Coffee analysis

Moreira R.F.A., Trugo L.C. and de Maria C.A.B. (1997) Application of exclusion chromatography and high-resolution gas chromatography to coffee analysis. Quim. Nova, Sociedade Brasileira de Quimica 20, 5-8. 

M. Pardo, G. SbervegUeri, Coffee analysis with an electronic nose. IEEE Trans. Instrum. Meas. 51(6), 1334-1339 (2002)... 

For example, to work in the linear range for coffee analysis, Roberts et al. used a short adsorption time. They found, however, that some rather polar compounds (e.g 2,3-pentanedione, pyrazine, furfural, and 2-acetylfuran) showed slight nonlinear behavior. 

Caffeine in coffee, tea, and soda is determined by a solid-phase microextraction using an uncoated silica fiber, followed by a GC analysis using a capillary SPB-5 column with an MS detector. Standard solutions are spiked with G3 caffeine as an internal standard. 

For more specific analysis, chromatographic methods have been developed. Using reverse-phase columns and uv detection, hplc methods have been appHed to the analysis of nicotinic acid and nicotinamide in biological fluids such as blood and urine and in foods such as coffee and meat. Derivatization techniques have also been employed to improve sensitivity (55). For example, the reaction of nicotinic amide with DCCI (AT-dicyclohexyl-0-methoxycoumarin-4-yl)methyl isourea to yield the fluorescent coumarin ester has been reported (56). After separation on a reversed-phase column, detection limits of 10 pmol for nicotinic acid have been reported (57). 

Analysis for the butanals is most conveniendy carried out by gas chromatography. Trace quantities of -butyraldehyde (18 ppb) in exhaust gases have been determined employing a combination of capillary gas chromatography with thermionic detection (35). Sinulady, trace amounts of -butyraldehyde in cigarette smoke and coffee aroma have been determined by various capillary gc techniques (36,37). 

A relatively new methodology caEed aroma dEution analysis (ada), which combines aroma dEution and gas chromatography-olfactometry to gain a better understanding of the relative importance of aroma compounds, was recently done for coffee. In a roasted Colombian coffee brew, 41 impact compounds were found with flavor dEution threshold factors (FD) greater than 25, and 26 compounds had FD factors of 100 or above. WhEe the technique permits assessment of the impact of individual compounds, it does not evaluate synergistic effects among compounds (13). 

The paper describes the different chemical sensors and mathematical methods applied and presents the review of electronic tongue application for quantitative analysis (heavy metals and other impurities in river water, uranium in former mines, metal impurities in exhaust gases, ets) and for classification and taste determination of some beverages (coffee, bear, juice, wines), vegetable oil, milk, etc. [1]. 

The dense fluid that exists above the critical temperature and pressure of a substance is called a supercritical fluid. It may be so dense that, although it is formally a gas, it is as dense as a liquid phase and can act as a solvent for liquids and solids. Supercritical carbon dioxide, for instance, can dissolve organic compounds. It is used to remove caffeine from coffee beans, to separate drugs from biological fluids for later analysis, and to extract perfumes from flowers and phytochemicals from herbs. The use of supercritical carbon dioxide avoids contamination with potentially harmful solvents and allows rapid extraction on account of the high mobility of the molecules through the fluid. Supercritical hydrocarbons are used to dissolve coal and separate it from ash, and they have been proposed for extracting oil from oil-rich tar sands. 

We can obtain a crude estimate the time required for a precise quantum mechanical calculation to analyse possible syntheses of bryosta-tin. First, the calculation of the energy of a molecule of this size will take hours. Many such calculations will be required to minimise the energy of a structure. A reasonable estimate may be that a thousand energy calculations would be required. Conformation searching will require many such minimisations, perhaps ten thousand. The reactivity of each intermediate will require a harder calculation, perhaps a hundred times harder. Each step will have many possible combinations of reagents, temperatures, times, and so on. This may introduce another factor of a thousand. The number of possible strategies was estimated before as about a million, million, million. In order to reduce the analysis of the synthesis to something which could be done in a coffee break then computers would be required which are 10 times as powerful as those available now. This is before the effects of solvents are introduced into the calculation. 

A sample thought to be caffeine, the stimulant found in coffee, tea, and cola beverages, gave the following elemental analysis 49.5 % C 5.2%H 28.8%N 16.5 % O Does this elemental... 

A number of handbooks and monographs are available with detailed descriptions of a variety of plant products and their use (Shahidi and Naczk, 1995). From a more practical point of view, an interlaboratory comparison between six university and industry laboratories of 17 extracts of spices, teas, coffees, and grape skin and of tomato peel slurry established within the framework of an EU sponsored programme, would be of interest (Schwarz et al, 2001). In this collaboration, detailed chemical analysis of the content of different phenolic compounds is compared with six antioxidant assays for the 17 extracts including different extraction procedures. 

S. de Jong, J. Heidema and H.C.M. van der Knaap, Generalized Procrustes analysis of coffee brands tested by five European sensory panels. Food Qual. Pref., 9 (1998) 111-114. 

When a test confirms the presence of a substance without determining the amount of substance present, the process is called qualitative analysis. In this activity, you will detect the presence of potassium in coffee by the characteristic yellow color that appears when potassium ions react with sodium hexanitrocobaltate. To make it easier to detect the yellow color, the coffee solution will be decolorized with charcoal, an allotropic form of solid carbon. 

The NMR spectra using PCA and Linear Discriminant Analysis (LDA) obtained for instant spray dried coffees from a number of different manufacturers demonstrated [8] that the concentration of the extracted molecules is generally high enough for clear detection. The compound 5-(hydroxymethy)-2-furaldehyde was identified as the primary marker of differentiation between two groups of coffees. This method may be used to determine whether a fraudulent retailer is selling an inferior quality product marked as being from a reputable manufacturer [8]. 

The analysis of the methylxanthines (caffeine, theobromine, and theophylline) is important in the areas of nutrition and clinical chemistry. These three compounds compose the majority of the alkaloids present in coffee, tea, cocoa, cola nuts, and guarana. 

GC has seen wide use in food analysis but has not seen a large following in the determination of the nonvolatile alkaloids in foods when compared to HPLC. The 13th edition of the AO AC Methods of Analysis22 lists a GC method for the determination of caffeine in coffee or tea using a thermionic KCI detector with a glass column 6 ft x 4 mm i.d. packed with 10% DC-200 on 80 to 100-mesh Gas Chrom Q. 

Capillary GC was used to obtain high resolution profiles of 27 organic acids, caffeine, and sucrose in dimethylsulphoxide extracts of roast and ground coffees in a 60-min analysis.26 A shortened procedure is also reported for quantitative detection of 5-caffeoylquinic (5-CQA) and quinic (QA) acids and sucrose ng detection limits were achieved. Major commer-... 

HPLC allows a quantitative determination with relatively simple extractions. In many cases, extraction only involves a heating of the commodity with water, followed by filtration and injection onto an HPLC column. In the determination of caffeine, theobromine, and theophylline in cocoa, coffee, or tea, as well as in other foods, there is scarcely a month that passes without a new paper on this assay. Kreiser and Martin provide typical conditions for analysis.28 In their studies, samples were extracted in boiling water and filtered prior to injection onto the HPLC column. The HPLC conditions used a Bondapak reversed phase column and a mobile phase of water methanol acetic acid (74 25 1) with detection at 280 nm. This method is accurate, precise, and conserves time. It has also been adopted by the AOAC as an official method for the determination of theobromine and caffeine in cocoa beans and chocolate products.29... 

Horwitz, W., Ed., Coffee and tea, spectrophotometric and chromatographic methods, in Official Methods of Analysis of AOAC, 13th ed., AOAC, Washington, D.C, 1980,p 234. 

Trugo, L.C. and Macrae, R., Application of high performance liquid chromatography to the analysis of some non-volatile coffee components, Archivos Latinoamericanos de NutrIclon, 39(1),96,1989. 

Radtke-Granzer, R., Piringer, O. G., Problems in the quality evaluation of roasted coffee by quantitative trace analysis of volatile flavor components, Dtsch Lebensm Rundsch, 77, 203, 1981. (CA95 95570j)... 

Bennat, C., Engelhardt, U. H., Kiehne, A., Wirries, F. M., Maier, H. G., HPLC analysis of chlorogenic acid lactones in roasted coffee, Z. Lebensm.-Unters. Forsch., 199(1), 17, 1994. (CA121 178291a)... 

Melo, M., Amorim, H. V., Chemistry of Brazilian green coffee and the quality of the beverage. VI, The uv and visible spectral analysis and chlorogenic acids content in TCA soluble buffer extracts, Turrialba, 25, 243, 1975. (CA84 57533q)... 

Arnold, U., Ludwig, E., Kuehn, R., Moeschwitzer, U., Analysis of free amino acids in green coffee beans, Part 1, Determination of amino acids after precolumn derivatization using 9-fluorenylmethylchloroformate, Z. Lebensm.-Forsch. 199(1), 22, 1994. (CA121 132515y)... 

Folstar, P., Van der Plas, H. C., Pilnik, W., Schols, H. A., Melger, P., Liquid chromatographic analysis of N alkanoyl-5-hydroxytryptamine (C-5-HT) in green coffee beans, J. Agric. Food Chem., 27, 12, 1979. (CA90 70640r)... 

Recent analysis of 1989 coffee consumption37 determined that annual coffee drinking was the highest per kilogram per person in Scandinavia consumption, expressed as green coffee equivalents, in Finland was 12.6... 

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