Coffee dietary fiber contents and structural characteristics as influenced by coffee type and technological and brewing procedures

Coffee brews contain considerable amounts of soluble dietary fiber, mainly low substituted galactomannans and type II arabinogalactans. Factors possibly influencing the content and structures of dietary fiber in coffee brews, such as type of coffee, roasting and grinding degree, and brewing procedure, were studied. In addition, several commercial samples such as instant espresso, instant coffee, instant cappuccino, decaffeinated coffees, and coffee pads were analyzed. The dietary fiber contents of the coffee brews ranged from 0.14 to 0.65 g/100 mL (enzymatic-gravimetric methodology), proving an influence of the factors investigated. For example, the drip brew of an arabica coffee contained significantly more soluble dietary fiber than the drip brew of a comparable robusta coffee, and depending on the brewing procedure, the soluble dietary fiber content of beverages obtained from the same coffee sample ranged from 0.26 to 0.38 g/100 mL. Dietary fiber contents of coffee brews were enhanced only up to a certain degree of roast. Drip brews of decaffeinated arabica coffees (commercial samples) contained significantly less dietary fiber than any non-decaffeinated drip brew investigated in this study. The observed differences in the dietary fiber contents were accompanied by changes in the structural characteristics of fiber polysaccharides, such as galactomannan/arabinogalactan ratio, galactose substitution degree of mannans, or galactose/arabinose ratio of arabinogalactans as analyzed by methylation analysis.     

Dietary fiber from coffee beverage: degradation by human fecal microbiota

Arabinogalactans and galactomannans from coffee beverages are part of the dietary fiber complex. Chemical structures and fermentability of soluble dietary fiber obtained from a standard filter coffee beverage (Coffea arabica, origin Colombia, medium roasted) by human intestinal bacteria were investigated. One cup (150 mL) of filter coffee contained approximately 0.5 g of soluble dietary fiber (enzymatic-gravimetric methodology), 62% of which were polysaccharides. The remainder was composed of Maillard reaction products and other nonidentified substances. Galactomannans and type II arabinogalactans were present in almost equal proportions. Coffee dietary fiber was readily fermented by human fecal slurries, resulting in the production of short-chain fatty acids (SCFA). After 24 h of fermentation, 85% of total carbohydrates were degraded. In general, arabinosyl units from the polysaccharide fraction were degraded at a slower rate than mannosyl and galactosyl units. In the process of depolymerization arabinogalactans were debranched and the ratio of (1-->3)-linked to (1-->6)-linked galactosyl residues decreased. Structural units composed of (1-->5)-linked arabinosyl residues were least degradable, whereas terminally linked arabinosyl residues were easily utilized. The impact of coffee fiber on numerically dominant population groups of the intestinal microbiota was investigated by fluorescence in situ hybridization combined with flow cytometry (FISH-FC). After 24 h of fermentation, an increase of about 60% of species belonging to the Bacteroides-Prevotella group was observed. The growth of bifidobacteria and lactobacilli was not stimulated.     

Analysis of coffee for the presence of acrylamide by LC-MS/MS

A variety of popular instant, ground, and brewed coffees were analyzed using a modified liquid chromatography-tandem mass spectrometry (LC-MS/MS) method specifically developed for the determination of acrylamide in foods. Coffee test portions were spiked with 13C3-labeled acrylamide as an internal standard prior to their extraction and cleanup. Ground coffees (1 g) and instant coffees (0.5 g) were extracted by shaking with 9 mL of water for 20 min. Brewed coffee test portions (9 mL) were taken through the cleanup procedure without further dilution with extraction solvent. Coffee test portions were cleaned up by passing 1.5 mL first through an Oasis HLB (hydrophilic/lipophilic copolymer sorbent) solid phase extraction (SPE) cartridge and then a Bond Elut-Accucat (cation and anion exchange sorbent) SPE cartridge. The cleaned up extracts were analyzed by positive ion electrospray LC-MS/MS. The MS/MS data was used to detect, confirm, and quantitate acrylamide. The limit of quantitation of the method was 10 ng/g for ground and instant coffees and 1.0 ng/mL for brewed coffee. The levels of acrylamide ranged from 45 to 374 ng/g in unbrewed coffee grounds, from 172 to 539 ng/g in instant coffee crystals, and from 6 to 16 ng/mL in brewed coffee.     

Decomposition of coffee residue in soil

In this study the changes in the chemical properties of coffee residue during decomposition in soil were investigated. 1) Coffee residue contained about 20 g kg^-1 N. The main N compound was a structural protein-No However, the content of easily decomposable N (soluble protein-N and nonprotein-N) extracted by 800 mL L^-1 ethanol and 0.1 mol L^-1 phosphate buffer (pH 7.5) was very low. 2) The rates of nonprotein-N and soluble protein-N which remained reached values of 59 and 66% at 314 d after application of the coffee residue (DAA) to soil, respectively. However, the amount of structural protein-N reached a value of 96% at 314 DAA. 3) The lipid fraction of the coffee residue decreased from 186 to 47 g kg^-1 by 314 d after application. Coffee residue has a high content of lipid fraction and a large fraction corresponding to structural protein-No Therefore, the decomposition of the coffee residue is slower than that of other organic materials.     

Natural occurrence of ochratoxin A and antioxidant activities of green and roasted coffees and corresponding byproducts

Ochratoxin A is an important mycotoxin that can enter the human food chain in cereals, wine, coffee, spices, beer, cocoa, dried fruits, and pork meats. Coffee is one of the most common beverages and, consequently, it has a potential risk factor for human health related to ochratoxin A exposure. In this study, coffee and corresponding byproducts from seven different geographic regions were investigated for ochratoxin A natural occurrence by HPLC-FLD, nutritional characterization, and antioxidant activities by spectrophotometric assay. The research focused on composition changes in coffee during the processing step "from field to cup". Costa Rica and Indian green coffees were the most contaminated samples, with 13 and 11 microg/kg, respectively, while the Ethiopian coffee was the least contaminated, with 3.8 microg/kg of ochratoxin A. The reduction of ochratoxin A contamination during the roasting step was comparable for any samples that were considered under the recommended level of 4 microg/kg. Total dietary fibers ranged from 58.7% for Vietnam and 48.6% for Ivory Coast in green coffees and ranged from 58.6% for Costa Rica to 61.2% for India in roasted coffee. Coffee silverskin byproduct obtained from Ivory Coast was the highest, with 69.2 and 64.2% of insoluble dietary fibers, respectively.     

Antioxidative activities of fractions obtained from brewed coffee

The antioxidative activity of column chromatographic fractions obtained from brewed coffee was investigated to find antioxidants and to assess the benefit of coffee drinking. The dichloromethane extract inhibited hexanal oxidation by 100 and 50% for 15 days and 30 days, respectively, at the level of 5 microg/mL. A GC/MS analysis of fractions, which exhibited oxidative activity, revealed the presence of antioxidative heterocyclic compounds including furans, pyrroles, and maltol. The residual aqueous solution exhibited slight antioxidative activity. The inhibitory activity (%) of the seven fractions from an aqueous solution toward malonaldehde formation from lipid oxidation ranged from 10 to 90 at a level of 300 microg/mL. The results indicate that brewed coffee contains many antioxidants and consumption of antioxidant-rich brewed coffee may inhibit diseases caused by oxidative damages.     

Quantitation of volatiles and nonvolatile acids in an extract from coffee beverages: correlation with antioxidant activity

The antioxidant activities of a commercial brewed coffee were investigated by measuring malonaldehyde (MA) formation from oxidized cod liver oil using a gas chromatographic method (MA-GC assay) and a thiobarbituric acid method (TBA assay). The highest antioxidant activity obtained by the MA-GC assay was from regular whole brewed coffee (97.8%) at a level of 20%, and the highest antioxidant activity obtained by the TBA assay was from decaffeinated whole brewed coffee (96.6%) at a level of 5%. Among 31 chemicals identified in a dichloromethane extract, guaiacol, ethylguaiacol, and vinylguaiacol exhibited antioxidant activities, which were comparable to that of alpha-tocopherol. Among nine chlorogenic acids (three caffeoylquinic acids, three feruloylquinic acids, and three dicaffeoylquinic acids) identified, 5-caffeoylquinic acid contained the greatest amount both in regular (883.5 microg/mL) and in decaffeinated (1032.6 microg/mL) coffees; it exhibited 24.5% activity by the MA-GC assay and 45.3% activity by the TBA assay at a level of 10 microg/mL. Caffeic and ferulic acids showed moderate antioxidant activities in both assays.     

Characterization and fermentability of an ethanol soluble high molecular weight coffee fraction

Brews from differently roasted Arabica coffees were shown to contain 8-12% ethanol soluble substances with molecular masses greater than 2 kDa, possibly contributing to their dietary fiber contents. About 13% of these substances were nondigestible carbohydrates, mainly arabinogalactans. The nondigestible high molecular weight ethanol soluble fraction (HESF) of the medium roasted coffee brew was further characterized and subjected to in vitro fermentation with human fecal bacteria. In addition to carbohydrates, HESF contained proteins/peptides (approximately 20%), but the main fraction was composed of structurally unknown Maillard reaction products. From NMR spectroscopy, we conclude that intact caffeic and ferulic acid derivatives were not incorporated into the melanoidins to a significant extent. Stepwise ultrafiltration and gel filtration indicated a large variation in the molecular weights of HESF constituents. Coffee HESF was shown to be less fermentable by fecal bacteria than soluble coffee fiber isolated by the enzymatic-gravimetric methodology, and because of its lower carbohydrate content, less short-chain fatty acids were produced during the fermentation. Total cell counts, destructive chemical analysis, and NMR spectroscopy indicated that coffee carbohydrates are the preferred substrates for colonic microbiota. However, NMR spectra, absorbances at 405 nm, and nonprotein nitrogen contents showed that noncarbohydrate and nonprotein compounds were also utilized to some extent but the bacterial species involved in this degradation remain to be identified.     

Comparison of the antioxidant activity of commonly consumed polyphenolic beverages (coffee, cocoa, and tea) prepared per cup serving.

In this study, the in vitro low-density lipoprotein oxidation model was used to assess the relative antioxidant activity of the polyphenolic beverages tea, coffee, and cocoa on a cup-serving basis. The beverages were prepared as 0.7-2.5% soluble coffee and 1.5-3.5% cocoa; teas (green, black, or herbal) were prepared as one tea bag infused over 5 min in 220 mL of hot water. Under these standard cup serving conditions, the antioxidant activity as determined by the lag time was in the range of 292-948 min for coffee, 217-444 min for cocoa, 186-338 min for green tea, 67-277 min for black tea, and 6-78 min for herbal tea. Addition of milk did not alter the antioxidant activity. The influence of coffee bean source and degree of roasting was further investigated. Green coffee beans of Robusta coffee exhibited a 2-fold higher antioxidant activity than Arabica coffee, but after roasting this difference was no longer significant. In conclusion, these commonly consumed beverages have a significant antioxidant activity, the highest being soluble coffee on a cup-serving basis.     

Studies of selenium-containing volatiles in roasted coffee

Coffee has been an important and heavily used beverage in many cultures over a long period of time. Although sulfur species have been found to be abundant constituents, no work to date has explored the presence of selenium analogues. Investigation of volatile selenium species from green coffee beans, roasted beans, and brewed coffee drink was performed using solid phase microextraction (SPME) sample preconcentration in conjunction with GC/ICP-MS. Several volatile selenium species at trace levels were detected from roasted coffee beans as well as in the steam from brewed coffee drinks. No detectable selenium (and sulfur) species, however, were found in the headspace of green beans, indicating that selenium-containing volatiles are formed during roasting, as is the case for the sulfur volatiles. Matching standards were prepared and used to identify the compounds found in coffee. Artificial supplementation of the green coffee beans with selenium before roasting was performed to further characterize the selenium-containing volatiles formed during the coffee-roasting process.     

Isolation, identification, and quantification of roasted coffee antibacterial compounds

Coffee brew is a widely consumed beverage with multiple biological activities due both to naturally occurring components and to the hundreds of chemicals that are formed during the roasting process. Roasted coffee extract possesses antibacterial activity against a wide range of microorganisms, including Staphylococcus aureus and Streptococcus mutans, whereas green coffee extract exhibits no such activity. The naturally occurring coffee compounds, such as chlorogenic acids and caffeine, cannot therefore be responsible for the significant antibacterial activity exerted by coffee beverages against both bacteria. The very low minimum inhibitory concentration (MIC) found for standard glyoxal, methylglyoxal, and diacetyl compounds formed during the roasting process points to these alpha-dicarbonyl compounds as the main agents responsible for the antibacterial activity of brewed coffee against Sa. aureus and St. mutans. However, their low concentrations determined in the beverage account for only 50% of its antibacterial activity. The addition of caffeine, which has weak intrinsic antibacterial activity, to a mixture of alpha-dicarbonyl compounds at the concentrations found in coffee demonstrated that caffeine synergistically enhances the antibacterial activity of alpha-dicarbonyl compounds and that glyoxal, methylglyoxal, and diacetyl in the presence of caffeine account for the whole antibacterial activity of roasted coffee.     

Coffee drinking influences plasma antioxidant capacity in humans

Coffee and tea are widely consumed beverages, but only tea has been studied for its antioxidant capacity (AC) in vivo. The aim of this study was to compare the capacities of coffee and tea to affect plasma redox homeostasis in humans. The AC of plasma before and after supplementation with 200 mL of beverages (0, 1, and 2 h) was measured by the TRAP and crocin tests. The crocin test detected an increase in plasma AC only in subjects supplemented with coffee (+7% at peak time), whereas the TRAP method showed an increase in plasma AC after consumption of both coffee and tea (+6 and +4%, respectively, at peak time). Both beverages induced a significant increase in plasma uric acid (+5 and +7%, respectively). Uric acid strongly affects the results obtained by the TRAP test and does not affect those obtained by the crocin test. We can thus argue that uric acid is the main component responsible for the plasma AC increase after tea drinking, whereas molecules other than uric acid (probably phenolic compounds) are likely to be responsible for the increase in plasma AC after coffee drinking.     

Green tea consumption in everyday life and mental health

OBJECTIVE: Green tea has been widely acknowledged in Japan to induce a pleasurable mental feeling. Recent laboratory studies have suggested positive psychological effects as a result of consuming green tea. The present study examined whether green tea consumption in everyday life in Japan is associated with positive mental health. DESIGN: A cross-sectional study was performed in February-March 2002. SETTING AND SUBJECTS: The subjects of the study consisted of a general population of 600 Japanese aged 20-69 years. Responses of 380 subjects, obtained by home-visit interview, were analysed. The questionnaire inquired about consumption of brewed green tea and other beverages, perceived mental health status, lifestyle and others. The 12-item General Health Questionnaire (GHQ 12) was used for the assessment of mental ill-health (GHQ score >or=4). RESULTS: After adjustments for age, area, perceived mental stress, lifestyle and daily caffeine intake, the consumption of brewed green tea was not statistically associated with any decrease in risk of mental ill-health among either males or females (odds ratio (OR)=0.78, 95% confidence interval (CI)=0.47-1.29 for males; OR=0.77, 95% CI=0.51-1.14 for females). Daily caffeine intake (100 mg) inclusive of green tea, black tea, coffee and other caffeine-containing beverages was associated with a higher risk of mental ill-health among females (OR=1.26, 95% CI=1.01-1.56). CONCLUSIONS: The results provide population-based evidence on the consumption of brewed green tea in everyday life and mental health, together with information on consumption patterns of various beverages and lifestyles.     

Phytoestrogen content of beverages, nuts, seeds, and oils

Phytoestrogens are secondary plant metabolites that have received increasing attention for their bioactivity, in particular due to their structural and functional similarity to 17beta-estradiol. Although urinary and plasma phytoestrogens can be used as biomarkers for dietary intake, this is often not possible in large epidemiological studies or in the assessment of general exposure in free-living individuals. Accurate information about dietary phytoestrogens is therefore important, but there are very limited data concerning food contents. In this study was analyzed a comprehensive selection of tea, coffee, alcoholic beverages, nuts, seeds, and oils for their phytoestrogen content using a newly developed sensitive method based on LC-MS incorporating (13)C 3-labeled standards. Phytoestrogens were detected in all foods analyzed, although the contents in gin and bitter (beer) were below the limit of quantification (1.5 microg/100 g). Lignans were the main type of phytoestrogens detected. Tea and coffee contained up to 20 microg/100 g phytoestrogens and beer (except bitter) contained up to 71 microg/100 g, mainly lignans. As these beverages are commonly consumed, they are a main source of dietary lignans. The results published here will contribute to databases of dietary phytoestrogen content and allow a more accurate determination of phytoestrogen exposure in free-living individuals.     

Characterization of a new potential functional ingredient: coffee silverskin

Dietary fiber (DF) is one of the main dietary factors contributing to consumers' well-being. In this work the possibility of using the roasted coffee silverskin (CS), a byproduct of roasted coffee beans, as a DF-rich ingredient has been evaluated. The results of our investigation showed that this material has 60% total DF, with a relevant component (14%) of soluble DF. Although a small amount of free phenol compounds is present in CS, it has a marked antioxidative activity, which can be attributed to the huge amount of Maillard reaction products, the melanoidins. Static batch culture fermentation experiments showed that CS induces preferential growth of bifidobacteria rather than clostridia and Bacteroides spp. CS can be proposed as a new potential functional ingredient in consideration of the high content of soluble DF, the marked antioxidant activity, and the potential prebiotic activity.     

Influence of Roasting Temperature of Barley on the Powder Characteristics and Preparation of Tea

Roasting improves the palatability of barley grains. After processing, the resulting powder is widely used to elaborate beverages such as coffee and tea. The objective of this research was to evaluate the influence of roasting on the characteristics of barley grains and the derived powder. The kinetics of release of soluble solids during the powder hydration at 80°C, performed to produce beverages such as tea, was also determined. In addition, the influence of roasting and rehydration temperatures on the physical composition of the beverages and on the release of soluble solids was investigated. After roasting, barley was ground and sieved. The powder retained in the 0.425 mm sieve was used in the analyses. Owing to roasting, the average protein content of barley increased from 10.56 to 12.88 g/100 g, and the sugar content decreased from 730 to 12.99 mg/mL, which is ascribed to the high process temperature. The phenolic compounds increased from 105.33 to 253.07 mg of ferulic acid per milliliter between the nonprocessed sample and the one roasted at 240°C, respectively. The antioxidant activity decreased with the roasting temperature rise (160–240°C) from 11.60 to 5.30 μg of 2,2‐diphenyl‐1‐picrylhydrazyl per milliliter. In the production of beverages such as tea, higher roasting temperatures led to a greater release of soluble solids in water.     

Phenolic acids in berries, fruits, and beverages

The contents of soluble and total phenolic acids were analyzed in samples of 29 berries and berry products, 24 fruits and fruit peels, and 12 beverages. Variation of phenolic acids in berries was also studied. Soluble phenolic acids were extracted with methanolic acetic acid, and a tentative quantification was performed by high-performance liquid chromatography (HPLC). The total phenolic acid content was determined by HPLC after alkaline and acid hydrolyses. The content of total phenolic acids as aglycones in the above samples varied from 0 (pear cider) to 103 mg/100 g fresh weight (rowanberry). Besides rowanberry, the best phenolic acid sources among berries were chokeberry (96 mg/100 g), blueberry (85 mg/100 g), sweet rowanberry (75 mg/100 g), and saskatoon berry (59 mg/100 g). Among fruits, the highest contents (28 mg/100 g) were determined in dark plum, cherry, and one apple variety (Valkea Kuulas). Coffee (97 mg/100 g) as well as green and black teas (30-36 mg/100 g) were the best sources among beverages. Caffeic acid dominated in all of these samples except in tea brews. Variation in the phenolic acid contents of the berries was either small or moderate.     

Contribution of chlorogenic acids to the iron-reducing activity of coffee beverages

The iron-reducing activity of coffee beverages was determined by the ferric reducing antioxidant power (FRAP) assay. The influence on FRAP due to the degree of roasting (light, medium, and dark), species (Coffea arabica and Coffea robusta), and caffeine content (regular and decaffeinated) was investigated using ground and soluble coffee samples. The concentration of specific chlorogenic acids and caffeine in the beverages was determined by high-performance liquid chromatography and related to FRAP using Pearson correlation coefficients. All measurements were expressed per unit of soluble solids. Beverages prepared with ground coffee had, on average, 27% higher FRAP values than those prepared with soluble coffee (p < 0.05). In the former beverages, FRAP of C. robusta samples was significantly higher (on average, 50.3%) when compared to that of C. arabica samples, and FRAP values decreased with increasing degree of roasting (p < 0.05). A strong correlation (r > 0.91) was found between FRAP and the total content of chlorogenic acids, particularly that of the caffeoylquinic acid isomers. The iron-reducing activity of coffee beverages was not influenced by caffeine.     

FTIR-ATR analysis of brewed coffee: effect of roasting conditions

FTIR-ATR was used to study the effect of roasting conditions on the flavor of brewed coffee using Guatemala Antigua coffee beans. The 1800-1680 cm(-1) carbonyl region for vinyl esters/lactones, esters, aldehydes, ketones, and acids was found to provide a flavor-print of the brewed coffee. A study of light, medium, and dark roasts indicated that when the rate of heating to the onset of the first and second cracks was kept constant, the types of carbonyl compounds formed were similar, varying only in their concentration. This difference in concentration is apparently due to the additional heating of the coffee bean beyond the second crack. When the heating rate to the onset of the first and second crack was varied, both the types and concentration of the carbonyl compounds formed during roasting were affected. Thus, heating rates of green coffee beans to the onset of the first and second cracks are important determinants of the basic taste and aroma of brewed coffee.     

Antioxidative activities of heterocyclic compounds formed in brewed coffee

Typical volatile heterocyclic compounds found in brewed coffee extracts-pyrroles, furans, thiophenes, and thiazoles-were examined for antioxidative activity, which was determined by measuring the oxidative conversion of hexanal to hexanoic acid using gas chromatography. 2-Acetylpyrrole, 1-methylpyrrole, and pyrrole inhibited hexanal oxidation by 98, 87, and 78%, respectively, at a concentration of 500 microgram/mL over a period of 30 days. 2-Methylfuran, which inhibited hexanal oxidation by 90% at all concentrations tested (500, 200, and 100 microgram/mL) for a 30-day period, exhibited the greatest activity among furans tested. Similarly, 2-methylthiophene, which inhibited hexanal oxidation by almost 100% at a concentration of 500 microgram/mL over 30 days, exhibited the greatest activity among the thiophenes tested. In general, thiazoles were ineffective antioxidants at all concentrations tested. However, 4,5-dimethylthiazole was able to inhibit hexanal oxidation by 50% at the highest level tested (500 microgram/mL). 2-Acetylpyrrole, 2-methylfuran, and 2-methylthiophene at concentrations of 500, 200, and 100 microgram/mL and furan at a concentration of 500 microgram/mL exhibited antioxidative activities comparable to that of the synthetic antioxidant butylated hydroxytoluene at a concentration of 50 microgram/mL.