How Does Roasting Process Influence the Retention of Coffee Aroma Compounds by Lyophilized Coffee Extract?

ABSTRACT:  The aims of this study were (1) to study the effect of lyophilized coffee extract on the retention of aroma compounds and (2) to study if aroma compounds selected are differently affected by the lyophilized coffee extracts obtained from conventional and Torrefacto coffee brews prepared by filter coffeemaker and by espresso coffee machine. Variable amounts of lyophilized coffee extracts, relative to coffee powder, containing different percentages of high molecular weight compounds, mainly melanoidins (value given in parentheses), were obtained: 20.9% (14.8) and 24.9% (23.3), respectively, for conventional and Torrefacto coffee brew prepared by filter coffeemaker and 18.1% (18.8) and 20.7% (57.5), respectively, for conventional and Torrefacto coffee brew prepared by espresso coffee machine. The retention of aroma compounds increased by increasing the lyophilized coffee extract concentration and was found to be dependent on the aroma compounds. The retention of aroma compounds was found to be slightly different depending on the brewing procedure employed, showing lyophilized coffee extracts obtained with espresso coffee machine had higher retention values that those extracted by filter coffeemaker. Retention capacity of lyophilized coffee extracts obtained from the conventional and the Torrefacto roasted coffee did not show differences except in the case of ethyl nonanoate.     

Influence of roasting and brew preparation on the ochratoxin A content in coffee infusion

A study of the effect of coffee processing in the ochratoxin A (OTA) level has been carried out from the green beans to the drinking form. The analysis of OTA has been carried out by an in-house validated HPLC method with fluorescence detection. The limits of detection were 0.04 µg/kg for green and roasted coffee, and 0.01 µg/L for coffee brew. Thirty-six green coffee samples of different origin (Colombia, Costa Rica, Brazil, Vietnam, India and Uganda) were analysed. The highest concentrations of OTA were found in Vietnamese samples - Robusta species treated by dry processing - (range 0.64-8.05 µg/kg), that also showed the highest percentage of defective beans (7.6%). These contaminated samples were roasted in a process that controlled loss of weight and color, as in the industry. A mean reduction of 66.5% was obtained, but the reduction seems to be heterogeneous. Coffee brew was prepared by the three brewing processes more utilized in Europe: moka, auto-drip and espresso. A reduction of the OTA level has been attained, being greater when using a espresso coffee maker (49.8%) than when using auto-drip (14.5%) or moka brewing (32.1%). Therefore, the method of coffee brew preparation plays a key role in the final OTA human exposure.     

Bioactive composition and antioxidant potential of different commonly consumed coffee brews affected by their preparation technique and milk addition

Coffee is one of the most popular beverages in the world, prepared and consumed in many different ways. Taste, aroma and composition of the coffee brew vary depending on the preparation method. Therefore, this study investigates the effect of different brewing methods on the polyphenol and methylxanthine composition and antioxidant capacity of thirteen different coffee brews. The content of total phenols and flavonoids was determined spectrophotometrically and the content of chlorogenic acid derivates (3-CQA, 4-CQA and 5-CQA) and caffeine using the high performance liquid chromatography (HPLC-PDA). Antioxidant capacity of coffee brews was evaluated by using the ABTS (2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)) and FRAP (ferric-reducing antioxidant power) assays. Instant coffee brews showed the highest values in content of total phenols, chlorogenic acid derivates, caffeine and antioxidant capacity, which significantly decreased by milk addition. The antioxidant capacity of coffee brews was in compliance with the total phenol content and content of chlorogenic acid derivates.     

烘焙度对冷萃咖啡理化指标与风味成分的影响

以亚洲咖啡豆为研究对象,分别选取浅、中、深3 种烘焙度的中国云南和印度尼西亚苏门答腊产的卡蒂姆种咖啡豆,比较分析冷萃与热萃方式对萃取浓度、萃取率、可滴定酸、总酚、总糖、咖啡因、葫芦巴碱、绿原酸、抗氧化活性与挥发性成分的差异,并进行主成分分析,从而探究烘焙度对冷萃咖啡理化指标与风味成分的影响规律。结果表明,随着烘焙度增加,冷萃咖啡的萃取浓度、萃取率均显著上升,可滴定酸、总酚、葫芦巴碱、绿原酸、抗氧化活性均显著下降（P＜0.05）。冷萃咖啡较热萃咖啡拥有更高的萃取浓度、萃取率与总糖含量（P＜0.05）,而可滴定酸、总酚含量、抗氧化活性较热萃显著偏低（P＜0.05）。经顶空固相微萃取-气相色谱-质谱检测分析发现,浅烘咖啡豆萃取液中的挥发性成分含量显著低于烘焙度高的咖啡萃取液,深烘咖啡豆萃取液中挥发性成分种类与总含量最多。进一步通过主成分分析能较好区分冷萃和热萃咖啡,两者挥发性成分贡献率具有较大差异。2-丁酮、2-丁烯醛等花香类物质对浅烘冷萃咖啡贡献率更高,而2-甲基吡嗪、糠醇等呈现烘焙坚果类香气物质对浅烘热萃咖啡贡献率更高;2,6-二乙基吡嗪、川芎嗪等烘焙坚果类香气物质对中烘冷萃和热萃咖啡具有较高的贡献率;2-乙烯基呋喃、甲基糠硫醇、2,5-二乙基吡嗪、糠基甲基硫醚等物质对深烘冷萃咖啡有较高贡献率,二甲基二硫、对甲酚、1-甲基吡咯等物质对深烘热萃咖啡贡献率更高。相对于热萃咖啡,烘焙度对冷萃咖啡抗氧化能力与挥发性成分的影响更大。     

Caffeine and chlorogenic acids intake from coffee brew: influence of roasting degree and brewing procedure

The influence of coffee cultivar, roasting degree and brewing procedure in the presence and transfer of caffeine and caffeoylquinic acids (CQAs) from ground roasted coffee to the brew was evaluated. Two coffee cultivars were roasted in three roasting degrees and brewed using two different procedures. Compounds were determined simultaneously by HPLC‐DAD. Caffeine levels ranged from 87.3 to 122.5 mg/100 mL for Coffea arabica cv. Catuaí Amarelo and from 123.3 to 192.0 mg/100 mL for C. canephora cv. Apoatã. The sum of CQA isomers ranged from 24.2 to 41.3 mg/100 mL for brews prepared with dark roasted coffee and from 187.7 to 295.6 mg/100 mL for light roasted ones. Brews prepared by boiling showed higher content of the compounds than the corresponding filtered ones. C. arabica cv. Catuaí Amarelo light roasted coffee brew presented the lowest caffeine/CQA ratio, regardless of the brewing procedure used, in comparison with the highest ratio of the dark boiled brews.     

Investigation on the extractability of melanoidins in portioned espresso coffee

Coffee melanoidins have attracted interest as a result of its potential health benefits. This investigation aims to elucidate the extraction behavior of melanoidins and their populations during the preparation of portioned espresso coffee and its relationship with the antioxidant activity of the coffee brew. Filter-paper pods, FAP capsule, and clone capsule containing light roasted coffee have been investigated. An accumulative fractionation approach has applied to model the extraction kinetics of melanoidins, melanoidin populations, browning, chlorogenic acids (CGA), and antioxidant activity. Melanoidins were very efficiently extracted in clone capsules since less than 9 s was necessary to extract the 50% of the melanoidin content as compared with pods and FAP capsules, and the kinetic of extraction is slower than CGA. The extraction profile of melanoidins and browning fitted better with the antioxidant capacity than CGA and total solids profile. Melanoidin populations were obtained according to ethanol solubility. Total melanoidin content and the ratio between melanoidin populations did not change during extraction volume for espresso coffee. Melanoidin populations soluble at 75% ethanol showed the highest antioxidant activity. However, melanoidins with higher antioxidant activity are extracted at higher volumes. This investigation could make possible the adjustment of the technological requirements of espresso coffeemakers to produce an espresso coffee with high levels of beneficial compounds.     

Comparison of nine common coffee extraction methods: instrumental and sensory analysis

The preparation of a cup of coffee may vary between countries, cultures and individuals. Here, an analysis of nine different extraction methods is presented regarding analytical and sensory aspects for four espressi and five lunghi. This comprised espresso and lungo from a semi-automatic coffee machine, espresso and lungo from a fully automatic coffee machine, espresso from a single-serve capsule system, mocha made with a percolator, lungo prepared with French Press extraction, filter coffee and lungo extracted with a Bayreuth coffee machine. Analytical measurements included headspace analysis with HS SPME GC/MS, acidity (pH), titratable acidity, content of fatty acids, total solids, refractive indices (expressed in °Brix), caffeine and chlorogenic acids content with HPLC. Sensory analysis included visual, aroma, flavor and textural attributes as well as aftersensation. The technical differences in the extraction methods led to a higher concentration of the respective quantities in the espressi than in the lunghi. Regarding the contents per cup of coffee, the lunghi generally had a higher content than the espressi. The extraction efficiency of the respective compounds was mainly driven by their solubility in water. A higher amount of water, as in the extraction of a lungo, generally led to higher extraction efficiency. Comparing analytical data with sensory profiles, the following positive correlations were found total solids ? texture/body, headspace intensity ? aroma intensity, concentrations of caffeine/chlorogenic acids ? bitterness and astringency.     

Effect of ultra high temperature (UHT) treatment on coffee brew stability

In this work, the influence of an Ultra High Temperature (UHT) treatment on chemical and sensory composition of Arabica coffee brews for a longer shelf-life has been studied. A temperature of 120 °C for 2 s allows to obtain a microbiologically safe coffee brew, good valued from the sensory point of view. The behavior of the UHT vs non UHT treated coffee brew was followed throughout 120 days of storage at 4 °C. The UHT treatment keeps the typical acidity of the brews longer, delaying and softening the pH decrease and the development of sourness, which is one of the main causes for the rejection of stored coffee brews. The UHT treatment hardly affects the concentrations of caffeine and trigonelline, and of some phenolic compounds such as 5-caffeoylquinic (5-CQA), caffeic or ferulic acids. Sixteen key odorants and staling volatiles were analyzed by HS–GC–MS and lower changes were observed in the UHT treated coffee brew throughout storage. Higher DPPH scavenging activity was observed in the UHT treated coffee brew from days 60 to 120. In conclusion, the application of an UHT treatment is proposed to extend the shelf-life (up to 60 days) of stored coffee brews.     

Sensory study of the character impact aroma compounds of a coffee beverage

The more potent odorants in a sample of medium-roasted Arabica coffee and in the corresponding brew were quantified. Large amounts ( >75%) of acetaldehyde, 2,3-butanedione, 2,3-pentanedione, vanillin and some furanones were extracted from the coffee brew, whereas the yields of the more unpolar compounds, such as 3-isobutyl-2-methoxypyrazine, (E)-β-damascenone and the unstable 2-furfurylthiol were low (<25%). On the basis of quantitative data an aroma model was prepared for the brew. In triangle tests, models containing the complete set of 24 odorants were compared with a model missing one or more odorants. These experiments indicated that the aroma of the brew was mainly caused by some alkylpyrazines, furanones and phenols, and by 2-furfurylthiol, methional and 3-mercapto-3-methylbutyl formate. The higher impact of both methional and the formate on the aroma of the brew and the lower aroma activity of 4-vinylguaiacol were in contrast to results obtained in a previous study for ground coffee of the same provenance and roast degree. Received: 13 December 1999 / Revised version: 31 January 2000     

Screening and distinction of coffee brews based on headspace solid phase microextraction/gas chromatography/principal component analysis

The volatile profiles of espresso and plunger (cafetière) coffees prepared from (1) an 80:20 (w/w) blend of natural roasted Robusta and Arabica (Robusta Natural blend), (2) a 40:40:20 (w/w/w) blend of Robusta Natural blend, Robusta torrefacto roast (850 g kg^?1 Robusta, 150 g kg^?1 sugar) and (3) natural roasted pure Arabica were established by headspace solid phase microextraction (SPME) after selection of the fibre coating (polyacrylate or polydimethylsiloxane) and the temperature and time of extraction. For the analysis of furans and indoles the polyacrylate coating proved to be more suitable; however, for the overall characterisation of the volatile composition of espresso and plunger coffees the polydimethylsiloxane coating was chosen. SPME/gas chromatography (GC)/mass spectrometry (MS) analyses allowed the identification of 37 compounds: four aldehydes, two ketones, 11 furans, 10 pyrazines, two pyridines, three phenolic compounds, two indoles, one lactone, one ester and one benzothiazine. The volatile composition was related more to the botanical variety (Arabica or Robusta) than to the method of preparation of the brew (espresso or plunger). Furthermore, use of the variability provided solely by the GC peak areas and respective retention times, combined with principal component analysis (PCA), yielded the information necessary for discrimination. The combined technique of headspace SPME/GC/PCA, as an alternative to conventional techniques based on GC/MS, is proposed as a lower‐cost, fast and reliable technique for the screening and distinction of coffee brews. Copyright © 2003 Society of Chemical Industry     

Fate of 14C-acrylamide in roasted and ground coffee during storage

Acrylamide (AA) is formed during heating of carbohydrate rich foods in the course of the Maillard reaction. AA has been classified as probably carcinogenic to humans. Storage experiments with roasted coffee have shown that AA levels decrease depending on storage time and temperature. In the present study the fate of AA lost during storage of roasted and ground (R&G) coffee was studied, using 14C-labeled AA as radiotracer. Radiolabel was measured in coffee brew, filter residue, and volatiles. In the brew, total (14)C-label decreased during storage of R&G coffee, while activity in the filter residue built up concomitantly. [2,3-14C]-AA (14C-AA) was the only 14C-related water extractable low molecular compound in the brew detected by radio-HPLC. No formation of volatile 14C-AA-related compounds was detected during storage and coffee brewing. Close to 90% of the radiolabel in the filter residue (spent R&G coffee, spent grounds) remained firmly bound to the matrix, largely resisting extraction by aqueous ammonia, ethyl acetate, chloroform, hexane, and sequential polyenzymatic digest. Furanthiols, which are abundant as aroma components in roasted coffee, have not been found to be involved in the formation of covalent AA adducts and thus do not contribute substantially to the decrease of AA during storage.     

黑枣果酒发酵过程主要成分变化规律及香气成分分析

以河北涉县产无核黑枣为原料,对黑枣果酒发酵过程中可溶性固形物、还原糖、酒精度、总酸、蛋白质、脂肪、VC、多酚等主要成分的变化规律进行分析,气相色谱质谱联用测定黑枣果酒香气主要成分。结果表明,黑枣果酒发酵过程中,可溶性固形物、还原糖、蛋白质、脂肪、VC的含量随着发酵时间的变化而降低,而酒精度、总酸的含量却随着发酵时间的延长而上升,在发酵初期多酚含量略有增加,随后缓慢下降并保持稳定的水平。黑枣果酒香气成分中鉴定出匹配度较高的18种化合物,包括烷烃类物质9种、酯类物质8种和1种羟胺物质。     

Factors affecting tocopherol contents in coffee brews: NP-HPLC/FLD,RP-UPLC-ESI/MSn and spectroscopic study

Qualitative and quantitative determination of tocopherols in filtered and unfiltered coffee brews was investigated. The NP-HPLC/FLD and RP-UPLC-ESI/MSⁿ techniques as well as fluorescence spectroscopy turned out to be very useful tools not only to estimate tocopherol contents, but also to detect contaminants in coffee brew tocopherol extracts. In all analysed coffee brew samples, only α- and β-T were detected. In Arabica coffee brews, the content of the β homologue was three to four times higher than that of the α homologue; however, in Robusta, they were almost identical. Unfiltered coffee brews contained about ten times more tocopherols, 3.02–5.26 and 3.39–16.52, than filtered brews, 0.4–0.71 and 1.26–1.77 μg/100 ml for α-T and β-T, respectively. The reduction in the size of ground coffee beans from 0.7 to 0.3 mm increases the concentration of tocopherols almost three times. Suspended coffee bean dust was the main source of tocopherols in coffee brews.     

Optimization and Application of a HS-SPME-GC-MS Methodology for Quantification of Furanic Compounds in Espresso Coffee

A headspace solid-phase microextraction gas chromatography (GC)-mass spectrometry (MS) method previously optimized for analyses of volatiles in coffee was used for simultaneous quantification of major furanic compounds (2-furfural, furfuryl alcohol, 5-methylfurfural and furfuryl acetate) and furan, in espresso coffee prepared from hermetically closed capsules. High sensitivity was achieved with low limits of detection and limits of quantification. Good linearity was observed with correlation coefficients higher than 0.999. Recovery percentages were 102 % for furan, 99.7 % for 2-furfural, 98.0 % for furfuryl alcohol, 99.8 % for 5-methylfurfural and 99.9 % for furfuryl acetate. The method was applied to the analyses of espresso coffee from hermetically closed capsules. A total of 69 volatiles for Blend Roast and Blend Dark Roast samples, 64 volatiles for Arabica Dark Roast samples, 91 volatiles for Arabica Light Roast samples, 96 volatiles for Caramel coffee, 90 volatiles for Vanilla coffee and 92 volatiles for Almond coffee. In general, furanic compounds were the major chemical family, ketones, aldehydes, acids, pyrazines, pyrroles, alcohols, pyridines, aromatic compounds, hydrocarbons, and ethers were also detected. Total content of these furanic compounds varied from 105 to 199 μg ml^?1. The optimized method proved to be a reliable methodology for quantification of major furanic compounds and furan present in different types of espresso coffee. Although relative percentage of peak area is a good method for discriminate volatiles in different coffee brews with closer composition, the quantification of furanic compounds is more accurate for understand the real intake amount.     

Phytochemical and microbiological stability of spent espresso coffee grounds in capsules

Wet spent coffee grounds (SCGs) from espresso capsules, a post-consumer organic solid residue produced worldwide, were analysed to determine their chemical and microbiological stability during storage. In particular, the changes in the total phenolic content and antioxidant capacity (based on two free radical scavenging assays and one oxygen radical absorbance assay) were determined on espresso SCG stored in capsules for up to one month at room temperature in a container open to the air. Phenolic compounds were also identified and quantified using high performance liquid chromatography coupled with diode array and mass detectors. Microbiological analysis was performed in parallel on the same stored SCG to determine the total counts and quantify the main microbial groups present during the storage. The total phenolic content, antioxidant capacity and the most important bioactive compounds, such as the total caffeoylquinic acids, were significantly stable during storage for up to one month, while overall microbial stability was observed for up to two weeks of storage. Overall, the recovery of espresso coffee capsules within 15 days could guarantee the maintenance of microbiological stability as well as the content of valuable antioxidant compounds.     

Furanic compounds and furfural in different coffee products by headspace liquid-phase micro-extraction followed by gas chromatography–mass spectrometry: survey and effect of brewing procedures

In this study, the levels of furan, 2-methylfuran, 2,5-dimethylfuran, vinyl furan, 2-methoxymethyl-furan and furfural in different coffee products were evaluated. Simultaneous determination of these six furanic compounds was performed by a head space liquid-phase micro-extraction (HS-LPME) method. A total of 67 coffee powder samples were analysed. The effects of boiling and espresso-making procedures on the levels of furanic compounds were investigated. The results showed that different types of coffee samples contained different concentrations of furanic compounds, due to the various processing conditions such as temperature, degree of roasting and fineness of grind. Among the different coffee samples, the highest level of furan (6320 µg kg^?1) was detected in ground coffee, while coffee-mix samples showed the lowest furan concentration (10 µg kg^?1). Levels in brewed coffees indicated that, except for furfural, brewing by an espresso machine caused significant loss of furanic compounds.     

Method Validation for Cafestol and Kahweol Quantification in Coffee Brews by HPLC-DAD

Cafestol and kahweol are two diterpenes exclusively found in coffee. Negative effects on health, like the increase in total lipid blood levels as well as positive effects like carcinogenic protective and antioxidant activity, have been reported for these two compounds. A simple and expeditious method for the quantification of total cafestol and kahweol levels in coffee brews by high-performance liquid chromatography with diode array detection was developed and validated. Esterified diterpenes were hydrolysed and resulting diterpene alcohols extracted with diethyl ether. For cafestol limit of detection was 0.01 mg L^?1 and limit of quatification was 0.04 mg L^?1. Coefficient of variation for cafestol ranged between 0.2 and 2.8 % for repeatability and between 1.4 and 15.3 % for intermediate precision. Average recoveries of cafestol-spiked coffee samples were from 96 to 110 %. Kahweol was quantified using cafestol calibration data and corrected by an appropriate conversion factor. Different kinds of coffee brews were analysed. Cafestol levels ranged from 0.04 to 0.80 mg/cup and for kahweol levels were between 0.01 and 0.40 mg/cup. Highest levels of diterpenes per cup were present in espresso coffee, while the lowest were found in filter coffee and instant coffee.     

Leaching of residues of certain pesticides from black tea to brew

Tea is the most commonly consumed beverage in the world. It is prepared after infusing processed black tea in hot water. During the process of brewing, along with flavour and aroma, the residues of plant protection chemicals may also be transferred into the tea brew or infusion. The leaching of certain pesticides, such as ethion, endosulfan, dicofol, chlorpyrifos, deltamethrin, hexaconazole, fenpropathrin, propargite, quinalphos and lambdacyhalothrin from powdered black tea into the brew was studied. The rate of transfer of the pesticide residue from black tea to the hot brew was largely influenced by physicochemical parameters, such as water solubility and octanol-water partition coefficient. Tea brews prepared from untreated black tea samples were fortified with standard solutions of the respective pesticides, extracted and analysed using GC and HPLC by following standardised methods. Results revealed that the rate of leaching of residues of these pesticides into the tea brew was low due to their low solubilities in aqueous medium and high octanol-water partitioning coefficients.