10.5 C21H25O6N2 [HexYL-3H2O-H]−
419.1815 419.1813 0.6 9.5 C21H27O7N2 [HexYL-2H2O-H]−
437.1921 437.1918 0.59 8.5 C21H29O8N2 [HexYL-H2O-H]−
455.2027 455.2024 0.67 7.5 C21H31O9N2 [HexYL-H]−
503.1609 503.1607 0.55 3.5 C18H31O16 [Hex3-H]−
545.2133 545.213 0.53 12.5 C27H33O10N2 [Hex2YL-4H2O-H]−
563.2237 563.2235 0.34 11.5 C27H35O11N2 [Hex2YL-3H2O-H]−
581.2342 581.2341 0.12 10.5 C27H37O12N2 [Hex2YL-2H2O-H]−
599.2448 599.2447 0.24 9.5 C27H39O13N2 [Hex2YL-H2O-H]−
617.255 617.2552 −0.31 8.5 C27H41O14N2 [Hex2YL-H]−
707.266 707.2658 0.25 13.5 C33H43O15N2 [Hex3YL-4H2O-H]−
725.2764 725.2764 0.11 12.5 C33H45O16N2 [Hex3YL-3H2O-H]−
731.3499 731.3498 0.16 13.5 C36H51O12N4 [Hex(YL)2-H]−
743.287 743.2869 0.13 11.5 C33H47O17N2 [Hex3YL-2H2O-H]−
761.2977 761.2975 0.25 10.5 C33H49O18N2 [Hex3YL-H2O-H]−
779.3081 779.3081 0.03 9.5 C33H51O19N2 [Hex3YL-H]−
869.3182 869.3186 −0.49 14.5 C39H53O20N2 [Hex4YL-4H2O-H]−
887.3288 887.3292 −0.41 13.5 C39H55O21N2 [Hex4YL-3H2O-H]−
905.3395 905.3397 −0.31 12.5 C39H57O22N2 [Hex4YL-2H2O-H]−
923.3493 923.3503 −1.05 11.5 C39H59O23N2 [Hex4YL-H2O-H]−
941.3579 941.3609 −3.15 10.5 C39H61O24N2 [Hex4YL-H]−
1085.4015 1085.4031 −1.49 12.5 C45H69O28N2 [Hex5YL-H2O-H]−
1247.454 1247.456 −1.54 13.5 C51H79O33N2 [Hex6YL-H2O-H]−
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Table 13.

Compounds identified after roasting of the mixture Man3-YL: the m/z values of the ions identified, the proposed assignments, the retention time (RT), and the most abundant product ions observed in the respective LC-MS2 spectrum, with the indication of the m/z values, mass differences relative to the precursor ion, and the identification of the most informative product ions.

m/z Assignment RT LC-MS2
203 [Hex+Na]+ 4.0 aNo LC-MS2 spectrum
277 [YL-H2O+H]+ 10.4–15.6 249 (-28), 136 (-141, a1), 171 (-106)
294 [YL-NH3+O+H]+ 17.7–29.9 248 (-46), 276 (-18), 132 (-162, -(Y-NH3+O)res, [L+H]+), 266 (-28), 220 (-74)
295 [YL+H]+ 7.2–16.6 136 (-159, a1), 278 (-17, -NH3), 249 (-46, -HCO2H), 119 (-176, a1-NH3)
311 [Hex2-3H2O+Na]+ 4.3 185 (-126, -(Hex-3H2O)), 149 (-162, -Hexres)
329 [Hex2-2H2O+Na]+ 3.9 167 (-162, -Hexres), 185 (-144, -(Hex-2H2O)), 203 (-126, -(Hex-2H2O)res)
347 [Hex2-H2O+Na]+ 4.1 329 (-18), 287 (-60), 185 (-162, -Hexres), 203 (-144, -(Hex-H2O)res)
365 [Hex2+Na]+ 4.2 347 (-18), 305 (-60), 203 (-162, -Hexres), 185 (-180, -Hex)
385 [HexYL-4H2O+H]+ 35.6 339 (-46), 367 (-18), 357 (-28), 226 (-159, (a1+(Hex-4H2O)res)), 311 (-74),
254 (-131, -L)
385 [HexYL-4H2O+H]+ 41.1 339 (-46), 367 (-18), 357 (-28), 226 (-159, (a1+(Hex-4H2O)res)), 311 (-74),
254 (-131, -L)
403 [HexYL-3H2O+H]+ 17.6 385 (-18), 244 (-159, (a1+(Hex-3H2O)res)), 126 (-277), 357 (-46), 278 (-125)
403 [HexYL-3H2O+H]+ 25.1 272 (-131, -L), 244 (-159, (a1+(Hex-3H2O)res)), 385 (-18), 357 (-46), 279 (-124)
421 [HexYL-2H2O+H]+ 18.1 290 (-131, -L), 262 (-159, (a1+(Hex-2H2O)res)), 403 (-18), 393 (-28), 375 (-46)
421 [HexYL-2H2O+H]+ 20.2 290 (-131, -L), 262 (-159, (a1+(Hex-2H2O)res)), 403 (-18), 375 (-46), 391 (-30)
421 [HexYL-2H2O+H]+ 29.9 262 (-159, (a1+(Hex-2H2O)res)), 403 (-18), 290 (-131, -L), 244 (-177)
439 [HexYL-H2O+H]+ 18.0 280 (-159, (a1+(Hex-H2O)res)), 393 (-46), 295 (-144, -(Hex-H2O)res, [YL+H]+)
457 [HexYL+H]+ 5.7–16.9 439 (-18), 373 (-84), 421 (-36), 307 (-150), 295 (-162, -Hexres, [YL+H]+), 403 (-54), 136 (-321, a1), 298 (-159, (a1+Hexres))
473 [Hex3-3H2O+Na]+ 4.2 347 (-126, -(Hex-3H2O)), 311 (-162, -Hexres)
491 [Hex3-2H2O+Na]+ 4.1 329 (-162, -Hexres), 347 (-144, -(Hex-2H2O)), 365 (-126, -(Hex-2H2O)res)
509 [Hex3-H2O+Na]+ 4.2 347 (-162, -Hexres), 491 (-18), 449 (-60), 365 (-144, -(Hex-H2O)res), 185 (-324, -2xHexres)
527 [Hex3+Na]+ 4.2 365 (-162, -Hexres), 347 (-180, -Hex), 509 (-18), 467 (-60), 185 (-342, [Hexres+Na]+)
547 [Hex2YL-4H2O+H]+ 18.4–24.9 529 (-18), 388 (-159, (a1+(Hex2-4H2O)res)), 501 (-46), 385 (-162, -(Hex-H2O)),
416 (-131, -L), 511 (-36), 421 (-126, -(Hex-3H2O)), 403 (-144, -(Hex-3H2O)res)
565 [Hex2YL-3H2O+H]+ 16.5 288 (-277), 547 (-18), 403 (-162, -Hexres), 406 (-159, a1+(Hex2-3H2O)res), 529 (-36)
565 [Hex2YL-3H2O+H]+ 19.6–21.2 547 (-18), 406 (-159, a1+(Hex2-3H2O)res), 403 (-162, -Hexres), 529 (-36),
439 (-126, -(Hex-3H2O))
583 [Hex2YL-2H2O+H]+ 24.1 421 (-162, -Hexres), 565 (-18), 262 (-321, a1+(Hex-2H2O)res)), 290 (-293, -(Hexres+L), 403 (-180, -Hex)
601 [Hex2YL-H2O+H]+ 16.9 439 (-162, -Hexres), 280 (-321, a1+(Hex-H2O)res)), 295 (-306, [YL+H]+),
393 (-208, -(Hexres+HCO2H))
619 [Hex2YL+H]+ 5.8–16.4 457 (-162, -Hexres), 601 (-18), 307 (-312, -(Hexres+150)), 373 (-246, -(Hexres+84))
689 [Hex4+Na]+ 3.9 527 (-162, -Hexres), 365 (-324, -2xHexres), 203 (-486, -3xHexres)
709 [Hex3YL-4H2O+H]+ 15.7–21.1 547 (-162, -Hexres), 691 (-18), 635 (-74), 529 (-180, -Hex), 583 (-126, -(Hex-3H2O)), 550 (-159, (a1+(Hex3-4H2O)res))
727 [Hex3YL-3H2O+H]+ 16.6–20.6 565 (-162, -Hexres), 709 (-18), 403 (-324, -2xHexres), 547 (-180, -Hex), 295 (-270, [YL+H]+)
733 [Hex(YL)2+H]+ 26.3 439 (-294, -YL), 280 (-453), 602 (-131, -L), 574 (-159), 393 (-340), 715 (-18),
295 (-438, [YL+H]+), 571 (-162, -Hexres)
733 [Hex(YL)2+H]+ 31.6 602 (-131, -L), 439 (-294, -YL), 280 (-453), 393 (-340), 715 (-18), 574 (-159),
295 (-438, [YL+H]+), 571 (-162, -Hexres)
745 [Hex3YL-2H2O+H]+ 22.3 421 (-324, -2xHexres), 583 (-162, -Hexres), 262 (-483, a1+(Hex-2H2O)res)),
403 (-342, -(Hexres+Hex)), 290 (-455, -((2xHexres)+L))
745 [Hex3YL-2H2O+H]+ 23.2 421 (-324, -2xHexres), 583 (-162, -Hexres), 403 (-342, -(Hexres+Hex)),
262 (-483, a1+(Hex-2H2O)res)), 290 (-455, -((2xHexres)+L))
763 [Hex3YL-H2O+H]+ 16.7 601 (-162, -Hexres), 439 (-324, -2xHexres), 280 (-483, (a1+(Hex-H2O)res)), 745 (-18), 295 (-468, [YL+H]+)
763 [Hex3YL-H2O+H]+ 18.7 439 (-324, -2xHexres), 601 (-162, -Hexres), 280 (-483, (a1+(Hex-H2O)res)), 745 (-18), 393 (-370, -((2xHexres)+HCO2H))
781 [Hex3YL+H]+ 5.3–16.2 457 (-324, -2xHexres), 619 (-162, -Hexres), 373 (-408, -((2xHexres)+84),
298 (-483, (a1+Hexres))
851 [Hex5+Na]+ 4.2 689 (-162, -Hexres), 527 (-324, -2xHexres), 671 (-180, -Hex), 365 (-486, -3xHexres)
871 [Hex4YL-4H2O+H]+ 15.6–21.3 709 (-162, -Hexres), 547 (-324, -2xHexres), 745 (-126, -(Hex-3H2O))
889 [Hex4YL-3H2O+H]+ 18.6 727 (-162, -Hexres), 565 (-324, -2xHexres), 871 (-18), 709 (-180, -Hex), 373 (-516)
889 [Hex4YL-3H2O+H]+ 19.8 565 (-324, -2xHexres), 727 (-162, -Hexres), 871 (-18), 272 (-455, -((2xHexres)+L))
889 [Hex4YL-3H2O+H]+ 22.1 565 (-324, -2xHexres), 403 (-486, -3xHexres), 727 (-162, -Hexres), 871 (-18),
709 (-180, -Hex)
895 [Hex2(YL)2+H]+ 22.8 733 (-162, -Hexres), 439 (-456, -(Hexres+YL)), 602 (-293, -(Hexres+L)), 764 (-131, -L), 280 (-615), 571 (-324, -2xHexres)
895 [Hex2(YL)2+H]+ 27.3 733 (-162, -Hexres), 602 (-293, -(Hexres+L)), 439 (-456, -(Hexres+YL)), 764 (-131, -L), 280 (-615), 571 (-324, -2xHexres)
907 [Hex4YL-2H2O+H]+ 16.8 745 (-162, -Hexres), 583 (-324, -2xHexres)
907 [Hex4YL-2H2O+H]+ 27.4 745 (-162, -Hexres), 583 (-324, -2Hexres)
925 [Hex4YL-H2O+H]+ 16.4 907 (-18), 601 (-324, -2xHexres), 763 (-162, -Hexres), 889 (-36),
583 (-342, -(Hexres+Hex))
943 [Hex4YL+H]+ 4.3–15.3 619 (-324, -2xHexres), 925 (-18), 781 (-162, -Hexres), 457 (-486, -3xHexres), 373 (-570, -((3xHexres)+84)), 295 (-648, -4xHexres, [YL+H]+)
1013 [Hex6+Na]+ 4.4 851 (-162, -Hexres), 527 (-486, -3xHexres), 689 (-324, -2xHexres), 953 (-60), 833 (-180, Hex)
1057 [Hex3(YL)2+H]+ 21.7 733 (-324, -2xHexres), 439 (-618, -((2xHexres)+YL)), 895 (-162, -Hexres),
602 (-455, -((2xHexres)+L))
1057 [Hex3(YL)2+H]+ 25.3 733 (-324, -2xHexres), 602 (-455, -((2xHexres)+L)), 439 (-618, -((2xHexres)+YL)), 895 (-162, -Hexres), 926 (-131, -L)
1087 [Hex5YL-H2O+H]+ 16.2 925 (-162, -Hexres), 1069 (-18), 763 (-324, -2xHexres)
1105 [Hex5YL+H]+ 4.2–16.7 943 (-162, -Hexres), 781 (-324, -2xHexres)
1249 [Hex6YL-H2O+H]+ 15.9 aNo LC-MS2 spectrum
1267 [Hex6YL+H]+ 5.3–16.7 aNo LC-MS2 spectrum
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a

No LC-MS2 spectrum, but the ion assignment is corroborated by the observation of other ions of the same series, eluting at a similar retention time (RT). Abbreviations: a1 – peptide fragment (Fig. 2A); Hexres – Hexose residue; L – Leucine; Lres – Leucine residue; Y – Tyrosine; Yres – Tyrosine residue.

1.1. GC–MS data of silylated methanolysis products of phenolic compounds standards

See Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5–5.

1.2. Chemical composition of coffee beans and derived fractions

See Table 1, Table 2, Table 3, Table 4, Table 5, Table 6

1.3. Data on the model mixtures mimicking coffee composition

See Fig. 6 and Table 7, Table 8, Table 9, Table 10, Table 11, Table 12, Table 13

Some of the Hexn and dehydrated derivatives identified by HPLC-ESI-MS (Table 8) were not observed in the negative ESI-MS spectrum acquired on the LTQ-Orbitrap mass spectrometer (Table 9). This is due to the fact that neutral oligosaccharides ionize better in positive than in negative mode.

The analysis of the reconstructed ion chromatograms (RICs) corroborates the presence of isomeric compounds, i.e. compounds with the same elemental composition but different structures, eluting at different RTs. However, the exact structural differences were not possible to be inferred based on the respective LC-MSn spectra (n=2–3) because they were very similar, most probably due to the presence of positional isomers. In the case of the compounds bearing a sugar moiety, the structural differences of the isomers can be related to different structures of the sugar moiety, differing on glycosidic linkage positions, and anomeric configuration.

2. Experimental design, materials and methods

The methodologies that allowed the data here presented are described in [1] and in cited references. Here, only the protocol for glycosidic linkage analysis is provided, giving a large number of experimental details, usually omitted in research articles due to the words limit.

2.1. Glycosidic linkage analysis

A sample (0.5–1 mg) of each unroasted and roasted model (Man3 and mixtures) was dissolved with DMSO (1 mL), and then powdered NaOH (40 mg) was added to the solution. After 30 min at room temperature with continuous stirring, samples were methylated by adding of CH3I (80 µL), allowed to react 20 min under vigorous stirring. Distilled water (2 mL) was then added, and the solution was neutralized using HCl 1 M. Dichloromethane (3 mL) was then added and, upon vigorous manual shaking and centrifugation, the dichloromethane phase was recovered and washed two times by addition of distilled water (2–3 mL). The organic phase was evaporated to dryness and the resulting material was remethylated using the same procedure. The remethylated material was hydrolyzed with 500 µL of TFA 2 M at 121 °C for 1 h, and the acid was then evaporated to dryness. For carbonyl-reduction, the resulting material was then suspended in 300 µL of NH3 2 M and 20 mg of NaBD4 were added. The reaction mixture was incubated at 30 °C for 1 h. After cooling, the excess of borodeuteride was destroyed by the addition of glacial acetic acid (2×50 µL). The partially methylated alditol derivatives were acetylated with acetic anhydride (3 mL) in the presence of 1-methylimidazole (450 μL) during 30 min at 30 °C. To decompose the excess of acetic anhydride, distilled water (3 mL) was added while the tubes were in ice. Dichloromethane (2.5 mL) was then added and, upon vigorous manual shaking and centrifugation, the dichloromethane phase was recovered. The addition of water (3 mL) and dichloromethane (2.5 mL), and the recovery of the organic phase were performed once more. The dichloromethane phase was then washed two times by addition of distilled water (3 mL) and evaporated to dryness. The dried material was dissolved with anhydrous acetone (2 × 1 mL) followed by the evaporation of the acetone to dryness. The partially methylated alditol acetates (PMAAs) were redissolved with anhydrous acetone and identified by gas chromatography-mass spectrometry (GC–MS) on an Agilent Technologies 6890 N Network GC system (Santa Clara, CA) equipped with a DB-1ms column with 30 m of length, 0.25 mm of internal diameter, and 0.1 µm of film thickness (J&W Scientific, Folsom, CA). The GC was connected to an Agilent 5973 Network Mass Selective Detector operating with an electron impact mode at 70 eV, and scanning the m/z range 40–500 in a 1 s cycle in a full scan mode acquisition. The oven temperature program used was: initial temperature 50 °C, a linear increase of 8 °C/min up to 140 °C, standing at this temperature for 5 min, followed by linear increase of 0.5 °C/min up to 150 °C, ollowed by linear increase of 40 °C/min up to 250 °C, standing at this temperature for 1 min. The injector and detector temperatures were 220 and 230 °C, respectively. Helium was used as carrier gas at a flow rate of 1.7 mL/min. Relative abundance of each PMAA identified in both unroasted and roasted samples was determined upon integration of each peak using the equipment׳s software.

Acknowledgements

Thanks are due FCT/MEC for the financial support to QOPNA (UID/QUI/00062/2013), and CESAM (UID/AMB/50017/2013) at University of Aveiro and CQ-VR at UTAD Vila Real (PEst-OE/QUI/UI0616/2014) through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement. Thanks are also due to FCT for funding the Portuguese Mass Spectrometry Network (REDE/1504/REM/2005), and the grants of A.S.P. Moreira (SFRH/BD/80553/2011) and E. Maciel (SFRH/BPD/104165/2014).

Footnotes

Transparency document

Transparency data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.dib.2017.05.027.

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Reference

  • 1.Moreira A.S.P., Nunes F.M., Simões C., Maciel E., Domingues P., Domingues M.R.M., Coimbra M.A. Transglycosylation reactions, a main mechanism of phenolics incorporation in coffee melanoidins: inhibition by Maillard reaction. Food Chem. 2017;227:422–431. doi: 10.1016/j.foodchem.2017.01.107. [DOI] [PubMed] [Google Scholar]

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