Research Article Received: 10 April 2013
Revised: 10 October 2013
Accepted article published: 12 December 2013
Published online in Wiley Online Library: 22 January 2014
(wileyonlinelibrary.com) DOI 10.1002/jsfa.6532
Chlorogenic acid in raw materials for the production of chicory coffee ´ b Renata Zawirska-Wojtasiak,a∗ El˙zbieta Wojtowicz,b Krzysztof Przygonski and Mariola Olkowiczc Abstract BACKGROUND: Chicory coffee is produced from traditional raw materials. Other materials are added to improve its aroma. The aim of this study was to test new raw materials with a high content of chlorogenic acid (CGA) as the criterion for their selection. This acid is degraded in the course of roasting and is a source of phenolic compounds affecting coffee aroma. For this reason, contents of CGAs were analyzed in traditional and new materials before and after roasting and compared with the chemicals formed in the roasted pure standard of chlorogenic acid (5-CQA). RESULTS: It was shown that the novel raw materials contained considerable amounts of 5-CQA, frequently higher than in traditional chicory. The roasting process caused significant losses of 5-CQA in the tested raw materials, amounting to 55–91%. In turn, the analysis of volatile compounds in roasted materials showed the presence of certain phenolic and heterocyclic compounds that were also formed as degradation products of the pure 5-CQA chemical standard. CONCLUSION: Novel raw materials, mainly chokeberry, artichoke and lovage, are rich sources of CGAs, particularly 5-CQA. Their application in the production of chicory coffee may result in an increased content of primarily phenolic compounds in its aroma. c 2013 Society of Chemical Industry Keywords: chlorogenic acid; chicory coffee; raw materials; aroma; roasting
INTRODUCTION
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Chicory coffee is a beverage obtained from chicory, barley, rye and sugar beet. Its sensory attributes are similar to those of natural coffee, making it a beverage of choice for people who because of health concerns should not consume natural coffee (e.g. owing to its caffeine content). Chicory coffee is becoming increasingly popular as a wellness product. Coffee drinkers value first of all its unique aroma. For gourmets the aroma of coffee released in the course of brewing is associated with one of the most pleasant moments in their everyday routine. Components found in raw materials used to produce chicory coffee and substances formed during the roasting process provide it with unique sensory attributes. For the aroma of chicory coffee to resemble that of natural coffee, apart from traditional raw materials in its production, we may also use novel materials rich in chlorogenic acid (CGA),1 – 3 which is one of the precursors of aroma compounds in natural coffee and results in the formation of coffee pigments and taste.4 – 9 Coffee is a very rich aroma product studied by many authors.4,8,10 – 13 Over 1200 compounds have been reported, among them the main important furans, pyrazines, pyrroles and thiols. The formation of most of these compounds has been characterized by pathways derived via the Maillard reaction. However, the formation of some compounds such as phenols, benzoic acid and catechols in roasted coffee is difficult to explain by the Maillard reaction alone.7 According to some authors, CGAs are precursors of the important coffee volatiles mentioned above.4 – 8 A high content of CGA was the criterion for selection of the novel raw materials used in this study, namely artichoke, hawthorn J Sci Food Agric 2014; 94: 2118–2123
fruit, lovage, blueberry and chokeberry. Independently of the typical aromas of these novel raw materials, during the roasting process they changed dramatically to develop a roasted-like aroma together with the scent of coffee. Since CGA is found in the form of various isomers, we may refer to CGAs. CGAs are a family of esters formed between quinic acid and certain trans-cinnamic acids, most commonly caffeic, p-coumaric and ferulic acids. Using a more general definition, all esters of quinic acids and their diastereomers can be considered as CGAs.14 The following CGAs are most commonly found in nature: 5-O-caffeoylquinic acid, conventionally called chlorogenic acid (5-CQA), 4-O-caffeoylquinic acid, also referred to as cryptochlorogenic acid (4-CQA), and 3-O-caffeoylquinic acid, also called neochlorogenic acid (3-CQA). Green coffee beans are a rich source of 5-CQA, which is transformed during the roasting process. Many literature sources indicate considerable losses of 5-CQA, which is degraded or
∗
Correspondence to: Renata Zawirska-Wojtasiak, Department of Food Science and Nutrition, Pozna´n University of Life Sciences, PL-60-637, Pozna´n, Poland. E-mail: [email protected]
a Department of Food Science and Nutrition, Pozna´n University of Life Sciences, PL-60-637, Pozna´n, Poland b Department of Food Concentrates and Starch Products, Institute of Agricultural and Food Biotechnology, Pozna´n, Poland c Department of Biotechnology and Food Microbiology, Pozna´n University of Life Sciences, Pozna´n, Poland
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Chlorogenic acid in raw materials for chicory coffee isomerized as a result of roasting.4,15 With very dark roasting, these losses may be as high as 90%. Farah and Donangelo8 found that after a short roasting time (∼7% weight loss) the level of 5-CQA decreased considerably while those of 4-CQA and 3-CQA increased twofold as a result of isomerization occurring at the beginning of the roasting process. A longer roasting time led to the complete loss of 5-CQA. Clifford16,17 stated that during the early roasting stages the isomerization process is accompanied by partial hydrolysis of quinic acid and cinnamic acids (including caffeic acid). Released cinnamic acids may undergo decarboxylation, degradation to simple phenolic acids and further transformations. The remaining quinic acid is dehydrated and a lactone ring is formed. Lactones are formed only with those acids in which position 5 of quinic acid is free, i.e. 4-CQA and 3-CQA.8,17 Literature sources report that thermal degradation of 5-CQA causes the formation of phenolic derivatives, resulting in marked differences between the aroma of natural coffee and those of its substitutes.2,5,16 The major volatile phenolic compounds in natural coffee are guaiacol, 4-ethylguaiacol and 4-vinylguaiacol, while di- and triphenolic compounds primarily include catechol, 4-ethylcatechol and pirogalol. Model studies have shown that guaiacol comes from the degradation of ferulic acid arising from feruloylquinic acid (FQA). In turn, catechol and pirogalol come from transformations of quinic acid and 5-CQA. Certain catechols may also come from derivatives of caffeic acid.6 According to a recent study, 1,4-diketones such as 1,4cyclohexanedione are among the degradation products obtained in model roasting of 5-CQA. However, their share in the aroma of roasted coffee has not been explained. It was only stated that 5-CQA and its lactones are also responsible for the bitter and tart taste of coffee.7 5-CQA is a secondary metabolite produced by plants in response to environmental stress conditions such as infections caused by pathogenic microorganisms, mechanical damage and excessive UV radiation.5,8,18 – 20 In relation to its protective function in plants, considerable amounts of 5-CQA are found during plant growth and fruit ripening. This compound is contained in many fruits and vegetables, e.g. potatoes, cacao beans, plums, apples, artichokes, hawthorn fruits, blueberries and lovage.15,20,21 The main CGAs found in artichoke (Cynara scolymus L.) include 5-CQA and 1,5O-dicaffeoylquinic acid (cynarine), with 5-CQA present at 0.2–2.1 g kg−1 dry matter (DM) depending on the plant genotype and plant part analyzed.22 – 24 In hawthorn (Crataegus spp.) the 5-CQA level ranges from 0.2 to 1.6 g kg−1 DM, with its content varying depending on the species and variety.24,25 Traditional chicory coffee is produced primarily from roasted chicory roots, a mixture of roasted cereal grains and sugar beet. In order to improve or add variety to the aroma of chicory coffee, small amounts of additives characterized by attractive aromas are also used. This study evaluated five novel raw materials for the production of chicory coffee, with a high content of 5-CQA being the selection criterion.
EXPERIMENTAL
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(Vaccinium myrtillus L.) and chokeberry (Aronia melanocarpa), were purchased from retail outlets. Artichokes were reprocessed to isolate their hearts, which were dried then in a laboratory drier at 60 ◦ C. Novel raw materials were roasted. All raw materials before and after roasting were ground using a WZ˙ 1 laboratory mill (ZBPP, Bydgoszcz, Poland). Roasting treatment All raw materials were roasted in a BRZ 2/4/6 sample roaster battery (PROBAT, Emmerich am Rhein, Germany). Raw materials (100 g) were roasted under various conditions – 180 ◦ C/10 min for chicory, 170 ◦ C/12 min for rye, barley and sugar beet, 160 ◦ C/8 min for artichoke, hawthorn fruit, blueberry and chokeberry and 160 ◦ C/18 min for lovage – to obtain dark roasts. Samples of 2 g of standard 5-CQA were roasted in sealed 10 mL vials at 160 ◦ C for 20 min. Assay of chlorogenic acid Extraction CGAs contained in plant origin raw materials were extracted using AOAC method 957.04.26 In order to ensure greater efficiency and to adapt the method for assays of the tested materials, the procedure was modified by increasing the amount of sample and repeating the extraction four times. Samples of approximately 0.5 g of raw material were weighed into 10 mL test tubes. Then 3 mL of deionized water was added and the test tube contents were mixed thoroughly to prevent caking. Next, 7 mL of 960 mL L−1 99.9% ethanol was added and the test tube contents were shaken. Finally, the samples were centrifuged and the eluates were transferred to 50 mL volumetric flasks and supplemented with deionized water. The whole procedure was repeated three times. Analysis of CGAs by liquid chromatography/mass spectrometry (LC/MS) and high-performance liquid chromatography (HPLC) HPLC analysis was performed using an Agilent Technologies (Wilmington, Del, USA) 1200 HPLC system equipped with a Supelco ˚ 3 (Bellefonte, PA., USA) C18 column (150 mm × 4.6 mm, 100 A, µm). Binary gradient elution was carried out using a solvent system with phase A consisting of water/methanol (95:5 v/v) containing 1 mL L−1 99.0% formic acid and phase B consisting of methanol/water (60:40 v/v) containing 1 mL L−1 99.0% formic acid. The gradient profile was as follows: 0–1 min, 0% B; 1–5 min, 0–25% B; 5–9 min, 25% B; 9–15 min, 25–80% B; 15–16 min, 80–100% B; 16–30min, 100% B; 30–31 min, 100–0% B; 31–36 min, 0% B. The flow rate was 0.4 mL min−1 , the column temperature was 30 ◦ C and the injection volume was 10 µL. An Agilent 6224 time-of-flight (TOF) LC/MS system with electrospray ionization (ESI) and a TOF analyzer (in negative ion polarization mode for acid analyses and in positive ion polarization mode for other phenolic compounds) was used for ion monitoring within the range m/z 50–1700. The voltage applied to the capillary column was 4 kV, the gas pressure in the nebulizer was 20 psi and the fragmenter voltage was 214 V. Assays of 5-CQA were performed in a Dionex Corporation (Sunnyvale, CA, USA) LC system equipped with the same column and using the same gradient parameters. The 5-CQA present in each sample was identified by comparing its retention time and spectrum with the standard using a photodiode array detector (PAD). CGAs were quantified from absorbances recorded in the chromatograms relative to external standards of 5-CQA, with detection at 325 nm. A standardization curve was prepared based on the following concentrations of 5-CQA standard (SigmaAldrich, Steinheim, Germany): 1, 5, 10, 20, 50 and 100 µg mL−1 .
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Samples Traditional raw materials for the production of chicory coffee were obtained from a production plant of CYKORIA SA (Wierzchosławice, Poland). They included chicory (Cichorium intybus), rye (Secale L.), barley (Hordeum L.) and sugar beet (Beta vulgaris L.) before and after roasting. Novel raw materials, i.e. artichoke (C. scolymus L.), hawthorn fruit (Rosaceae), lovage (Levisticum officinale), blueberry
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Table 1. Identification and proportions of individual isomers in total CGAs by LC/MS in raw materials before/after roasting (%/%) Compound (abbreviation)
RT (HPLC)
3-O-Caffeoylquinic acid (3-CQA)
17.385
Glycoside of delphinidin 3-O-p-Coumaroylquinic acid (3-pCoQA)
18.719 19.394
5-O-Caffeoylquinic acid, chlorogenic acid (5-CQA)
19.803
4-O-Caffeoylquinic acid (4-CQA)
20.172
Caffeoylshikimic acid (CSA)
21.375
5-O-p-Coumaroylquinic acid (5-pCoQA) 3-O-Feruloylquinic acid (3-FQA)
21.361 22.084
3,5-Di-O-caffeoylquinic acid (3,5-diCQA)
22.487
Derivative of p-coumaric acid 4,5-Di-O-caffeoylquinic acid (4,5-diCQA)
22.860 23.065
Caffeoylhexose
23.287
Derivative of apigenin Quercetin glycosides Quercetin-3-rutinoside
24.324 23.407 23.410
m/z (MS/MS)
C
S
A
191.0875 179.0653 161.0534 135.0713 303.0525 191.0871 173.0757 163.0691 191.0878 161.0536 191.0872 179.0649 163.0694 135.0707 179.0657 161.0538 135.0716 191.0883 193.1187 191.0929 149.1011 353.1330 191.0897 135.0737 163.0705 353.1334 179.0678 179.0659 135.0722 269.0825 303.0527 463.1378 300.0686
–/–
–/–
–/10
–/–
–/–
–/–
H
L
B
Ch
42/–
2/7
–/–
46/15
–/–
–/–
–/–
tr/–
–/–
–/–
–/–
17/–
–/–
–/–
–/–
61/100
61/100
48/52
39/100
72/71
100/100
51/73
–/–
–/–
–/tr
2/–
tr/3
tr/tr
3/1
–/–
–/–
–/5
–/–
–/19
–/–
–/11
–/– –/–
–/– –/–
2/8 –/–
–/– –/–
1/– 10/–
–/– –/–
–/– –/–
26/–
39/–
44/24
–/–
8/–
–/–
–/–
–/– 13/–
–/– –/–
–/– 6/1
–/– –/–
–/– 5/–
tr/tr –/–
–/– –/–
–/–
–/–
–/–
–/–
tr/–
–/–
–/–
–/– –/– –/–
–/– –/– –/–
tr/– –/– –/–
–/– –/– tr/–
–/– –/– –/–
–/– tr/– –/–
–/– –/– –/–
RT, retention time (min); C, chicory; S, sugar beet; A, artichoke; H, hawthorn; L, lovage; B, blueberry; Ch, chokeberry; –, not identified; tr, trace amount.
The coefficient of determination of the standardization curve was 0.999. The detection limit was 0.03 µg mL−1 . The applied method was characterized by a high recovery rate of 101.4%. The proportions of individual CGA isomers assayed in the raw materials were determined as a percentage of total CGAs. Analysis of volatile compounds Volatile compounds were identified using an Agilent 5975C VL GC/MSD system equipped with an HP-5MS capillary column (30 m × 0.25 mm, 0.25 µm). Extraction was performed by the solid phase microextraction (SPME) technique using a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibre at 70 ◦ C for 20 min. The carrier gas used was helium at a flow rate 1 mL min−1 . The temperature programme was as follows: hold for 5 min at 35 ◦ C; increase at 30 ◦ C min−1 to 60◦ C; increase at 6 ◦ C min−1 to 200 ◦ C; increase at 30 ◦ C min−1 to 280 ◦ C. Mass spectra were compared with data from the NIST05 library (containing 163 198 unique compounds).
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Statistical analysis All data were expressed as mean ± standard deviation (n = 3). Statistical analyses were conducted using Student’s t test. Values with P < 0.05 were considered statistically significant. STATISTICA 9.0 software (StatSoft, Krakow, Poland) was used for all analyses.
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RESULTS AND DISCUSSION CGAs were identified by HPLC/LC/MS. Identified compounds are listed in Table 1 along with their proportions before and after roasting. Based on collected data, 5-CQA was found in chicory and sugar beet but was not detected in the other two traditional raw materials, i.e. rye and barley. However, it was found in all novel raw materials selected to improve the aroma of chicory coffee. In this study the presence of several other compounds from the CGA family was also detected. These included 3-CQA, 4-CQA, 3-O-feruloylquinic acid (3-FQA), 3,5-di-O-caffeoylquinic acid (3,5diCQA) and 4,5-di-O-caffeoylquinic acid (4,5-diCQA), as similarly found by Farah et al.27 in natural coffee. However, 4-FQA, 5-FQA and 3,4-diCQA were not detected in any tested raw material, in contrast to the results presented by Farah et al.27 Other CGAs were detected in artichoke and lovage before roasting, i.e. 5-O-p-coumaroylquinic acid (5-pCoQA), and in hawthorn before roasting, i.e. 3-O-p-coumaroylquinic acid (3-pCoQA). Apart from the above-mentioned compounds, the following were also detected: caffeoylshikimic acid (CSA), a derivative of p-coumaric acid, caffeoylhexose, a glycoside of delphinidin, quercetin-3rutinoside, quercetin glycosides and a derivative of apigenin. Another interesting finding is the disappearance of some of the above-mentioned compounds after the roasting process; for
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Chlorogenic acid in raw materials for chicory coffee
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Table 2. 5-CQA content in traditional raw materials for chicory coffee production estimated by HPLC Before roasting Raw material Chicory Sugar beet Rye Barley
mg g−1 1.23 ± 0.03a 0.03 ± 0.01a ND ND
% of total CGAs 61.4 61.0 ND ND
Roasted % of total CGAs
mg g−1 0.43 ± 0.02b 0.02 ± 0.01b ND ND
99.9 99.0 ND ND
Results are mean ± standard deviation (n = 3). Values with the same letter in a row are not statistically different at P < 0.05 (Student’s t test). ND, not determined.
Table 3. 5-CQA content in novel raw materials for chicory coffee production estimated by HPLC Before roasting Raw material Artichoke Hawthorn Lovage Blueberry Chokeberry
mg g−1 2.90 ± 0.02a 0.19 ± 0.01a 3.25 ± 0.20a 1.07 ± 0.07a 3.97 ± 0.03a
% of total CGAs 47.8 39.4 72.5 100.0 51.2
Roasted % of total CGAs
mg g−1 0.27 ± 0.01b 0.04 ± 0.01b 0.30 ± 0.05b 0.53 ± 0.02b 2.11 ± 0.11b
51.7 100.0 70.8 100.0 73.5
Results are mean ± standard deviation (n = 3). Values with the same letter in a row are not statistically different at P < 0.05 (Student’s t test).
Isomer Chicory 3,5-diCQA 4,5-diCQA Sugar beet 3,5-diCQA Artichoke 3-CQA 4-CQA CSA 5-pCoQA 3,5-diCQA 4,5-diCQA Derivative of apigenin Hawthorn 3-CQA 3-pCoQA 4-CQA Quercetin-3-rutinoside Lovage 3-CQA 4-CQA CSA 5-pCoQA 3-FQA 3,5-diCQA 4,5-diCQA Caffeoylhexose Blueberry 4-CQA Quercetin-3-rutinoside Chokeberry 3-CQA 4-CQA CSA
Before roasting
Roasted
0.53 ± 0.08 0.27 ± 0.04
ND ND
0.02 ± 0.04
ND
ND ND ND 0.13 ± 0.02a 2.66 ± 0.12a 0.37 ± 0.08a tr
0.05 ± 0.01 tr 0.02 ± 0.01 0.04 ± 0.01b 0.13 ± 0.03b 0.01 ± 0.01b ND
1.07 ± 0.07 0.09 ± 0.02 0.01 ± 0.01 tr
ND ND ND ND
0.10 ± 0.01a tr ND 0.04 ± 0.01 0.46 ± 0.02 0.38 ± 0.01 0.27 ± 0.02 tr
0.03 ± 0.01b 0.01 ± 0.01 0.10 ± 0.01 ND ND ND ND ND
tr tr
tr ND
3.66 ± 0.24a 0.20 ± 0.02a ND
0.44 ± 0.08b 0.03 ± 0.01b 0.32 ± 0.02
Results are mean ± standard deviation (n = 3). Values in a row with the same letter are not statistically different at P < 0.05 (Student’s t test). ND, not determined; tr, trace.
content ranged from 0.19 mg g−1 in hawthorn to 3.97 mg g−1 in chokeberry. These results are comparable to those reported in the literature.22 – 25,30 Differences may be due to different cultivation conditions for the raw materials tested by other authors. Available literature sources did not present contents of 5-CQA in these raw materials after roasting. Farah et al.27 and Ferruzzi15 stated that the 5-CQA content in coffee decreased as a result of roasting and that an extended time and increased temperature of roasting caused a greater reduction in its content, amounting to as much as 85–90% in dark-roasted beans. A longer roasting time resulted in the loss of the entire 5-CQA content. In this study, 5-CQA losses after roasting reached 55–91%, which suggests that this compound was transformed and the process of its degradation was progressing. The greatest losses were recorded in artichoke and lovage, exceeding 90% of initial contents, similarly as in darkroasted coffee beans. A high loss was also found in hawthorn (79%). Contents of 5-CQA in roasted blueberry and chokeberry
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example, 3-CQA and 3-pCoQA normally found in hawthorn and 5-pCoQA normally found in artichoke were not detected in those raw materials after roasting. Thus it may be assumed that, as a result of roasting, other acids belonging to the CGA family are also degraded in hawthorn and artichoke. In turn, after roasting, some CGAs appeared that had not been found in the raw materials before roasting; for example, 4-CQA detected in artichoke after roasting was not identified in that plant prior to roasting. This is an example of isomerization.8,17 In roasted artichoke, lovage and chokeberry, CSA was also identified, which is a product of 5-CQA dehydratation.17,27 Some authors reported the total content of compounds belonging to the CGA family.16 This study focused on the determination of 5-CQA content. In the tested raw materials before roasting, this compound was found in highest amounts, its proportion being 48–100% of total CGAs. After roasting, the proportion of 5-CQA in the raw materials amounted to 52–100% of total CGAs. Hawthorn was an exception in this respect, as the proportion of 5-CQA before roasting was only 39% of total CGAs. Among the traditional raw materials used for the production of chicory coffee, a significant amount of 5-CQA was contained only in chicory, namely 1.23 ± 0.03 g kg−1 (Table 2). In sugar beet, only 0.03 g kg−1 5-CQA was detected, while no 5-CQA was detected in the other two traditional raw materials, i.e. rye and barley. Literature sources also did not indicate the presence of CGAs in cereals. The main phenolic acids found in barley and rye included ferulic, sinapic, coumaric and caffeic acids.28,29 Contents of 5-CQA in the novel raw materials before and after roasting are presented in Table 3. Prior to roasting, its J Sci Food Agric 2014; 94: 2118–2123
Table 4. Content of isomers other than 5-CQA in traditional and novel raw materials for chicory coffee production estimated by HPLC (mg g−1 )
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Table 5. Identification and composition of chemicals formed from pure chlorogenic acid (5-CQA) and present in roasted raw materials (% of total volatiles) Compound
Odour description
RI
Acetic acid Hexanal Furfural Oxime-methoxy-phenyl 5-Methylfurfural Phenol Hexanoic acid 3-Furylmethyl acetate 1-Hexanol-2-ethyl 2-Methoxy-6-methyl-pyrazine 2-Ethylhexanoic acid 2,3-Dihydroxybenzaldehyde 5-Hydroxymethyl-2-furancarboxaldehyde 2-Ethylfuran 4-Methoxyphenol 2-Methoxy-4-vinylphenol (vinylguaiacol) 4-Ethylphenol 4-Ethylcatechol
Pungent Fresh, green Freshly baked bread
667 817 855 915 965 982 991 998 1029 1086 1142 1209 1225 1242 1255 1264 1356 1454
Almond, carmel Sweet, tarry Sweat-like
Roasted nut
Cotton candy Smoky, burnt Spicy, smoky, clove Phenolic, spicy Phenolic, spicy
Coffee
5-CQA
+ + + + + +
+ + + +
22.7 0.9 8.4 0.9 2.7 16.0 1.3 3.6 1.8 7.3 2.7 0.7 6.9 1.1 8.4 7.1 1.3 6.2
C
A
H
L
B
Ch
2.0 — 25.0 — 9.4 — 0.3 — 0.2 0.8 — — 20.2 — 0.2 — — —
6.6 0.4 10.7 0.6 9.1 2.3 — 1.0 — 1.0 — 0.4 2.5 0.4 1.3 2.8 0.5 1.1
10.7 0.2 1.7 — 2.5 — — — — — — — — — — 1.4 1.1 —
— — 8.9 — 1.4 — — — 0.8 1.4 — — 1.8 — 1.3 1.6 0.5 —
0.6 0.5 47.5 — 2.3 — 0.2 — — — — — — — — — — —
5.2 — 7.0 — 1.3 — — — 0.5 — — 0.2 1.0 — — — — —
RI, retention index; C, chicory; A, artichoke; H, hawthorn; L, lovage; B, blueberry; Ch, chokeberry; +, compounds identified in coffee from literature.31 – 33
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amounted to 50% of initial levels. In roasted chicory the content of 5-CQA decreased by 65%, which is comparable to that in medium-roasted coffee beans. Observations for sugar beet cannot be compared owing to the low level of 5-CQA, which prevented sufficiently precise determinations. The roasting process resulted also in losses of other compounds from the CGA family in the raw materials before and after roasting, causing changes in their percentage contents (Table 1). These changes result from the depletion of compounds contained in low amounts and the potential formation of the above-mentioned isomers. In some cases, only 5-CQA remained (in hawthorn, chicory and sugar beet). The contents of isomers other than 5-CGA identified in the traditional and novel materials are presented in Table 4. Significant amounts (>1 mg g−1 ) of other isomers were found for 3,5-diCQA in artichoke, 3-CQA in hawthorn and 3-CQA in chokeberry, but only before roasting. In the roasted materials the amounts of these compounds were very low or even undetectable. The differences seen in this work may depend only on the character and composition of the raw materials. This is because the conditions of roasting, which undoubtedly influence the reactions, were the same for all materials used. According to the data obtained, the content of CGAs in the individual raw materials was different. The amount of 5-CQA remaining after roasting depended mostly on its concentration in the material before the process. In the novel raw materials the presence of higher numbers of isomers other than 5-CQA in comparison with traditional chicory might be the reason for the distinction in composition after processing. It results from literature data on natural coffee that phenolic volatile compounds may be formed from 5-CQA.2,4 For this reason the present study included experimental degradation of the pure 5-CQA standard under similar conditions to those applied in roasting the novel raw materials. Volatile compounds formed as a result of this process were identified and are listed in Table 5. Their amounts are expressed as a percentage of total volatiles identified with spectral similarity over 80%. The amounts of presented
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compounds derived from CGAs ranged from 15.2% (chokeberry) to 58.1% (chicory) of total volatiles. They include heterocyclic compounds, acids and phenols (oxime-methoxy-phenyl, phenol, 2,3-dihydroxybenzaldehyde, 4methoxyphenol, 2-methoxy-4-vinylphenol, 4-ethylphenol, 4ethylcatechol). The data in Table 5 also show that some of them are present in the novel raw materials used in this study. It is noteworthy that they were identified by other authors7 as products of thermal degradation of CGAs as well as in the aroma of natural coffee.9 – 13 Some of them are recognized as important odorants in coffee aroma, such as 4-methoxyphenol and 2-methoxy-4-vinylphenol originating from 5-CQA. The latter compound was present in roasted artichoke, hawthorn and lovage but not in chicory (Table 5). Odours of the identified chemicals formed from CGAs are described as caramel-like, burnt, smoky and spicy. Taking into account the amounts and composition of the compounds originating from 5-CQA, the most interesting new raw material seems to be artichoke. The results of this study confirm the opinion of other authors that the formation pathways of the compounds discussed above start with CGAs.7
CONCLUSIONS 1. In the traditional and proposed novel raw materials for the production of chicory coffee, apart from 5-CQA, other compounds from the CGA family were also identified, e.g. 3CQA, 4-CQA, 3,5-diCQA, 4,5-diCQA and 3-pCoQA. The highest numbers of these compounds were recorded in chicory, artichoke, lovage and hawthorn. 2. Among the traditional raw materials, chicory was the only significant source of 5-CQA. The novel raw materials proved to be good sources of 5-CQA, and even such materials as
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Chlorogenic acid in raw materials for chicory coffee chokeberry, artichoke and lovage contained greater amounts of this acid than chicory. 3. 5-CQA was the predominant acid, but its content was considerably depleted as a result of roasting. Moreover, losses of other CGAs caused by roasting were also observed. 4. In the proposed novel raw materials for the production of chicory coffee the same compounds were detected after roasting as those identified after experimental degradation of pure 5-CQA. 5. The best of the raw materials analyzed for chicory coffee production was artichoke, since it was a good source of CGAs and produced the highest number of volatiles during roasting, particularly those important in coffee aroma such as 2-methoxy4-vinylphenol.
ACKNOWLEDGEMENT This study was financially supported by the National Centre of Science, Poland (grant 2011/01/B/NZ9/01060).
REFERENCES 1 Olthof MR, Hollman PCH and Katan MB, Chlorogenic acid and caffeic acid are absorbed in humans. J Nutr 131:66–71 (2001). 2 Ky CL, Louarn J, Dussert S, Guyot B, Hamon S and Noirot M, Caffeine, trigonelline, chlorogenic acids and sucrose diversity in wild Coffea arabica L. and C. canephora P. accessions. Food Chem 75:223–230 (2001). 3 Yen WJ, Wang BS, Chang LW and Duh PD, Antioxidant properties of roasted coffee residues. J Agric Food Chem 7:2658–2663 (2005). 4 Moon JK, Yoo HS and Shibamoto T, Role of roasting conditions in the level of chlorogenic acid content in coffee beans: correlation with coffee acidity. J Agric Food Chem 57:5365–5369 (2009). 5 Nebesny E, Budryn G, Kula J and Majda T, The effect of roasting method on headspace composition of robusta coffee bean aroma. Eur Food Res Technol 225:9–19 (2007). 6 Belitz HD and Grosch W, Food Chemistry. Springer, Berlin, pp. 344–346 (1999). 7 Moon JK and Shibamoto T, Formation of volatile chemicals from thermal degradation of less volatile coffee components: quinic acid, caffeic acid, and chlorogenic acid. J Agric Food Chem 58:5465–5470 (2010). 8 Farah A and Donangelo CM, Phenolic compounds in coffee. Braz J Plant Physiol 18:23–36 (2006). 9 Kreppenhofer S, Frank O and Hofmann T, Identification of (furan-2yl)methylated benzene diols and triols as a novel class of bitter compounds in roasted coffee. Food Chem 126:441–449 (2011). 10 Moon JK and Shibamoto T, Role of roasting conditions in the profile of volatile flavor chemicals formed from coffee beans. J Agric Food Chem 57:5823–5831 (2009). 11 Blank I, Sen A and Grosch W, Potent odorants of the roasted powder and brew of Arabica coffee. Z Lebensm Unters Forsch 195:239–245 (1992). 12 Czerny M and Grosch W, Potent odorants of raw Arabica coffee. Their changes during roasting. J Agric Food Chem 48:868–872 (2000). 13 Ryan D, Shellie R, Tranchida P, Casilli A, Mondello L and Marriott P, Analysis of roasted coffee bean volatiles by using comprehensive two dimensional gas chromatography–time-offlight mass spectrometry. J Chromatogr A 1054:57–65 (2004).
www.soci.org 14 Jaiswal R, Sovdat T, Vivan F and Kuhnert N, Profiling and characterization by LC-MSn of the chlorogenic acids and hydroxycinnamoylshikimate esters in Mat´e (Ilex paraguariensis). J Agric Food Chem 58:5471–5484 (2010). 15 Ferruzzi MG, The influence of beverage composition on delivery of phenolic compounds from coffee and tea. Physiol Behav 100:33–41 (2010). 16 Clifford MN, Chlorogenic acids – their complex nature and routine determination in coffee beans. Food Chem 4:63–71 (1979). 17 Clifford MN, Chlorogenic acids and other cinnamates – nature, occurrence, dietary burden, absorption and metabolism. J Sci Food Agric 80:1033–1043 (2000). 18 Marques V and Farah A, Chlorogenic acid and related compounds in medicinal plants and infusions. Food Chem 113:1370–1376 (2009). 19 Jeszka M, Flaczyk E, Kobus-Cisowska J and Dziedzic K, Zwia¸ zki fenolowe – charakterystyka i znaczenie w technologii z˙ ywno´sci. Nauka Przyroda Technol 2:1–13 (2010). 20 Budryn G and Nebesny E, Fenolokwasy – ich wła´sciwo´sci, wystepowanie w surowcach ro´slinnych, wchłanianie i przemiany ¸ metaboliczne. Bromatol Chem Toksyk 2:103–110 (2006). 21 Gawlik-Dziki U, Fenolokwasy jako bioaktywne składniki z˙ ywno´sci. Zywn-Nauk Technol Ja 4:29–40 (2004). ¨ 22 Lombardo S, Pandino G, Mauromicale G, Knodler M, Carle R and Schieber A, Influence of genotype, harvest time and plant part on polyphenolic composition of globe artichoke. Food Chem 119:1175–1181 (2010). 23 Pandino G, Lombardo S, Mauromicale G and Williamson G, Profile of polyphenols and phenolic acids in bracts and receptacles of globe artichoke (Cynara cardunculus var. scolymus) germplasm. J Food Compos Anal 24:148–153 (2011). 24 Lutz M, Henr´ıquez C and Escobar M, Chemical composition and antioxidant properties of mature and baby artichokes (Cynara scolymus L.), raw and cooked. J Food Compos Anal 24:49–54 (2011). 25 Liu P, Kallio H, Lu¨ D, Zhou C and Yang B, Quantitative analysis of phenolic compounds in Chinese hawthorn (Crataegus spp.) fruits by high performance liquid chromatography–electrospray ionization mass spectrometry. Food Chem 127:1370–1377 (2011). 26 AOAC International, Official Methods of Analysis (17th edn). AOAC International, Gaithersburg, MD (2000). 27 Farah A, De Paulis T, Trugo LC and Martin PR, Effect of roasting on the formation of chlorogenic acid lactones. J Agric Food Chem 53:1505–1513 (2005). ´ 28 Makarska E and Michalak M, Aktywno´sc´ przeciwutleniaja¸ ca kwasow fenolowych jeczmienia jarego. Ann Univ Mariae Curie-Skłodowska ¸ 60:263–269 (2005). 29 Bondia-Pons I, Aura A-M, Vuorela S, Kolehmainen M, Mykk¨anen H and Poutanen K, Rye phenolics in nutrition and health. J Cereal Sci 49:323–336 (2009). 30 Zhang Z, Chang Q, Zhu M, Huang Y, Ho WKK and Chen Z-Y, Characterization of antioxidants present in hawthorn fruits. J Nutr Biochem 12:144–152 (2001). 31 Semmelroch P and Grosch W, Analysis of roasted coffee powders and brews by gas chromatography-olfactometry of headspace samples. Lebensm Wiss Technol 28:310–313 (1995). 32 Chin S-T, Eyres GT and Marriott PJ, Identification of potent odorants in wine and brewed coffee using gas chromatography-olfactometry and comprehensive two-dimensional gas chromatography. J Chromatogr A 1218:7487–7498 (2011). 33 Czerny M, Mayer F and Grosch W, Sensory study on the character impact odorants of roasted Arabica coffee. J Agric Food Chem 47:695–699 (1999).
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Revised: 10 October 2013
Accepted article published: 12 December 2013
Published online in Wiley Online Library: 22 January 2014
(wileyonlinelibrary.com) DOI 10.1002/jsfa.6532
Chlorogenic acid in raw materials for the production of chicory coffee ´ b Renata Zawirska-Wojtasiak,a∗ El˙zbieta Wojtowicz,b Krzysztof Przygonski and Mariola Olkowiczc Abstract BACKGROUND: Chicory coffee is produced from traditional raw materials. Other materials are added to improve its aroma. The aim of this study was to test new raw materials with a high content of chlorogenic acid (CGA) as the criterion for their selection. This acid is degraded in the course of roasting and is a source of phenolic compounds affecting coffee aroma. For this reason, contents of CGAs were analyzed in traditional and new materials before and after roasting and compared with the chemicals formed in the roasted pure standard of chlorogenic acid (5-CQA). RESULTS: It was shown that the novel raw materials contained considerable amounts of 5-CQA, frequently higher than in traditional chicory. The roasting process caused significant losses of 5-CQA in the tested raw materials, amounting to 55–91%. In turn, the analysis of volatile compounds in roasted materials showed the presence of certain phenolic and heterocyclic compounds that were also formed as degradation products of the pure 5-CQA chemical standard. CONCLUSION: Novel raw materials, mainly chokeberry, artichoke and lovage, are rich sources of CGAs, particularly 5-CQA. Their application in the production of chicory coffee may result in an increased content of primarily phenolic compounds in its aroma. c 2013 Society of Chemical Industry Keywords: chlorogenic acid; chicory coffee; raw materials; aroma; roasting
INTRODUCTION
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Chicory coffee is a beverage obtained from chicory, barley, rye and sugar beet. Its sensory attributes are similar to those of natural coffee, making it a beverage of choice for people who because of health concerns should not consume natural coffee (e.g. owing to its caffeine content). Chicory coffee is becoming increasingly popular as a wellness product. Coffee drinkers value first of all its unique aroma. For gourmets the aroma of coffee released in the course of brewing is associated with one of the most pleasant moments in their everyday routine. Components found in raw materials used to produce chicory coffee and substances formed during the roasting process provide it with unique sensory attributes. For the aroma of chicory coffee to resemble that of natural coffee, apart from traditional raw materials in its production, we may also use novel materials rich in chlorogenic acid (CGA),1 – 3 which is one of the precursors of aroma compounds in natural coffee and results in the formation of coffee pigments and taste.4 – 9 Coffee is a very rich aroma product studied by many authors.4,8,10 – 13 Over 1200 compounds have been reported, among them the main important furans, pyrazines, pyrroles and thiols. The formation of most of these compounds has been characterized by pathways derived via the Maillard reaction. However, the formation of some compounds such as phenols, benzoic acid and catechols in roasted coffee is difficult to explain by the Maillard reaction alone.7 According to some authors, CGAs are precursors of the important coffee volatiles mentioned above.4 – 8 A high content of CGA was the criterion for selection of the novel raw materials used in this study, namely artichoke, hawthorn J Sci Food Agric 2014; 94: 2118–2123
fruit, lovage, blueberry and chokeberry. Independently of the typical aromas of these novel raw materials, during the roasting process they changed dramatically to develop a roasted-like aroma together with the scent of coffee. Since CGA is found in the form of various isomers, we may refer to CGAs. CGAs are a family of esters formed between quinic acid and certain trans-cinnamic acids, most commonly caffeic, p-coumaric and ferulic acids. Using a more general definition, all esters of quinic acids and their diastereomers can be considered as CGAs.14 The following CGAs are most commonly found in nature: 5-O-caffeoylquinic acid, conventionally called chlorogenic acid (5-CQA), 4-O-caffeoylquinic acid, also referred to as cryptochlorogenic acid (4-CQA), and 3-O-caffeoylquinic acid, also called neochlorogenic acid (3-CQA). Green coffee beans are a rich source of 5-CQA, which is transformed during the roasting process. Many literature sources indicate considerable losses of 5-CQA, which is degraded or
∗
Correspondence to: Renata Zawirska-Wojtasiak, Department of Food Science and Nutrition, Pozna´n University of Life Sciences, PL-60-637, Pozna´n, Poland. E-mail: [email protected]
a Department of Food Science and Nutrition, Pozna´n University of Life Sciences, PL-60-637, Pozna´n, Poland b Department of Food Concentrates and Starch Products, Institute of Agricultural and Food Biotechnology, Pozna´n, Poland c Department of Biotechnology and Food Microbiology, Pozna´n University of Life Sciences, Pozna´n, Poland
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Chlorogenic acid in raw materials for chicory coffee isomerized as a result of roasting.4,15 With very dark roasting, these losses may be as high as 90%. Farah and Donangelo8 found that after a short roasting time (∼7% weight loss) the level of 5-CQA decreased considerably while those of 4-CQA and 3-CQA increased twofold as a result of isomerization occurring at the beginning of the roasting process. A longer roasting time led to the complete loss of 5-CQA. Clifford16,17 stated that during the early roasting stages the isomerization process is accompanied by partial hydrolysis of quinic acid and cinnamic acids (including caffeic acid). Released cinnamic acids may undergo decarboxylation, degradation to simple phenolic acids and further transformations. The remaining quinic acid is dehydrated and a lactone ring is formed. Lactones are formed only with those acids in which position 5 of quinic acid is free, i.e. 4-CQA and 3-CQA.8,17 Literature sources report that thermal degradation of 5-CQA causes the formation of phenolic derivatives, resulting in marked differences between the aroma of natural coffee and those of its substitutes.2,5,16 The major volatile phenolic compounds in natural coffee are guaiacol, 4-ethylguaiacol and 4-vinylguaiacol, while di- and triphenolic compounds primarily include catechol, 4-ethylcatechol and pirogalol. Model studies have shown that guaiacol comes from the degradation of ferulic acid arising from feruloylquinic acid (FQA). In turn, catechol and pirogalol come from transformations of quinic acid and 5-CQA. Certain catechols may also come from derivatives of caffeic acid.6 According to a recent study, 1,4-diketones such as 1,4cyclohexanedione are among the degradation products obtained in model roasting of 5-CQA. However, their share in the aroma of roasted coffee has not been explained. It was only stated that 5-CQA and its lactones are also responsible for the bitter and tart taste of coffee.7 5-CQA is a secondary metabolite produced by plants in response to environmental stress conditions such as infections caused by pathogenic microorganisms, mechanical damage and excessive UV radiation.5,8,18 – 20 In relation to its protective function in plants, considerable amounts of 5-CQA are found during plant growth and fruit ripening. This compound is contained in many fruits and vegetables, e.g. potatoes, cacao beans, plums, apples, artichokes, hawthorn fruits, blueberries and lovage.15,20,21 The main CGAs found in artichoke (Cynara scolymus L.) include 5-CQA and 1,5O-dicaffeoylquinic acid (cynarine), with 5-CQA present at 0.2–2.1 g kg−1 dry matter (DM) depending on the plant genotype and plant part analyzed.22 – 24 In hawthorn (Crataegus spp.) the 5-CQA level ranges from 0.2 to 1.6 g kg−1 DM, with its content varying depending on the species and variety.24,25 Traditional chicory coffee is produced primarily from roasted chicory roots, a mixture of roasted cereal grains and sugar beet. In order to improve or add variety to the aroma of chicory coffee, small amounts of additives characterized by attractive aromas are also used. This study evaluated five novel raw materials for the production of chicory coffee, with a high content of 5-CQA being the selection criterion.
EXPERIMENTAL
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(Vaccinium myrtillus L.) and chokeberry (Aronia melanocarpa), were purchased from retail outlets. Artichokes were reprocessed to isolate their hearts, which were dried then in a laboratory drier at 60 ◦ C. Novel raw materials were roasted. All raw materials before and after roasting were ground using a WZ˙ 1 laboratory mill (ZBPP, Bydgoszcz, Poland). Roasting treatment All raw materials were roasted in a BRZ 2/4/6 sample roaster battery (PROBAT, Emmerich am Rhein, Germany). Raw materials (100 g) were roasted under various conditions – 180 ◦ C/10 min for chicory, 170 ◦ C/12 min for rye, barley and sugar beet, 160 ◦ C/8 min for artichoke, hawthorn fruit, blueberry and chokeberry and 160 ◦ C/18 min for lovage – to obtain dark roasts. Samples of 2 g of standard 5-CQA were roasted in sealed 10 mL vials at 160 ◦ C for 20 min. Assay of chlorogenic acid Extraction CGAs contained in plant origin raw materials were extracted using AOAC method 957.04.26 In order to ensure greater efficiency and to adapt the method for assays of the tested materials, the procedure was modified by increasing the amount of sample and repeating the extraction four times. Samples of approximately 0.5 g of raw material were weighed into 10 mL test tubes. Then 3 mL of deionized water was added and the test tube contents were mixed thoroughly to prevent caking. Next, 7 mL of 960 mL L−1 99.9% ethanol was added and the test tube contents were shaken. Finally, the samples were centrifuged and the eluates were transferred to 50 mL volumetric flasks and supplemented with deionized water. The whole procedure was repeated three times. Analysis of CGAs by liquid chromatography/mass spectrometry (LC/MS) and high-performance liquid chromatography (HPLC) HPLC analysis was performed using an Agilent Technologies (Wilmington, Del, USA) 1200 HPLC system equipped with a Supelco ˚ 3 (Bellefonte, PA., USA) C18 column (150 mm × 4.6 mm, 100 A, µm). Binary gradient elution was carried out using a solvent system with phase A consisting of water/methanol (95:5 v/v) containing 1 mL L−1 99.0% formic acid and phase B consisting of methanol/water (60:40 v/v) containing 1 mL L−1 99.0% formic acid. The gradient profile was as follows: 0–1 min, 0% B; 1–5 min, 0–25% B; 5–9 min, 25% B; 9–15 min, 25–80% B; 15–16 min, 80–100% B; 16–30min, 100% B; 30–31 min, 100–0% B; 31–36 min, 0% B. The flow rate was 0.4 mL min−1 , the column temperature was 30 ◦ C and the injection volume was 10 µL. An Agilent 6224 time-of-flight (TOF) LC/MS system with electrospray ionization (ESI) and a TOF analyzer (in negative ion polarization mode for acid analyses and in positive ion polarization mode for other phenolic compounds) was used for ion monitoring within the range m/z 50–1700. The voltage applied to the capillary column was 4 kV, the gas pressure in the nebulizer was 20 psi and the fragmenter voltage was 214 V. Assays of 5-CQA were performed in a Dionex Corporation (Sunnyvale, CA, USA) LC system equipped with the same column and using the same gradient parameters. The 5-CQA present in each sample was identified by comparing its retention time and spectrum with the standard using a photodiode array detector (PAD). CGAs were quantified from absorbances recorded in the chromatograms relative to external standards of 5-CQA, with detection at 325 nm. A standardization curve was prepared based on the following concentrations of 5-CQA standard (SigmaAldrich, Steinheim, Germany): 1, 5, 10, 20, 50 and 100 µg mL−1 .
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Samples Traditional raw materials for the production of chicory coffee were obtained from a production plant of CYKORIA SA (Wierzchosławice, Poland). They included chicory (Cichorium intybus), rye (Secale L.), barley (Hordeum L.) and sugar beet (Beta vulgaris L.) before and after roasting. Novel raw materials, i.e. artichoke (C. scolymus L.), hawthorn fruit (Rosaceae), lovage (Levisticum officinale), blueberry
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R Zawirska-Wojtasiak et al.
Table 1. Identification and proportions of individual isomers in total CGAs by LC/MS in raw materials before/after roasting (%/%) Compound (abbreviation)
RT (HPLC)
3-O-Caffeoylquinic acid (3-CQA)
17.385
Glycoside of delphinidin 3-O-p-Coumaroylquinic acid (3-pCoQA)
18.719 19.394
5-O-Caffeoylquinic acid, chlorogenic acid (5-CQA)
19.803
4-O-Caffeoylquinic acid (4-CQA)
20.172
Caffeoylshikimic acid (CSA)
21.375
5-O-p-Coumaroylquinic acid (5-pCoQA) 3-O-Feruloylquinic acid (3-FQA)
21.361 22.084
3,5-Di-O-caffeoylquinic acid (3,5-diCQA)
22.487
Derivative of p-coumaric acid 4,5-Di-O-caffeoylquinic acid (4,5-diCQA)
22.860 23.065
Caffeoylhexose
23.287
Derivative of apigenin Quercetin glycosides Quercetin-3-rutinoside
24.324 23.407 23.410
m/z (MS/MS)
C
S
A
191.0875 179.0653 161.0534 135.0713 303.0525 191.0871 173.0757 163.0691 191.0878 161.0536 191.0872 179.0649 163.0694 135.0707 179.0657 161.0538 135.0716 191.0883 193.1187 191.0929 149.1011 353.1330 191.0897 135.0737 163.0705 353.1334 179.0678 179.0659 135.0722 269.0825 303.0527 463.1378 300.0686
–/–
–/–
–/10
–/–
–/–
–/–
H
L
B
Ch
42/–
2/7
–/–
46/15
–/–
–/–
–/–
tr/–
–/–
–/–
–/–
17/–
–/–
–/–
–/–
61/100
61/100
48/52
39/100
72/71
100/100
51/73
–/–
–/–
–/tr
2/–
tr/3
tr/tr
3/1
–/–
–/–
–/5
–/–
–/19
–/–
–/11
–/– –/–
–/– –/–
2/8 –/–
–/– –/–
1/– 10/–
–/– –/–
–/– –/–
26/–
39/–
44/24
–/–
8/–
–/–
–/–
–/– 13/–
–/– –/–
–/– 6/1
–/– –/–
–/– 5/–
tr/tr –/–
–/– –/–
–/–
–/–
–/–
–/–
tr/–
–/–
–/–
–/– –/– –/–
–/– –/– –/–
tr/– –/– –/–
–/– –/– tr/–
–/– –/– –/–
–/– tr/– –/–
–/– –/– –/–
RT, retention time (min); C, chicory; S, sugar beet; A, artichoke; H, hawthorn; L, lovage; B, blueberry; Ch, chokeberry; –, not identified; tr, trace amount.
The coefficient of determination of the standardization curve was 0.999. The detection limit was 0.03 µg mL−1 . The applied method was characterized by a high recovery rate of 101.4%. The proportions of individual CGA isomers assayed in the raw materials were determined as a percentage of total CGAs. Analysis of volatile compounds Volatile compounds were identified using an Agilent 5975C VL GC/MSD system equipped with an HP-5MS capillary column (30 m × 0.25 mm, 0.25 µm). Extraction was performed by the solid phase microextraction (SPME) technique using a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibre at 70 ◦ C for 20 min. The carrier gas used was helium at a flow rate 1 mL min−1 . The temperature programme was as follows: hold for 5 min at 35 ◦ C; increase at 30 ◦ C min−1 to 60◦ C; increase at 6 ◦ C min−1 to 200 ◦ C; increase at 30 ◦ C min−1 to 280 ◦ C. Mass spectra were compared with data from the NIST05 library (containing 163 198 unique compounds).
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Statistical analysis All data were expressed as mean ± standard deviation (n = 3). Statistical analyses were conducted using Student’s t test. Values with P < 0.05 were considered statistically significant. STATISTICA 9.0 software (StatSoft, Krakow, Poland) was used for all analyses.
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RESULTS AND DISCUSSION CGAs were identified by HPLC/LC/MS. Identified compounds are listed in Table 1 along with their proportions before and after roasting. Based on collected data, 5-CQA was found in chicory and sugar beet but was not detected in the other two traditional raw materials, i.e. rye and barley. However, it was found in all novel raw materials selected to improve the aroma of chicory coffee. In this study the presence of several other compounds from the CGA family was also detected. These included 3-CQA, 4-CQA, 3-O-feruloylquinic acid (3-FQA), 3,5-di-O-caffeoylquinic acid (3,5diCQA) and 4,5-di-O-caffeoylquinic acid (4,5-diCQA), as similarly found by Farah et al.27 in natural coffee. However, 4-FQA, 5-FQA and 3,4-diCQA were not detected in any tested raw material, in contrast to the results presented by Farah et al.27 Other CGAs were detected in artichoke and lovage before roasting, i.e. 5-O-p-coumaroylquinic acid (5-pCoQA), and in hawthorn before roasting, i.e. 3-O-p-coumaroylquinic acid (3-pCoQA). Apart from the above-mentioned compounds, the following were also detected: caffeoylshikimic acid (CSA), a derivative of p-coumaric acid, caffeoylhexose, a glycoside of delphinidin, quercetin-3rutinoside, quercetin glycosides and a derivative of apigenin. Another interesting finding is the disappearance of some of the above-mentioned compounds after the roasting process; for
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Chlorogenic acid in raw materials for chicory coffee
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Table 2. 5-CQA content in traditional raw materials for chicory coffee production estimated by HPLC Before roasting Raw material Chicory Sugar beet Rye Barley
mg g−1 1.23 ± 0.03a 0.03 ± 0.01a ND ND
% of total CGAs 61.4 61.0 ND ND
Roasted % of total CGAs
mg g−1 0.43 ± 0.02b 0.02 ± 0.01b ND ND
99.9 99.0 ND ND
Results are mean ± standard deviation (n = 3). Values with the same letter in a row are not statistically different at P < 0.05 (Student’s t test). ND, not determined.
Table 3. 5-CQA content in novel raw materials for chicory coffee production estimated by HPLC Before roasting Raw material Artichoke Hawthorn Lovage Blueberry Chokeberry
mg g−1 2.90 ± 0.02a 0.19 ± 0.01a 3.25 ± 0.20a 1.07 ± 0.07a 3.97 ± 0.03a
% of total CGAs 47.8 39.4 72.5 100.0 51.2
Roasted % of total CGAs
mg g−1 0.27 ± 0.01b 0.04 ± 0.01b 0.30 ± 0.05b 0.53 ± 0.02b 2.11 ± 0.11b
51.7 100.0 70.8 100.0 73.5
Results are mean ± standard deviation (n = 3). Values with the same letter in a row are not statistically different at P < 0.05 (Student’s t test).
Isomer Chicory 3,5-diCQA 4,5-diCQA Sugar beet 3,5-diCQA Artichoke 3-CQA 4-CQA CSA 5-pCoQA 3,5-diCQA 4,5-diCQA Derivative of apigenin Hawthorn 3-CQA 3-pCoQA 4-CQA Quercetin-3-rutinoside Lovage 3-CQA 4-CQA CSA 5-pCoQA 3-FQA 3,5-diCQA 4,5-diCQA Caffeoylhexose Blueberry 4-CQA Quercetin-3-rutinoside Chokeberry 3-CQA 4-CQA CSA
Before roasting
Roasted
0.53 ± 0.08 0.27 ± 0.04
ND ND
0.02 ± 0.04
ND
ND ND ND 0.13 ± 0.02a 2.66 ± 0.12a 0.37 ± 0.08a tr
0.05 ± 0.01 tr 0.02 ± 0.01 0.04 ± 0.01b 0.13 ± 0.03b 0.01 ± 0.01b ND
1.07 ± 0.07 0.09 ± 0.02 0.01 ± 0.01 tr
ND ND ND ND
0.10 ± 0.01a tr ND 0.04 ± 0.01 0.46 ± 0.02 0.38 ± 0.01 0.27 ± 0.02 tr
0.03 ± 0.01b 0.01 ± 0.01 0.10 ± 0.01 ND ND ND ND ND
tr tr
tr ND
3.66 ± 0.24a 0.20 ± 0.02a ND
0.44 ± 0.08b 0.03 ± 0.01b 0.32 ± 0.02
Results are mean ± standard deviation (n = 3). Values in a row with the same letter are not statistically different at P < 0.05 (Student’s t test). ND, not determined; tr, trace.
content ranged from 0.19 mg g−1 in hawthorn to 3.97 mg g−1 in chokeberry. These results are comparable to those reported in the literature.22 – 25,30 Differences may be due to different cultivation conditions for the raw materials tested by other authors. Available literature sources did not present contents of 5-CQA in these raw materials after roasting. Farah et al.27 and Ferruzzi15 stated that the 5-CQA content in coffee decreased as a result of roasting and that an extended time and increased temperature of roasting caused a greater reduction in its content, amounting to as much as 85–90% in dark-roasted beans. A longer roasting time resulted in the loss of the entire 5-CQA content. In this study, 5-CQA losses after roasting reached 55–91%, which suggests that this compound was transformed and the process of its degradation was progressing. The greatest losses were recorded in artichoke and lovage, exceeding 90% of initial contents, similarly as in darkroasted coffee beans. A high loss was also found in hawthorn (79%). Contents of 5-CQA in roasted blueberry and chokeberry
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example, 3-CQA and 3-pCoQA normally found in hawthorn and 5-pCoQA normally found in artichoke were not detected in those raw materials after roasting. Thus it may be assumed that, as a result of roasting, other acids belonging to the CGA family are also degraded in hawthorn and artichoke. In turn, after roasting, some CGAs appeared that had not been found in the raw materials before roasting; for example, 4-CQA detected in artichoke after roasting was not identified in that plant prior to roasting. This is an example of isomerization.8,17 In roasted artichoke, lovage and chokeberry, CSA was also identified, which is a product of 5-CQA dehydratation.17,27 Some authors reported the total content of compounds belonging to the CGA family.16 This study focused on the determination of 5-CQA content. In the tested raw materials before roasting, this compound was found in highest amounts, its proportion being 48–100% of total CGAs. After roasting, the proportion of 5-CQA in the raw materials amounted to 52–100% of total CGAs. Hawthorn was an exception in this respect, as the proportion of 5-CQA before roasting was only 39% of total CGAs. Among the traditional raw materials used for the production of chicory coffee, a significant amount of 5-CQA was contained only in chicory, namely 1.23 ± 0.03 g kg−1 (Table 2). In sugar beet, only 0.03 g kg−1 5-CQA was detected, while no 5-CQA was detected in the other two traditional raw materials, i.e. rye and barley. Literature sources also did not indicate the presence of CGAs in cereals. The main phenolic acids found in barley and rye included ferulic, sinapic, coumaric and caffeic acids.28,29 Contents of 5-CQA in the novel raw materials before and after roasting are presented in Table 3. Prior to roasting, its J Sci Food Agric 2014; 94: 2118–2123
Table 4. Content of isomers other than 5-CQA in traditional and novel raw materials for chicory coffee production estimated by HPLC (mg g−1 )
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R Zawirska-Wojtasiak et al.
Table 5. Identification and composition of chemicals formed from pure chlorogenic acid (5-CQA) and present in roasted raw materials (% of total volatiles) Compound
Odour description
RI
Acetic acid Hexanal Furfural Oxime-methoxy-phenyl 5-Methylfurfural Phenol Hexanoic acid 3-Furylmethyl acetate 1-Hexanol-2-ethyl 2-Methoxy-6-methyl-pyrazine 2-Ethylhexanoic acid 2,3-Dihydroxybenzaldehyde 5-Hydroxymethyl-2-furancarboxaldehyde 2-Ethylfuran 4-Methoxyphenol 2-Methoxy-4-vinylphenol (vinylguaiacol) 4-Ethylphenol 4-Ethylcatechol
Pungent Fresh, green Freshly baked bread
667 817 855 915 965 982 991 998 1029 1086 1142 1209 1225 1242 1255 1264 1356 1454
Almond, carmel Sweet, tarry Sweat-like
Roasted nut
Cotton candy Smoky, burnt Spicy, smoky, clove Phenolic, spicy Phenolic, spicy
Coffee
5-CQA
+ + + + + +
+ + + +
22.7 0.9 8.4 0.9 2.7 16.0 1.3 3.6 1.8 7.3 2.7 0.7 6.9 1.1 8.4 7.1 1.3 6.2
C
A
H
L
B
Ch
2.0 — 25.0 — 9.4 — 0.3 — 0.2 0.8 — — 20.2 — 0.2 — — —
6.6 0.4 10.7 0.6 9.1 2.3 — 1.0 — 1.0 — 0.4 2.5 0.4 1.3 2.8 0.5 1.1
10.7 0.2 1.7 — 2.5 — — — — — — — — — — 1.4 1.1 —
— — 8.9 — 1.4 — — — 0.8 1.4 — — 1.8 — 1.3 1.6 0.5 —
0.6 0.5 47.5 — 2.3 — 0.2 — — — — — — — — — — —
5.2 — 7.0 — 1.3 — — — 0.5 — — 0.2 1.0 — — — — —
RI, retention index; C, chicory; A, artichoke; H, hawthorn; L, lovage; B, blueberry; Ch, chokeberry; +, compounds identified in coffee from literature.31 – 33
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amounted to 50% of initial levels. In roasted chicory the content of 5-CQA decreased by 65%, which is comparable to that in medium-roasted coffee beans. Observations for sugar beet cannot be compared owing to the low level of 5-CQA, which prevented sufficiently precise determinations. The roasting process resulted also in losses of other compounds from the CGA family in the raw materials before and after roasting, causing changes in their percentage contents (Table 1). These changes result from the depletion of compounds contained in low amounts and the potential formation of the above-mentioned isomers. In some cases, only 5-CQA remained (in hawthorn, chicory and sugar beet). The contents of isomers other than 5-CGA identified in the traditional and novel materials are presented in Table 4. Significant amounts (>1 mg g−1 ) of other isomers were found for 3,5-diCQA in artichoke, 3-CQA in hawthorn and 3-CQA in chokeberry, but only before roasting. In the roasted materials the amounts of these compounds were very low or even undetectable. The differences seen in this work may depend only on the character and composition of the raw materials. This is because the conditions of roasting, which undoubtedly influence the reactions, were the same for all materials used. According to the data obtained, the content of CGAs in the individual raw materials was different. The amount of 5-CQA remaining after roasting depended mostly on its concentration in the material before the process. In the novel raw materials the presence of higher numbers of isomers other than 5-CQA in comparison with traditional chicory might be the reason for the distinction in composition after processing. It results from literature data on natural coffee that phenolic volatile compounds may be formed from 5-CQA.2,4 For this reason the present study included experimental degradation of the pure 5-CQA standard under similar conditions to those applied in roasting the novel raw materials. Volatile compounds formed as a result of this process were identified and are listed in Table 5. Their amounts are expressed as a percentage of total volatiles identified with spectral similarity over 80%. The amounts of presented
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compounds derived from CGAs ranged from 15.2% (chokeberry) to 58.1% (chicory) of total volatiles. They include heterocyclic compounds, acids and phenols (oxime-methoxy-phenyl, phenol, 2,3-dihydroxybenzaldehyde, 4methoxyphenol, 2-methoxy-4-vinylphenol, 4-ethylphenol, 4ethylcatechol). The data in Table 5 also show that some of them are present in the novel raw materials used in this study. It is noteworthy that they were identified by other authors7 as products of thermal degradation of CGAs as well as in the aroma of natural coffee.9 – 13 Some of them are recognized as important odorants in coffee aroma, such as 4-methoxyphenol and 2-methoxy-4-vinylphenol originating from 5-CQA. The latter compound was present in roasted artichoke, hawthorn and lovage but not in chicory (Table 5). Odours of the identified chemicals formed from CGAs are described as caramel-like, burnt, smoky and spicy. Taking into account the amounts and composition of the compounds originating from 5-CQA, the most interesting new raw material seems to be artichoke. The results of this study confirm the opinion of other authors that the formation pathways of the compounds discussed above start with CGAs.7
CONCLUSIONS 1. In the traditional and proposed novel raw materials for the production of chicory coffee, apart from 5-CQA, other compounds from the CGA family were also identified, e.g. 3CQA, 4-CQA, 3,5-diCQA, 4,5-diCQA and 3-pCoQA. The highest numbers of these compounds were recorded in chicory, artichoke, lovage and hawthorn. 2. Among the traditional raw materials, chicory was the only significant source of 5-CQA. The novel raw materials proved to be good sources of 5-CQA, and even such materials as
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Chlorogenic acid in raw materials for chicory coffee chokeberry, artichoke and lovage contained greater amounts of this acid than chicory. 3. 5-CQA was the predominant acid, but its content was considerably depleted as a result of roasting. Moreover, losses of other CGAs caused by roasting were also observed. 4. In the proposed novel raw materials for the production of chicory coffee the same compounds were detected after roasting as those identified after experimental degradation of pure 5-CQA. 5. The best of the raw materials analyzed for chicory coffee production was artichoke, since it was a good source of CGAs and produced the highest number of volatiles during roasting, particularly those important in coffee aroma such as 2-methoxy4-vinylphenol.
ACKNOWLEDGEMENT This study was financially supported by the National Centre of Science, Poland (grant 2011/01/B/NZ9/01060).
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