Coffee Aroma Research Articles

MULTIMODAL FEATURES OF DESCRIPTIVE TEXTS: CASE STUDY OF COFFEE BRANDS

The article considers descriptive texts of coffee brands as a multimodal ensemble composed of verbal, visual, and sensory modes. A visual modus is the shape of the beans and the color of the coffee roast. The sensory mode represents the perception of taste, aroma, and texture of the coffee. Verbal modus is the direct verbalization of the abovementioned visual and sensory characteristics of the coffee. Coffee descriptors are verbalization of coffee flavors, aromas, textures, and other characteristics of coffee as a product. Coffee descriptors are divided into seven groups.

Flavor precursors and sensory attributes of coffee submitted to different post-harvest processing

Post-harvest processing (PHP) modifies the quality of the coffee and increases the value of coffee production. The choice of PHP to apply depends primarily on the available infrastructure, local climatic conditions and the desired end-value. The objective of this study was to evaluate the influence of PHP on the physico-chemical characteristics of green and roasted coffee beans and their sensory attributes. Coffee cherries from IAPAR 59 cultivar were processed as natural coffee (CN), semi-dry coffee (CD), de-pulped coffee (CP) and floating coffee (CF). Total and reducing sugars, phenolic compounds, chlorogenic acids, lipids, proteins, caffeine and water content were determined in coffee beans collected during (10^thday) and at the end of each processing. The roasted beans and their sensory attributes were also analyzed. The greatest changes at the ending point of the processes were found in total and reducing sugars, phenolic compounds, chlorogenic acids and lipids contents. The PHP presented different weight loss to achieve the same visual brown color and luminosity. Beverage sensory attributes were influenced by the PHP: CN and CP coffees presented similar intensities of coffee aroma, but higher intensity of green grassy aroma, and taste were found in CF and CN coffees. Aroma and taste precursors were modified during the PHP and these were associated to husk removal of the coffee beans, suggesting an activation of the germination metabolism during the PHP. This study allowed the characterization of the effects of the different post-harvest processing on the roasted coffee beans and provides the foundations to monitor their efficiencies in the future.

Portable Electronic Nose for Discrimination of Indonesian Robusta Coffee Aroma with Varied Roasting Temperature Correlated with Gas Chromatography Mass Spectrometry

<p>The quality of coffee is strongly affected by its aroma, so that instrument for aroma testing is necessary especially for quality control. In this research, coffee aroma was tested using electronic nose and then correlated to gas chromatography-mass spectrometry (GC-MS). The green beans of robusta coffee (<em>coffee canephora </em>var.<em>robusta</em>) originated from Sumatra was used as a testing sample. The roasting temperature was varied to be 180 °C, 195 °C, and 210 °C, while the roasting time was set to be constant at 20 minutes. After the roasting process, the coffee beans were grounded using a coffee grinder. The feature of the response signal for each gas sensors of the electronic nose to ground coffee aroma, was extracted using two methods; i.e. gradient multiplied by signal peak and average value. The principle component analysis (PCA) was applied to discriminate the aroma of ground coffee with varied roasting temperature. The scoreplot of PCA analysis shows a clear discrimination of each coffee aroma, produced by different roasting temperature. From the GCMS analysis, it is clearly confirmed that more aromatic compounds detected when the roasting temperature increase. It is correlated with the discrimination result using electronic nose. The loading plot interpretation provides information that TGS822 and TGS826 are the most affecting sensors for discrimination of coffee aroma with varied roasting temperature. In the future, the electronic nose is potentially applied in coffee industry for quality control during process.</p>

Roasting optimization and kinetics of raw and instant controlled pressure drop pre-treated coffee beans

Introduction: Coffee is one of the most widely consumed beverages in the world. The desired aroma and flavour of coffee are developed duringroasting which is the most important step in coffee processing. Instant Controlled Pressure Drop Process (DIC) technology is controlled hightemperature and short time process which been used successfully to improving the kinetics of drying, extraction, and decontamination of fresh and dried natural products. The main advantages of DIC are that it is a master controlled temperature and time process, the dwell times are short, reducing the chemical degradation, so new products with superior quality attributes may be developed. Materials and Methods: Two coffee beans varieties were investigated by Brazilian and Ethiopian sources. The raw beans were pre-treated using the DIC process under adopted conditions prior to roasting. A two-factor central composite design was used to optimize the settings of roasting time and roasting temperature on response variables of bulk, true and normalized density, and roasting degree. Also, microscopic analysis using Scanning Electron Microscopy (SEM) and kinetics of the roasting processes are included. Results and Discussion: The obtained results confirmed that the roasted DIC treated beans for both varieties have lower densities, higher roasting degree and lower activation energy needed for roasting compared to the raw beans. The physical properties’ magnitude is highly relevant to coffee origin. Roasting time and the temperature seemed to be of significant regarding all the physical characteristics of the beans, however, time was of topmost significance. Besides, treating coffee been by DIC prior to roasting leads to texture modification and conservation of time and energy needed for roasting. Conclusions: The physical properties of the roasted coffee beans are highly affected and changed with the coffee origin, roasting conditions and pre-treatment of coffee beans prior to roasting using the DIC process. The incorporation of the DIC process prior to roasting seemed to achieve more conservation of time and energy needed for roasting compared to the raw untreated beans. The higher degree of roasting and the competitive roasting activation energy of Brazilian coffee beans give aconclusion that more economic roasting process could be achieved with the Brazilian coffee. The pre-treatment by DIC enhances the remarkable reduction in coffee beans density and increasing in the roasting degrees that are in line with the industrial needs of coffee beverages. Response Surface Methodology is an efficient tool for optimization and mathematical modeling of the coffee roasting process.

Kopi Arabika Kalosi Produk Unggulan Kabupaten Enrekang

Kopi Arabika merupakan salah satu produk unggulan perkebunan Kabupaten Enrekang. UMKM Maqfirah sebagai produsen kopi baik dalam bentuk green bean maupun produk kopi roasted di Kabupaten Enrekang menghadapi permasalahan belum memiliki peralatan produksi, sehingga perlu peralatan pendukung untuk menjamin mutu dan meningkatkan produksi. Target mengembangkan UMKM ini sebagai produsen kopi arabika kalosi dengan peningkatan kapasitas produksi, mutu, variasi produk, serta perluasan pasar. Program pendampingan UMKM ini dilaksanakan melalui sinergi antara Tim Politeknik Pertanian Negeri Pangkajene Kepulauan dan Dinas Perindustrian Kabupaten Enrekang pada Maret-Agustus 2018. Metode penerapan melalui sosialisasi program, penyuluhan, pendampingan, dan pengembangan aspek produksi dan pemasaran. Dengan mengimplementasikan ipteks didapat peningkatan produksi, peningkatan kualitas citarasa dan aroma kopi, peningkatan pendapatan, dan peningkatan jaringan pasar kopi arabika kalosi yang merambah keluar provinsi.

Impact of bitter tastant sub-qualities on retronasal coffee aroma perception.

The impact of different bitter taste compounds on the retronasal perception of coffee aroma was investigated. A sorted napping experiment was carried out on thirteen compounds at iso-intense bitter concentrations. Differences in perceptual bitter sub-qualities among the compounds were reported by Multidimensional Scaling (MDS) and Multiple Factor Analysis (MFA) analyses. Seven exemplar compounds were further selected to investigate the impact of taste sub-qualities on cross-modal flavor interactions. In general, the different bitter compounds, when paired with a coffee aroma isolate, significantly modified the perception of the retronasal coffee aroma profile. Interestingly, the three bitter compounds endogenous to coffee had the most similar impact on the coffee aroma profile. Further sensory analysis of these sample sets indicated no significant effect of the bitter compounds on the orthonasal perception. Gas Chromatography/Mass Spectrometry (GC/MS) analysis of the volatile composition of the samples headspace also indicated negligible impact of the bitter compounds on aroma release. Altogether evidence of cross-modal interactions occurring at a higher cognitive level were demonstrated in a complex food sample, supporting the importance of multi-modal sensory integration on flavor perception.

Greek Coffee Quality Loss During Home Storage: Modeling the Effect of Temperature and Water Activity

The aim of this study was to monitor and characterize Greek coffee staling during home storage (secondary shelf life, SSL) using sensory evaluation techniques. Storage temperature (T) and product water activity (aw ) are considered as the major factors affecting SSL. Water sorption isotherms fitted to Guggenheim Anderson-de Boer model were used to predict product stability; coffee samples were stable at aw < 0.52. Coffee samples equilibrated at aw = 0.15 (the fresh sample), 0.22, 0.33, and 0.52 were stored at T = 25 °C, 35 °C, and 45 °C under simulated home storage conditions. Samples were obtained at appropriate times for each T and aw condition and sensorially evaluated. Greek coffee brews were prepared and freshly served during sensory evaluation. The use of Weibull hazard analysis provided an effective approach to SSL determination as a function of T and aw . SSL values ranged from 20 (Τ = 45 °C, aw = 0.52) to 104 days (Τ = 25 °C, aw = 0.15). Quality loss based on coffee aroma changes (aroma quality, aroma intensity, aftertaste, off-flavor) was also studied (Si , sensory scoring using 9-point magnitude scale) and kinetically modeled. Quality loss rates (ki ) were calculated and used to predict SSL values. Based on the results of both Weibull hazard analysis and sensory scoring of individual aroma characteristics, it was concluded that the lowest SSL was calculated for aw = 0.52 at T = 35 °C to 45 °C. The temperature dependence of aftertaste, aroma quality loss, and off-flavor production was not statistically significant for 0.15 < aw < 0.33 (P > 0.05); the aroma intensity was the most sensitive parameter. PRACTICAL APPLICATIONS: Secondary shelf life (SSL) represents the time after pack opening during which a food maintains an acceptable quality level. During home/catering usage, coffee is not consumed immediately after pack opening. During consumption, quality degradation reactions proceed with higher rates due to variable storage conditions mainly related to atmosphere changes in the pack, leading to the entrance of oxygen/moisture and temperature. Therefore, SSL is important, and can be used as a tool for product management during consumption reducing food waste. There is a lack of studies dealing with SSL prediction of coffee, while no studies have been carried out on Greek coffee.

한국 고흥산 커피의 gas chromatograph-ion mobility spectrometer에 의한 향기 특성 분석

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.

Improved detection of key odourants in Arabica coffee using gas chromatography-olfactometry in combination with low energy electron ionisation gas chromatography-quadrupole time-of-flight mass spectrometry

Four Arabica coffees (Brazil, Colombia, Ethiopia, and Guatemala) yield highly variant odours, attesting to the complexities of coffee aroma that command advanced analytical tools. In this study, their volatiles were extracted using solvent-assisted flavour evaporation (SAFE) and headspace solid-phase microextraction (HS-SPME). Due to matrix complexity, some trace odourants were detected in SAFE extracts by aroma extract dilution analysis (AEDA) but remained difficult to quantify by gas chromatography-mass spectrometry (GC–MS). This prompted the application of low energy electron ionisation (EI) coupled with GC-quadrupole time-of-flight (GC-QTOF). Optimal low EI GC-QTOF parameters (EI energy: 15 eV, acquisition rate: 3 Hz) were applied to achieve improved molecular ion signal intensity and reproducibility (relative standard deviation < 10%) across five compounds, which resulted in good linearity (R2 ≥ 0.999) and lowered detection levels (e.g. 0.025 ± 0.005 ng/mL for 4-hydroxy-5-methyl-3(2H)-furanone). Therefore, this method potentially improves the measurement of trace odourants in complex matrices by increasing specificity and sensitivity.

Production of coffee (Coffea arabica) inoculated with yeasts: impact on quality.

The aim of this study was to evaluate the performance of yeasts Saccharomyces cerevisiae CCMA 0200 and Torulaspora delbrueckii CCMA 0684 in Mundo Novo and Catuaí varieties processed by the wet method and the impact on sensory quality and compounds profile. The microbiota was evaluated by surface plating, and the compounds were evaluated by high-performance liquid chromatography and gas chromatography-mass spectrometry. Sensorial analysis was performed using the cupping test (Specialty Coffee Association). T.delbrueckii CCMA 0684 was better adapted to the process and remained for up to 72 h of drying. Eighteen volatile compounds were detected in green coffee and 75 in roasted coffee. 2-Furanmethanol propanoate and 2-ethyl-3,5-dimethylpyrazine were identified only in the inoculated treatments, and these are important contributors to the coffee aroma. All treatments received scores greater than 80 in the sensory analysis. T.delbrueckii CCMA 0684 presented better results in relation to the sensorial analysis and is preferable for the varieties and processing method studied. The use of starter cultures is a viable method with which to obtain high-quality coffees with a distinct flavor and thus add to value to the product. © 2019 Society of Chemical Industry.

Influence of Roasting Process in Six Coffee Arabica Cultivars: Analysis of Volatile Components Profiles

The complex composition of coffee aroma depends on the several factors regarding green coffee such as species and variety of the beans, origin , seeds size, colour (Toci and Farah, 2014). The most important coffee varieties are known to be Coffea arabica with good organoleptic characteristics, and Coffea canephora , known as Robusta of inferior quality. Development of aroma compounds also is greatly dependent upon the degree of roasting (Lopez-Galilea et al., 2006). In the roasting process almost 840 volatile organic compounds (VOC) are evaluated (Saw et al., 2015). The aim of this work is to investigate of the aromatic profile of six Arabica cultivar from Africa, Central and South America at different roasting degrees (light, medium and dark) and to establish odordescriptor categories as indicators for the assessment of flavour differences. The three roasting degrees were obtained in laboratory considering as target the industrial products and coffee roasting intensity was evaluated by a polychromatic colorimeter. The aromatic compounds of espresso coffee were evaluated by static headspace gas mass chromatography. The 67 key odors identified were classified in ten smell groups: floral, ethereal, fruit, chocolate, sweet and sugary, nut, grain and cereals, roast, spice, vegetal and earthy as suggested by Flament (2001). Results showed a consistent difference between different origins, depending on roasting intensity and maturation time, reflecting the possibility to optimize espresso coffee mixtures in an analytic way.

Effect of harvesting altitude, fermentation time and roasting degree on the aroma released by coffee powder monitored by proton transfer reaction mass spectrometry

This study investigates the effect of harvesting altitude, fermentation time and roasting degree on the volatile profile released by coffee (Coffea arabica, variety Catimor) powder. The analysis of the volatile organic compounds was performed by proton transfer reaction mass spectrometer (PTR-MS). The experimental design consisted of three factors: altitude at two levels (900 m and 1500 m, milder and harsher climate, respectively), four different fermentation times (0, 24, 48 and 72 h) and roasting at three levels (light, medium and dark). Analysis of the released volatile organic compounds (VOCs) revealed that the intensity of m/z 45 and 59 dramatically decreases at a higher harvesting altitude. Longer fermentation times induce a decrease of m/z 61 and 75, probably related to the activity of the isocitrate lyase. Finally, a prolonged roasting degree induces a rise of the m/z 61, 75, 81 and 97. The total count per second measured by PTR-MS was used as an index of “overall coffee aroma intensity” to build a linear regression model. The model was used to predict the total VOCs intensity on the basis of the altitude, fermentation time and roasting level. The validation of the model (adjusted R2 = 0.91 and normalized relative standard deviation in prediction of 7%) reveals that, although the degree of roasting clearly affects the resulting aroma intensity, altitude and fermentation time also play a role in the formation of the volatile profile. Moreover, a significant interaction was observed between the altitude where the bean were grown and the roasting level. These results support the hypothesis that the type of process of the seeds has a strong impact on the resulting coffee’s quality. Furthermore, PTR-MS coupled with linear regression models is a powerful tool for the quality control of coffee process.

Impact of drying process on chemical composition and key aroma components of Arabica coffee

Influence of heat pump drying (HP at 40, 45 and 50 °C), tray drying (TD) and sun drying (SD) on the quality of Arabica coffee was evaluated. Drying process did not affect the caffeine content, but influenced levels of some amino acids. Sucrose content was higher in HP and TD than in SD green coffees. The perceived aroma of brewed coffee from SD was similar to HP, but differed from TD. Concentrations of 30 important odorants were compared for SD, HP (50 °C) and TD brewed coffees. 2-Furfurylthiol, a key odorant of coffee, was at the same level in SD and HP coffees and lowest in TD samples. Principal component analysis (PCA) separated SD from HP and TD, based on the concentrations of 23 odorants. Combined results of sensory and chemical analyses showed that in comparison to SD, HP was superior to TD for preserving overall flavor quality.

Coffee – from plant to popular beverage

Coffee, one of the most popular beverages in modern world, is obtained from the beans of perennial bush Coffea. The distinctive aroma and taste of coffee is obtained by thermal treatment (roasting) of raw coffee beans. There are different degrees of roasting that can be divided according to the color of the grain: easy, medium, dark and Italian. The most famous types of coffee used in the production of beverages are Arabica and Robusta. Raw coffee beans contain a certain amount of caffeine, sugar, essential oil, potassium, calcium and magnesium. Roasting the grains leads to the loss of dry matter through formation of carbon dioxide, water and volatile products of pyrolysis. Coffee also has a moderate healing effect, while in overdoses it causes rapid heartbeat, insomnia, even euphoria.

Enhancing the Aroma and Sensory Profiles of Decaffeinated Coffee: A Review.

The purpose of this review paper is to describe research related to improving the aroma and sensory properties of decaffeinated coffee. These studies underscore the intricate interplay between brewing methods, chemical transformations, and sensory outcomes in decaffeinated coffee. The methods used are as follows: Aroma Compound Recovery, smell-blocking technology, and the use of artificial aroma compounds. Future technology for enhancement of decaffeinated coffee aroma is through the identification of how the roasting process and the brewing technique significantly influence the concentration of volatile compounds in coffee brews. the transformation of these compounds during roasting and the subsequent extraction during brewing are critical for the development of the coffee’s aroma. This understanding is vital for the coffee industry, as aroma plays a pivotal role in consumer preference and overall sensory experience. The conclusion is that the exploration of decaffeinated coffee aroma has yielded significant findings that underscore the complex interplay between processing methods and aromatic compounds. interdisciplinary approaches that combine chemistry, sensory analysis, and consumer behavior can provide deeper insights into the relationship between aroma and consumer preferences, ultimately guiding the development of more appealing decaffeinated coffee products.

Enhancing Robusta coffee aroma by modifying flavour precursors in the green coffee bean

This study attempted to improve Robusta sensory properties by modifying the beans chemical composition. Building on our previous work, which modified bean pH through acid pre-treatment, a model system was developed where, sugar solutions (glucose, fructose, sucrose) were used to pre-treat Robusta coffee beans with the aim to modify the concentration/availability/location of these aroma precursors. Beans were then dried to equal water activity, subjected to equal roast intensity and ground to comparable particle size distributions. The treatment significantly impacted aroma generation during roasting leading to an altered level of pyrazines, furans, ketones, organic acid and heterocyclic nitrogen-containing compounds (p < 0.05). The optimum treatment was 15 g/100 g fructose. 80% treated Robusta could be blended with Arabica in coffee brew without significant aroma differences being perceived when compared to 100% Arabica brew. Furthermore the aroma of the fructose treated Robusta was more stable than Arabica over six weeks accelerated shelflife storage.

The significance of vapor pressure in quality preservation of stored commodities under gastight conditions

While investigating the preservation of the aroma of various spices we compared the effects of hermetic conditions, vacuum and carbon dioxide versus aerated storage. The quality of the tested spices stored under hermetic conditions was comparable to those stored in vacuum after 120 d of storage. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure. Throughout the investigation on specialty coffee, the volatility was evaluated as particularly important because coffee taste and aroma are influenced by compounds that are volatile. We hypothesize that hermetic storage reduces the rate of the volatiles to spread to the atmosphere. Dry food commodities can be stored for extended periods, provided there is no insect infestation and their water activity is low enough to prevent microbial growth. However, in aerated storages quantitative and qualitative losses still occur. If the moisture content is maintained sufficiently low, insects and quality loss remain the main concern for the quality preservation of durable agricultural commodities. Although in hermetic storage, the major emphasis is placed on the control of insect pests, for quality preservation just maintaining the vapor pressure in the sealed structure is sufficient. Quality preservation under hermetic conditions remains an aspect that deserves more attention. This characteristic of hermetic storage is the tendency to maintain within the hermetic structure the substances that have the ability to vaporize.

The Effects of Storage Temperature on the Aroma of Whole Bean Arabica Coffee Evaluated by Coffee Consumers and HS-SPME-GC-MS

Although from a food safety point, coffee is considered a shelf-stable product, changes in volatiles over time due to out-gassing and chemical reactions lead to perceivable differences in coffee aroma and “freshness”. Previous studies have looked at the impact of storage conditions on ground or brewed coffee. This study seeks to answer the question of how coffee consumers perceive the smell of coffee grounds of whole beans that have been stored under different conditions: freezer vs. room temperature for 9 weeks compared to a newly roasted control (stored for 1 day). Green beans from the same production lot were roasted to two different levels to also evaluate the impact of roast level on aroma changes. Using projective mapping (PM) followed by ultra-flash profiling (UFP), 48 coffee consumers evaluated, using only smell, 6 different freshly ground coffee samples presented in blind duplicates. In parallel, the profiles of 48 previously reported important coffee volatiles were measured by headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) to relate chemical changes to perceivable sensory aroma changes. Overall, consumer product maps mimicked the instrumental measurements in that the lighter roast coffees showed smaller changes due to storage conditions compared to the dark roast samples. Consumers also perceived the frozen dark roast samples to be more similar to the newly roasted control than the samples stored at room temperature.

A colorimetric sensor array-based classification of coffees

A method based on colorimetric sensor array (CSA) was used to classify different coffees. The array was fabricated by printing twelve sensing materials selective to key coffee aroma odorants on a hydrophobic membrane. The unique color profile for each coffee sample was obtained, resulting in facile differentiation by the naked eye without any statistical analysis. The color responses of CSA were evaluated by principal component analysis and hierarchical cluster analysis to identify classification patterns of ground roasted coffee, espresso coffee, and aero-press coffee samples, and the samples were successfully distinguished according to their categories such as variety and roast degree of coffee beans or brewing procedure. The results of hierarchical cluster analysis and linear discriminant analysis using the CSA data obtained from sixty coffee samples demonstrate that the CSA is a potentially promising methodology for rapid discrimination of different coffees.

Modifying Robusta coffee aroma by green bean chemical pre-treatment

Green Robusta beans were subjected to pre-treatment with the aim of reducing the perceived aroma difference between Arabica and Robusta coffee. Treatment was a short soaking procedure with varying concentrations of acetic acid (up to 5%). Samples were subjected to thermal treatment (roasted) and ground to a standardised particle size distribution. Aroma compounds were evaluated by headspace analysis using solid-phase microextraction and gas chromatography-mass spectrometry. Pre-treatment significantly affected aroma formation during roasting and resulted in a modified level of pyrazines, furanic compounds and sulfur-containing compounds (p < 0.05). Principal component analysis illustrated that the aroma profile of the pre-treated Robusta coffee was closer to the target Arabica coffee after roasting. Sensory results confirmed that the aroma of the 2% acetic acid pre-treated Robusta brew was similar to Arabica; the maximum inclusion level of Robusta coffee in a blend could be increased from 20% to 80%.