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This study examined the influence of consumer behavior on furan, 2-methylfuran, 3-methylfuran, 2,5-dimethylfuran and 2,3-dimethylfuran exposure in coffee. Coffees brewed using a filter, fully automatic, capsule machine or reconstituted instant coffee were found to have a significant different cup concentrations of furan derivatives. Coffee brewed with the fully automatic machine contained the highest furan and furan derivative concentrations (99.05 µg/L furan, 263.91 µg/L 2-methylfuran, 13.15 µg/L 3-methylfuran and 8.44 µg/L 2,5-dimethylfuran) whereas soluble coffee did not contain detectable levels, thereby contributing least to a consumer’s dietary exposure. Furan and furan derivative concentrations were found to decrease significantly upon cooling, reducing consumer exposure by 8.0–17.2 % on average once the coffee reached drinking temperature 55–60 °C, in ceramic cups. Serving coffee in a ceramic or disposable cup were found to influence the cooling dynamics of the coffee but did not statistically influence the consumers exposure at a given temperature.

Introduction Coffee is a widely consumed beverage containing antioxidant active compounds. During roasting the phytochemical composition of the coffee bean changes dramatically and highly polymeric substances are produced. Besides chlorogenic acids that are already present in green coffee beans, melanoidins show antioxidant capacity as well. Objective To employ post-column derivatisation by coupling high performance size exclusion chromatography (HPSEC) to an antioxidant assay to investigate the effect of roasting on the properties of antioxidant active compounds in coffee brews. Methodology We have investigated the antioxidant capacity of Coffea arabica (Arabica) and C. canephora (Robusta) beans that were roasted over the full spectrum of roast conditions (four roasting speeds to three roast degrees) by comparing the results from HPSEC coupled on-line to the ABTS assay with those from two batch assays, Folin Ciocalteu (FC) and oxygen radical absorbance capacity (ORAC) assay. Results The antioxidant capacity showed a general decrease towards slower and darker roasted coffee for all three assays, indicative of heat degradation of active compounds. Hence, low molecular weight (LMW) compounds such as chlorogenic acids (CGAs) decreased progressively already from relatively mild roasting conditions. In contrast, high molecular weight (HMW) compounds (e.g. melanoidins) increased from light to dark roast degrees with lowering magnitude towards slower roasting profiles. Conclusion By coupling HPSEC on-line to the ABTS assay we were able to separately quantify the contribution of HMW and LMW compounds to the total antioxidant capacity, increasing our understanding of the roast process. © 2016 The Authors. Phytochemical Analysis Published by John Wiley & Sons Ltd.

An oxygen scavenger based on a catalytic system with palladium (CSP) was recently developed to remove oxygen in food packagings. Although the CSP worked with various types of food, with some foods, an inhibition of the CSP was observed. Because such catalytic systems are susceptible to poisoning by sulfur-containing compounds, the aim of this study was to understand the inactivation of palladium-based catalysts in presence of foods containing volatile sulfur compounds (VSCs). To achieve this, the oxygen scavenging activity (OSA) of the CSP was evaluated in presence of selected food products. Afterwards, VSCs mainly present in these foods were exposed to the CSP, and the influence on the OSA was evaluated. Finally, headspace analysis was performed with the diluted VSCs and with the packaged food products using proton transfer reaction time-of-flight mass spectrometry. It was found that the catalytic activity of the CSP was inhibited when VSCs were present in the headspace in concentrations ranging between 10.8–36.0 ppbv (dimethyl sulfide, DMS), 1.2–7.2 ppbv (dimethyl disulfide), 0.7–0.9 ppbv (dimethyl trisulfide), 2.1–5.8 ppbv (methional) and 4.6–24.5 ppbv (furfuryl thiol). It was concluded that in packaged roast beef and cheese, DMS may be the compound mainly responsible for the inactivation of the CSP. In packagings containing ham, the key compounds were hydrogen sulfide and methanethiol; in peanuts, it was methanethiol; and in par-baked buns, an accumulation of methional, DMS, butanethiol and methionol. When potato chips were packaged, it was demonstrated that when VSCs are present in low concentrations, oxygen can still be scavenged at a reduced OSA.

Oxygen scavenging film based on a catalytic system with palladium (CSP) was used to prevent lipid oxidation in linseed oil. Linseed oil was packaged under normal (NA) or modified atmosphere with 2 vol% oxygen (MA) with or without the CSP and stored at 45 °C for 6 months in darkness. To evaluate the evolution of primary and secondary oxidation products, conjugated dienes/trienes, peroxide and para-anisidine values were measured. Additionally, volatile oxidation products in the headspace were analyzed. While a significantly higher level of oxidation products was measured in linseed oil stored under NA compared to MA without CSP, thresholds indicating good quality oil based on the peroxide value (15 milliequivalents O2/g oil) and the para-anisidine value (2 absorbance units/g oil) were exceeded under both packaging conditions. In packages with the CSP, however, removal of headspace oxygen kept oxidation parameters below these thresholds, indicating good quality oil over the whole storage period.

Coffee is a relatively young caffeinated beverage, known in Western Europe since the 17th century. Initially consumed in Europe by the aristocracy, coffee has developed into one of the world's most popular beverages. The unique aroma is without doubt one of the key drivers for its rise in consumption. Over the past two decades, research on coffee aroma has mostly focused on two areas. (1) Identification and quantification of aroma relevant volatile compounds. This led to the publication of lists of sensory relevant (impact/key) compounds, together with their chemical and sensory properties. (2) Elucidation of the formation and degradation mechanisms of coffee aroma compound. After a period of consolidation of all these insights, the focus is shifting to new areas: (i) time-resolved studies of coffee aroma formation, release and degradation; (ii) study of different types of interactions and the development of an increasingly holistic approach to aroma perception; (iii) prediction of sensory profiles from instrumental data.

Coffee has been determined as the dominant source of furan within an adult’s diet. This study investigates the influence of coffee condiment use and stirring on the retention of furan. Three condiment lipid compositions were investigated, 0%, 3.5% and 35%, and kept at either 4 °C, 20 °C or 70 °C before addition to a freshly brewed cup of filter coffee which was subsequently mechanically stirred at three intensities, not stirred and moderately or heavily stirred. While five furans were monitored, furan, 2-methylfuran, 3-methylfuran, 2,5-dimethylfuran and 2,3-dimethylfuran, only two were quantifiable: furan and 2-methylfuran. Increasing condiment lipid concentration significantly increased retention of furan and 2-methylfuran, whereas stirring the coffee significantly increased furan release. A condiment temperature of 70 °C was found to significantly increase furan release.

During the roasting of coffee, thermally driven chemical reactions lead to the formation of gases, of which a large fraction is carbon dioxide (CO2). Part of these gases is released during roasting while part is retained inside the porous structure of the roasted beans and is steadily released during storage or more abruptly during grinding and extraction. The release of CO2 during the various phases from roasting to consumption is linked to many important properties and characteristics of coffee. It is an indicator for freshness, plays an important role in shelf life and in packaging, impacts the extraction process, is involved in crema formation, and may affect the sensory profile in the cup. Indeed, and in view of the multiple roles it plays, CO2 is a much underappreciated and little examined molecule in coffee. Here, we introduce an accurate, quantitative, and time-resolved method to measure the release kinetics of gases from whole beans and ground coffee using a gravimetric approach. Samples were placed in a container with a fitted capillary to allow gases to escape. The time-resolved release of gases was measured via the weight loss of the container filled with coffee. Long-term stability was achieved using a customized design of a semimicro balance, including periodic and automatic zero value measurements and calibration procedures. The novel gravimetric methodology was applied to a range of coffee samples: (i) whole Arabica beans and (ii) ground Arabica and Robusta, roasted to different roast degrees and at different speeds (roast air temperatures). Modeling the degassing rates allowed structural and mechanistic interpretation of the degassing process.

Resonance-enhanced multiphoton ionisation time-of-flight mass spectrometry (REMPI-TOFMS) enables the fast and sensitive on-line monitoring of volatile organic compounds (VOC) formed during coffee roasting. On the one hand, REMPI-TOFMS was applied to monitor roasting gases of an industrial roaster (1500 kg/h capacity), with the aim of determining the roast degree in real-time from the transient chemical signature of VOCs. On the other hand, a previously developed μ-probe sampling device was used to analyse roasting gases from individual coffee beans. The aim was to explore fundamental processes at the individual bean level and link these to phenomena at the batch level. The pioneering single-bean experiments were conducted in two configurations: (1) VOCs formed inside a bean were sampled in situ, i.e. via a drilled μ-hole, from the interior, using a μ-probe (inside). (2) VOCs were sampled on-line in close vicinity of a single coffee bean's surface (outside). The focus was on VOCs originating from hydrolysis and pyrolytic degradation of chlorogenic acids, like feruloyl quinic acid and caffeoyl quinic acid. The single bean experiments revealed interesting phenomena. First, differences in time–intensity profiles between inside versus outside (time shift of maximum) were observed and tentatively linked to the permeability of the bean's cell walls material. Second, sharp bursts of some VOCs were observed, while others did exhibit smooth release curves. It is believed that these reflect a direct observation of bean popping during roasting. Finally, discrimination between Coffea arabica and Coffea canephora was demonstrated based on high-mass volatile markers, exclusively present in spectra of Coffea arabica. Copyright © 2013 John Wiley & Sons, Ltd.

We introduce a real-time method to monitor the evolution of oak aromas during the oak toasting process. French and American oak wood boards were toasted in an oven at three different temperatures, while the process-gas was continuously transferred to the inlet of a proton-transfer-reaction time-of-flight mass spectrometer for online monitoring. Oak wood aroma compounds important for their sensory contribution to oak-aged wine were tentatively identified based on soft ionization and molecular mass. The time-intensity profiles revealed toasting process dynamics illustrating in real-time how different compounds evolve from the oak wood during toasting. Sufficient sensitivity was achieved to observe spikes in volatile concentrations related to cracking phenomena on the oak wood surface. The polysaccharide-derived compounds exhibited similar profiles; whilst for lignin-derived compounds eugenol formation differed from that of vanillin and guaiacol at lower toasting temperatures. Significant generation of oak lactone from precursors was evident at 225 oC. Statistical processing of the real-time aroma data showed similarities and differences between individual oak boards and oak wood sourced from the different origins. This study enriches our understanding of the oak toasting process and demonstrates a new analytical approach for research on wood volatiles.

The formation of acrylamide was measured in real time during thermal treatment (120-170 degrees C) of potato as well as in Maillard model systems composed of asparagine and reducing sugars, such as fructose and glucose. This was achieved by on-line monitoring of acrylamide released into the headspace of the samples using proton transfer reaction mass spectrometry (PTR-MS). Unambiguous identification of acrylamide by PTR-MS was accomplished by gas chromatography coupled simultaneously to electron-impact MS and PTR-MS. The PTR-MS ion signal at m/z 72 was shown to be exclusively due to protonated acrylamide obtained without fragmentation. In model Maillard systems, the formation of acrylamide from asparagine was favored with increasing temperature and preferably in the presence of fructose. Maximum signal intensities in the headspace were obtained after approximately 2 min at 170 degrees C, whereas 6-7 min was required at 150 degrees C. Similarly, the level of acrylamide released into the headspace during thermal treatment of potato was positively correlated to temperature.

The goal of this study was to better understand the correspondence between sensory perception and in-nose compound concentration. Five aroma compounds at three different concentrations increasing by factors of 4 were added to four matrixes (water, skim milk, 2.7% fat milk, and 3.8% fat milk). These were evaluated by nosespace analysis with detection by proton transfer reaction mass spectrometry (PTR-MS), using five panellists. These same panellists evaluated the perceived intensity of each compound in the matrixes at the three concentrations. PTR-MS quantification found that the percent released from an aqueous solution swallowed immediately was between 0.1 and 0.6%, depending on the compound. The nosespace and sensory results showed the expected effect of fat on release, where lipophilic compounds showed reductions in release as fat content increases. The effect is less than that observed in headspace studies. A general correlation between nosespace concentration and sensory intensity ratings was found. However, examples of perceptual masking were found where higher fat milks showed reductions in aroma compound intensity ratings, even if the nosespace concentrations were the same.

We report on the in vivo breath-by-breath analysis of volatiles released in the mouth during eating of ripe and unripe banana. The air exhaled through the nose, nosespace (NS), is directly introduced into a proton transfer reaction mass spectrometer and the time-intensity profiles of a series of volatiles are monitored on-line. These include isopentyl and isobutyl acetate, two characteristic odour compounds of ripe banana, and 2E-hexenal and hexanal, compounds typical of unripe banana. Comparing the NS with the headspace (HS) profile, two differences are outlined. First, NS concentrations of some compounds are increased, compared to the HS, while others are decreased. This indicates that the in-mouth situation has characteristics of its own—mastication, mixing/dilution with saliva, temperature and pH—which modify the aroma relative to an HS aroma. Second, we discuss the temporal evolution of the NS. While 2E-hexenal and hexanal steadily increase in the NS during mastication of unripe banana, no such evolution is observed in volatile organic compounds (VOCs) while eating ripe banana. Furthermore, ripe banana shows high VOC concentrations in the swallow breath in contrast to unripe banana.

The quality of green coffee is influenced by the degree of ripeness of the fruit at harvest. The aim of this study was to identify chemical markers differentiating between degrees of ripeness. Two coffee varieties, Catuai and Tipica, from the same farm were analysed using the following parameters and methods: caffeine and chlorogenic acid content using high-performance liquid chromatography (HPLC), sucrose content using hydrophilic interaction chromatography, high-molecular weight fraction (HMW) using high-performance size-exclusion chromatography (HPSEC) and volatile compounds using headspace solid phase micro extraction gas chromatography/mass spectrometry. The best method for differentiating between degrees of ripeness was found to be principal component analysis (PCA) based on HPLC data. HPSEC showed differences in the HMW fraction for different degrees of ripeness and both coffee varieties. Volatile profiles allowed separation of both varieties; yet, except for ripe Catuai, no separation was achieved for the degree of ripeness.

This chapter briefly reviews the roles played by free radical processes during the roasting and storage of coffee beans and solid coffee products. During roasting, free radical production occurs in distinct phases, possibly related to the Maillard and caramelization reactions. At the same time there is also generation of large quantities of molecules with antioxidant properties, thus demonstrating that antioxidant production does not necessarily equate to free radical scavenging, insofar as it is measured by current assays. Furthermore, with respect to chemical components that are associated with desirable sensory properties of coffee, free radical processes may have both beneficial and detrimental effects.

A platform composed of three complementary and validated antioxidant assays is proposed for the routine and fast assessment of the antioxidant capacity of coffee brews. Firstly, a brief review of the principles underlying antioxidant measurements in foods, and the rationale behind the development of an analytical platform for measuring the antioxidant capacity of coffee is given. A range of complementary methods is described based on either hydrogen atom or electron transfer reactions. Secondly, three total antioxidant capacity (TAC) assays are recommended for the platform. Two are based on electron-transfer reactions—the Folin–Ciocalteu (FC) assay for total phenols, and the ABTS assay, which on oxidation forms the cationic chromophore, 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonate) (ABTS•+). The third, which is based on hydrogen-atom transfer, is the oxygen radical absorbance capacity (ORAC), in which the antioxidant and the substrate fluorescein compete for thermally generated peroxyl radicals after their formation by decomposition of 2,​2′-​azobis-​2-​amidinopropane,​dihydrochloride (AAPH). Finally, validated protocols for conducting these three assays, using flow injection analysis (FIA), are presented along with actual results to illustrate their reproducibility and robustness. The three assays are combined into an analytical platform to profile and compare the antioxidant potential of a series of roasted coffee samples. Antioxidant values obtained with the same dark-roast coffee are 2103, 710, and 5868 gallic acid equivalents (GAE) for the FC, ABTS, and ORAC assays, respectively. These numbers thus reflect the different types of chemical reaction that are performed, and illustrate the fact that assays for TAC are actually selective (and hence complementary) for specific types of antioxidant molecule.

Coffee is a major source of dietary antioxidants; some are present in the green bean, whereas others are generated during roasting. However, there is no single accepted analytical method for their routine determination. This paper describes the adaption of three complementary assays (Folin-Ciocalteu (FC), ABTS and ORAC) for the routine assessment of antioxidant capacity of beverages, their validation, and use for determining the antioxidant capacities of extracts from coffee beans at different stages in the roasting process. All assays showed a progressive increase in antioxidant capacity during roasting to a light roast state, consistent with the production of melanoidins having a higher antioxidant effect than the degradation of CGAs. However, the three assays gave different numbers for the total antioxidant capacity of green beans relative to gallic acid (GA), although the range of values was much smaller when chlorogenic acid (CGA) was used as reference. Therefore, although all three assays indicated that there was an increase in antioxidant activity during coffee roasting, and the large differences in responses to GA and CGA illustrate their different sensitivities to different types of antioxidant molecule.

During coffee roasting major changes occur in coffee bean composition. Among others dark coloured melanoidins are formed, which are high molecular weight Maillard reaction products. A new approach is presented here to monitor the influence of roasting conditions on the antioxidant capacity of melanoidins and chlorogenic acids (CGAs) in a coffee brew. Validated Folin–Ciocalteu (FC) and ABTS assays were used as on-line antioxidant assays coupled (post-column) with high performance size-exclusion chromatography (HPSEC). HPSEC enabled the separation of melanoidins from CGAs and the determination of the antioxidant capacity of each fraction, within a total elution time of 25 min. Besides the on-line assay measurements, both assays were also applied off-line with flow injection analysis (FIA). The maximum antioxidant capacity was determined to be at a light-to-medium roast degree, measured with both ABTS-FIA and FC-FIA assays as well as on-line ABTS assay. With FC on-line assay the maximum was found to be at a very light roast degree. Based on the peak areas obtained with the new coupled technique the roasting effects on the variability of melanoidin and CGA contents in coffee brews were studied. The majority of melanoidins are already formed in the early stage of the roasting process and the relative contribution of melanoidins to the total antioxidant capacity increases towards darker roasts, mainly because CGAs degrade during roasting. A new parameter, the ratio of melanoidin to CGA peak area, was introduced as a possible predictor of the roast degree.

� 2016 IOP Publishing Ltd. The persistence of aroma compounds in breath after swallowing is an important attribute of the overall aroma experience during eating and drinking. It is mainly related to the coating of the oral tract with food residues and the interaction between volatile compounds and airway mucosa. We have studied the persistence of eight compounds (2,5-dimethylpyrazine, guaiacol, 4-methylguaiacol, phenylethylalcohol, ethylbutanoate, ethyloctanoate, isoamylacetate and 2-heptanone) both in-nose and in-mouth after administration of volatiles in gas phase (vapor) to five different panelists. By using volatiles in the gas phase, only the interaction with the mucosa is highlighted and the formation of a liquid coating in the oral and tracheal airway is avoided. The physicochemical properties of the compounds, mainly polarity and vapor pressure, determine the interactions of the volatiles with the airway mucosa. The use of different breathing protocols allowed the study of the differences between nasal and oral mucosa in volatile retention, with higher persistence of volatiles obtained in-mouth. Initial concentration also affected persistence, but only for compounds with high volatility and at low concentration.

Among the 100 different known Coffea species, Coffea arabica L. (Arabica) and Coffea canephora Pierre (Robusta) are the only two of commercial interest. They differ in a range of agronomic, genetic, and chemical properties. Due to the significant price difference between Arabica and Robusta, there is an economic incentive to illicitly replace Arabica with Robusta. Therefore, it is crucial to have accurate methods to determine the Robusta-to-Arabica-ratio in blends. This paper presents the proof of principle of a new and fast approach to determine the Robusta fraction in a blend based on Raman spectroscopy. The oils of two references (a pure Robusta and pure Arabica coffee) and six blends thereof consisting of different Robusta and Arabica fractions were extracted using a Soxhlet system. The solutes were analyzed by means of Raman spectroscopy without further workup. Using the intensity ratio between two Raman peaks, one characteristic for kahweol and one characteristic for fatty acids, allowed determinination of the Robusta content in a given mixture. The intensity ratio is linearly dependent on the Robusta content of the compound. Above a Robusta content of 75 wt %, kahweol was not detectable. The Raman data are in agreement with results obtained from the very time-consuming multistep DIN 10777 procedures based on HPLC.

The formation of 4-vinylguaiacol, guaiacol, and phenol during coffee roasting was monitored in real-time, using resonance enhanced multiphoton ionization and time-of-flight mass spectrometry. A model is proposed, based on two connected reaction channels. One channel, termed the “low activation energy” channel, consists of ester hydrolysis of 5-FQA followed by decarboxylation of the ferulic acid to form 4-vinylguaiacol, and finally polymerization at the vinyl group to form partly insoluble polymers (coffee melanoidins). The second “high activation energy” channel opens up once the beans have reached higher temperatures. It leads to formation of guaiacol, via oxidation of 4-vinylguaiacol, and subsequently to phenol and other phenolic VOCs. This work aims at developing strategies to modify the composition of coffee flavor compounds based on the time−temperature history during roasting. Keywords: Coffee; aroma; roasting; real-time analysis; mass spectrometry; resonant laser ionization

The stability of the coffee flavor compound furfuryl mercaptan has been investigated in aqueous solutions under Fenton-type reaction conditions. The impact of hydrogen peroxide, iron, ascorbic acid, and ethylenediaminetetraacetic acid was studied in various combinations of reagents and temperature. Furfuryl mercaptan reacts readily under Fenton-type reaction conditions, leading to up to 90% degradation within 1 h at 37 degrees C. The losses were lower when one or more of the reagents was omitted or the temperature decreased to 22 degrees C. Volatile reaction products identified were mainly dimers of furfuryl mercaptan, difurfuryl disulfide being the major compound. In addition, a large number of nonvolatile compounds was observed with molecular masses in the range of 92-510 Da. The formation of hydroxyl and carbon-centered radicals was indicated by electron paramagnetic resonance spectra using alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone or 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide as spin traps. Whereas *OH was generated by Fenton-type reactions, the C-centered radical is probably a secondary product of the reaction of *OH with various organic molecules, the reaction with furfuryl mercaptan appearing to be the most important. No evidence for S-centered radicals was seen in the spin-trapping experiments, but a sulfur-containing radical was detected when measurements were made at 77 K in the absence of spin traps.

Erworben im Rahmen der Schweizer Nationallizenzen (http://www.nationallizenzen.ch), Volatile organic compounds (VOCs), emitted from green coffee beans, during coffee roasting and from a cup of coffee, were all analysed by proton-transferreaction mass spectrometry. Firstly, the headspace (HS) of green beans was investigated. Alcohols dominate the HS, but aldehydes, hydrocarbons and organic acids were also abundant. Secondly, we roasted coffee under two different conditions and monitored on-line the VOCs emitted during the process. In a first roasting series, a batch of beans was roasted. After an initial drying phase, dominated by evaporation of water and methanol, the HS concentrations of VOCs such as acetic acid, acetaldehyde, pyridine and methylbutanal rapidly increased and went through a maximum at medium roast level. In a second series, just six beans were roasted. We observed sporadic bursts of some volatiles (furans, butanal, 2,3- pentanedione), coinciding with popping sounds. Other VOCs showed smooth time-intensity profiles (pyridine, pyrazine). These experiments gave a real-time insight into the complex processes taking place during roasting. Finally, the HS of coffee extracts, prepared from beans roasted to different roast levels, were analysed. Most VOCs showed a maximum concentration at medium roast level (e.g. pentanedione, furfural, 5-methyl furfural), while others showed a gradual increase (e.g. pyrrol) or decrease (e.g. methanol).

Erworben im Rahmen der Schweizer Nationallizenzen (http://www.nationallizenzen.ch), The aromas of a reference green Mexican coffee (Arabica) and of a coffee from the same origin, but having a pronounced earthy/mouldy off-taint, were characterised. From comparison of the two aroma profiles, the compounds causing the defect were detected by gas chromatography olfactometry, isolated and concentrated by preparative bi-dimensional gas chromatography, and characterised by gas chromatography mass spectrometry. Six compounds participated in the off-flavour. Geosmin, 2-methylisoborneol, 2,4,6-trichloroanisole were found to be the main culprits, while three methoxy pyrazines (2-methoxy-3-isopropyl/-3-sec-butyl/-3-isobutyl pyrazine) contributed to a lesser extent to the earthy/ green undertone. The occurrence of the off-flavour could tentatively be linked to post-harvest drying.

Using REMPI@266 nm or 248 nm several phenolic compounds, such as Phenol or the flavor-active 4-vinylguaiacol, can be detected in the roast off-gas.