Coffee roasted

The composition of green coffee is dependent on variety, origin, processing and climate. A review of the differences between Arabica and Robusta coffee is provided in Table 21.2. The constituents will be covered in more detail in the section dealing with roasted coffee. 

Soluble carbohydrates Monosaccharides 9-12.5 0.2-0.5 6-11.5 Fmctose, glucose, galactose, arabinose (traces) 

Polysaccharides 3 Polymers of galactose (55-65%), mannose (10-20%), arabinose (20-35%), glucose (0-2%) 

Volatile acids Nonvolatile aliphatic acids 2-2.9 0.1 1.3-2.2 Citric acid, malic acid, quinic acid 

Chlorogenic acid° 6.7-9.2 7.1-12.1 Mono-, dicaffeoyl- and feruloylquinic acid 

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Caffeine. About 3% by weight of the roasted coffee bean is caffeine (16). The second U.S. Department of Agriculture world coffee crop estimate for 1988—1989 was 4.24 x 10 kg (93.3 million 100-lb bags) (102). World coffee consumption was predicted to rise in the foreseeable future at the rate of 1—2% per year and thus the total amount of caffeine and related alkaloids ingested from this source can also be expected to increase. Caffeine and related bases (eg, theophylline) are also found in various teas but, because most of the major producers (India, China, etc) export relatively Htfle of thek crops and keep most for domestic consumption, accurate figures on year-to-year production are more difficult to obtain. Nevertheless, these crops are of significant economic import (103). 

Lactisole [13794-15-5] the sodium salt of racemic 2(4-methoxyphenoxy)propionic acid, is a sweet-taste inhibitor marketed by Domino Sugar. It was affirmed as a GRAS flavor (FEMA no. 3773). At a concentration of 100 to 150 ppm, lactisole strongly reduces or eliminates the sweet taste of a 10% sugar solution. This inhibition appears to be receptor-related because lactisole also inhibits the sweet taste of aspartame. The 5 -( —)-enantiomer [4276-74-8] (38), isolated from roasted coffee beans, is the active isomer the i -(+)-enantiomer is inert (127). 

Instant coffee is the dried water-extract of ground, roasted coffee. Although used in Army rations as eady as the U.S. Civil War, the popularity of instant coffee as a grocery product grew only after World War II, coincident with improvements in manufacturing methods and consumer trends toward convenience. Extensive patent Hterature dates back to 1865. Instant coffee products represented 15% of the coffee consumed in the United States in 1991 (31). 

To make an instant decaffeinated coffee product, the decaffeinated roast and ground coffee is extracted in a manner similar to nondecaffeinated coffee. Alternatively, the caffeine from the extract of untreated roasted coffee is removed by using the solvents described previously. 

In 1990, the United States import from producing countries totaled 21 million bags of green coffee equivalent (Table 5). This includes 19.6 million bags of green coffee, 0.2 million bags of roasted coffee, and 1.2 million bags of soluble coffee with a total value of 1.9 biUion (42). More than 79% of this import came from countries in the western hemisphere. 

Decaffeination Regulations. Eor decaffeinated roasted coffee, EEC standards indicate the maximum content of caffeine as 0.1% db for decaffeinated instant coffee it is 0.3% db. In the United States, decaffeination usually signifies that 97% of the caffeine has been removed. Permissible solvents for decaffeination processes are defined by national legislation, eg, EDA or EEC directive. The maximum residual solvent content after decaffeination, roasting, or instant coffee processing is to be kept within good manufacturing practice, ie, very low ppm levels or below at point of sale (46). 

Coffee Biotechnology. A number of advanced biotechnology techniques are being investigated to improve and/or develop coffee varieties as well as to better utilize roasted coffee (56). 

The basic process outline is depicted in Figure 5.2 moist un-roasted coffee beans and CO2 are fed counter-currently into the extractor under supercritical conditions. Caffeine is selectively extracted into the CO2 and this stream is led to a water-wash column to remove caffeine at a reduced pressure, the CO2 being recycled back to the extraction column. Extraction of the caffeine into water is necessary to avoid dropping the CO2 pressure too low, since compression is energy-intensive. There is now the problem of separating the caffeine (which is used in soft drinks and pharmaceu-... 

Caffeine was extracted from ficw varieties of roasted coffee beans and was determined in parallel by (1) measurement of spot area after thin layer chromatography on silica gel GF plates (development with chloroform/ cyclohexane/glacial acetic acid, 8 2 1, visualization in UV light), and (2) Kjeldahl N determination. Caffeine contents by (1) and (2), respectively, in the five varieties analyzed were (percent in DM) Santos lave 0, 1.10, and 1.12 Java Robusta 3, 1.19, and 1.22 Camerun Robusta 2, 1.16, and 1.19 Mocca 2, 1.21, and 1.26 Guatemala 0, 1.18, and 1.20. (1) is considered slightly less accurate than (2) but rather easier and more rapid.21... 

A French Standard, which corresponds to ISO 10095 issued in 1992, specifies a method for determination of caffeine in green or roasted coffee or in coffee extracts (decaffeinated or not).33 Caffeine is extracted with water at 90°C in the presence of MgO. The extract is filtered, then cleaned-up on a mini-column packed with a silica phenyl group derivative, and analyzed by HPLC on a C18 column with a methanol/water (30 70) mobile phase and a UV detector operating at 254 to 280 nm. 

A method for determining the caffeine content of regular and decaffinated green and roasted coffee beans and of regular and decaffeinated coffee extract powders, using HPLC, is specified in a British Standard Instruction.34 Caffeine is extracted from the sample with water at 90°C in the presence of magnesium oxide. The mixture is filtered and an aliquot purified on a silica microcolumn modified with phenyl groups. The caffeine content is then determined by HPLC with UV detection.35... 

Washuettl, J., Bancher, E., and Riederer, P., A new thin-layer chromatographic method for determination of caffeine in roasted coffee beans, Zeitschrift fuer Lebensmitteluntersuchung und Forschung, 143,253,1970. 

D. Roasting, Grinding, and Storage of Roasted Coffee 1. Roasting... 

It is evident that different roasting practices will produce a variety of chemical effects in the bean. Recycling of hot effluent gases, perforation of the rotating drum, and use of radiant heat will each give different chemical character to the final roasted coffee bean. 

Expelled coffee oil differs from solvent-extracted coffee oil in that it can only be produced from roasted coffee that has been softened by steam treatment. The oil is expelled at temperatures close to 180°F. Expelled coffee oil quickly stales unless the densest fraction is centrifuged away. 

The coffee beans with the most desirable flavor to many tastes are the highest grown Arabicas prepared by the wet method. Coffee beverages need to be prepared within 8 h of grinding the freshly roasted coffee beans if the volatile flavor and aroma compounds are to be retained. Brew... 

The quality of an ideally prepared coffee beverage can still be reduced or even spoiled if the water quality affects the coffee. Hardness is one of the main problems in the U.S. because it is usually associated with alkalinity. The acidity, which is a substantial part of the flavor character of coffee, is partly neutralized by hard water. Ion-exchange softened water is even worse, since the excess sodium ions present form soaps with the fatly acids in the roasted coffee. Demineralization of the water is the most effective way to obtain water for the preparation of a clean-flavored cup of coffee in hard-water areas. Oxygen in the water is easily removed by boiling. Chlorine in the water can spoil the flavor of a good coffee, as can organic matter and metal ions, such as iron and copper. 

A list of the main components of roasted coffee, in highly approximated proportions, is given in Table 1. 

The principal sources of aliphatic compounds in roasted coffee are fragmented carbohydrates and proteins. 

Several of the lower molecular weight aliphatic compounds, in a mixture, are part of the roasted coffee aroma. A nine-compound mixture with roasted coffee aroma contained isopentane, n-hexane, acetaldehyde, dimethyl sulfide, propanal, isobutanal, isopentanal, methanol, and 2-methylfuran.20 In addition, the freshness of aroma and taste has been correlated with 2-methylpropanal and diacetyl. When the concentration of these falls off, so does the taste.21 Other aliphatic compounds that are steadily lost from ground roasted coffee, unless it is vacuum packaged, include methyl formate, methyl acetate, methyl thioacetate, and acetone.22 The concentrations in roast coffee for four compounds whose contribution to the fresh flavor have long been known are dimethyl sulfide (4 ppm), methyl formate (12 ppm), isobutanal (20 ppm), and diacetyl (40 ppm). The taste thresholds are 0.1, 0.5, 0.5, and 1.0 ppm, respectively, in the brew made with 5 g coffee per 100 ml water.15... 

A list of aliphatic compounds that have been recognized in green and roasted coffees is given in Table 3. 

Several alicyclic compounds identifiable in roasted coffee are terpenes and these contribute presumably to the coffee oil. The kaurane and furokaurane type diterpenes are discussed in Section VIII.D. 

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