Physicochemical characteristics of Ethiopian Coffea arabica cv. Heirloom coffee extracts with various roasting conditions

This study aimed to investigate the physicochemical characteristics of Ethiopian Coffea arabica cv. Heirloom coffee extracts with various roasting conditions. Green coffee beans were roasted at four different conditions (Light-medium, Medium, Moderately dark, and Very dark) and used to extract espresso and drip coffee. Moisture content in coffee beans was decreased as the roasting degree increased. The contents of crude fat and ash were lower in the Light-medium roasted coffee beans than in green coffee beans but increased as the roasting degree increased. The values of lightness (L^*), redness (a^*), yellowness (b^*), and browning index of coffee extracts were decreased as the roasting degree increased. Total dissolved solids in espresso coffee were increased with increasing roasting degree but decreased in drip coffee. In both the extracts, the contents of reducing sugar, titratable acidity, organic acids, and chlorogenic acid were decreased, but that of caffeine was increased with the roasting degree increased.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10068-020-00865-w.     

Identification of Chemical Clusters Discriminators of Arabica and Robusta Green Coffee

The chemical parameters pH, soluble solids, caffeine, trigonelline, total chlorogenic acids, total caffeoylquinic acids, 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, total dicaffeoylquinic acids, 3,4-O-dicaffeoylquinic acid, 3,5-O-dicaffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, total feruloylquinic acids, 3-O-feruloylquinic acid, and 5-O-feruloylquinic acid were measured in Arabica (C. arabica) and Robusta (C. canephora) green coffees in order to determine discrimination parameters. In general, Robusta green coffee showed higher values for pH, soluble solids, caffeine, total caffeoylquinic acids, total dicaffeoylquinic acid, and total feruloylquinic acid, but the content of soluble solids was not significantly different in both species of green coffee. Through application of a multivariate analysis, it was concluded that these chemicals form three clusters, being the group of caffeine, trigonelline, 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, 3-O-feruloylquinic acid, 5-O-feruloylquinic acid, 3,4-O-dicaffeoylquinic acid, 3,5-O-dicaffeoylquinic acid, and 4,5-O-dicaffeoylquinic acid highly discriminating for Arabica and Robusta green coffees.     

Comparison of nine common coffee extraction methods: instrumental and sensory analysis

The preparation of a cup of coffee may vary between countries, cultures and individuals. Here, an analysis of nine different extraction methods is presented regarding analytical and sensory aspects for four espressi and five lunghi. This comprised espresso and lungo from a semi-automatic coffee machine, espresso and lungo from a fully automatic coffee machine, espresso from a single-serve capsule system, mocha made with a percolator, lungo prepared with French Press extraction, filter coffee and lungo extracted with a Bayreuth coffee machine. Analytical measurements included headspace analysis with HS SPME GC/MS, acidity (pH), titratable acidity, content of fatty acids, total solids, refractive indices (expressed in °Brix), caffeine and chlorogenic acids content with HPLC. Sensory analysis included visual, aroma, flavor and textural attributes as well as aftersensation. The technical differences in the extraction methods led to a higher concentration of the respective quantities in the espressi than in the lunghi. Regarding the contents per cup of coffee, the lunghi generally had a higher content than the espressi. The extraction efficiency of the respective compounds was mainly driven by their solubility in water. A higher amount of water, as in the extraction of a lungo, generally led to higher extraction efficiency. Comparing analytical data with sensory profiles, the following positive correlations were found total solids ? texture/body, headspace intensity ? aroma intensity, concentrations of caffeine/chlorogenic acids ? bitterness and astringency.     

Effect of the roasting process on glass transition and phase transition of Colombian Arabic coffee beans

This paper presents results of the analysis of organic coffee beans cultivated in Departamento del Cauca - Colombia. Beans studied are of the Coffea Arabica species cultivated in mountain soils of altitude close to 1500 m. Samples from green and roasted beans were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffractometry (XRD). We intend to relate the features of the heating spectra with the transformation experimented by the coffee. Glass transition and phase transitions were examined. DSC and TGA spectra show that the green coffee experiments a high and fast decomposition after 200 ^°C until 289 ^°C with a remarkable transformation in a close range around 210 ^°C. XRD shows significant changes for green and roasted beans associated to the amount of caffeine hydrates and caffeine anhydrous. Fit of XRD curves by Lorentzian shows a considerable increase of the active crystalline phase at 2θ equal to 20.4⁰ for the roasted coffee. The results obtained from this study contribute to the insight associated with the final quality of coffee dependent on roasting methods. Better quality of coffee requires a refined and very controlled roasting process around of 218 ^°C with a slow thermal treatment since the room temperature until the 200 ^°C.     

Bisphenol A migration from cans containing coffee and caffeine

This study was conducted to reconfirm the possibility and level of bisphenol A (BPA) migration from cans containing coffee and test the relationship between caffeine concentration and BPA migration from the can coating. BPA migration from cans containing decaffeinated and non-decaffeinated instant coffee averaged 66.2 and 84.0 ng ml -1 , respectively. In our study, the possibility of BPA migration from cans containing coffee after processing was found. In addition, the more caffeine content in the water solution of caffeine increased, the more BPA migration grew. This means that caffeine can have an effect on BPA migration from the can coating.     

Determination of the caffeine contents of various food items within the Austrian market and validation of a caffeine assessment tool (CAT)

The caffeine content of 124 products, including coffee, coffee-based beverages, energy drinks, tea, colas, yoghurt and chocolate, were determined using RP-HPLC with UV detection after solid-phase extraction. Highest concentrations of caffeine were found for coffee prepared from pads (755?mg?l^?1) and regular filtered coffee (659?mg?l^?1). The total caffeine content of coffee and chocolate-based beverages was between 15?mg?l^?1 in chocolate milk and 448?mg?l^?1 in canned ice coffee. For energy drinks the caffeine content varied in a range from 266 to 340?mg?l^?1. Caffeine concentrations in tea and ice teas were between 13 and 183?mg?l^?1. Coffee-flavoured yoghurts ranged from 33 to 48?mg?kg^?1. The caffeine concentration in chocolate and chocolate bars was between 17?mg?kg^?1 in whole milk chocolate and 551?mg?kg^?1 in a chocolate with coffee filling. A caffeine assessment tool was developed and validated by a 3-day dietary record (r ^2?=?0.817, p?<?0.01) using these analytical data and caffeine saliva concentrations (r ^2?=?0.427, p?<?0.01).     

Evaluation of acrylamide and selected parameters in some Turkish coffee brands from the Turkish market

The purpose of this study was to measure acrylamide (AA) levels and selected parameters of different traditional Turkish coffees. AA, 5-hydroxymethylfurfural (HMF), total reducing sugar, protein, pH, moisture, dry matter (DM) as well as ash, caffeine and soluble solids content (SSC) in DM, L*, a*, b* colour parameters of coffee samples were determined and the correlation between AA level and these parameters were investigated. A total of 36 coffee samples (20 Turkish, 8 Dibek and 8 Terebinth coffee) from the Turkish market were examined. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was validated for the detection and quantitation of AA in coffee samples. The calibration curve was linear (R² ≥ 0.999) over the range of 30–1000 μg kg^?1. The limit of detection (LOD) and limit of quantification (LOQ) were found as 4.6 μg kg^?1 and 15.5 μg kg^?1, respectively. The amounts of AA in analysed coffee samples were in the range 31.1 ± 0.6 to 323.4 ± 5.4 µg kg^?1. The highest mean AA levels were found in Terebinth coffees (240.3 μg kg^?1) followed by Turkish coffees (204.3 µg kg^?1) and then Dibek coffees (78.6 µg kg^?1). No tested Turkish coffee samples had an AA concentration above the indicative value (450 µg kg^?1) for roast coffee recommended by the European Commission (EC) in 2011. In addition, a strong positive correlation was found between HMF values and AA amounts of selected coffee types.     

Measurement of caffeine in coffee beans with UV/vis spectrometer

In this research work using UV/vis spectrophotometer the molar decadic absorption coefficients and transitional dipole moment of pure caffeine in water and dichloromethane were obtained at 272 and 274.7 nm. The molar decadic absorption coefficients of caffeine in water and dichloromethane at these wavelengths are 1115 and 1010 m² mol⁻¹, respectively. The calculated values for the transitional dipole moment of caffeine in water and in dichloromethane are 10.40 × 10⁻³⁰ and 10.80 × 10⁻³⁰ C m, respectively. After characterizing caffeine in water and dichloromethane, fast and simple methods were developed that enable to quantify the content of caffeine in coffee beans. The methods helped in extracting caffeine from coffee dissolved in water by dichloromethane, and Gaussian fit was applied to eliminate the possible interference with the caffeine spectra.     

Identification of chemical clusters discriminators of the roast degree in Arabica and Robusta coffee beans

To identify chemical parameters that might be used as discriminators, pH, soluble solids, caffeine, trigonelline, total caffeoylquinic acids, 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, total dicaffeoylquinic acids, 3,4-O-dicaffeoylquinic acid, 3,5-O-dicaffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, total feruloylquinic acids, 3-O-feruloylquinic acid, and 5-O-feruloylquinic acid were measured in Arabica and Robusta coffees submitted to three roasting levels. It was found that the fraction of soluble solids increased with roasting level, being slightly higher in Robusta roasted coffee. The contents of caffeine did not vary significantly between roasting degrees within the Arabica and Robusta samples, respectively, revealing a considerable stability during browning. The contents of trigonelline in Arabica and Robusta coffee decreased significantly with browning intensification. Overall, the levels of chlorogenic acids remained higher in Robusta roasted coffee beans but decreased sharply with roast increase. With roasting intensification, the ratio of total caffeoylquinic acids, total dicaffeoylquinic acids, and total feruloylquinic acids varied markedly in both species, with the proportion of total caffeoylquinic acids and total feruloylquinic acids increasing significantly, whereas the opposite occurred with dicaffeoylquinic acids. One can conclude, through the application of a multivariate analysis, that these chemicals form four clusters, constituting caffeine, trigonelline, total dicaffeoylquinic acids, and total feruloylquinic acids a relevant group for T₃ roasting level discrimination, in both coffee species. Additionally, detailing discriminators for roasting intensity in Arabica coffee might be caffeine, trigonelline, 3-O-caffeoylquinic acid, and 4-O-caffeoylquinic acid, whereas in Robusta roasted coffee are trigonelline, 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, 3,4-O-dicaffeoylquinic acid, 3,5-O-dicaffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, 3-O-feruloylquinic acid, and 5-O-feruloylquinic acid.     

Comparative study of polyphenols and caffeine in different coffee varieties affected by the degree of roasting

The bioactive composition of coffee, as one of the most popular beverages in the world, has attracted interest as a potential source of beneficial bioactive compounds, especially polyphenols and caffeine. Since the content of these compounds is affected by the processing conditions, the objective of this study was to determine the content of polyphenolic compounds and caffeine in four different coffee varieties: Minas and Cioccolatato (Coffea arabica), and Cherry and Vietnam (Coffea canephora syn. Coffea robusta), roasted by three varying degrees (light, medium and dark). The content of the polyphenolic compounds and the antioxidant capacity of coffees were determined using UV/Vis spectrophotometric methods, while the content of chlorogenic acid derivatives was determined using HPLC analysis. The caffeine content was determined by means of two spectrophotometric methods, as well as HPLC analysis. Additionally, raw caffeine was also obtained by an isolation procedure with chloroform. Cherry coffee, a variety of C. canephora exhibited the highest overall content of total phenols (42.37 mg GAE/g), followed by Minas coffee, while Cioccolatato contained the lowest TPC (33.12 mg GAE/g). Cherry coffee also exhibited the highest content of individual classes of polyphenols (flavan-3-ols, procyanidins and tannins), while the highest content of chlorogenic acid (CQA) derivatives was determined in Minas and Cioccolatato coffees (C. arabica). The highest content of total and individual polyphenolic compounds was determined in coffees roasted in both light and medium roasting conditions, which was also observed for the content of CQA derivatives and antioxidant capacity of roasted coffees. The highest caffeine content in the coffee samples was determined by employing the HPLC analysis (0.06–2.55%). Light roasted Cherry coffee contained the highest overall content of caffeine among all coffees, which exhibited a decrease with intensified roasting.     

Genetic diversity and correlation of bean caffeine content with cup quality and green bean physical characteristics in coffee (Coffea arabica L.)

BACKGROUND: Although people began to consume coffee for its stimulating effect, the demand for decaffeinated coffee is increasing and now accounts for 10% of the total amount of coffee consumed in the world. Forty‐two arabica coffee genotypes originating from Ethiopia were tested to assess caffeine content variability among them, and the correlation of caffeine content with cup quality and green bean physical characteristics. RESULTS: Green bean caffeine content was measured using high‐performance liquid chromatography, while cup quality was determined by professional coffee tasters. Caffeine content ranged from 9.1 to 13.2 g kg^?1 on dry mass basis (d.m.b.). Six genotypes—AD0291, AD0591, AD2491, AD2691, AD2791 and AD2891—had a caffeine content of less than 10.0 g kg^?1. Caffeine content showed negative and statistically significant correlations with cup quality attributes. Correlations between caffeine content and green bean physical characteristics were non‐significant. CONCLUSIONS: Simultaneous selection for low caffeine content and good cup quality is possible. Some accessions had low caffeine content, and may serve as a source of desirable genes for variety development of types with relatively low caffeine content. Copyright © 2008 Society of Chemical Industry     

Simultaneous Determination of Alkaloids in Green Coffee Beans from Ethiopia: Chemometric Evaluation of Geographical Origin

The alkaloid compositions of 99 green coffee (Coffea arabica L.) bean samples comprising eight varieties (Harar, Jimma, Kaffa, Wollega, Sidama, Yirgachefe, Benishangul and Finoteselam) from the major production regions of Ethiopia were investigated. High performance liquid chromatography was applied for the simultaneous determination of four coffee alkaloids in the aqueous extracts of the beans. The limits of detection for the method were established as 13 mg kg^?1 for trigonelline, 7 mg kg^?1 for theobromine, 8.5 mg kg^?1 for caffeine and 4 mg kg^?1 for theophylline in the dry coffee beans. Theophylline was not detected in any of the samples. The determined concentrations (% w/w dry coffee beans) ranged from 0.98 to 1.32 % for trigonelline, 0.0048 to 0.0094 % for theobromine and 0.87 to 1.38 % for caffeine. The concentrations of the alkaloids varied significantly, depending on the geographical origin of the beans. Theobromine was not detected in coffee beans from the East (Harar coffees), and its absence in samples can be used to ascertain whether the coffee originates from this region. Coffee beans from the Northwest were characterized by higher concentrations of caffeine. Application of linear discriminant analysis provided 75 % correct classification of samples into the respective production regions, with a 74 % prediction success rate. The moderate classification efficiency obtained when using alkaloid data demonstrates the potential of using this class of compounds in discriminant models for determination of the geographical origin of green coffee beans from Ethiopia.     

Economic production of probiotics from kitchen waste

In the present work, a novel treatment method of kitchen waste for economic production of probiotics was investigated. This required the selection of suitable probiotic microorganisms. Based on the pure cultures of probiotic strains for the fermentation kitchen waste, 5 strains of microorganisms including 1 strain of Lactobacillus, 2 strains of Bacillus, and 2 strains of yeast were selected, respectively. These probiotic microorganisms were mixed at the same ratio and cultured using the kitchen waste as culture medium at pH of 7.2 and temperature of 37°C. After 24 h, the total count of the viable cells reached 2.24 ×10¹⁰ CFU/g, which was higher than that obtained in any single probiotic strain pure culture. It was found that the presence of yeasts and Bacillus species enhanced the growth of Lactobacillus strain. Bench scale experiments were also done in a self-designed rotating drum type bioreactor. The experimental results indicate that there is a good possibility of utilizing kitchen waste for the economic production of probiotics.     

Caffeine content in coffee as influenced by grinding and brewing techniques

The caffeine content of coffee as influenced by various coffee preparation methods was investigated. The variables studied included the coffee solids to water volume ratio, the volume of coffee prepared, home versus store grinding, and drip/filtered versus boiling. Caffeine contents per 177 ml (6 oz) of coffee ranged from 50 to 143 mg, depending upon the mode of preparation. As expected, more coffee solids and larger extents of grinding led to significantly higher caffeine contents in filtered coffee. Larger volumes of coffee prepared at a constant coffee solids to water ratio also yielded significantly higher caffeine contents. Homegrinding yielded caffeine contents similar to that of store-ground coffee. Boiled coffee had caffeine contents equal to or greater than filtered coffee, depending upon the length of boiling time. The variable caffeine contents in coffee resulting from the mode of preparation should be recognized and addressed by both food composition data bases and epidemiologists.     

Kinetics of coffee infusion: a comparative study on the extraction kinetics of mineral ions and caffeine from several types of medium roasted coffees

A comparative study of the equilibrium concentrations, rates of infusion and intra‐bean diffusion coefficients of caffeine, P (as H₂PO ), K⁺, Mg²⁺ and Mn²⁺ in Milli‐Q‐Water at 80 °C was carried out. Medium roasted coffees of particle size range 1.70–2.00 mm from six different countries—Special Kenya (Kenya), Santos (Brazil), Blue Mountain Java (Sumatra), Mocha (Ethiopia), Zimbabwe (Zimbabwe) and South African Grown (South Africa)—were used in the investigation. High‐performance liquid chromatography was used for the analyses of caffeine, and inductively coupled plasma atomic emission spectrometry for the chosen elements. The equilibrium concentrations of all the species and the trend were found to be independent of the various coffee beans. The order of the rate of infusion was found to be K⁺ > caffeine > P (as H₂PO) > Mg²⁺ > Mn²⁺. Examination of the rate constants clearly indicated that P (as H₂PO), Mg²⁺ and Mn²⁺ cannot be used for identification of the coffee origin, but the values for caffeine and K⁺ can be used. Diffusion coefficients of caffeine and mineral ions were calculated in two separate ways using rate constants and half‐lives of infusion. These were then compared with known diffusion coefficients of the same species in water for determination of hindrance factors. The hindrance factor for caffeine was found to be much smaller than the corresponding factors recorded at 25.5 °C. In general the hindrance factors in the bean were all of the order of 10, with Mn²⁺ being the most hindered species. This is an indication that the infusion of the various species through the coffee bean is a hindered process. This is because of the association of caffeine and mineral ions with other coffee solubles and the physical restraint within the bean matrix. © 2000 Society of Chemical Industry     

Application of Near-Infrared Hyperspectral Imaging with Variable Selection Methods to Determine and Visualize Caffeine Content of Coffee Beans

Hyperspectral imaging covering the spectral range of 874–1734 nm was used to determine caffeine content of coffee beans. Spectral data of 958.24–1628.89 nm were extracted and preprocessed. Partial least squares regression (PLSR) model on the preprocessed full spectra obtained good performance with coefficient of determination of prediction (R ² _p ) of 0.843 and root mean square error of prediction (RMSEP) of 131.904 μg/g. In addition, 10 variable selection methods were applied to select the best optimal wavelengths. The PLSR models on the different optimal wavelengths obtained satisfactory results. The PLSR model on the wavelengths selected by random frog (RF) performed the best, with R ² _p of 0.878 and RMSEP of 116.327 μg/g. The RF wavelength selection combined with the PLSR model also achieved satisfactory visualization of caffeine content between different coffee beans. The overall results indicated that optimal wavelength selection was an efficient method for spectral data preprocessing, and hyperspectral imaging was illustrated as a potential technique for real-time online determination for caffeine content of coffee beans.     

Physico-chemical,antioxidant and antimicrobial properties of Indian monsooned coffee

Monsooned coffee is one of the world specialty coffees processed only in India. Monsooned Malabar (MM) and Monsooned Robusta (MR) are processed from native Arabica and Robusta coffees. Few of the parameters like moisture, density, pH, color, soluble solids, phenols, caffeine and chlorogenic acids differed significantly compared to the native coffees. Antioxidant activity of MM and MR were 62.23 and 69.53%, respectively. The in vitro antimicrobial activities of the water-soluble extracts of MM and MR were investigated on food-borne pathogens by the well diffusion method and the results indicated maximum inhibition in E. coli followed by Yersinia and Listeria species. Fungal isolates were resistant to water-soluble extracts compared to bacteria. MR was more sensitive in inhibition of growth compared to MM. The chromatographical fractions other than caffeine, chlorogenic acid and theobromine, MC4 and MC5 exhibited antimicrobial activity. The fractions MC4 and MC5 were identified as quinic acid and spinasterol by LC–MS analyses. The antioxidant and antimicrobial activity of the water-soluble extracts of monsooned coffee have been reported for the first time.     

Qualitative relationship between caffeine and chlorogenic acid contents among wild Coffea species

Chlorogenic acids, sensu largo (CGA), are secondary metabolites of great economic importance in coffee: their accumulation in green beans contributes to coffee drink bitterness. Previous evaluations have already focussed on wild species of coffee trees, but this assessment included six new taxa from Cameroon and Congo and involved a simplified method that generated more accurate results. Five main results were obtained: (1) Cameroon and Congo were found to be a centre of diversity, encompassing the entire range of CGA content from 0.8% to 11.9% dry matter basis (dmb); (2) three groups of coffee tree species – CGA1, CGA2 and CGA3 – were established on the basis of discontinuities; (3) means were 1.4%, 5.6% and 9.9% dmb, respectively; (4) there was a qualitative relationship between caffeine and ACG content distribution; (5) only a small part of the CGA is trapped by caffeine as caffeine chlorogenate.     

Caffeine levels in beverages from Argentina's market: application to caffeine dietary intake assessment

The caffeine content of different beverages from Argentina's market was measured. Several brands of coffees, teas, mates, chocolate milks, soft and energy drinks were analysed by high-performance liquid chromatography (HPLC) with ultraviolet detection. The highest concentration level was found in short coffee (1.38 mg ml^?1) and the highest amount per serving was found in instant coffee (95 mg per serving). A consumption study was also carried out among 471 people from 2 to 93 years of age to evaluate caffeine total dietary intake by age and to identify the sources of caffeine intake. The mean caffeine intake among adults was 288 mg day^?1 and mate was the main contributor to that intake. The mean caffeine intake among children of 10 years of age and under was 35 mg day^?1 and soft drinks were the major contributors to that intake. Children between 11 and 15 years old and teenagers (between 16 and 20 years) had caffeine mean intakes of 120 and 240 mg day^?1, respectively, and mate was the major contributor to those intakes. Drinking mate is a deep-rooted habit among Argentine people and it might be the reason for their elevated caffeine mean daily intake.     

The microbiology of instant tea

The microbial ecology of an instant tea line was studied using samples from different points of the line. Only lactic acid bacteria were found at certain manufacturing stages. The main contaminant was identified as Lactobacillus plantarum. As no other bacteria were found in this line, lactic acid bacteria may be considered as quality ‘indicators’ and their determination might be a means to monitor Good Manufacturing Practices (GMP). In addition, the total tea solids (TS) concentration that inhibits the growth of certain isolated L. plantarum strains was determined on the instant tea line. A TS concentration of 60% inhibited these organisms during 48 h. The same TS concentration did not inhibit the growth of a non-identified cluster of Lactobacilli isolated from the same line.The bacteriostatic effects of pure theophylline and pure theobromine on the growth of L. plantarum were also examined. No bacteriostatic effect in the presence of either compound was observed at normal concentration or at concentrations higher than those calculated to be normally present in tea lines.The standard aroma profile of an instant tea solution was modified as a result of inoculation with a wild strain of L. plantarum. This implies that heavy contamination and fermentation by such organisms might result in products with altered aroma profiles that are unacceptable to the consumer.It should be noted that altered tea aroma might eventually be used as an indicator of microbial build-up by analysing certain of the altered aroma components. Further work is needed to investigate this possibility.Challenge tests with known pathogens and spoilage organisms revealed that, although pathogens were unable to multiply in instant tea solutions, spoilage organisms could grow or survive and thus might pose problems.