Discrimination between arabica and robusta coffee species on the basis of their tocopherol profiles

The tocopherol profiles of arabica and robusta coffee beans, both green and roasted, were ascertained. A solid-liquid micro-extraction method was used, and the quantification performed by normal-phase HPLC/diode-array/fluorescence detection. Regarding green arabicas, the mean contents were 2.7 ± 0.4 mg/100 g, for α-tocopherol, and 8.0 ± 0.9 mg/100 g, for β-tocopherol. For green robustas, mean values of 1.7 ± 0.3 and 2.1 ± 0.3 mg/100 g were found for α- and β-tocopherol, respectively. Generally, more than 90% of tocopherols remained after the roasting procedure, except for β-tocopherol in robustas, whose mean degradation was approximately 25% when expressed as dry weight. No γ-tocopherol was detected in any sample. The results show that tocopherol profile could be useful in the discrimination of arabica and robusta coffees (either green or roasted).     

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.     

Metabolomic approach for understanding phenolic compounds and melanoidin roles on antioxidant activity of Indonesia robusta and arabica coffee extracts

Our experiments investigated roles of phenolic compounds and melanoidins on antioxidant activity of Indonesia robusta and arabica coffee extracts. The 2,2,-diphenyl-1-picrylhydrazyl (DPPH) assay and a ferric reducing antioxidant power (FRAP) method were used to determine the antioxidant activity. An increase in the roasting degree (green, light, medium, and dark) reduced phenolic compounds and the antioxidant activity of coffee extracts, but enhanced melanoidin content. Principle component analysis (PCA) demonstrated that phenolic compounds showed stronger effects on antioxidant activity of coffee extracts in comparison with melanoidins. This finding was supported by the results of metabolomic fingerprint by partial least square (PLS), which describes the correlation of functional groups of coffee extracts on antioxidant activity. Based on the PLS analysis, hydroxyl groups (O–H) were observed to show a positive correlation, but carbonyl (C=O) and amine (N–H) groups were attributed to a negative correlation on antioxidant activity of coffee extracts.     

Characterization of commercial chili sauce varieties according to their chemical and physical properties using chemometric methods

Different varieties of chili sauces that are commercially available in Malaysia were randomly collected and their physical and chemical parameters were determined. Initially, pattern recognition techniques were applied in order to categorize the chili sauce varieties. With the aid of principal component analysis and cluster analysis, it is possible to visualize the clustering tendencies of the different varieties of chili sauces where four major clusters, namely chili sauces, general chili ketchups, hot/garlic added ketchups, and Thai ketchups have been successfully partitioned. Color and taste parameters have been found to be the most discriminating variables among them. With the K-nearest neighbor technique, a good prediction of chili sauces’ categories could be achieved. With appropriate customer preference survey, it would be possible to map these characteristics to the preferences. This would certainly help producers of chili sauces in upgrading the quality and taste of their products.     

Contribution of coffee proteins to roasted coffee volatiles in a model system

A simple roasting model using a mineral oil bath was set up to study the effects of coffee proteins on the formation of coffee volatiles during roasting. Green coffee powder was separated into four fractions, and the highest concentration of volatile compounds was observed in the roasted sample of the water extract fraction. Sugar degradation products were the dominant compounds. The addition of coffee proteins into the nonprotein water extract fraction catalysed sugar degradation and enhanced the production of selected volatiles. Higher amounts of coffee protein correlated with the concentration of pyrazines. Coffee protein also increased sucrose degradation in the roasting of sucrose with coffee protein. However, the results from colour measurements indicated that a greater amount of protein produced a lighter colour. These results demonstrated the important contribution of coffee proteins in the formation of coffee volatiles and colour.     

Detection of ground roasted coffee adulteration with roasted soybean and wheat

Coffee as high-price commodity is quite vulnerable to adulteration by cheaper roasted grains. Frauds are conventionally detected by microscopy; however, this technique is limited semi-quantitative assays that require training and skilled analysts. In this regard, carbohydrates as major macronutrients of grains can be used as chemical markers to qualitatively and quantitatively assess coffee authenticity. Although, some tamper's studies have already been reported, this paper approaches on new analytical resources for detection of ground roasted coffee adulteration, applying roasted soybean and wheat as sources of fraud. The characterization of the pure roasted coffee beans and of adulterations profiles was taken by total carbohydrates validated method based on high-performance anion-exchange chromatography with pulsed amperometric detection. The influence of each matrix was evaluated employing the simplex-centroid design for experiments with mixtures thus relating the mixing ratio with each monosaccharide by response surface. The proposed models were effective in recognition and prediction of different mixture proportions, thereby allowing the distinction of genuine coffee by principal component analysis and linear discriminant analysis. Predominantly, pure roasted coffee presented higher levels of galactose and mannose. Glucose can be considered as a marker for wheat adulteration and fructose for soybean, respectively. These results correspond to polysaccharides of pure raw grains, confirming this approach as a feasible analytical tool for detection of adulterants in ground roasted coffee.     

Differentiation of heat-treated pork liver pastes according to their metal content using multivariate data analysis

The heavy metal composition of 80 samples of heat treated pork liver pastes from different brands canned in three different type of container was analysed. The metal concentration in the pastes together with multivariate techniques such as linear discriminant analysis, principal component analysis and factor analysis allow us to study the latent structure in the samples and follow the influence of the material of the container or/and the brand of origin.     

Analytical method to detect adulteration of ground roasted coffee

In this work, an HPLC-based detection method for identification of coffee powder adulterated with roasted barley, wheat and rice powders was developed by using various chemical indices such as monosaccharides (mannose, rhamnose, glucose, galactose, xylose and arabinose), trigonelline and nicotinic acid. As a quality assurance, the recovery efficiencies were 84.1%–90.2% for the monosaccharides, 113.6% for trigonelline and 114.9% for nicotinic acid. The limits of detection were 0.047–0.070 mmol kg⁻¹ for the monosaccharides, 0.209 mg kg⁻¹ for trigonelline and 0.117 mg kg⁻¹ for nicotinic acid. The glucose concentration in coffee samples adulterated with roasted barley, wheat and rice at 99:1 (w/w) mixing ratio was significantly different from the control coffee sample. The limit of discrimination from adulterated coffee samples was 1% (w/w) when glucose was used as a chemical index (P < 0.05).     

Water content of roasted coffee: impact on grinding behaviour,extraction, and aroma retention

Normal and long time roasting trials were carried out on industrial scale. Different amounts of water were applied during quenching, resulting in water contents in the range of 2.3–8.8 g/100 g wb. Coffees were ground immediately after cooling, and after equilibration times of 6 and 24 h. Particle size distribution of ground coffees, percolation time, and extraction properties were investigated on an espresso coffee machine. Coffees ground after 24 h resting time were subjected to storage trials to determine aroma stability as influenced by water content. Coffees with high moisture content exhibited coarser particles upon grinding, and equilibration time prior to grinding was needed for coffees with high water content to improve grinding results. Coffees with low water content did not exhibit this time dependency prior to grinding. Coffees with low water content were extracted more effectively than high moisture coffees, and percolation was slower. During open and closed storage, evolution of hexanal and sulfides was highly sensitive to water content. However, differences in evolution of other aroma compounds were found during closed storage only, where moisture content had a negative impact on aroma stability of the coffees subjected to investigation.     

Effect of UV-C irradiation on inactivation of Aspergillus flavus and Aspergillus parasiticus and quality parameters of roasted coffee bean (Coffea arabica L.)

ABSTRACT

This study investigated the antifungal effect of ultraviolet-C (UV-C) against Aspergillus flavus and Aspergillus parasiticus on roasted coffee beans. Also, any changes in the quality of the roasted coffee beans were measured after UV-C irradiation. As UV-C irradiation time increased (0–2 h), the number of surviving A. flavus and A. parasiticus spores significantly (P < .05) decreased. The reduction values of A. flavus in round part, crack part, and whole roasted coffee beans were 2.16, 0.71, and 1.58 log₁₀ CFU g^?1, respectively, and the reduction values of A. parasiticus in round part, crack part, and whole roasted coffee beans were 1.03, 0.37, and 0.72 log₁₀ CFU g^?1, respectively, after 2 h of UV-C irradiation. Field emission scanning electron microscopy showed that the morphology of A. flavus and A. parasiticus spores included expanded wrinkles that were deformed by UV-C irradiation. The Hunter colours were significantly reduced (P < .05). There was no significant change (P > .05) in moisture content, but the pH was significantly decreased (P < .05). Most of the sensory parameters did not change, but there was a significant difference (P < .05) in flavour. Based on this study, 2 h of UV-C irradiation was effective in reducing 90% of A. flavus, but it was not effective against A. parasiticus present on roasted coffee beans. Also, Hunter colour, pH, and sensory parameters (flavour) were changed by UV-C irradiation.     

咖啡主要烘焙风味物质的形成及变化规律

咖啡以其独特的风味和功能特性受到人们的喜爱。烘焙温度及烘焙时间决定了咖啡的烘焙程度,并对咖啡风味物质的产生及变化产生重要影响。咖啡主要烘焙风味物质是与咖啡风味直接相关且代表性强的香气成分,本文通过综合分析烘焙程度与咖啡主要风味物质的形成和变化规律的关系,为系统了解和掌握精品咖啡烘焙工艺提供科学参考。     

Geographical and genotypic segmentation of arabica coffee using self-organizing maps

Several statistical methods have been developed in an attempt to reproduce the human capability of pattern recognition. Self-organizing maps (SOMs) are a type of artificial neural network (ANN) with unsupervised learning designed to examine the structure of multidimensional data. This study aimed to conduct a segmentation of the geographical and genotypic coffee grown in the coffee region of Paraná — Brazil using the SOM for cluster analysis. Fourteen arabica coffee genotypes from two different cities were collected (Paranavaí and Cornélio Procópio). Density, caffeine, chlorogenic acids, tannins, total and reducing sugars, proteins, and lipids of the green coffee beans were analyzed. Using these data, the SOM was able to discriminate the 14 genotypes and also segmentation of the geographical origin was observed. Reducing sugars, caffeine, and chlorogenic acid were the most important variables for separation of the region of cultivation of arabica coffee genotypes. It was concluded that the SOM was able to recognize the coffee genotypes and geographical origin using the chemical profile data.     

咖啡主要烘焙风味物质的形成及变化规律

咖啡以其独特的风味和功能特性受到人们的喜爱。烘焙温度及烘焙时间决定了咖啡的烘焙程度,并对咖啡风味物质的产生及变化产生重要影响。咖啡主要烘焙风味物质是与咖啡风味直接相关且代表性强的香气成分,本文通过综合分析烘焙程度与咖啡主要风味物质的形成和变化规律的关系,为系统了解和掌握精品咖啡烘焙工艺提供科学参考。      

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.     

Potent odorants of the roasted powder and brew of Arabica coffee

Summary Aroma extract dilution analysis (AEDA) revealed 13 compounds as important contributors to the aroma of roasted coffee (powder): 2-methyl-3-furanthiol (I), 2-furfurylthiol (II), methional (III), 3-mercapto-3-methylbutylformate (IV), 3-isopropyl-2-methoxypyrazine (V), 2-ethyl-3,5-dimethylpyrazine (VI), 2,3-diethyl-5-methylpyrazine (VII), 3-isobutyl-2-methoxy-pyrazine (VIII), 3-hydroxy-4,5-dimethyl-2(5H)-furanone (sotolon, IX), 4-ethylguaiacol (X), 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone (XI), 4-vinylguaiacol (XII), and (E)--damascenone (XIII). A comparative AEDA of the coffee powder and brew showed in the brew an increase of III, IX, vanillin and 4-hydroxy-2,5-dimethyl-3(2H)-furanone and a decrease of I, II, IV, V, VII, and VIII.

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Intensive Geruchsstoffe von Röstkaffee und Röstkaffeeaufguß aus Arabica-Kaffee

Zusammenfassung Die Aromaextrakt-Verdünnungsanalyse (AEVA) von Röstkaffee ergab 13 wichtige Geruchsstoffe: 2-Methyl-3-furanthiol (I), 2-Furfurylthiol (II), Methional (III), 3-Mercapto-3-methylbutylformiat (IV), 3-Isopropyl-2-methoxypyrazin (V), 2-Ethyl-3,5-dimethylpyrazin (VI), 2,3-Diethyl-5-methylpyrazin (VII), 3-Isobutyl-2-methoxypyrazin (VIII), 3-Hydroxy-4,5-dimethyl-2(5H)-furanon (Sotolon, IX), 4-Vinylguajacol (XII) und (E)--Damascenon (XIII). Die vergleichende AEVA von Röstkaffee und daraus hergestelltem Aufguß zeigte im Aufguß eine Zunahme von III, IX, Vanillin und 4-Hydroxy-2,5-dimethyl-3(2H)-furanon und eine Abnahme von I, II, IV, V, VII und VIII.

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Results presented in part at the 14th International Conference on Coffee Science, San Francisco, USA (July 14–19, 1991)     

Fate of 14C-acrylamide in roasted and ground coffee during storage

Acrylamide (AA) is formed during heating of carbohydrate rich foods in the course of the Maillard reaction. AA has been classified as probably carcinogenic to humans. Storage experiments with roasted coffee have shown that AA levels decrease depending on storage time and temperature. In the present study the fate of AA lost during storage of roasted and ground (R&G) coffee was studied, using 14C-labeled AA as radiotracer. Radiolabel was measured in coffee brew, filter residue, and volatiles. In the brew, total (14)C-label decreased during storage of R&G coffee, while activity in the filter residue built up concomitantly. [2,3-14C]-AA (14C-AA) was the only 14C-related water extractable low molecular compound in the brew detected by radio-HPLC. No formation of volatile 14C-AA-related compounds was detected during storage and coffee brewing. Close to 90% of the radiolabel in the filter residue (spent R&G coffee, spent grounds) remained firmly bound to the matrix, largely resisting extraction by aqueous ammonia, ethyl acetate, chloroform, hexane, and sequential polyenzymatic digest. Furanthiols, which are abundant as aroma components in roasted coffee, have not been found to be involved in the formation of covalent AA adducts and thus do not contribute substantially to the decrease of AA during storage.