DITERPENES AND DITERPENE ESTERS IN COFFEE

Coffee oil contains pentacyclic diterpenes as typical lipid constituents which have not been detected in any other foods. Major representatives are 16-O-methylcafestol, cafestol, and kahweol. Cafestol is contained in Arabica as well as in Robusta coffee. 16-O-Methylcafestol is found only in Robusta coffee. Larger quantities of kahweol were detected in Arabica coffee, but only trace amounts are present in Robusta.

In coffee oil, the diterpenes are hardly present in free form. They are largely esterified with fatty acids. Up to 14 fatty acid esters of 16-O-methylcafestol and cafestol have been identified. Palmitate followed by linoleate, oleate, stearate, arachidate, and behenate comprise almost 98% of the acid moieties. In Robusta coffee, the total amount of these six 16-O-methylcafestol esters are between 1.0 and 3.0 g/kg d.m. The contents of the corresponding cafestol esters vary between 2.0 and 8.0 g/kg d.m. in Robusta coffee and 9.0 and 22.0 g/kg d.m. in Arabica coffee.

Roasting has little influence on the percentage compositions of the diterpene ester fractions. Accordingly, the percentage distribution of diterpene esters in coffee powder is reflected in the resulting coffee brew. The absolute amounts depend on the type of preparation. In Scandinavian-type coffee, about 23% of the diterpene esters present in the powder can be found in the beverage. The lowest amount (0.3% of the initial quantity) is found in filtered coffee. An intermediate position is taken by espresso coffee with up to 2.5% of the initial concentration.     

Roasting process affects the profile of diterpenes in coffee

There is no consensus in the literature regarding the decrease of kahweol and cafestol contents during coffee roasting, but it has been reported that these compounds can undergo dehydration under heat. Kahweol and cafestol were quantified in Arabica and Robusta coffees with different roasting degrees (2, 4, 6, 8 and 10 min at 230 °C). The structures of the diterpenes and the presence of derivative compounds were determined by liquid chromatography with UV–Vis and mass spectrometry detection. In the dark roast samples, dehydro derivatives were found. The roasting process influenced the level of diterpenes in both species of coffee, but the effect was dependent on the intensity of the process. Cafestol and kahweol were degraded (general losses from 60 to 75 % on a lipid basis) to dehydrocafestol and dehydrokahweol, respectively, after 8 min of process, which corresponds to the commercial roasting degree. On the other hand, the amounts of cafestol and kahweol (mg/100 g of coffee) remained stable during the roasting process due to relative increase in lipid concentration.     

Authentication of Italian Espresso coffee blends through the GC peak ratio between kahweol and 16-O-methylcafestol

Since the price of Arabica is currently more than twice higher than Robusta, a rapid and reliable method for the determination of the roasted coffee blend composition is fundamental for the authentication of commercial blends used for the Italian Espresso coffee. A GC-FID method based on the ratio between the integrated peak areas of kahweol (K) divided by the sum of K and 16-O-methylcafestol (16MCF) was developed. No internal/external standard was used. Moreover, the quantitation of the unsaponifiable compounds is not necessary, as well as the calculation of any response factors. The percentage of Robusta in 34 samples of coffee blends with known composition, and in 48 samples of pure varieties was used to build a cubic polynomial function with R(2)=0.998. The roasting conditions did not affect the results. Considering eight commercial blends (ranging 0-90% Robusta), no significant difference (two-tailed P=0.817) was registered between the claimed and the predicted composition.     

Method Validation for Cafestol and Kahweol Quantification in Coffee Brews by HPLC-DAD

Cafestol and kahweol are two diterpenes exclusively found in coffee. Negative effects on health, like the increase in total lipid blood levels as well as positive effects like carcinogenic protective and antioxidant activity, have been reported for these two compounds. A simple and expeditious method for the quantification of total cafestol and kahweol levels in coffee brews by high-performance liquid chromatography with diode array detection was developed and validated. Esterified diterpenes were hydrolysed and resulting diterpene alcohols extracted with diethyl ether. For cafestol limit of detection was 0.01 mg L^?1 and limit of quatification was 0.04 mg L^?1. Coefficient of variation for cafestol ranged between 0.2 and 2.8 % for repeatability and between 1.4 and 15.3 % for intermediate precision. Average recoveries of cafestol-spiked coffee samples were from 96 to 110 %. Kahweol was quantified using cafestol calibration data and corrected by an appropriate conversion factor. Different kinds of coffee brews were analysed. Cafestol levels ranged from 0.04 to 0.80 mg/cup and for kahweol levels were between 0.01 and 0.40 mg/cup. Highest levels of diterpenes per cup were present in espresso coffee, while the lowest were found in filter coffee and instant coffee.     

Profiles of volatile compounds and sensory analysis of three blends of coffee: influence of different proportions of Arabica and Robusta and influence of roasting coffee with sugar

One hundred and forty‐six volatile compounds were identified and quantified using a static headspace sampler in three blends of coffee: Arabica/Robusta 80:20 (A80:R20) natural roasted coffee, Arabica/Robusta 20:80 (A20:R80) natural roasted coffee and Arabica/Robusta 20:80 with 50% of Robusta coffee roasted with sugar (A20:R80 50% Torrefacto). The different proportion of Arabica and Robusta coffee in the blend A80:R20 versus A20:R80 influenced the amounts of 20 chemical families of volatile compounds. Aldehydes, ketones, alcohols, pyrroles, pyrazines, furans, thiazoles, thiophenes, esters, oxazoles, lactones, sulphur compounds, pyridines, alkanes, alkenes, phenolic compounds, benzenic compounds, acids, pyranones and terpenes were present in higher quantities in the sample containing 80% of Arabica coffee, whereas sulphur compounds were more abundant in the coffee with 80% of Robusta. Sensory differences were also found between the two blends of coffee in the burnt, caramel, nutty, earthy and roasty notes. Torrefacto coffee, widely consumed in Spain, is obtained by roasting coffee with sugar. Higher quantities of ketones, alcohols, pyrazines, furans, pyridines, alkanes, phenolic compounds, pyranones and terpenes were found in the blend A20:R80 50% Torrefacto coffee versus A20:R80 natural roasted coffee. These differences in the volatile fraction were perceived by our panellists in the intensities of the nutty, roasty, earthy, burnt and caramel notes. © 2002 Society of Chemical Industry     

Extraction of coffee diterpenes and coffee oil using supercritical carbon dioxide

Commercial green and roasted coffee beans were used to maximize oil extraction and conditions were studied to obtain the highest and lowest diterpene levels on green and roasted coffee oil, respectively. Thus, operational temperatures (60–90 °C) and pressure (235–380 bar) were optimized for coffee oil extraction. Oil content levels and diterpene oil concentration were compared to the results obtained with the extraction with Soxhlet apparatus, using hexane as solvent. In general, an inverse correlation was observed between the amount of extracted oil and diterpene concentration levels. As a result, different oil contents with different diterpene concentrations could be obtained. The HPLC analysis of cafestol and kahweol in the oil extracted from green coffee beans at 70 °C/253 bar resulted in the highest concentration (453.3 mg 100 g⁻¹), which was 48% lower than in the oil extracted with hexane while in the oil extracted from roasted coffee beans at 70 °C/371 bar, resulted in 71.2% reduction of diterpenes.     

The chemistry of coffee extraction in relation to polysaccharides

Technically produced extracts from roasted Arabica and Robusta coffees contain, just like the infusions prepared in the home, 20–36% carbohydrates, depending on the degree of extraction. They are composed predominantly of mannan and galactan in about the same proportions, the share of glucan and araban making up only 1–3% of the extracts. With dialysis a group of polysaccharides with a molecular weight of more than 10 000 can be separated. They make up about half of the carbohydrates of the extracts. Their composition corresponds to that of the latter. Finally, one can obtain yet another group of almost intact high polymeric carbohydrates as copper complexes. However, they consist only of mannan and galactan, mannan predominating significantly. Arabica and Robusta coffees showed differences in this respect. Whereas Arabica coffee was able to release only a certain amount of these very high-polymeric carbohydrates, Robusta coffee delivered ever greater amounts of these polysaccharides with increasing extract yields.     

Coffee and health: a review of recent human research

Coffee is a complex mixture of chemicals that provides significant amounts of chlorogenic acid and caffeine. Unfiltered coffee is a significant source of cafestol and kahweol, which are diterpenes that have been implicated in the cholesterol-raising effects of coffee. The results of epidemiological research suggest that coffee consumption may help prevent several chronic diseases, including type 2 diabetes mellitus, Parkinson's disease and liver disease (cirrhosis and hepatocellular carcinoma). Most prospective cohort studies have not found coffee consumption to be associated with significantly increased cardiovascular disease risk. However, coffee consumption is associated with increases in several cardiovascular disease risk factors, including blood pressure and plasma homocysteine. At present, there is little evidence that coffee consumption increases the risk of cancer. For adults consuming moderate amounts of coffee (3-4 cups/d providing 300-400 mg/d of caffeine), there is little evidence of health risks and some evidence of health benefits. However, some groups, including people with hypertension, children, adolescents, and the elderly, may be more vulnerable to the adverse effects of caffeine. In addition, currently available evidence suggests that it may be prudent for pregnant women to limit coffee consumption to 3 cups/d providing no more than 300 mg/d of caffeine to exclude any increased probability of spontaneous abortion or impaired fetal growth.     

A neuro‐fuzzy computational approach for multicriteria optimisation of the quality of espresso coffee by pod based on the extraction time,temperature and blend

We demonstrate how soft computing methods can be exploited to solve multicriteria quality optimisation problems in food science and technology. In particular, we link neuro‐fuzzy modelling techniques with simulated annealing to optimise/design the quality of espresso coffee by pod. The design variables are the extraction time (ranging from 10 to 30 s), temperature (80–110 °C) and blends (100% Arabica, 100% Robusta and Arabica Robusta: A20R80, A80R20 and A40R60); they are not the only variables that affect the sensory profile of a cup of espresso coffee, but have a strong impact on the sensory quality of the beverage. Based on the framework, we show that the particular problem is a nonlinear one. Hence, an espresso coffee characterised by a specific sensory profile can be extracted using different sets of parameter values. For example, the same sensory profile can be obtained using either pure Robusta extracted at 22 s and 94 °C or 90% Arabica and 10% Robusta extracted at 25 s and 99 °C. Yet, the global optimum with respect to the distance to the optimum sensorial values is obtained using 70% Arabica and 30% Robusta extracted at 15 s around 93 °C.     

Quantification of Free 2-Furfurylthiol in Coffee Brew Using a Prefabricated Coffee Model

A reliable and sensitive method was developed to quantify the free 2-furfurylthiol (2-FFT) in coffee brew. Using cysteine addition combined with vacuum distillation, a coffee model with trace 2-FFT and similar physicochemical properties as coffee brew was prepared for standard curve construction. During the model preparation, 2-FFT in bound form was released to free 2-FFT and removed from coffee brew through vacuum distillation. The method sensitivity, precision, accuracy and selectivity were evaluated. The limit of quantification (LOQ) was 3.0 μg/L. The coefficient of variation (CV) was 7.1%. The average recovery rates were 86.8–106.2% at spiked concentrations of 22.6, 135.8 and 181 μg/L. Coffee brews prepared using Robusta and Arabica roasted coffee beans were analyzed, and results showed that coffee brew from Robusta coffee beans had a greater amount of free 2-FFT (20.94 μg/L) than Arabica coffee beans from Yunnan (11.34 μg/L) and Columbia (15.33 μg/L), respectively. This method would be beneficial to investigate the free amount of 2-FFT in coffee brew and the sensorial assay based on free 2-FFT concentration.     

Daily intake of trace metals through coffee consumption in India

The trace element contents of five varieties of instant coffee powder available in the Indian market have been analysed. Ca, Cr, Fe, K, Mg, Mn, Ni, Sr, Zn and Pb, Cd, Cu have been determined using atomic absorption spectrophotometry and differential pulse anodic stripping voltammetry, respectively. The metal levels in the coffee powders observed in this study are comparable with those reported for green coffee beans (Arabica and Robusta variety) reported worldwide with the exception of Sr and Zn, which were on the lower side of the reported values. Concentrations of these metals have been converted into intake figures based on coffee consumption. The daily intakes of the above metals through ingestion of coffee are 1.4mg, 1.58 mu g, 124 mu g, 41.5mg, 4.9mg, 17.9 mu g, 2.9 mu g, 3.8 mu g, 12.5 mu g, 0.2 mu g, 0.03 mu g and 15.5 mu g, respectively. The values, which were compared with the total dietary intake of metals through ingestion by the Mumbai population, indicate that the contribution from coffee is less than or around 1% for most of the elements except for Cr and Ni which are around 3% .     

Discrimination between Arabica and Robusta green coffee using visible micro Raman spectroscopy and chemometric analysis

We have applied visible micro Raman spectroscopy combined with principal component analysis (PCA) as a powerful technique for the fast discrimination between the two coffee species, Arabica and Robusta, based on their chlorogenic acid (CGA) and lipid contents. The Raman spectra reveal different CGA and lipid compositions when comparing Arabica and Robusta green coffee. Analysing the whole Raman spectrum, the PCA yielded a clear separation between Arabica and Robusta with 93% of the total spectral variation. Here, the most significant spectral range lies between 1000 and 1750 cm⁻¹ and is dominated by the Raman bands of CGA. Also, by restricting the PCA analysis to the spectral range from 2700 to 3050 cm⁻¹, which is dominated by lipid bands, a reliable discrimination between the two coffee species could be achieved. In this case, the first two principal components of the PCA accounted for 85% of the explained total spectral variation.     

Isolation, identification and toxigenic potential of ochratoxin A-producing Aspergillus species from coffee beans grown in two regions of Thailand

In 2006 and 2007, 32 Thai dried coffee bean samples (Coffea arabica) from two growing sites of Chiang Mai Province, and 32 Thai dried coffee bean samples (Coffea canephora var. robusta) from two growing sites of Chumphon Province, Thailand, were collected and assessed for the distribution of fungi with the potential to produce ochratoxin A (OTA). The overall percentage of fungal contamination in coffee was 98% and reduced to 60% after surface disinfection. There were remarkable ecological differences in the composition of ochratoxigenic species present in these two regions. Arabica coffee bean samples from the North had an average of 78% incidence of colonization with Aspergillus of section Circumdati with Aspergillus westerdijkiae and A. melleus as the predominant species. Aspergillus spp. of section Nigri were found in 75% of the samples whereas A. ochraceus was not detected. Robusta coffee beans from the South were 98-100% contaminated with predominantly A. carbonarius and A. niger. A. westerdijkiae was only found in one sample. The diversity of the fungal population was probably correlated with the geographical origin of the coffee, coffee cultivar, and processing method. Representative isolates of section Circumdati (52) and Nigri (82) were examined for their OTA production using HPLC with fluorescence detection. Aspergillus westerdijkiae (42 isolates out of 42), A. steynii (13/13), and A. carbonarius (35/35) in general produced large amounts of OTA, while one isolate of A. sclerotiorum produced intermediate amounts of OTA. 13% of the A. niger isolates produced OTA in intermediate amounts. OTA levels in coffee bean samples were analyzed using the Ridascreen OTA ELISA kits. Of the 64 coffee bean samples analyzed, 98% were contaminated with OTA in levels of <0.6-5.5 microg/kg (Arabica) and 1-27 microg/kg (Robusta). Presence of OTA in representative coffee samples was also confirmed by LC-MS/MS after ion-exchange purification.     

Influence of coffee/water ratio on the final quality of espresso coffee

Espresso coffee is a polyphasic beverage in which the physico‐chemical and sensory characteristics obviously depend on both the selection of ground roasted coffee and the technical conditions of the percolation process. The aim of this work was to evaluate the influence of the coffee/water ratio on the physico‐chemical and sensory quality of espresso coffee. Furthermore, the influence of botanical varieties (Arabica and Robusta) and the type of roast (conventional and torrefacto) on the selection of coffee/water ratio was studied. The relationship between pH and the perception of acidity intensity is discussed in relation to the influence of the coffee/water ratio, type of coffee and roast. The optimisation of other technical parameters in previous studies seemed to minimise the influence of an increase in the coffee/water ratio on the extraction of soluble and solid compounds. In fact, only some sensory attributes, such as bitterness, astringency and burnt, acrid and earthy/musty flavours were proposed as relevant to the selection of 6.5 g 40 mL^?1 or 7.5 g 40 mL^?1 in conventional roasted coffees (Arabica 100% and Robusta blend), and 6.5 g 40 mL^?1 in torrefacto roasted coffees. On the other hand, the addition of sugar during the roasting process in torrefacto roast coffees seemed to contribute to a higher generation of acids, melanoidins and other compounds by the Maillard reaction or caramelisation, which led us to select the lowest coffee/water ratio. Copyright © 2006 Society of Chemical Industry     

Screening and distinction of coffee brews based on headspace solid phase microextraction/gas chromatography/principal component analysis

The volatile profiles of espresso and plunger (cafetière) coffees prepared from (1) an 80:20 (w/w) blend of natural roasted Robusta and Arabica (Robusta Natural blend), (2) a 40:40:20 (w/w/w) blend of Robusta Natural blend, Robusta torrefacto roast (850 g kg^?1 Robusta, 150 g kg^?1 sugar) and (3) natural roasted pure Arabica were established by headspace solid phase microextraction (SPME) after selection of the fibre coating (polyacrylate or polydimethylsiloxane) and the temperature and time of extraction. For the analysis of furans and indoles the polyacrylate coating proved to be more suitable; however, for the overall characterisation of the volatile composition of espresso and plunger coffees the polydimethylsiloxane coating was chosen. SPME/gas chromatography (GC)/mass spectrometry (MS) analyses allowed the identification of 37 compounds: four aldehydes, two ketones, 11 furans, 10 pyrazines, two pyridines, three phenolic compounds, two indoles, one lactone, one ester and one benzothiazine. The volatile composition was related more to the botanical variety (Arabica or Robusta) than to the method of preparation of the brew (espresso or plunger). Furthermore, use of the variability provided solely by the GC peak areas and respective retention times, combined with principal component analysis (PCA), yielded the information necessary for discrimination. The combined technique of headspace SPME/GC/PCA, as an alternative to conventional techniques based on GC/MS, is proposed as a lower‐cost, fast and reliable technique for the screening and distinction of coffee brews. Copyright © 2003 Society of Chemical Industry     

Chemical characterisation of non-defective and defective green arabica and robusta coffees by electrospray ionization-mass spectrometry (ESI-MS)

The coffee roasted in Brazil is considered to be of low quality, due to the presence of defective coffee beans that depreciate the beverage quality. These beans, although being separated from the non-defective ones prior to roasting, are still commercialized in the coffee trading market. Thus, it was the aim of this work to verify the feasibility of employing ESI-MS to identify chemical characteristics that will allow the discrimination of Arabica and Robusta species and also of defective and non-defective coffees. Aqueous extracts of green (raw) defective and non-defective coffee beans were analyzed by direct infusion electrospray ionization mass spectrometry (ESI-MS) and this technique provided characteristic fingerprinting mass spectra that not only allowed for discrimination of species but also between defective and non-defective coffee beans. ESI-MS profiles in the positive mode (ESI(+)-MS) provided separation between defective and non-defective coffees within a given species, whereas ESI-MS profiles in the negative mode (ESI(−)-MS) provided separation between Arabica and Robusta coffees.     

Effect of different extraction methods on the recovery of chlorogenic acids,caffeine and Maillard reaction products in coffee beans

Water and ethanolic extracts were obtained from green and roasted (3 different roast degrees) Arabica and Robusta coffee beans. Three types of water extracts were prepared from the examined, finely ground material through: (a) brewing with boiling water, (b) boiling in water, and (c) boiling in water under elevated pressure. All these extracts were lyophilized. Two types of ethanolic extracts were derived from the examined material through (a) extraction of the finely ground coffee beans and (b) extraction of the solid residue that remained after boiling the coffee beans in water under elevated pressure. These ethanolic extracts were dried. Both water and ethanolic extracts were analyzed for concentration of potential antioxidants such as chlorogenic acids and caffeine (by HPLC) and Maillard reaction products (measurements of absorbance at 420 nm). Concentration of chlorogenic acids in Robusta extracts varied between 0.4 and 36.0 g × 100 g⁻¹ dry extract weight (db.), while in Arabica extracts it ranged from 0.1 to 22.4 g × 100 g⁻¹ db. Extracts of dark roasted Arabica contained more chlorogenic acids than those of Robusta. Concentration of caffeine, which in green and roasted coffee beans is maintained at the similar level, tended to increase in Robusta extracts with the roast degree and temperature of extraction with water, while in case of Arabica extracts there was no noticeable tendency. Caffeine concentrations varied between 0.12 and 8.41 g × 100 g⁻¹ db. and between 0.03 and 6.53 g × 100 g⁻¹ db. in Robusta and Arabica extracts, respectively. Ethanolic extracts were characterized by relatively higher caffeine concentrations and lower contents of brown pigments and chlorogenic acids as compared to water extracts. The richest in antioxidants were extracts of green Robusta coffee beans derived through boiling in water under elevated pressure.     

Coffee consumption and human health – beneficial or detrimental? – Mechanisms for effects of coffee consumption on different risk factors for cardiovascular disease and type 2 diabetes mellitus

Coffee is probably the most frequently ingested beverage worldwide. Especially Scandinavia has a high prevalence of coffee-drinkers, and they traditionally make their coffee by boiling ground coffee beans and water. Because of its consumption in most countries in the world, it is interesting, from both a public and a scientific perspective, to discuss its potential benefits or adverse aspects in relation to especially two main health problems, namely cardiovascular disease and type 2 diabetes mellitus. Epidemiological studies suggest that consumption of boiled coffee is associated with elevated risk for cardiovascular disease. This is mainly due to the two diterpenes identified in the lipid fraction of coffee grounds, cafestol and kahweol. These compounds promote increased plasma concentration of cholesterol in humans. Coffee is also a rich source of many other ingredients that may contribute to its biological activity, like heterocyclic compounds that exhibit strong antioxidant activity. Based on the literature reviewed, it is apparent that moderate daily filtered, coffee intake is not associated with any adverse effects on cardiovascular outcome. On the contrary, the data shows that coffee has a significant antioxidant activity, and may have an inverse association with the risk of type 2 diabetes mellitus.     

咖啡豆烘焙过程中油脂脂肪酸组成、挥发性风味及活性成分的演变规律

以云南小粒种咖啡豆为试材,系统研究烘焙过程中咖啡油脂理化性质、脂肪酸组成、挥发性成分及活性成分的变化规律。结果表明：随着烘焙度加深,油脂色泽加深;酸价呈增加的趋势,由1.60 mg/g增至3.75 mg/g;碘值反之,由142.04 g/100 g降至83.12 mg/100 g;茴香胺值先增大后减少,其值在3.40～16.26之间;皂化值略有降低,但无显著差异;共鉴定出11 种脂肪酸,主要为亚油酸相对含量在43.06%～64.39%之间,其次为硬脂酸和棕榈酸相对含量在12.67%～27.55%之间,油酸相对含量为9.03%～17.20%;脂肪酸组成影响不明显,但各脂肪酸的含量存在一定差异;利用气相色谱-质谱从极浅度到法式重度的咖啡油脂样品中分别检出25、33、36、53、54、59、64 种和58 种挥发性成分,主要成分有呋喃类化合物、吡嗪类化合物、酮类化合物、吡咯类化合物等,其种类和含量均呈减小趋势;活性成分中咖啡豆醇、α-生育酚、γ-生育酚、δ-生育酚含量均减少;而总酚含量不断增加,由7.75 mg/100 g升至15.96 mg/100 g。本研究结果可为咖啡精深加工及资源高值化利用提供理论依据和技术支撑。