Roasted Beans Research Articles

The effect of roasting method on headspace composition of robusta coffee bean aroma

Robusta coffee beans were roasted by three methods, i.e. convectively at 230 °C, by microwaves at 700 W, and by the coupled convective–microwave (CMR) method (the simultaneous convective heating at 230 °C and microwaving at 700 W) for 590, 670, and 370 s, respectively. The ultimate temperature of roasted beans was 238, 207, and 228 °C, respectively. Volatile compounds were determined in the headspace by GC-SPME both in samples of roasted coffee and in green beans to find effects of roasting methods on their formation and retention. Eighty-two and 148 odorants were identified in green and roasted coffee, respectively. The highest contents of the latter were found in coffee roasted by the coupled method because both the relatively short time of roasting and moderately high final temperature of beans favored retention of volatile aroma compounds. Because of these reasons, the contents of odorants were the lowest in convectively roasted coffee.

Molecular Definition of the Taste of Roasted Cocoa Nibs (Theobroma cacao) by Means of Quantitative Studies and Sensory Experiments

Sensory-guided decomposition of roasted cocoa nibs revealed that, besides theobromine and caffeine, a series of bitter-tasting 2,5-diketopiperazines and flavan-3-ols were the key inducers of the bitter taste as well as the astringent mouthfeel imparted upon consumption of roasted cocoa. In addition, a number of polyphenol glycopyranosides as well as a series of N-phenylpropenoyl-l-amino acids have been identified as key astringent compounds of roasted cocoa. In the present investigation, a total of 84 putative taste compounds were quantified in roasted cocoa beans and then rated for the taste contribution on the basis of dose-over-threshold (DoT) factors to bridge the gap between pure structural chemistry and human taste perception. To verify these quantitative results, an aqueous taste reconstitute was prepared by blending aqueous solutions of the individual taste compounds in their "natural" concentrations. Sensory analyses revealed that the taste profile of this artificial cocktail was very close to the taste profile of an aqueous suspension of roasted cocoa nibs. To further narrow down the number of key taste compounds, finally, taste omission experiments and human dose/response functions were performed, demonstrating that the bitter-tasting alkaloids theobromine and caffeine, seven bitter-tasting diketopiperazines, seven bitter- and astringent-tasting flavan-3-ols, six puckering astringent N-phenylpropenoyl-l-amino acids, four velvety astringent flavonol glycosides, gamma-aminobutyric acid, beta-aminoisobutyric acid, and six organic acids are the key organoleptics of the roasted cocoa nibs.

Analysis of 3-aminopropionamide: A potential precursor of acrylamide

An analytical method for the analysis of 3-aminopropionamide (3-APA) based on derivatization with dansyl chloride and liquid chromatography/fluorescence detection was developed. We have analysed 3-APA formation in raw potatoes, grown and stored under different condition, green and roasted coffee beans and in freeze dried mixtures of asparagine with sucrose and glucose in molar ratio of 1:0.5, 1:1, and 1:1.5. In potatoes the 3-APA content varied depending on the potato variety. We detected 3-APA in potatoes up to 14 μg/g fresh weight. In the model experiment glucose had a stronger capacity to form 3-APA. The substance was formed at temperatures as low as 130 °C. However, in the model experiment with sucrose 3-APA was formed not below 150 °C. In heated mixtures with increasing molar ratio of sucrose at 170 °C we noticed a decrease of 3-APA and in the same mixtures at 150 °C we observed an increase of 3-APA. In coffee 3-APA was not formed, neither in green nor in roasted beans.

Gas chromatographic determination and mechanism of formation of D-amino acids occurring in fermented and roasted cocoa beans, cocoa powder, chocolate and cocoa shell

Fermented cocoa beans of various countries of origin (Ivory Coast, Ghana, Sulawesi), cocoa beans roasted under defined conditions (100-150 degrees C; 30-120 min), low and high fat cocoa powder, various brands of chocolate, and cocoa shells were analyzed for their contents of free L-and D-amino acids. Amino acids were isolated from defatted products using a cation exchanger and converted into volatile N(O)-pentafluoropropionyl amino acid 2-propyl esters which were analyzed by enantioselective gas chromatography mass spectrometry on a Chirasil-L-Val capillary column. Besides common protein L-amino acids low amounts of D-amino acids were detected in fermented cocoa beans. Quantities of D-amino acids increased on heating. On roasting cocoa beans of the Forastero type from the Ivory Coast at 150 degrees C for 2 h, relative quantities of D-amino acids approached 17.0% D-Ala, 11.7% D-Ile, 11.1% D-Asx (Asp + Asn), 7.9% D-Tyr, 5.8% D-Ser, 4.8% D-Leu, 4.3% D-Phe, 37.0% D-Pro, and 1.2% D-Val. In cocoa powder and chocolate relative quantities amounted to 14.5% D-Ala, 10.6% D-Tyr, 9.8% D-Phe, 8.1% L-Asx, and 7.2% D-Ile. Lower quantities of other D-amino acids were also detected. In order to corroborate our hypothesis that D-amino acids are generated from Amadori compounds (fructose amino acids) formed in the course of the Maillard reaction, fructose-L-phenylalanine and fructose-D-phenylalanine were synthesized and heated at 200 degrees C for 5-60 min. Already after 5 min release of 11.7% D-Phe and 11.8% L-Phe in the free form could be analyzed. Based on the data a racemization mechanism is presented founded on the intermediate and reversible formation of an amino acid carbanion in the Amadori compounds.

Evaluation of sensory attributes of coffee brews from robusta coffee roasted under different conditions

Robusta coffee beans with a different initial moisture of 5, 7.5 and 10% were convectively roasted at 230 °C, microwaved at 700 W, and roasted by the coupled convective-microwave method. Sensory attributes of brews prepared from these coffee samples were evaluated. Final temperature of microwaved coffee beans was lower than that of the beans processed by the two other methods, which resulted in a higher content of volatile aroma compounds and a lesser degree of charring of their surface. Lower initial humidity of coffee beans shortened the time of roasting. However, the aroma developed upon roasting of the moistest beans was the most intense and pleasant. Modification of roasting conditions increased shifting of the overall acceptability of coffee infusions by 2 points in a 10-point hedonic scale, which implies that, if roasting conditions are adequate to the type of coffee, its sensory characteristics can be improved. Thus, optimization of roasting parameters can increase the share of robusta in well-accepted commercial coffee blends, a convenient fact because of the significant difference in price between the latter and arabica coffee.

On-line HPLC analysis of the antioxidant activity of phenolic compounds in brewed, paper-filtered coffee

Caffeoyl-, feruloyl- and dicaffeoylquinic acids (chlorogenic acids) in infusions from green and medium roasted coffee beans were identified and quantified by reverse phase HPLC with photodiode array and MS³ detection prior to assessment of the antioxidant activity using an HPLC system with post-column on-line antioxidant detection based on 2,2'-azinobis-3-ethylbenzothiazoline-6-sulphonic acid radical scavenging activity. Caffeoylquinic acids were the most abundant antioxidants and roasting induced isomerisation with a decline in 5-O-caffeoylquinic acid and concomitant increases in the 3- and 4-O-derivatives. This did not affect the level of caffeoylquinic acid-derived antioxidant activity in the roasted coffee. Roasting did, however, result in the appearance of additional unidentified HPLC peaks with antioxidant activity. Because of this and an increase in the antioxidant activity of components that did not elute from the reversed phase HPLC column, the antioxidant capacity of the beverage derived from medium roast beans was double that of the unroasted coffee. The antioxidant activity of coffees that have undergone different degrees of roasting would, therefore, appear to be due to combinations of different components. The effect of roasting on chlorogenic acids in coffee beans is considered, and the possible contribution of Maillard reaction products to the antioxidant capacity of roasted coffees is discussed.

Performance of Rotary Cutter Type Breaking Machine for Breakingand Deshelling Cocoa Roasted Beans

Conversion of cocoa beans to chocolate product is, therefore, one of the promising alternatives to increase the value added of dried cocoa beans. On the other hand, the development of chocolate industry requires an appropriate technology that is not available yet for small or medium scale of business. Breaking and deshelling cocoa roasted beans is one important steps in cocoa processing to ascertain good chocolate quality. The aim of this research is to study performance of rotary cutter type breaking machine for breaking and deshelling cocoa roasted beans. Indonesian Coffee and Cocoa Research Institute has designed and tested a rotary cutter type breaking machine for breaking and deshelling cocoa roasted beans. Breaker unit has rotated by ½ HP power, single phase, 110/220 V and 1440 rpm. Transmission system that use for rotating breaker unit is pulley and single V belt. Centrifugal blower as separator unit between cotyledon and shell has specification 0.5 m 3 /min air flow, 780 Pa, 370 W, and 220 V. Field tests showed that the optimum capacity of the machine was 268 kg/h with 500 rpm speed of rotary cutter, 2,8 m/s separator air flow, and power require was 833 W. Percentage product in outlet 1 and 2 were 94.5% and 5.5%. Particle distribution from outlet 1 was 92% as cotyledon, 8% as shell in cotyledon and on outlet 2 was 97% as shell, 3% as cotyledon in shell. Key words:cocoa, breaking, rotary cutter, quality.

Carbon Dioxide Evolution and Moisture Evaporation During Roasting of Coffee Beans

ABSTRACT: Evolution of carbon dioxide and water vapor during roasting of coffee was followed in an isothermal high-temperature short-time and a low-temperature long-time roasting process. In addition, CO2 release during storage of roasted beans was followed. CO2 and water vapor concentration were assayed in the exhaust air by nondispersive infrared gas analysis. Although CO2 evolution rates differed in the 2 processes, the final total amount of CO2 released after 63 d of storage remained equal. CO2 evolution and differentiation between evaporation of initial water and chemically formed water showed that chemical reactions leading to relevant amounts of CO2 and water start at ap -proximately 180°C. A mass balance established on the present measurements was able to account fairly well for the gravimetrically measured roast loss.

Analytical determination of the suitability of different processes for the treatment of odorous waste gas

In order to determine the efficiency of different treatment systems for the reduction of odorous emissions, a gas chromatographic method followed by simultaneous mass spectrometry and olfactometry (GC–MS/O) was developed. Samples from a coffee bean roasting and a fat and oil processing plant were analyzed, respectively. The results were compared with the data obtained by olfactometric measurements. At a coffee bean roasting plant, cooling gases were analyzed prior to and after treatment in a full scale bioscrubber. The GC–MS/O analysis showed that the amounts of aldehydes and ketones decreased after treatment of cooling gases of coffee bean roasting in the bioscrubber, whereas the contents of the heterocyclic compounds, like pyridine and the pyrazines, and acetophenone and guaiacol remained almost unchanged. The amounts of dimethyl disulfide, 3-hydroxy-2-butanone, and the carboxylic acids increased after bioscrubber treatment. Furthermore, the performance of each stage of a combined experimental plant for the treatment of exhaust air of fat and oil processing was investigated. This treatment plant consisted of a bioscrubber, a biofilter, and an activated carbon adsorber. The important odor-active compounds of the exhaust air of fat and oil processing were the typical fat oxidation products (aldehydes, ketones) and with lower importance 2-pentylfuran, a few terpenes and aromates. Again, the key odor-active compounds, aldehydes and ketones, were degraded in the bioscrubber. Further degradation of aliphatic, unsaturated, methylated, and cyclic alkanes, as well as aromates, terpenes, and furans by the biofilter was observed. After the last treatment stage, the activated carbon filter, only small amounts of aliphatic, unsaturated, methylated, and cyclic alkanes and aromates remained in the waste gas. For both applications, the results of the developed GC–MS/O method correlated very well with olfactometric measurements.

Identification and evaluation of volatile odor-active pollutants from different odor emission sources in the food industry

In order to elucidate the nature of different odor-emission sources in the food industry, odor-active pollutants of the exhaust air in the cooling gases from coffee bean roasting, the exhaust air of fish meal production, and the exhaust air of swine breeding were investigated. Knowledge of what pollutants are present in the odor emission and are responsible for the malodor is vital to the development of suitable adsorbers/absorbers and filters, and combinations of the same. Therefore, the objective of these investigations was to identify and evaluate the characteristic impact of compounds in the exhaust air of these odor-emission sources. The volatile compounds were collected by using a microprocessor-controlled gas sampler through sorbent tubes of Tenax TA. The adsorbed compounds were analyzed by thermal desorption into a cryotrap and subsequent gas chromatography separation, followed by simultaneous olfactometry and mass spectrometry. In cooling gases of the coffee bean roasting numerous compounds (up to 100) were identified of which only 22 were important for the characteristic odor. These compounds were aldehydes (2-methyl propanal, 2- and 3-methyl butanal, 2-furancarboxyaldehyde, 5-methyl-2-furancarboxyaldehyde), diketones (2,3-butandione, 2,3-pentandione), pyrazines, pyridine, acetic acid, and furanmethanol. Other compounds with low concentrations but with a very low odor threshold and, therefore, important for the total odor were 3-methyl butanoic acid and guaiacol. Up to 50 compounds were identified in the exhaust air of fish meal production, the most significant of these being trimethylamine. Trimethylamine, with a very low odor threshold (0.0025 μg/l air) and the highest content (up to 60% in the total ion chromatogram, more than 100 μg/l) in the exhaust air of fish meal production, was responsible for the characteristic fishy odor. Beside trimethylamine only a few compounds, e.g., sulfides (dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide), aldehydes (2-methyl propanal, 2- and 3-methyl butanal), ethanol, and guaiacol, played a secondary role for the total odor. In the exhaust air of the pig house up to 50 compounds were identified. Beside ammonia, the most important odor-active compounds were various carboxylic acids (acetic acid, butanoic acid, 3-methyl butanoic acid), sulfides (dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide), trimethylamine, and the intensive odor-active p-cresol and 4-ethylphenol.

QUANTIFYING ADULTERATION IN ROAST COFFEE POWDERS BY DIGITAL IMAGE PROCESSING

Abstract A new method based on digital image processing used to quantify adulteration in roast and ground coffee beans is presented in this study. Pure arabica coffee and mixtures of coffee husks and straw, maize, brown sugar and soybean were produced in our laboratory as investigation materials. Red/Green/Blue (RGB) color composites, magnified twelve times, were generated using a Charge Coupled Device (CCD) camera connected to a stereo microscope and a personal computer with an image processing software package. The percent areas of the contaminants in each image were calculated by the Maximum Likelihood supervised classification technique. Best‐fit equations relating weight percentage (g.kg‐1) and the percent areas were obtained for each coffee contaminant. To test the method, 247 coffee samples of different amounts and types of adulterants were analyzed in the laboratory. The results showed that the new method developed can analyze precisely and quickly a large number of ground coffee powders.

Antioxidative activity of green and roasted coffee beans as influenced by convection and microwave roasting methods and content of certain compounds

Antioxidative activity of green and roasted coffee beans and its correlation with the concentrations of certain substances (polyphenols, caffeine, 5-hydroxymethylfurfural) and the roasting method (convection and microwave) was determined. Antioxidative capacity was estimated based on the capability of synthetic free radical (1,1-diphenyl-2-picryl hydrazyl, DPPH˙) scavenging and counteracting an oxidation of the model system composed of β-carotene and linoleic acid. Green coffee appeared to display the highest effectiveness. In the case of roasted coffee samples, the results of neither test showed distinct correlation; however they indicated that an application of microwave heating for coffee roasting better protected its antioxidative properties. This relationship corresponded to the polyphenol content in roasted beans.

Identification of odor-active 3-mercapto-3-methylbutyl acetate in volatile fraction of roasted coffee brew isolated by steam distillation under reduced pressure.

In a roasted Arabica coffee brew, the potent roasty odor quality compound was identified as 3-mercapto-3-methylbutyl acetate by comparison of its Kovats gas chromatography retention index, mass spectrum, and odor quality to those of the synthetic authentic compound. 3-Mercapto-3-methylbutyl acetate has been identified for the first time in the coffee, and according to the results of the aroma extract dilution analysis, the contribution of this compound to the flavor of the roasted coffee brew varied depending on the degree of the coffee bean roasting. The concentration of this compound in the coffee brews as with 3-mercapto-3-methylbutyl formate increased with an increase in the degree of roasting. However, the slope of the amount of both esters was different, and 3-mercapto-3-methylbutyl acetate hardly increased with a low degree of roasting at more than a 21 luminosity (L)-value, but it rapidly increased when the roasting degree of the coffee beans reached the L-value of 18. These results suggested that the contribution of 3-mercapto-3-methylbutyl acetate to the overall flavor is peculiar to the flavor of the highly roasted coffee.

Incidence, level, and behavior of aflatoxins during coffee bean roasting and decaffeination.

Screening for aflatoxins (Afs), isolation and identification of Aspergillus flavus, and the effect of decaffeination and roasting on the level of contamination in coffee beans are studied. The percent frequency of A. flavus ranged between 4 and 80% in green coffee beans (GCB), whereas in ground roasted coffee beans (GRCB), it ranged between 1 and 71%. Aflatoxins were detected in 76.5 and 54.6% of the infected samples with averages of 4.28 and 2.85 microg/kg of GCB and GRCB, respectively. Roasting was demonstrated to lower the concentration of Afs in GCB. The Afs levels were reduced by approximately 42.2-55.9% depending on the type and temperature of roasting. The highest yields of Afs were detected in the decaffeinated green coffee beans (24.29 microg/kg) and roasted coffee beans (16.00 microg/kg). The growth of A. flavus in liquid medium containing 1 or 2% caffeine was reduced by 50%, and the level of aflatoxin in the medium was undetectable.

Identification and occurrence of the bioactive β-carbolines norharman and harman in coffee brews

Norharman and harman, two heterocyclic β-carboline alkaloids with biological activity, were found in brewed coffee. Identification and analysis were carried out by HPLC-MS and RP-HPLC-fluorescence, respectively. All tested samples of brewed coffee including ground coffee, decaffeinated coffee, instant coffee and espresso contained both norharman and harman in variable amounts. Norharman was the major β-carboline alkaloid in brewed coffee at levels up to 9.34 μg g-1 in instant ground coffee compared with harman, which had levels up to 1.67 μg g-1. The two β-carbolines appeared to be formed during roasting of the coffee beans. It is concluded that drinking coffee is a major exogenous dietary source of these bioactive β -carboline alkaloids previously reported as mild psychoactive compounds in animal studies and in vitro co-mutagens. These results support our previous conclusion that foods containing β -carbolines are an important exogenous source of these alkaloids in humans.

Effect of the roasting method on the content of 5-hydroxytryptamides of carboxylic acids in roasted coffee beans.

Coffee beans of Coffea liberica (robusta) variety were roasted using convection and microwave heating. For roasting we used green coffee beans of 7.5% moisture content, and beans wetted to 10% moisture content and dried to 5% moisture content. The content of 5-hydroxytryptamides of carboxylic acids C-5-HT (determined by TLC) as the index of substances irritating alimentary canal was investigated in the roasted beans, depending on the bean treatment before roasting and applied roasting method. Analytical results show that predrying of the coffee beans caused 15-30% loss of C-5-HT, depending on the applied drying conditions. The content of C-5-HT in the roasted beans depended on the roasting method and preliminary treatment of the beans prior to roasting. A higher C-5-HT loss occurred in the case of beans subjected to two-stage processing, predrying and roasting. Convection roasting caused higher degradation of C-5-HT than microwave roasting.

DETERMINATION OF TOTAL IMIDACLOPRID RESIDUES IN COFFEE BY GAS CHROMATOGRAPHY–MASS SPECTROMETRY

ABSTRACT The insecticide imidacloprid and its metabolites in green beans, roasted beans, and freeze–dried coffee were extracted with a mixture of methanol and 1% H2SO4 (1/3, v/v). The cleanup procedure involved hexane partitioning and XAD-4 resin cleanup eluted with methanol. Imidacloprid and its metabolites in the 5-hydroxy-, olefin-, and desnitro-forms in the extracts were oxidized with KMnO4 (pH 14) to 6-chloronicotinic acid which was then recovered with methyl t-butyl ether (MTBE). The residue was dissolved in acetonitrile after the evaporation of MTBE, and 6-chloronicotinic acid was derivatized with methyl trimethylsilyl trifluoroacetamide for gas chromatography-mass spectrometric quantification. Recoveries of total imidacloprid residues ranged from 90 to 110% at different fortification levels. The method was applied to the analysis of coffee samples collected from trees that received five foliar applications of the insecticide. All treated samples of green and roasted beans, and freeze–dried coffee were found to contain imidacloprid residues.

Comparison of raw and roasted narbon beans ( Vicia narbonensis) on performance and meat sensory attributes of lambs fed a roughage-based diet

This study examined the effect of raw and roasted narbon bean ( Vicia narbonensis) in a roughage-based diet on growth performance and meat sensory attributes of sheep. Roasting was examined to determine whether it improved protein utilisation. Lambs ([Border Leicester×Merino]×Poll Dorset; 6 months old, mean liveweight of 34.9 kg) were allocated to three treatments ( n=8 per treatment): Nil, lucerne and oaten chaff; raw WNB (chaff plus raw whole narbon bean); and roasted WNB (chaff plus whole narbon bean roasted at 150°C for 45 min). Raw and roasted narbon bean supplied 56% of total protein (approximately 15% DM) and were fed for a period of 8 weeks. Growth performance was evaluated over 6 weeks followed by a 7 day nitrogen balance measurement in five lambs from each treatment. Remaining three lambs were maintained on their treatment diets and all lambs were slaughtered at the end of the nitrogen balance study after blood samples were taken. For Nil, raw and roasted WNB ADG was 84.3, 158.1 and 171.6 g per day; FCE 16.5, 7.7, 7.2 kg/kg DM and nitrogen retained 6.4, 6.9, and 8.3 g per day, respectively. At slaughter, HCW, was 18.5, 21.4, 22.3 kg; fat depth 12.6, 17.9, 17.6 mm, and dressing percentage 45.9, 49.9, and 51.4% for Nil, raw and roasted WNB, respectively. There was no significant difference between raw and roasted WNB for any performance trait. In contrast, all performance traits except for nitrogen retained were significantly ( P<0.05) different between Nil and raw and roasted WNB. Dry matter and organic matter (average 1233 and 1157 g per day, respectively) intakes were similar across treatments but there was a significant ( P<0.05) increase in dry matter (raw, 11.4% and roasted WNB, 11.9%) and organic matter digestibility (roasted WNB, 10.9%) compared with Nil. Changes in metabolite concentrations were variable. However, change in PUN concentration at 3 h after feeding was significantly different ( P<0.05) between Nil (1.39 mmol/l) and roasted WNB (0.29 mmol/l) indicating a reduction in level of rumen-degradable protein in roasted WNB. There were no significant differences in ‘aroma liking’, ‘flavour liking’, ‘juiciness’, ‘overall acceptability’ and ‘tenderness’ of meat between treatments. However, compared with Nil ‘aroma strength’ and ‘flavour strength’ was significantly higher ( P<0.05) in roasted WNB. We conclude that inclusion of raw or roasted narbon beans in a roughage-based diet improved FCE in young sheep through an increase in ADG and has no detrimental effect on meat sensory properties of lamb. Improvement in performance was achieved through an increase in total tract digestibility and hence an increase in ME intake. Roasting narbon beans provided no additional benefit for lamb performance.

Pore Structure of Coffee Beans Affected by Roasting Conditions

ABSTRACT:Hot‐air roasting of coffee beans not only forms color and flavor compounds but also leads to a complete alteration of the bean microstructure. The resulting pore structure controls mass transfer phenomena during roasting and storage. The principal objective of the present project was to investigate the influence of different roasting conditions on volume increase and pore‐structure development. Coffee beans were roasted in 2 different, well‐defined roasting processes to equal degree of roast. Volumetry, mercury porosimetry, and electron microscopy were employed to study structural product properties. The roasting conditions were found to have a major impact on microstructure. High‐temperature roasted coffees had greater bean volume, pore volume and larger micropores in the cell walls as compared to low‐temperature roasted beans.

Influence of Dry Roasting of Whole Faba Beans (Vicia faba) and Whole Lupin Seeds (Lupinus albus) on Rumen Disappearance and Estimated Intestinal Digestion of CP Using the Optimal Three-Step In Vitro Technique in Dairy Cows

Influence of Dry Roasting of Whole Faba Beans (Vicia faba) and Whole Lupin Seeds (Lupinus albus) on Rumen Disappearance and Estimated Intestinal Digestion of CP Using the Optimal Three-Step In Vitro Technique in Dairy Cows