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A Study of Coffee Bean Characteristics and Coffee Flavors in Relation to Roasting
Abstract
This study investigated changes in the physicochemical characteristics and coffee flavors of coffee beans under different roasting conditions. Four different kinds of roasted coffees were analyzed using a headspace gas chromatographic technique. The moisture content and total acidity of roasted coffee decreased whereas the pH and weight loss (%) increased, as coffee beans were roasted at higher temperatures. The Hunter's color values of the roasted coffee (indicating L (lightness) and b (yellowness)) decreased as the roasting temperature of the coffee beans increased, but a (redness) value only increased with light roasting. We also noted that the color of the Arabica coffee was darker than that of the Robusta coffee. The aroma compounds, acetaldehyde, acetone, 2-methylfuran, 2-methylbutanol, 2-methylpyrazine, furfural, 2-propanone, furfuryl alcohol, 2,5-dimethylpyrazine and furfuryl acetate were mainly analyzed. A sensory evaluation of all light-roasted coffees had flavor and sourness and those of all medium-roasted coffees had heaviness and finishness.
... Roasted degree also evaluated based on the acidity of coffee using pH metric and titration. Light roast of coffee has the strongest acidity, while the darkest roast tend to lowest [31] [31]. Herawati [20] categorized the degree of roasted coffee according to popping sound and associated to visual intensity (lightness) and water activity. ...
... Roasted degree also evaluated based on the acidity of coffee using pH metric and titration. Light roast of coffee has the strongest acidity, while the darkest roast tend to lowest [31] [31]. Herawati [20] categorized the degree of roasted coffee according to popping sound and associated to visual intensity (lightness) and water activity. ...
Due to its chemical compounds, coffee has a good taste, pleasant aroma, stimulant effect, and health benefits. Roasting is a critical process to develop a good flavor and cup quality of the coffee brew. This article reviews the coffee chemical reaction proceeds during roasting, evaluates the roasted degree by physic and chemical approach and biochemical changes. The articles were compiled from ScienceDirect, SpringerLink, ResearchGate, and Google Scholar. Out of all of the collected papers, 40 articles were covered in this paper. The initial process of roasting is water content evaporating and continuously is followed by roasting phase including pyrolysis, Maillard reaction and caramelization. The roasted coffee degree is determined by visual, weight loss, acidity, and pop beans sound. The bioactive compounds of coffee such as chlorogenic acids, caffeine, and trigonelline affect brewed coffee’s cup quality. Chlorogenic acid and trigonelline significantly decrease during the roasting process. However, caffein is quite stable during roasting. The roasted coffee performs a function in the consumers’ health since in vitro and in vivo analysis present that bronze roasted espresso has the most powerful activity as anti-inflammatory and antioxidant.
... There is only a limited information in order to compare the chlorogenic acids contents of the collected coffee samples with the chlorogenic acids present in other Ethiopian coffee beans (Alonso-Salces et al., 2009;Moon et al., 2013). An article by Farah et al. (2006) reported that raw Harar coffee beans contain about 5.6% (w/w) of total chlorogenic acids. ...
... An article by Farah et al. (2006) reported that raw Harar coffee beans contain about 5.6% (w/w) of total chlorogenic acids. (Moon et al., 2013), while studying the role of coffee roasting conditions on the level of chlorogenic acids, reported total chlorogenic acid contents of 6.91%, 3.21%, and 1.97% (w/w) in the green, light roasted, and medium roasted coffee beans of Ethiopian origin, respectively. After studying the chemical composition of green coffee beans grown in different parts of Ethiopia, Sherge (2017) reported that the total chlorogenic acids produced during medium roasting of Harar as 1.93% (w/w). ...
The effects of drum, fluidized bed, and traditional type of coffee roasting technologies
on the cup quality and bioactive compounds of Yirgacheffe, Harar, and Sidama
variety specialty coffee beans grown in Ethiopia were investigated at light, medium,
and dark degree of roast from 150°C to 200°C for 7 to 15 min. No significant differences
in cup quality were detected among the roasted coffee varieties disregard of
the type of roasters. Varietal difference was found to have significant (p < .05) effect
on caffeine content of the coffee beans. A significant reduction in trigonelline and
total chlorogenic acids content of the coffee beans was observed during roasting
process, with darker roasts attaining the least values. Drum roaster was found to be
the best type of coffee roaster for specialty coffee beans at medium degree of roast
with the highest cup quality, optimum bioactive compounds content, and minimum
acrylamide formation. However, traditional roaster resulted at the least average cup
score of 80% among the three coffee samples and the highest acrylamide content
of 2.306 mg/L for Yirgacheffe coffee sample at light degree of roast. There are still
some bottlenecks that need to be addressed via advancements using novel food processing
technologies in order to devise the next generation of coffee processing.
K E Y W O R D S
acrylamide, caffeine, chlorogenic acids, coffee roaster, high-quality coffee, trigonelline
... Different roasting levels and techniques contribute to varying dimensions of coffee tastes. One of the coffee tastes directly impacted by the roasting process is sourness, which can be measured by the acidity level on the standard pH scale (Lee et al., 2013). However, the current practical solution to measuring coffee's sourness from its roasted beans involves using scientific tools to quantify the pH level of the samplebrewed coffee beans. ...
Sourness is one of the basic yet essential tastes of coffee that is chemically composed of acids and quantitatively represented in the pH scale. Current tools for measuring the acidity level in roasted coffee beans, including traditional methods, require brewing sample coffee and probing the chemical components, limiting the applicability to end customers seeking to estimate the acidity level before choosing the right coffee beans to purchase. This paper proposes a novel approach to directly estimate the acidity levels from roasted coffee beans images by framing the problem into an image classification task, where a picture of roasted coffee beans is categorized into its appropriate pH range. As a result, end customers could simply estimate coffee beans' acidity levels by taking photos with conventional cameras. Multiple traditional machine learning and deep learning algorithms are validated for their ability to predict the correct acidity levels. The experiment results reveal that EfficientNet yields the best performance with an average F1 of 0.71 when trained with images from separate portable devices.
Practical Applications
The research's findings could also be extended to applications in the coffee‐industrial settings, such as automatically monitoring roasted coffee beans' quality from image and video streams. For end customers, the trade‐off between efficacy and efficiency of the EfficientNet algorithm is also investigated, which sheds light on the implementation aspects of state‐of‐the‐art deep learning models in portable devices such as smartphones or cameras. Such applications could prove to be a cost‐effective and convenient solution for customers to quickly measure roasted coffee beans' sourness before deciding to purchase.
... Similar findings were reported by Nicoli et al. (1997), who quantified how increased roasting times led to increased degrees of browning. The color of the grounds remains an important quantitative measure of roast even when examining other physicochemical aspects of coffee such as antioxidant activity and volatile compounds (Cangussu et al., 2020;Lee et al., 2013;Nicoli et al., 1997;Sacchetti et al., 2009). Qualitatively, color can affect perceived sensory characteristics (Lawless & Heymann, 2010a). ...
Beverage color significantly affects perceived sensory quality and consumer preference. Although the color of coffee beans is well known to vary strongly with roast level, little work has examined how roast level and brewing conditions affect the color of the final beverage. Here, we report that the color of full immersion brewed coffee is significantly affected by both roast level and brewing temperature. Coffees from three different origins were each roasted to three different levels (light, medium, and dark) and then brewed at three different temperatures (4, 22, and 92°C). Each sample was brewed toward full extraction and then diluted to precisely 2% total dissolved solids so that differences in concentration would not confound color measurements. Absorbance spectra (UV‐vis) and color tristimulus values (L*a*b*) were then collected and analyzed. We find that roast level had the strongest impact on brew color, and that brew temperature had a significant impact on color for light and medium roasts, with less impact on dark roasts. Qualitatively, the cold brewed coffees tended to be redder, while the hot brewed coffees were blacker. The results suggest that there is an opportunity to manipulate and brand brewed coffee color through judicious choices of roast level and brewing temperature. Color serves as an indicator of coffee quality and potentially could affect perceived sensory characteristics. Our results suggest that appropriate control of roast level and brew temperature could yield desired colors for novel coffee products.
... A representative raw material for roasting is coffee beans; it is known that the variety and roasting conditions of the beans through the roasting and extraction process affect the flavour of the final coffee drink [22][23][24][25]. Research performed on coffee revealed that the processing of raw coffee materials under appropriate roasting conditions can be used to improve the quality of the raw material itself. ...
Roasting has been widely used in manufacturing food products, ensuring microbial safety, and improving extraction efficiency. Roasting treatment affects various qualities such as the chemical composition, physical properties, colour, aroma, and texture of food. This study determined the effect of novel convection heated roasting on aroma and taste components, that is, amino acids (AAs) and nucleotides in vegetables, meat, and their products. Heat treatment conditions were confirmed with a temperature condition of 250°C for 20–50 min for each raw material. The individual raw materials were each subjected to a convection oven process, then mixed together, and pressurised by heating at 121°C for 3 hours to prepare a key-based broth for use in Korean soup dishes. As for aroma components, aroma of fermented spirits, unpleasant aroma, and bad aroma were observed in the absence of roasting. By contrast, convection heated roasting-related aroma components such as savoury fatty aroma, coffee aroma, and roasted barley aroma were observed in the finished products after roasting. The products’ sensory profile presumably changed from negative to positive owing to roasting. By roasting, in the case of raw material extracts, the total AA and glutamic acid contents increased to 24.1–38.1%, and for the finished product, the total AA and glutamic acid contents slightly increased to 5.8–8.9%. However, no significant effect of roasting was found on nucleotides. In conclusion, it was concluded that the positive aroma component as well as the total amount of AA (umami taste) increased owing to roasting. The present results contribute immensely to the food industry as the enhancement of taste and aroma can help with the production of more palatable foods as desired by food consumers, thereby increasing the sales of nutritious foods that otherwise consumers may not buy.
... is implies that the highest roasting time and lowest particles sizes are negatively correlated to the flavor value of the coffee brew. As the roasting time increased, flavor components escape the bean in form of gas or undergo different chemical degradations and result in minimum flavor value [37,38]. ...
Optimum flavor and aroma of the coffee are developed during the roasting process. However, certain problems exist in the coffee roasting process such as partial charring, over roasting, and poor temperature distribution across the coffee bean (due to the low thermal conductivity of bean), if conditions are not optimized. Hence, uniform temperature distribution across the coffee bean in the roasting process is highly desirable. To achieve these requirements, the broken coffee beans were positioned in a single layer packed bed arrangement using the closed system by circulating hot air. In this experiment, three factors were arranged in a completely randomized design with three levels and three replications. The first factor considered was roasting temperature (200°C, 230°C, and 260°C), second factor was roasting time (5 min, 10 min, and 15 min), and third was particle size (4–6 mm, 2.36–3.35 mm, and 1.7–2.36 mm). The initial moisture content of raw beans (cv. Limu) was determined. The data were collected on selective physical properties of roasted coffee beans and sensory acceptability of prepared beverage. The results showed that the physical properties and sensory acceptability are significantly high (P
... Similar to the results for pH, the titration volumes for the extracts of puffed beans (0.61-0.71 mL) were significantly greater than those of roasted beans, indicating that puffing increased the liberation of acids. In this regard, it was reported that the acids in the polycrystalline structure of coffee decompose, and volatile acids are subsequently passed off in the roasting process, causing the pH to decrease with the degree of roasting (Lee, Kim, Kim, Lee, & Yeum, 2013). However, the puffing process did not seem to cause the breakdown of acids. ...
Puffing of coffee beans, which induces heat- and pressure-derived physicochemical changes, was applied as an alternative to roasting. Roasted or puffed coffee beans with equivalent lightness values were compared. The moisture content was higher while the crude fat and protein compositions were lower in puffed beans than in roasted beans. The pH was lower and the acid content was higher in puffed beans than in roasted beans. The roasted beans exhibited greater specific volumes, while the puffed beans displayed greater extraction yields. The trigonelline and total phenolic contents were greater in puffed beans than in roasted beans resulting in an enhanced antioxidant capacity. Sensory evaluation of roasted and puffed coffee bean brews revealed that puffing did not affect the flavor or overall acceptance. The current study provides evidence that puffing is an alternative to roasting coffee beans with various benefits.
This study investigated the effects of four brewing methods (cold and hot brew, espresso, and cezve) on the chemical sensory properties of green and roasted coffee beans (cv. Yellow Bourbon) extract. The caffeine and chlorogenic acid contents of the coffee were analyzed using HPLC. The taste and volatile aromatic compounds of coffee were analyzed using an electronic tongue and nose, respectively, and the results were analyzed using principal component analysis. For the taste components analyzed using the electronic tongue, the degree of separation was relatively large depending on the extraction method, and the degree of separation was larger depending on roasting for the volatile compounds analyzed using the electronic nose. Our findings provide basic data for the coffee industry. The use of an electronic sensor will provide flavor characteristics for four different types of coffee extracted from green beans and roasted beans. In this study, it was confirmed that the extraction method had a greater effect on the taste of coffee, and in the case of the volatile aromatic compounds of coffee, there was a large difference depending on the green beans and roasted beans. Therefore, our findings will provide data based on the sensory properties of coffee.
Wet fermentation of coffee beans is critical for developing sensory and perception properties of coffee beverages. This study aimed to investigate its impact on the appearance, chemical composition, and volatile compounds in coffee from four grinding sizes. There was no significant difference (p<0.05) between fermented and unfermented coffee in salt content whereas fermented coffee had lighter appearance and relatively lower pH values (4.78). The total voltage of e-nose obtained from fermented coffee were significantly higher, particularly with 250 and 350 µm coffee powder. Although the most of overtones detected by NIR from both coffee types were within 1700 – 2000 nm and 2200 – 2396 nm, the enhanced peaks responses of fermented coffee were lower. A total of 15 volatiles were identified using SPME/GC-MS. Fermented coffee showed lower total concentration but higher content in furfuryl acetate and 2-methoxy-4-vinylphenol, which could contribute to its unique caramel and fruity flavour.
In this study, the chemosensory components of microwave- or oven-roasted Coffea arabica L. were compared using high-performance liquid chromatography and electronic sensors. The contents of caffeine and chlorogenic acid were the highest in green bean extract and were decreased with micro- and oven-roasting time. The decreases in the content of the two components were observed more in oven roasting. In electronic tongue analysis, green bean extract had a relatively higher bitterness, sweetness, and sourness than others. After the roasting process, the bitterness decreased at 10 min, however, increased after 15 min. In addition, sourness tended to decrease over time. Microwave-roasted extracts were lower shifted than those of oven-roasted extracts during each roasting process. Accordingly, higher changes of taste patterns were represented during oven-roasting processes. In electronic nose analysis, volatile alcohols and esters were abundant in the green bean extract, and thus, these components were considered as the main volatiles in the green bean. Through the roasting process, the number of volatiles has increased. In particular, pyrazines were generated in those of roasted samples, and the amounts of furans increased. These results provide basic data regarding the chemosensory components of Yellow Bourbon and may be utilized to optimize the roasting conditions.
Coffee comprises of numerous bioactive compounds, and has recently been cultivated in temperate regions. We investigated the morphological and phytochemical changes in beans of Coffea arabica cvs. Catuai, Caturra, and Geisha cultivated in the Republic of Korea, at three roasting stages: green bean, 1st crack, and 2nd crack. Morphological changes were estimated by considering the size parameters and weights. Total polyphenols were determined using spectrophotometry, and caffeine and chlorogenic acid were quantified using high-performance liquid chromatography with the appropriate standards. Increased volume and decreased weight were observed in the beans of all three cultivars after roasting. The content of total polyphenols was about 13.74 mg gallic acid equivalent/g dry weight. The analysis of variance revealed that the contents of total polyphenols was insignificant among the cultivars and there was no significant change in the roasting stages. Compared to green bean, decreased contents of caffeine were obtained in the 1st crack and 2nd crack of ‘Catuai’. Chlorogenic acid contents were dramatically decreased in the 1st and 2nd crack of all three cultivars, as compared to green bean. Among the cultivars, ‘Geisha’ showed maximum decrease in chlorogenic acid (about 96%, 1.87 mg/mL) at 2nd crack, compared to the green bean (44.72 mg/mL). These results provide information about the characteristics of various coffee cultivars grown in the Republic of Korea during roasting. © 2022 The Korean Society of Food Science and Nutrition. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/lice nses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
We investigated pesticide residues in green coffee beans. Toward this, we collected 80 samples of green coffee beans and analyzed the presence of 41 different pesticides using a combination of the QuEChERS method and GC-MS/MS and LC-MS/MS. In the validation study, the values of limit of detection and limit of quantitation were in the range of 0.0003-0.0031 mg/kg and 0.0009-0.0093 mg/kg, respectively. The coefficient of determination (R2) was > 0.99. The recovery rate was satisfied except for 2 pesticides at the concentration level of 0.01 mg/kg, and except for 5 pesticides at the concentration level of 0.1, 0.5 mg/kg. The pesticide residue detection rate in the green coffee beans was 18.8% (15 of 80 samples). Pesticide residues were detected in 11 samples from Brazil, 2 samples from Colombia, 1 sample from Kenya, and 1 sample from India, all of which were Coffea arabica. Five kinds of residual pesticides were detected. Chlorpyrifos is an organophosphorus insecticide, triadimenol is a triazol fungicide, imidacloprid, thiamethoxam, and clothianidin are neonicotinoid insecticides. All 15 green coffee beans in which detected pesticide residues were evaluated at a safe level below the Maximum Residual Limits (MRLs), but since coffee consumption is increasing day by day, the levels of pesticide residues in green coffee beans should be monitored continuously.
This study investigated taste and aroma characteristics of 10 commercial coffee samples using an electronic tongue (E-tongue), an electronic nose (E-nose), gas chromatography-mass spectrometry (GC/MSD), and GC-olfactometry (GC-O). In electronic tongue analysis, sourness, umami, and bitterness were high in the non-franchise#2 (N-FC#2), saltiness was high in the franchise#1 (FC#1), and sweetness was high in the non-franchise#4 (N-FC#4). In the electronic nose analysis, a total of 22 volatile compounds were identified in the 10 coffee samples, and 3-methyl- 1-butanol, 2-methyl furan, and propan-2-one were the dominant content in these samples. In GC/MSD with GC-O analysis, a total of 40 volatile active compounds were identified, which include 3 alcohols, 2 aldehydes, 3 esters, 3 furans, 5 hydrocarbons, 5 heterocyclics, 4 ketones, 6 pyrazines, 5 pyrroles, 2 pyridines, and 2 phenolic compounds. Pyrazines were the dominant volatiles in the samples. 1-(2-Furanylmethyl)-1H-pyrrole was detected in all samples and showed a relatively higher content compared to other pyrroles. Our results which included taste and aroma patterns in commercial coffee brands may provide basic research data for the chemosensory research field.
This study investigated nutritional, physicochemical, and sensory characteristics of coffee brewed with conventional and high-oleic peanut extracts. Compared to normal coffee, peanut coffee exhibited more diverse amino acids compositions. In constituent amino acids composition, peanut coffee exhibited increased proportions of glutamic and aspartic acids but decreased phenylalanine. Peanut coffee had higher thiamin, niacin, and sugar contents, improved antioxidant capacity, and lower caffeine contents. In electronic tongue analysis, peanut coffee showed an increased intensity of sweetness and umami taste but decreased bitterness, corresponding to the result of amino acids compositions and caffeine and sugar contents. In volatile compounds analysis using gas chromatography-mass spectrometry (GC/MS) with the sniffing test, peanut coffee had high concentrations of 2-ethyl-3,6-dimethylpyrazine, 2,2′-methylenebis-furan, and furfuryl propionate, which were perceived as peanut and roasted odors in the sniffing test. This study will provide informative data in extending the application of peanut to coffee and developing novel coffee, with added peanut, that is nutritionally beneficial.
The physicochemical characterstics of El Salvadoran Coffea arabica cv. Bourbon coffee extracts under various roasting conditions were investigated. Green beans were roasted under four different conditions (Light-medium, Medium, Moderately dark, and Very dark). The coffee extracts were prepared by using the espresso or drip methods. As the roasting degree increased, the coffee bean moisture content decreased and the ash content increased. The lightness and yellowness of the beans and coffee extracts decreased along with the increasing roasting degree. In the drip coffee, the reducing sugar content decreased and the pH value increased along with the increasing roasting degree. Both in the espresso and drip coffee, total organic acid and chlorogenic acid contents decreased, while the caffeine content increased along with the increasing roasting degree. Therefore, it is suggested that the roasting degree affects the physicochemical characteristics of coffee extracts.
In this study, we investigated the aroma characteristics of Goheung coffee in Jeonnam, which was firstly tested and cultivated as a special crop in Korea, using GC-IMS electronic nose. As a result of principal component analysis of the aroma pattern detected by electronic nose, the aroma of Goheung coffee was distinguished from five foreign species of origin (Colombia, Guatemala, Ethiopia, Brazil, India). Of the volatile compounds in Korea's Goheung coffee, the nine components that showed high sensitivity were not found in other foreign coffee. The unique fragrance composition of coffee from Goheung in Korea was observed, and the fragrance components of buttery, oily, caramel-like 1-heptene, 2-methyl- and 1-propanol, which have strongly fruity and floral aroma, were strongly detected in ethiopia coffee, and strongly detected in Guatemala. Sweet and fruity components such as 2-pentanone and isopropyl tert-butyl ether and components such as amine and pyridine with negative aroma characteristics such as sour, putrid, bitter, and fishy were found to be the lowest in the five foreign coffees. From these results, the aroma characteristics of Korean Goheung coffee are expected to a good response to domestic consumers.
Qualitative properties of roasting defect coffee beans and their classification methods were studied using hyperspectral imaging (HSI). The roasting defect beans were divided into 5 groups: medium roasting (Cont), under developed (RD-1), over roasting (RD-2), interior under developed (RD-3), and interior scorching (RD-4). The following qualitative properties were assayed: browning index (BI), moisture content (MC), chlorogenic acid (CA), trigonelline (TG), and caffeine (CF) content. Their HSI spectra (1000–1700 nm) were also analysed to develop the classification methods of roasting defect beans. RD-2 showed the highest BI and the lowest MC, CA, and TG content. The accuracy of classification model of partial least-squares discriminant was 86.2%. The most powerful wavelength to classify the defective beans was approximately 1420 nm (related to OH bond). The HSI reflectance values at 1420 nm showed similar tendency with MC, enabling the use of this technology to classify the roasting defect beans.
Recently, increased caffeine intake has led to an increase in caffeine addiction and withdrawal symptoms. Coffee is surreptitiously consumed in as an additive to milk and caramel. There are few studies on how coffee affects the health of modern people. The purpose of this study is to determine the efficacy and side effects of coffee by awareness of coffee consumption patterns among college students, who are the principal consumers. A survey was conducted from May 11 to 17, 2015 and 302 questionnaires were analyzed. The respondents were 140 men (46.4%) and 162 women (53.6%). In terms of coffee additives, 151 (50.0%) respondents chose `americano` and 111 (36.8%) `variation`. The frequency of coffee intake and sleep time for college students was negatively correlated, with the correlation coefficient of -0.145 and significance probability of 0.019. The group that was `positively` aware of the principal ingredients of coffee had a higher level of academic training than those with `negative` awareness (p
An experimental study on the automation of the coffee roasting process was conducted. For this study, a temperature sensor, controllers, and motors were added to a manually operated coffee roaster. The temperature, time, and exhausting damper control were selected as the control parameters. The thermocouple measurements were severely influenced by the thermocouple size and location of the roaster. As a result, the standard thermocouple size and location of the roaster were experimentally set to show a similar trend of temperature change by using a previously installed thermometer. A standard roasting process was chosen through repeated roasting experiments and the advice of a roasting expert. The automation of the roasting process was successfully executed using temperature criteria, such as the bean input and first and second crack occurrence, and by controlling the exhausting damper opening time. The control parameters and roaster skills can be used for similar types of roasters for process automation.
This study was conducted to determine the optimal roasting temperature (90, 100, 110, and 120; fixed time of 20 minutes) of small black coffee beans under various roasting conditions. The roasting temperature range and fixed time were the same as our preceding study. After roasting, the general composition, isoflavone contents, and antioxidant activities were measured. As the results of the proximate composition analysis of small black beans according to roasting conditions, only moisture decreased among them, whereas other general compositions were not affected. The DPPH and ABTS radical scavenging activities were the highest at a roasting temperature of 120°C. Total polyphenol and total flavonoid contents were also highest at 120°C. Isoflavone contents showed a positive correlation with DPPH and ABTS radical scavenging activities, as well as total phenol and flavonoid contents. These results suggest that the optimal roasting conditions of small black beans were determined to be 120°C for 20 minutes.
Four different kinds of coffee beans (CS, Colombia supremo; EY, Ethiopia yirgacheffee; IM, Indonesia mandheling; and IMM, India monsooned malabar) were roasted at 200 and 250°C for 10, 15, and 20 min. To determine the optimum roasting conditions, various components of the coffee beans such as pyrazines produced during the roasting, and their antioxidant and antidiabetic effects were analyzed. The different roasting condition did not affect on the concentration of caffeine. However, the amount of 5-caffeoylquinic acid and the total phenolics decreased significantly, at a greater temperature and a longer roasting time. The greatest amount of pyrazines was produced from the IMM however, the amount of pyrazines decreased rapidly at 250°C according to increasing in roasting time. The DPPH free radical scavenging activity was mostly 80% more effective than that of BHT and α-tocopherol activities at the same concentration. In the case of the FRAP assay, the reducing power of the coffee slightly decreased at a greater temperature pand longer time. While the inhibitory effect on α-glucosidase was negligible, the activity decreased by more than 80% when the coffee beans were roasted at 250°C for 20 min. The inhibitory effect on α-amylase showed similar results. Taken together, the optimum roasting conditions were determined to be 200°C and 15 min, which provided the best physiological activity and nutty and chocolatey aromas from the pyrazine of coffee.
Dutch coffee is extracted in low temperature for a longer time than espresso and drip coffee. This study was conducted to investigate changes in the flavor compounds in Dutch coffee resulting from different extraction times and storage days. The fifty six flavor compounds in Dutch coffee were identified using a headspace mass-spectrometer. Major flavor compounds were 2-furfuryl acetate, 5-methylfurfural, pyridine, furfural, 2-acetylfuran, pyridine, 2-methoxyphenol, furfuryl alcohol and some compounds varied with espresso and drip coffee. It was worthy of notice that more diverse compounds were composed of total flavor in Dutch coffee. There were more kinds of flavor compounds in early extracts than in latter ones. The duration of storage didn`t significantly affected the peak area percentage of flavor compounds in Dutch coffee except with 2-furfuryl acetate.
Supremo coffee was light and dark brewed and grinded using different beans sizes. We determined physicochemical properties of Supremo coffee in the form of moisture, crude fat, crude protein, and crude ash contents. Moisture content was higher in beans of the dark brew than the light brew. Carbohydrate content was lower in the dark brew. However, crude fat, crude protein, and crude ash contents were higher in the dark brew. pH level was higher in beans of the dark. L value (brightness) decreased in the dark brew. a value (red coloring) and b value (yellow coloring) were both increased in the light brew and decreased in the dark brew. Stronger brewing resulted in lower a and b values. The contents of Ca, Fe, K, Na, and P were measured, and the results showed that K content was the highest. Total dietary fiber content was significantly higher than all other brewing parameters. Soluble dietary fiber content was 4.25 g/100 g in the dark brew and week grinding while insoluble dietary fiber was 63.49 g/100 g in the light brew and week grinding, which was the highest. Fatty acid composition was not significantly different according to brewing and grinding conditions. Supreme coffee contained acetic acid, propionic acid, oxalic acid, citric acid, and numeric acid. In particular, contents of acetic acid and numeric acid were highest. These results suggest that physicochemical properties of Supreme coffee are affected by different brewing and grinding conditions.
In the present paper we study the C 1-robustness of the three properties: average shadowing, asymptotic average shadowing and limit shadowing within two classes of conservative flows: the incompressible and the Hamiltonian ones. We obtain that the first two properties guarantee dominated splitting (or partial hyperbolicity) on the whole manifold, and the third one implies that the flow is Anosov.
This study was investigated the optimal time that enhanced the functional activities of mung beans for use of functional food resources. Mung beans were roasted according three levels of roasting time levels (10, 20 and 30 minutes) at and then the physicochemical compositions were determined. The reducing sugar content was decreased with the increased roasting time. Moisture was decreased with increased roasting time, whereas, crude fat, crude ash, crude protein and carbohydrate were increased with prolonged roasting time. The highest contents of total phenol and flavonoid were shown at a roasting condition for 30 minutes. The highest inhibitory activities of DPPH radical, ABTS radical and xanthine oxidase was the best at the condition of for 30 min. From these results optimal roasting time of mung beans were 30 minutes for use of functional food resources.
Variations in the chemical composition profile of the gas evolved during roasting of coffee were qualitatively monitored with the aim of further establishing a chemical criterion for determination of the degree of roast. Simultaneously, the variations in the beans physical properties, such as volume, weight loss, and moisture content, were also monitored. Three hundred grams of coffee were roasted in a lab-scale roaster and the optimum degree of roast was reached in 9 min. The gas evolved during roasting was collected for gas chromatographic analysis. The chromatograms representing the evolution of the gas composition profile showed that a group of compounds will first appear close to the optimum degree of roast time. This indicated the feasibility of using such compounds as chemical descriptors when establishing a scientific criterion for determination of the degree of roast.
Aroma extract dilution analysis (AEDA) revealed 13 compounds as important contributors to the aroma of roasted coffee (powder): 2-methyl-3-furanthiol (I), 2-furfurylthiol (II), methional (III), 3-mercapto-3-methylbutylformate (IV), 3-isopropyl-2-methoxypyrazine (V), 2-ethyl-3,5-dimethylpyrazine (VI), 2,3-diethyl-5-methylpyrazine (VII), 3-isobutyl-2-methoxy-pyrazine (VIII), 3-hydroxy-4,5-dimethyl-2(5H)-furanone (sotolon, IX), 4-ethylguaiacol (X), 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone (XI), 4-vinylguaiacol (XII), and (E)--damascenone (XIII). A comparative AEDA of the coffee powder and brew showed in the brew an increase of III, IX, vanillin and 4-hydroxy-2,5-dimethyl-3(2H)-furanone and a decrease of I, II, IV, V, VII, and VIII.Die Aromaextrakt-Verdnnungsanalyse (AEVA) von Rstkaffee ergab 13 wichtige Geruchsstoffe: 2-Methyl-3-furanthiol (I), 2-Furfurylthiol (II), Methional (III), 3-Mercapto-3-methylbutylformiat (IV), 3-Isopropyl-2-methoxypyrazin (V), 2-Ethyl-3,5-dimethylpyrazin (VI), 2,3-Diethyl-5-methylpyrazin (VII), 3-Isobutyl-2-methoxypyrazin (VIII), 3-Hydroxy-4,5-dimethyl-2(5H)-furanon (Sotolon, IX), 4-Vinylguajacol (XII) und (E)--Damascenon (XIII). Die vergleichende AEVA von Rstkaffee und daraus hergestelltem Aufgu zeigte im Aufgu eine Zunahme von III, IX, Vanillin und 4-Hydroxy-2,5-dimethyl-3(2H)-furanon und eine Abnahme von I, II, IV, V, VII und VIII.
The majority of the more than 800 volatiles which have been identified in roasted coffee, are formed by Maillard reactions. However, recent sensory specific investigations showed that only a small number of these contribute to the flavor complex of roasted coffee and that many odorants with a strong flavor impact are generated by formation pathways besides Maillard reaction. This chapter gives an overview of aroma compounds of roasted coffee and their corresponding formation pathways during roasting. Apparently certain pathways are specific for roasted coffee flavor formation.
The consumer awareness concerning coffee beverages has increased in Korea. The objective of this study was to optimize the roasting conditions of coffee bean for consumer's attribute. The optimal roasting conditions for Colombian coffee beans were analyzed by using a central composite design with a quadratic polynomial model by response surface methodology (RSM). The experimental conditions for coffee bean roasting were and 7.93~22.07 minutes. The responses of sensory attributes. physicochemical and physical properties were analyzed with RSM. The width. length and height of green beans increased when the beans were roasted. The higher degree of roasting gave the higher pH and solid contents but the lower total acidity and total phenolic compounds. In sensory tests, the roasting temperature and time had a significant effect on the flavor score. The optimum roasting condition of Colombian coffee bean predicted for maximizing the length, width, solid contents, total phenolic compounds and flavor score were 20 minutes at by RSM.
Changes in flavor characteristics of roasted coffee in 6 package models during storage were investigated by GC/MS analysis and sensory evaluation to establish the criteria of the shelf-life of the roasted coffee in three flavor quality-'fresh', 'satisfying' and 'minimally acceptable' levels. In direct headspace method of GC/MS, 47 volatile compounds were analyzed and the light volatile compounds were reduced sharply at initial stage of storage and faster in the package with air. The correlation between % retention of 2,3-butanedione and overall aroma of roasted coffee showed good linear-relation, of which correlation coefficient (R) were from 0.999 to 0.904 depending on package models, indicating that 2,3-butanedione would be an index chemical for evaluating the freshness of roasted coffee. In sensory evaluation of 6 package models during storage, roasted whole beans (RB) and roasted and ground (RG) coffee in air-package were preserved in 'fresh quality' for week, 'satisfying quality' for weeks and 'minimally acceptable quality' for 12 weeks, while roasted whole beans in valve-package and roasted and ground coffees in vacuum-package, nitrogen-package and oxygen absorbent-package were preserved in 'fresh quality' for weeks, 'satisfying quality' for weeks and 'minimally acceptable quality' for 52 weeks. The oxygen absorbent-package was slightly less effective than other three methods.
In this study, the supercritical extraction was applied for the enrichment of coffee flavors. The extraction efficiency of coffee flavors was dependent on the pressure and temperature and optimized as 350 bar and 80C. Five flavors of high aroma values were analyzed. The flavors extracted by the supercritical extraction were 76.6 times higher than those by the traditional method, espresso extraction. The modified headspace system proved the enhanced efficiency of supercritical extraction. The coffee beverage containing the extract of supercritical resulted 2.3 times of flavor enrichment when it was compared to that without the supercritical extract.
The objective of this study was to analyze the volatile profiles of both green and roasted coffee beans, for assessment of roasting degrees under two different processing temperatures. Volatiles extraction and concentration were performed by solid phase micro-extraction (SPME) of the ground coffee headspace and analysis of the volatiles profile was performed by GC–MS. Four SPME fibers were evaluated, with the one that extracted the highest amount of substances (DVB/CAR/PDMS) being selected. Statistical analysis of the data by principal components (PCA/clusters) showed that the volatile components profile provided separation of green and roasted coffees and also separation according to roasting degree and roasting temperature. Results also indicate that color and weight loss measurements alone are not reliable for roasting degree assessment.
With the objective of optimizing the roasting of robusta coffee (Coffea canephora Conillon), a two factor central composite design (11 samples) was used to optimise the settings for roasting time and the initial internal temperature of the roaster drum on response variables of acceptance with 25 consuming assessors, for the sensory attributes of beverage aroma, flavour and colour. Predictive models were also obtained for the instumental measurement of the colour of the beans and ground coffee. The optimum range for roasting was shown to be a time of 22–28 min at a temperature of 225–230°C, corresponding to the degree of roasting characterized by the following range of colour of roasted robusta beans: L* between 37.05 and 40.69, a* between 2.29 and 4.15 and b* between 2.70 and 6.29.
During the roasting process, coffee beans change their textural properties, losing strength and toughness and becoming progressively more brittle, owing to chemical, physical and structural modifications.The aim of this paper is to evaluate the factors—such as density and moisture—affecting the mechanical properties of coffee beans roasted at 170, 200°C and under so-called high yield conditions. To distinguish the effects due to roasting (where both density and moisture changes occur) from those due to the water removal alone, heat treatments on coffee bean samples at dehydration temperatures (90–105°C) have been also carried out. Results showed that the typical brittleness of roasted and high yield coffee beans seems to be related both to the water loss and to the change of tissue structure owing to the pyrolysis phenomena and to the decrease of density. In fact, even if dried and roasted coffee beans showed, at similar moisture content, a reduced and weak significant difference in the resistance to fracture and in toughness, roasting caused a decrease of the deformability, the index of a brittle and fragile texture.
Twenty-eight potent odorants were quantified by stable isotope dilution assays of medium-roasted Arabica coffee blends from
Colombia (Col), Brazil (Bra), El Salvador (El) and Kenya (Ken) as well as the varieties Tipica (Tip) from Colombia and Caturra
from the regions Pinas (Cat-P) and Quevedo (Cat-Q) in Ecuador. The blends from Col and Bra were similar in their composition
of odorants. Ken contained higher amounts of 3-mercapto-3-methylbutylformate than Col and Bra, while 2-furfurylthiol, guaiacol
and 4-ethylguaiacol were present in lower concentrations. El contained less 4-vinylguaiacol and 2-furfurylthiol, but more
3-methyl-2-buten-1-thiol. Tip, Cat-P and Cat-Q differed from Col, Bra and Ken in having lower amounts of 2,3-butanedione,
2,3-pentanedione and 4-hydroxy-2,5-dimethyl-3(2H)-furanone and higher contents of guaiacol, 3-mercapto-3-methylbutylformate
and 3-methyl-2-buten-1-thiol. The largest amount of 2-furfurylthiol was found in Tip and Cat-P. The blends from Col and Ken
and the variety Tip showed a significant increase of guaiacol, 4-ethylguaiacol and 3-methyl-2-buten-1-thiol when the roast
degree was raised. 2-Furfurylthiol and 2(5)-ethyl-4-hydroxy-5(2)-methyl-3(2H)furanone increased only in Col and Ken, while
in Tip the amounts of carbonyl compounds, 4-hydroxy-2,5-dimethyl-3(2H)furanone, methional and (E)-β-damascenone decreased during roasting from medium to dark.
The antioxidant properties of coffee were studied in relation to roasting degree. In particular, the extent of the chain-breaking activity and oxygen scavenging properties of Maillard reaction products contained in coffee brews were evaluated. Samples showed very high chain-breaking and oxygen consumption activities, which did not increase linearly with increasing roasting degree. In our experimental conditions, the highest antioxidant properties were found for the medium-dark roasted coffee brews.
Aroma extract dilution analysis of raw Arabica coffee revealed 3-isobutyl-2-methoxypyrazine (I), 2-methoxy-3,5-dimethylpyrazine (II), ethyl 2-methylbutyrate (III), ethyl 3-methylbutyrate (IV), and 3-isopropyl-2-methoxypyrazine (V) as potent odorants. The highest odor activity value was found for I followed by II, IV, and V. It was concluded that I was responsible for the characteristic, peasy odor note of raw coffee. Twelve odorants occurring in raw coffee and (E)-beta-damascenone were also quantified after roasting. The concentration of I did not change, whereas methional, 3-hydroxy-4, 5-dimethyl-2(5H)-furanone, vanillin, (E)-beta-damascenone, and 4-vinyl- and 4-ethylguaiacol increased strongly during the roasting process.
The impact of time-temperature combinations of roasting processes on the kinetics of aroma formation in coffee was investigated. The development of 16 aroma compounds and the physical properties of coffee beans was followed in a commercial horizontal drum roasting process and in laboratory scale fluidizing-bed roasting processes at high temperature-short time and low temperature-long time conditions. All trials were run to an equal roast end point as defined by the lightness of coffee beans. In addition, the effect of excessive roasting on aroma composition was studied. Compared to low temperature-long time roasting, high temperature-short time roasting resulted in considerable differences in the physical properties and kinetics of aroma formation. Excessive roasting generally led to decreasing or stable amounts of volatile substances, except for hexanal, pyridine, and dimethyl trisulfide, whose concentrations continued to increase during over-roasting. When the drum roaster and the fluidizing bed roaster were operated in the so-called temperature profile mode, that is, along the identical development of coffee bean temperature over roasting time, the kinetics of aroma generation were similar in both processes.
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