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.     

Gender preference in hedonic ratings for espresso and espresso-milk coffees

Espresso, cappuccino and latte are new coffee products entering the daily lives of many consumers. There is increasing consumption of such speciality coffees but no sensory basis for new product development. This study was designed to meet this need. Preference in 100 consumers was studied using six espresso blends of coffee beans. Blends were specifically developed to match key European and North American styles. Products prepared were both espresso and espresso-milk coffees. It was observed that females and males had different preferences for espresso coffee but that this effect was reduced on addition of milk. Gender of target consumer, and end use of espresso, should be thus considered in developing coffee blends. In this way acceptability in specific or target groups of consumers can be maximised. In addition individuals may experience a development of appreciation of coffee character reflected in a change in preference.     

High‐resolution 1H NMR investigation of coffee

Recent successful applications of NMR spectroscopy and imaging in food science prompted the authors to use these new techniques for the analysis of espresso coffee. The target of this work was to identify an experimental procedure to obtain maximum information from high‐resolution ¹H spectra. Only the espresso coffee was considered as the true food, since it includes all aromatic substances responsible for the coffee aroma and taste. A big effort was made in order to select an easy, quick and non‐degrading procedure to analyse the espresso cup content, preventing artificial or natural degradation effects with a particular care in the measurement of labile and volatile components. The procedure was tested on two arabica and one robusta samples; each sample was prepared with three roasting degrees to follow the chemical changes due to the roasting process. Moreover, one water extract was prepared also from ground green coffees. As a comparison, each coffee extract was prepared both with a standard ‘espresso coffee machine’ and with a ‘mocha’ as used in the domestic setting. Significant differences among the three samples were observed. Moreover, for all samples, as a function of the roasting degree, a clear trend in the chemical composition was observed. © 1999 Society of Chemical Industry     

Influence of extraction temperature on the final quality of espresso coffee

The final quality of espresso coffee (EC) depends upon certain technical conditions, such as the extraction temperature used in preparing it. The aim of this work was to investigate the effects of water temperature (88, 92, 96 and 98 °C) on the final quality of three types of EC (Arabica, Robusta Natural blend and Robusta Torrefacto blend) in order to select the optimal temperature. Volatile compound (analysed by Static headspace gas chromatography/mass spectrometry) and sensory flavour profiles were the most relevant parameters, whereas physicochemical, taste and mouthfeel parameters were not very useful for selecting the water temperature. For Arabica and Robusta Natural blend ECs, 92 °C was the optimal water temperature. For Robusta Torrefacto blend EC the overall acceptability might lead to the selection of 88 °C as the ideal water temperature, but the high percentages of key odorants related to roasty and earthy/musty flavours and the ‘not hot enough’ perception dictated the selection of 92 °C in this case as well. © 2003 Society of Chemical Industry     

Tocopherols in espresso coffee: Analytical method development and validation

The present paper reports the development and validation of an analytical micro-method for tocopherols quantification in espresso coffee by normal-phase HPLC with fluorescence detection. The proposed method consists in a liquid–liquid extraction with n-hexane:ethyl acetate, followed by a clean-up with dimethylformamide to eliminate co-eluting interferences. The method showed good intra- and inter-day precisions (coefficient of variation < 6.5%), good accuracies (98 ± 6%), and high correlation coefficients (r > 0.999) for standards subjected to the entire procedure. Only α- and β-tocopherols were identified in the brews. The detection and quantification limits were 0.5 and 1.4 ng/ml, for α-tocopherol, and 0.4 and 1.1 ng/ml, for β-tocopherol, respectively. A mean total tocopherol content (α + β) of 3.5 ± 0.9 μg in commercial espresso coffee blends (30 ml) was detected. The proposed method requires low solvent consumption and proved to be sensitive, precise and accurate.     

云南临沧产区咖啡干香感官特征解析及杯品质量分析

以云南临沧产区咖啡为原料,利用顶空固相微萃取气相色谱-质谱联用技术和香气活度值（odor activity value,OAV）法确定咖啡干香特征组分,通过查询明确其风味感官特征,并邀请专业咖啡质量品鉴师团队评价杯品品质。结果表明：临沧咖啡中共有干香组成85 种,样品间组分含量差异不大;特征干香组分27 种（OAV＞1）,为临沧咖啡赋予蜂蜜、黑巧克力、奶油、焦糖、烤坚果的底香,同时具有枫糖浆、酸奶酪、热带水果、果酱和花香等风味;临沧咖啡杯测得分整体较高;同时可知杯品质量受区域环境影响较大。本实验结果可为临沧咖啡销售和推广提供理论参考。     

Acrylamide in espresso coffee: Influence of species,roast degree and brew length

Espresso coffees were analysed for acrylamide contents by matrix solid-phase dispersion and GC–MS. The influence of coffee species, roast degree, and brew length were ascertained. Mean acrylamide contents of medium roasted espressos (30 mL) were 1.16 ± 0.25 and 2.31 ± 0.43 μg for pure arabica and robusta samples, respectively. Espressos prepared from commercial blends contained an average acrylamide level of 1.26 ± 0.28 μg. A 25% decrease was observed when comparing espressos prepared with medium and dark roasted coffee. The extraction efficacy of acrylamide for standard espressos of 30 mL was near 80%, being only affected by brew volume, with long espressos (70 mL) containing practically all acrylamide of the coffee cake (99%), almost double that of short ones (20 mL). When compared with other common coffee beverages, espresso acrylamide concentration (μg/L) was higher. However, due to the small volume per cup, it may contribute less to acrylamide ingestion.     

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.     

Impact of Roasting Conditions on the Formation of Aroma Compounds in Coffee Beans

ABSTRACT: Hot air roasting of coffee beans results in a large number of aroma compounds. For a given coffee, the aroma profile is determined by the specific conditions for chemical reactions as controlled by the process parameters. Therefore, the influence of roasting temperatures on the formation of key aroma compounds was investigated. Coffee was roasted in 6 different processes to equal degrees of roast and the developing aroma compound profiles were characterized by gas chromatography, mass spectrometry, and olfactometry. A majority of aroma compounds showed the highest increase in concentration at medium stage of dehydration with bean water content from 7 to 2% (wb). Different time-temperature histories led to distinct aroma compound profiles. To reach a specific flavor profile, precise control of roasting time and temperature is required.     

A neuro‐fuzzy computational approach for multicriteria optimisation of the quality of espresso coffee by pod based on the extraction time,temperature and blend

We demonstrate how soft computing methods can be exploited to solve multicriteria quality optimisation problems in food science and technology. In particular, we link neuro‐fuzzy modelling techniques with simulated annealing to optimise/design the quality of espresso coffee by pod. The design variables are the extraction time (ranging from 10 to 30 s), temperature (80–110 °C) and blends (100% Arabica, 100% Robusta and Arabica Robusta: A20R80, A80R20 and A40R60); they are not the only variables that affect the sensory profile of a cup of espresso coffee, but have a strong impact on the sensory quality of the beverage. Based on the framework, we show that the particular problem is a nonlinear one. Hence, an espresso coffee characterised by a specific sensory profile can be extracted using different sets of parameter values. For example, the same sensory profile can be obtained using either pure Robusta extracted at 22 s and 94 °C or 90% Arabica and 10% Robusta extracted at 25 s and 99 °C. Yet, the global optimum with respect to the distance to the optimum sensorial values is obtained using 70% Arabica and 30% Robusta extracted at 15 s around 93 °C.     

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.     

Neapolitan coffee brew chemical analysis in comparison to espresso,moka and American brews

The aim of the present study was to characterize the chemical composition of Neapolitan coffee brew in comparison to espresso, American, and moka coffee brews. Despite the similarity of brewing principle of Neapolitan and American coffee-making techniques, i.e. percolation of hot water through ground coffee, the characteristics of Neapolitan coffee brew in terms of antioxidant activity, total phenolic compounds and total solids were more similar to moka coffee brew. Espresso and moka showed higher antioxidant activity, and espresso exhibited higher caffeine concentration, total phenolic compounds, and total solids with respect to other coffee brews studied. For the first time a characterization of the Neapolitan coffee aroma, a traditional Italian brewing procedure, was reported. A significant higher amount in hexanal, β-damascenone and some pyrazines was found in Neapolitan coffee aroma with respect to other procedures. These compounds could be considered as a distinctive characteristic of Neapolitan coffee aroma. Moka was characterized by higher guaiacol content with respect to other procedures, while espresso showed significantly higher levels in aldehydes and 2-furanmethanol acetate.     

Espresso coffee (EC) by POD: Study of thermal profile during extraction process and influence of water temperature on chemical–physical and sensorial properties

In this work the thermal profiles of five coffee pods (pure Arabica, pure Robusta, and Arabica Robusta blends: A20R80, A80R20, and A40R60) at 90, 100 and 110 °C are reported. Moreover the chemical–physical and sensorial properties of espresso coffee (EC) obtained from five different coffee pods were investigated. The analysis of the thermal profiles highlighted that the extraction process can be considered as an isothermal process because, after a starting phase, the recorded temperatures stayed around a mean temperature (T_m). In addition the T_m recorded for each extraction temperature was significantly lower than those set up by the controller. The chemical–physical parameters of EC samples increased proportionally with extraction temperature highlighting that the effectiveness of extraction process scales up with percolation temperature. The solid and caffeine contents of the EC samples extracted at 110 °C are related to an over extraction process. Principal Component Analysis (PCA) was applied to identify relationships and differences among EC samples. Pure Arabica and A80R20 EC samples at 100 and 110 °C have shown sensorial attributes typical for a fine espresso coffee.     

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.     

酿酒酵母多物混合发酵对咖啡豆风味品质的影响

中国咖啡主产于云南,云南咖啡在花果风味及甜香风味方面有所欠缺,发酵是影响咖啡风味品质的重要因素之一.利用酿酒酵母在低温厌氧条件下发酵咖啡鲜果,添加香草、肉桂、热带水果、蜂蜜等原料为基底共同发酵,最终对发酵咖啡豆进行理化、香气成分分析及主观评价,探究发酵对咖啡品质的影响.结果表明:添加香草、肉桂、苹果、甜橙、香蕉、蜂蜜发酵的咖啡与无添加的对照组咖啡相比,灰分和脂肪含量无差异(P>0.05),可溶性蛋白质含量显著提高(P<0.05),底物的添加对最终咖啡豆中多糖、还原糖、总蛋白质、多酚有不同程度的影响,无明显规律.采用气相离子迁移色谱(gas chromatography-ion mobility spectrometry,GC-IMS)对发酵咖啡生豆挥发性成分进行分析,共定性出36种化合物,9种酯、6种酮、8种醛、6种醇、5种烯萜、1种呋喃、1种酸类,其中酮、醛、醇、酯类共占挥发性成分的60％以上.结合感观评价结果,香草、肉桂、热带水果与咖啡发酵可赋予咖啡水果香气,提升咖啡花果香特质,其中香料组、甜橙组达精品咖啡标准,香蕉组香气较为突出,蜂蜜组在香气方面未有突出特点,且酸度过高对甜度提升不足.研究为进一步改善云南咖啡花果甜香特质,提升咖啡风味提供一定理论依据和数据支持.     

Impact of crema on expected and actual espresso coffee experience

The formation and stabilization of crema on espresso coffee are areas that have been well studied during the last 2 decades. In contrast, the contribution of the sensory perception of crema in the coffee consumption experience has not received a lot of attention. Crema being a key visual differentiator between espresso coffees, it may influence the overall sensory and hedonic experiences through the process of assimilation or contrast of visually induced expectations. The objective of this research was therefore to investigate the role of the expectation generated by crema visual cues on actual sensory and hedonic espresso coffee consumption experience. The study was designed to measure the impact of absence, presence and amount of crema on expectation for espresso coffee in liking, quality, overall taste intensity, bitterness and smoothness. Four espresso coffees with different amounts of crema were rated on each characteristic by espresso coffee consumers in three evaluation conditions: visual condition (expectation induced by crema visual cues), in-mouth condition (espresso coffee tasting while participants were blindfolded), full condition (standard tasting). The aim of this procedure was to quantify the respective contribution of crema visual cues and in-mouth espresso coffee tasting to the overall espresso coffee experience. Results showed that espresso coffee without crema was expected to be moderately liked, low in quality and weakly smooth as compared to espresso coffee with crema. Such expectations negatively impacted hedonic and sensory in-mouth experience through assimilation effect. Change in crema amount also impacted consumers' expectation which in turn modulated hedonic and sensory experience for espresso coffee. For the first time, this study highlighted the key role of crema visual cues on espresso coffee consumption experience.     

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.     

Methylglyoxal Content in Drinking Coffee as a Cytotoxic Factor

Abstract: A causal relationship between metabolic syndrome and methylglyoxal (MG) has been suggested. Consumption of coffee and other types of beverages has been known to produce MG, thus resulting in both nutritional and health concerns. The purpose of this study was to determine the ideal combination of coffee, cream, and sugar in order to minimize MG consumption. Four types of black coffee were tested: espresso, bold, mild, and a decaffeinated mild roast. Sugar and/or cream were added to the coffee samples to test whether MG levels were altered. Using high-performance liquid chromatography, the concentration of MG in various coffee samples was determined. The espresso coffee sample was found to contain the highest level of MG at 230.9 μM. The bold coffee roast had the 2nd highest amount of MG, followed by the mild and decaffeinated varieties. Adding cream to bold coffee significantly reduced its MG level in comparison to the coffee sample without cream. On the other hand, the addition of sugar to the bold coffee did not further increase the MG level in the samples. The cellular damaging effect of MG was shown as there were decreased numbers of cultured HEK-293 cells after 24 h of MG treatment (100 and 300 μM), which is consistent with an increased cell apoptosis induced by MG treatment (100 and 300 μM). Due to the overconsumption of exogenous MG, drinking an excess of any type of coffee poses health risks.     

Influence of coffee/water ratio on the final quality of espresso coffee

Espresso coffee is a polyphasic beverage in which the physico‐chemical and sensory characteristics obviously depend on both the selection of ground roasted coffee and the technical conditions of the percolation process. The aim of this work was to evaluate the influence of the coffee/water ratio on the physico‐chemical and sensory quality of espresso coffee. Furthermore, the influence of botanical varieties (Arabica and Robusta) and the type of roast (conventional and torrefacto) on the selection of coffee/water ratio was studied. The relationship between pH and the perception of acidity intensity is discussed in relation to the influence of the coffee/water ratio, type of coffee and roast. The optimisation of other technical parameters in previous studies seemed to minimise the influence of an increase in the coffee/water ratio on the extraction of soluble and solid compounds. In fact, only some sensory attributes, such as bitterness, astringency and burnt, acrid and earthy/musty flavours were proposed as relevant to the selection of 6.5 g 40 mL^?1 or 7.5 g 40 mL^?1 in conventional roasted coffees (Arabica 100% and Robusta blend), and 6.5 g 40 mL^?1 in torrefacto roasted coffees. On the other hand, the addition of sugar during the roasting process in torrefacto roast coffees seemed to contribute to a higher generation of acids, melanoidins and other compounds by the Maillard reaction or caramelisation, which led us to select the lowest coffee/water ratio. Copyright © 2006 Society of Chemical Industry