Coffee Aroma Research Articles

Microencapsulation of Roasted Coffee Oil by Complex Coacervation with Gelatin/Gum Arabic Enzymatically Crosslinked

The roasted coffee oil is a coffee industry byproduct composed by a great number of compounds including the volatiles, responsible by coffee aroma. The main objetive of the present work is the encapsulation of roasted coffee oil in enzimatically crosslinked gelatin and gum Arabic microcapsules. The microcapsules were obtained by complex coacervation. The effect of the roasted coffee oil amount used and the stirring rate on the average diameter, oil recovery and encapsulation efficiency were evaluated. The microcapsules presented average diameter up to 29.30 ± 1.28 µm with narrow size distributions. The results varied from 78.45 ± 2.47 to 100.70 ± 5.23 % (oil recovery) and 32.50 ± 3.53 to 71.00 ± 4.24 % (encapsulation efficiency). The water sorption isotherm of microcapsules was evaluated at 25 oC and the results were fitted with the Guggenhein-Anderson-de Boer (GAB) model, presenting a R 2 equal to 0.9892 and “J” shape behavior. Finally, the crosslinking reaction was investigated by Fourier Transform Infrared Spectroscopy (FTIR), showing that the crosslinking reaction promoted by transglutaminase introduced a band in microcapsules spectra located at 1550 cm -1 corresponding to the monosubstituted amide.

Assessment of black coffee temperature profiles consumed from paper‐based cups and effect on affective and descriptive product sensory attributes

SummarySensory acceptance testing was used to determine whether the serving temperature of black filter coffee had an effect on the hedonic sensory quality of the imbibed product using naïve assessors (n = 25) analysed in duplicate. Additionally, descriptive sensory evaluation was used to assess coffee aroma, flavour and aftertaste attributes at different temperatures using a total of fourteen attributes. Prior to consumption, exothermic spectral analysis was assessed using a thermal imaging camera on each cup of coffee to ensure that the correct drinking temperature was recorded prior to being consumed by assessors. anova Partial Least‐Squares Regression (APLSR) was used to analyse experimental data accumulated. This study established that various sensory attributes of coffee are affected by the temperature coffee is imbibed at. Coffee served at 31.0 °C was negatively correlated (P < 0.05) to hedonic attributes. In contrast, coffees served at the higher temperatures of 70.8 °C and 74.4 °C were positively (P < 0.05) correlated to hedonic attributes.

Coffee aroma: Chemometric comparison of the chemical information provided by three different samplings combined with GC–MS to describe the sensory properties in cup

This study is part of a wider project aiming to correlate the chemical composition of the coffee volatile fraction to its sensory properties with the end-goal of developing an instrumental analysis approach complementary to human sensory profiling. The proposed investigation strategy compares the chemical information concerning coffee aroma and flavor obtained with HS-SPME of the ground coffee and in-solution SBSE/SPME sampling combined with GC–MS to evaluate their compatibility with the cupping evaluation for quality control purposes. Roasted coffee samples with specific sensory properties were analyzed. The chemical results obtained by the three samplings were compared through multivariate analysis, and related to the samples’ sensory attributes. Despite the differences between the three sampling approaches, data processing showed that the three methods provide the same kind of chemical information useful for sample discrimination, and that they could be used interchangeably to sample the coffee aroma and flavor.

Personal characteristics of coffee consumers and non-consumers, reasons and preferences for foods eaten with coffee among adults from the Federal District, Brazil

The aim of this study is to describe the characteristics of consumers and non-consumers, the reasons and foods associated with coffee intake among adults from the Federal District, Brazil. This is a cross-sectional population-based survey conducted by telephone interview (n= 1,368). We collected information on detailed coffee intake, socio-demographic aspects and personal characteristics. The coffee had an average daily intake of 319 mL. Individuals were more likely to drink coffee at an older age (68%) and with higher body mass index (58%). The most cited reason for consuming coffee was the “personal pleasure” (48%), followed by “habit / tradition” of consuming coffee. Among non-consumers of this beverage, the main reason was not liking the taste and / or aroma of coffee (62%). The method of coffee preparation used was by infusion (86%) and sugar was the main sweetener used by 83% of consumers. The majority of consumers (59%) reported consuming coffee with certain foods such as bakery products. The results from our study may suggest that the popularity of coffee can be attributed to its taste, personal pleasure and habit, and the consumption is more likely to occur with the advance of age and with intake of other foods.

Modulation of coffee aroma via the fermentation of green coffee beans with Rhizopus oligosporus: I. Green coffee

Modulation of coffee aroma via the biotransformation/fermentation of different coffee matrices during post-harvest remains sparingly explored despite some studies showing their positive impacts on coffee aroma. Therefore, this is an unprecedented study aimed at modulating coffee aroma via the fermentation of green coffee beans with a food-grade fungus Rhizopus oligosporus. The objective of part I of this two-part study was to characterize the volatile and non-volatile profiles of green coffee beans after fermentation. Proteolysis during fermentation resulted in 1.5-fold increase in the concentrations of proline and aspartic acid which exhibited high Maillard reactivity. Extensive degradation of ferulic and caffeic acids led to 2-fold increase in the total concentrations of volatile phenolic derivatives. 36% of the total volatiles detected in fermented green coffee beans were generated during fermentation. Hence, the work presented demonstrated that R. oligosporus fermentation of green coffee beans could induce modification of the aroma precursors of green coffees.

Modulation of coffee aroma via the fermentation of green coffee beans with Rhizopus oligosporus: II. Effects of different roast levels

This study aims to evaluate how changes of the volatile and non-volatile profiles of green coffees induced by Rhizopus oligosporus fermentation of green coffee beans (Part I) translated to changes in the volatile and aroma profiles of light, medium and dark roasted coffees and non-volatile profile of roasted coffee where fermentation effects were most distinctive (light roast). R. oligosporus fermentation resulted in 1.7-, 1.5- and 1.3-fold increases in pyrazine, 2-methylpyrazine and 2-ethylpyrazine levels in coffees of all roast degrees, respectively. This corresponded with the greater extent of amino acids degradation in light roasted fermented coffee. Ethyl palmitate was detected exclusively in medium and dark roasted fermented coffees. The sweet attribute of light and dark roasted coffees were increased following fermentation along with other aroma profile changes that were roast degree specific. This work aims to develop a direct but novel methodology for coffee aroma modulation through green coffee beans fermentation.

Characterization of Turkish-Style Boiled Coffee Aroma by Gas Chromatography and Mass Spectrometry and Descriptive Analysis Techniques

The characteristic volatiles of light, medium, and dark roasted Turkish-style boiled coffee brews were studied by headspace solid-phase micro extraction/gas chromatography-mass spectrometry and sensory flavor profile analysis. Sixty-five volatile compounds, including furans, pyrazines, pyrroles, phenols, pyridines, ketones, oximes, alcohols, aldehydes, thiophenes, benzenes, and terpenes, were isolated from Turkish-style boiled coffee samples. The flavor profile analysis showed Turkish coffee brews as roasted/burnt, spicy, bitter, acidic, sweet, salty, astringent (dry), woody, fermented, earthy, and tobacco-like flavor characteristics. It was concluded that Turkish coffee was rich in furans, pyrazines, pyrroles, and phenols giving its roasted/burnt, spicy, woody, and fermented flavor characteristics.

Sulfur aroma compounds in gum Arabic/maltodextrin microparticles

The sulfur compounds 2-furfurylthiol (2FFT), dimethyl disulfide (DMDS) and thiophene (THIO) are important sulfur contributors to roasted coffee aromas. Their loss by evaporation and/or degradation directly impacts the freshness and aroma intensity of coffee brews. To improve their stability, 2FFT, DMDS and THIO were microencapsulated by spray drying in Gum arabic (GA) and maltodextrin (MD). A CG-qMS method was developed and validated to accurately quantify the sulfur compounds as well as their microencapsulation process and storage stability. Selectivity was obtained by CG-SIM-qMS despite an observed matrix effect. The calibration curves were linear over the tested range. The LOQ for 2FFT, THIO and DMDS were 10, 15 and 23 μg mL−1, respectively, and the corresponding LOD were 3, 5 and 7 μg mL−1. Repeatability, reproducibility and recoveries were obtained within acceptable levels. Microparticles production was tested at different inlet temperatures, and the best encapsulation efficiency was found to be 67% for 2FFT, at 140 °C. The microcapsules were characterized in terms of moisture content, hygroscopicity, solubility, surface morphology, particle size distribution and X-ray diffraction characteristic. A fifteen-week storage stability study at −18 °C indicated that GA and MD offered good protection for the sulfur aromas, especially for THIO and DMDS.

Extraction kinetics of coffee aroma compounds using a semi-automatic machine: On-line analysis by PTR-ToF-MS

The hot-water extraction process used to make an espresso coffee is affected by a large number of factors. A proper understanding of how these factors impact the profile of the final cup is important to the quality of an espresso coffee. This work examines the effect of water temperature and pressure on the extraction kinetics of volatile organic compounds (VOCs) in coffee. This was achieved by on-line monitoring of the volatiles directly from the coffee flow, using proton-transfer-reaction time-of-flight mass-spectrometry (PTR-ToF-MS). Using hierarchical cluster analysis (HCA), tentatively identified compounds were grouped into 5 families according to their time–intensity profiles. VOCs grouped into each family had similar physicochemical properties while polarity was found to be one of the main forces driving VOC extraction kinetics. The effect of pressure was studied by extracting espresso coffees at 7, 9 and 11bar. A pressure of 11bar resulted in an increased extraction of volatiles over the entire extraction time (25s). To study the effect of temperature, espresso coffees were extracted at 82, 92 and 96°C. An increase in temperature produced a significant increase in the extraction of VOCs, especially during the last part of the extraction. The effect of temperature on extractability was more pronounced for the less polar compounds.

Volatile thiols in coffee: A review on their formation, degradation, assessment and influence on coffee sensory quality

Thiols are among the compounds that have the greatest impact on the flavor of coffee. Due to their extremely low odor thresholds, they have a significant sensory impact even at very low concentrations. Thiols are formed during coffee roasting and are described as the key odorants responsible for the typical “coffee” and “roasty” odor notes, greatly influencing the sensory characteristics of coffee. They are particularly reactive and prone to oxidation; their rapid depletion after preparation of a coffee brew and during storage of roasted coffee has been associated with sensory quality decrease and coffee going stale. For these reasons, their determination and insight into their formation and degradation mechanisms could help us to preserve the sensory quality of coffee and to modulate its sensory features. Coffee aroma has been widely studied in recent decades, and it has become evident that the role of certain volatile thiols is paramount. Nevertheless, a limited number of studies have specifically addressed this class of compounds, and several aspects have not yet been satisfactorily elucidated. The aim of this review is to provide an overview of the current state on knowledge about coffee thiols, focusing on their occurrence, determination, sensory impact, formation and evolution in roasted and brewed coffee.

The study of carbohydrate composition of chicory products

The main products produced from chicory in the food industry are soluble roasted chicory, roasted crushed chicory, chicory flour, inulin, oligofructose and others. Fried products are used as a substitute for coffee, because it is caffeine-free and has coffee taste and aroma. Chicory flour is used in the production of bakery products. Inulin and oligofructose are widely used in the manufacture of bakery and dairy products. The aim of this study was to investigate the carbohydrate composition of the products from chicory. The objects of research in this research work were Fried chicory (Leroux), Instant chicory (Leroux), Instant chicory (LLC Flagistom), Instant chicory with hawthorn (Iceberg Ltd and K), Instant chicory (LLC SlavKofe), Instant chicory (Ltd. Around the World), Instant chicory (LLC Favorit), Instant chicory (LLC Beta +), Dried Chirory and Dried crushed chicory № 1,2,3 (LLC Sovremennik), Chicory flour (Leroux), Inulin and Oligofructose (Spinnrad GmbH). Determination of fructans and their average degree of polymerization, the content of glucose, fructose, sucrose, which are contained in foods from chicory was carried out using biochemical method with kit Sucrose / D-Glucose / D-Fructose (R-Biopharm). Studies are suggested that fried chicory products do not contain fructans. Dried products of chicory are contained inulin, the contents of which are about 60–70%, and contained other biologically active substances. Content of fructans in commercial products, such as inulin and oligofructose is about 93% and 79%.

EVALUATION OF SDE, SFE AND SPME/GC-MS FOR EXTRACTION AND DETERMINATION OF AROMA COMPOUNDS FROM VILCABAMBA - ECUADORIAN ROASTED COFFEE

The aim of this study was to compare the usefulness of three extraction methods: solid-phase microextraction (SPME) with four different coating (PDMS, PDMS/DVB, DVB/CAR/PDMS and PA), supercritical fluid extraction with carbon dioxide (SCF) and simultaneous distillation and extraction (SDE) for isolation of flavor compounds from roasted ground coffee (Coffea arabica L. var. Typica) of Vilcabamba (Ecuador). Identification and characterization of volatile compounds were achieved using gas chromatography / mass spectrometry (GC-MS). Analysis of variance and principal components analysis was done. For the SPME method the coating material affect the amount and concentration of compounds extracted, the DVB/CAR/PDMS coating provided the most representative aroma extract (44 compounds were identified). The SCF method allowed extracting a higher amount of compounds and also their identification by GC-MS (72) that SDE (64) and SPME (57), in addition provide higher extractions. The acetic acid, caffeine, furfuryl alcohol, furfural, 5-methylfurfural, butylated hydroxytoluene and maltol were the compounds with higher concentrations found with SPME and SDE, with SCF were found higher concentration to compounds with high molecular weights (> 194 g mol-1). Preferably SPME-DVB/CAR/PDMS method should be used for a characterization of coffee aroma compounds.

The influence of different types of preparation (espresso and brew) on coffee aroma and main bioactive constituents

Coffee is one of the most popular hot drinks in the world; it may be prepared by several methods, but the most common forms are boiled (brew) and pressurized (espresso). Analytical studies on the substances responsible for the pleasant aroma of roasted coffee have been carried out for more than 100 years. Brew coffee and espresso coffee (EC) have a different and peculiar aroma profile, demonstrating the importance of the brewing process on the final product sensorial quality. Concerning bioactive compounds, the extraction mechanism plays a crucial role. The differences in the composition of coffee brew in chlorogenic acids and caffeine content is the result of the different procedures of coffee preparation. The aim of the present review is to detail how the brewing process affects coffee aroma and composition.

Effects of dicarbonyl trapping agents, antioxidants, and reducing agents on the formation of furan and other volatile components in canned-coffee model systems

The formation of furan and certain volatiles related to furan formation mechanisms was studied using gas chromatography–mass spectrometry combined with solid-phase micro extraction after adding dicarbonyl trapping agents [epicatechin (EC), epigallocatechin gallate (EGCG), and catechin], water-soluble antioxidants (Trolox, caffeic acid, ferulic acid, and chlorogenic acid), fat-soluble antioxidants (α-tocopherol, BHT, and β-carotene), and reducing agents (glutathione and sodium sulfite) to canned-coffee model systems (CMS). The level of furan formation decreased significantly following the addition of EC (by 65.3%), EGCG (by 60.0%), and catechin (by 44.7%). In addition, the formation of Maillard reaction products, including furan derivatives (furfural and 5-methylfurfural), Strecker aldehyde (2-methylbutanal), pyrazines (2,6-dimethylpyrazine), and lipid oxidation products (including hexanal and 2-pentylfuran) was suppressed when any of the dicarbonyl trapping agents was added. Among the water-soluble antioxidants studied, chlorogenic acid most significantly decreased the furan level, by 67.0%, followed by ferulic acid (57.6%), Trolox (50.1%), and caffeic acid (48.2%) in the CMS. Chlorogenic acid also reduced the formation of furfural and lipid oxidation products. However, the addition of caffeic acid, ferulic acid, and chlorogenic acid decreased the generation of key coffee aroma components, such as Strecker aldehydes (2-methylpropanal and 2-methylbutanal), 5-methylfurfural, and pyrazines (2,6-dimethylpyrazine and 2-ethyl-5-methylpyrazine). Among the fat-soluble antioxidants, BHT and α-tocopherol decreased the furan level by 49.3% and 39.3%, respectively, while β-carotene increased the furan level by 34.8%. The addition of sodium sulfite and glutathione to CMS also led to considerable reductions in furan, of 64.1% and 44.9%, respectively.

Concentration of aroma compounds from an industrial solution of soluble coffee by pervaporation process

Pervaporation experiments with PDMS membrane have been performed in a plate and frame module to investigate its ability to concentrate volatile compounds identified in an industrial soluble coffee solution. Eight compounds were chosen to depict key aroma of soluble coffee. The effect of feed flow rate, temperature and permeate pressure on the pervaporation performance has been analyzed. Concentration polarization phenomena was not identified in the feed flow rate studied. The temperature effect showed a good agreement with the nonlinear Arrhenius equation. The permeate pressure followed the solution–diffusion model behavior. Results showed that pervaporation is a promising alternative to concentrate aroma compounds from soluble coffee.

Improving the performance of an electronic nose by wine aroma training to distinguish between drip coffee and canned coffee.

Coffee aroma, with more than 600 components, is considered as one of the most complex food aromas. Although electronic noses have been successfully used for objective analysis and differentiation of total coffee aromas, it is difficult to use them to describe the specific features of coffee aroma (i.e., the type of smell). This is because data obtained by electronic noses are generally based on electrical resistance/current and samples are distinguished by principal component analysis. In this paper, we present an electronic nose that is capable of learning the wine related aromas using the aroma kit “Le Nez du Vin,” and the potential to describe coffee aroma in a similar manner comparable to how wine experts describe wine aroma. The results of our investigation showed that the aromas of three drip coffees were more similar to those of pine and honey in the aroma kit than to the aromas of three canned coffees. Conversely, the aromas of canned coffees were more similar to the kit coffee aroma. In addition, the aromatic patterns of coffees were different from those of green tea and red wine. Although further study is required to fit the data to human olfaction, the presented method and the use of vocabularies in aroma kits promise to enhance objective discrimination and description of aromas by electronic noses.

Improving the extraction of headspace volatile compounds: development of a headspace multi-temperature solid-phase micro-extraction-single shot-gas chromatography/mass spectrometry (mT-HSSPME-ss-GC/MS) method and application to characterization of ground coffee aroma

mT-HSSPME-ss-GC/MS compensates for temperature bias during extraction.

Fixed-bed column adsorption of the coffee aroma compound benzaldehyde from aqueous solution onto granular activated carbon from coconut husk

This paper evaluated the performance of fixed-bed columns with activated carbon as the adsorbent for the removal of benzaldehyde present in an aqueous solution. The effects of the following parameters were evaluated: inlet concentration (91.9 mg L−1 – 440.0 mg L−1), feed flow rate (3.9 mL min−1 – 11.8 mL min−1), bed depth (30 mm–90 mm) and column inner diameter (6.2 mm–12.2 mm). All of the experiments were performed at 293.15 K. The results showed that the bed capacity, total bed capacity and saturation time decreased as the feed flow rate was increased. The opposite effect was observed with an increase in bed depth. Increasing the inlet concentration resulted in higher aroma adsorption. An increase in the inner diameter without changing the feed flow rate resulted in better aroma recovery. The results showed that the column performed well at all of the analyzed parameter values. Data obtained from the analysis of the effects of feed flow rate and bed depth were used for a scale-up study using the bed depth service time model, which showed good results with errors of less than 12%. The experimental data obtained in this study will be useful for further applications involving coffee aroma recovery.

The kinetics of coffee aroma extraction

To obtain a cup of coffee with a balanced aroma, every step in the coffee production chain is crucial, including the final brew preparation, in order to achieve the optimal result in-cup. In this study, the role of the physico-chemical properties (volatility and polarity) of coffee odorants during extraction was investigated. The extraction kinetics of 20 key coffee odorants from a coffee bed were measured using quantitative in-cup aroma analysis. The kinetics differed depending on the coffee odorants' properties. The extraction speed could be correlated with the odorants' polarity. Higher polar components, such as 2,3-butanedione, were released much faster from the coffee bed as compared to lower polar ones such as β-damascenone. In contrast, the odorants' volatility did not seem to play a major role. Due to the different kinetics of extraction of the coffee odorants, the in-cup aroma balance changed continuously as more water passed through the coffee bed.

Chlorogenic acid in raw materials for the production of chicory coffee.

Chicory coffee is produced from traditional raw materials. Other materials are added to improve its aroma. The aim of this study was to test new raw materials with a high content of chlorogenic acid (CGA) as the criterion for their selection. This acid is degraded in the course of roasting and is a source of phenolic compounds affecting coffee aroma. For this reason, contents of CGAs were analyzed in traditional and new materials before and after roasting and compared with the chemicals formed in the roasted pure standard of chlorogenic acid (5-CQA). It was shown that the novel raw materials contained considerable amounts of 5-CQA, frequently higher than in traditional chicory. The roasting process caused significant losses of 5-CQA in the tested raw materials, amounting to 55-91%. In turn, the analysis of volatile compounds in roasted materials showed the presence of certain phenolic and heterocyclic compounds that were also formed as degradation products of the pure 5-CQA chemical standard. Novel raw materials, mainly chokeberry, artichoke and lovage, are rich sources of CGAs, particularly 5-CQA. Their application in the production of chicory coffee may result in an increased content of primarily phenolic compounds in its aroma.