Green coffee beans

A. G. W. Bradbury and D. J. HaUiday, "Polysaccharides in Green Coffee Beans," Proceedings of the 12th Colloquium ofyiSIC, Montreux, 1987, pp. 265-269. 

Green coffee bean dust Coffee processing and food industries... 

Organic Solvents Environmentally Benign Solutions Green coffee beans... 

Decaffeination of Coffee and Tea This application is driven by the environmental acceptability and nontoxicity of CO2 as well as by the ability to tailor the extraction with the adjustable solvent strength. It has been practiced industrially for more than two decades. Caffeine may be extracted from green coffee beans, and the aroma is developed later by roasting. Various methods have been proposed for recovery of the caffeine, including washing with water and adsorption. 

The production of green coffee beans involves successive removal of the outermost red skin and the pulp of the coffee berry, followed by removal of the mucilage, parchment covering, and, finally, the silverskin surrounding the green coffee bean (endosperm) (Figure 1). 

There are two methods currently used to produce green coffee beans they will be described here as the wet and the dry methods. However, an alternative nomenclature is often used washed and natural processing , respectively, and to avoid a misunderstanding it is often necessary to obtain a definition of the processing used on a given batch of coffee beans. 

The dry method produces green coffee beans much less expensively than the wet method. A high proportion of Brazilian Arabica coffee is processed in this way, and almost all Robusta coffees are treated in this way. The final beverage produced from dry-processed coffee has a full flavor that is often described as hard and sometimes is characteristic of a region, for example Rio coffees. 

Decaffeination of green coffee beans is most usually carried out with a water/solvent partition system. The green coffee beans are first steamed until they are hot, wet, and swollen, to make the caffeine available. Solvent is then used to extract the caffeine out of the aqueous phase of the beans. Finally, the beans are steamed to drive off residual solvent. The coffee beans lose their wax surface covering in the process, as well as some flavor components. For this reason, the Robusta and Brazilian Arabica coffees that are dry-processed and have the most powerful flavors are usually the types that are decaffeinated. They become milder in the process. Mechanical polishing is used to improve the appearance of decaffeinated green coffee beans if they are not to be roasted immediately. Extra care is required, however, to store these decaffeinated beans since the loss of wax covering as well as caffeine renders them much more susceptible to fungal attack. 

A great deal of effort has been put into methods for removing only the caffeine from the extracting solvent, and somehow returning all of the other components to the coffee beans for reabsorption. The principle of the method most generally seen involves exposure of the extract-laden solvent to a caffeine-specific adsorbent. Once the solvent has been treated in this way, it is returned to remove more caffeine. Flowever, the solvent is already saturated with the other solvent-soluble components and does not extract them from the second and subsequent batches of steamed green coffee beans. Adsorbants used for this purpose include activated char-... 

Coffee Roasting Styles Correlated with Approximate Value for Green Coffee Bean Weight Loss, Color, and Temperature... 

Methods for the decaffeination of green coffee beans, mainly with solvents after a steaming, have already been described. Even with the selective adsorption techniques to remove only caffeine, it is unlikely that the full character of the starting beans can be realized in a final decaffeinated beverage the result is that Robusta coffees are generally used to prepare decaffeinated coffee. The cost is kept down and the treatment, anyway, reduces any harsh or bitter flavor that the Robusta coffee may have had. The resulting beverage will be relatively caffeine-free, but Robusta coffee will contribute more soluble carbohydrates, phenols, and volatile fatty acids, and much less of the diterpenes found in Arabica coffees. 

Model systems indicate that aldehydes may also be produced by the action of polyphenoloxidases on amino acids in the presence of catechin, all of which are present in coffee beans at some stage between green and roasted. For example, valine yields isobutanal, leucine yields isopentanal, and isoleucine yields 2-methyl-butanal.14 Some of these aldehydes probably undergo condensation reactions in the acidic medium of the roasted bean when moisture is present.15 Some dienals in green coffee beans have recently been identified as (E,E)-2,4- and (E,Z)-2,4-nonadienal and (E,E)-2,4- and (E,Z)-2,4-decadienal.18... 

The aliphatic polyamines, putrescine, spermine, and spermidine, are present in green coffee beans, but they are all decomposed during the roasting process.17... 

Some flavanols obtained from steam-treated green coffee beans.36... 

The treatment and environment of green coffee beans affects the concentrations of both caffeoyl- and feruloyl quinic acids,52 and several decomposition products have been recognized. Some of these products, in this case from steam-treated green coffee beans, are given in Figure 5.53... 

Almost all the heterocyclic compounds listed are volatile and have been recognized as present in roasted coffee or its aroma, suggesting that almost all are thermal transformation products rather than compounds present in the green coffee bean. 

Some particular proteins, recognizable thus far by little more than their biological effect, have been documented. An allergen in the green coffee bean of between 18,000 and 40,000 da is probably a heterogeneous glycoprotein it can be precipitated out at pH 4.0 to 4.5.92 93... 

Green coffee beans, as expected, contain storage polysaccharides such as starch, and structural support compounds such as cellulose and lignin. Mono- and di-saccharides are represented, as well as the related compounds quinic acid and myo inositol. 

The bulk of the heteropolysaccharides in the green coffee bean are formed from mannan, galactan, and araban.95 96 Three fractions can be... 

Coffee oil is generally described as the petroleum ether-soluble fraction from green coffee beans. Arabica coffees contain 11.1 to 13.6% oil, whereas Robusta coffees contain only 4.4 to 4.8% oil.106 Triglycerides constitute 79% of this oil, terpene esters 17%, and the remaining 4% is contributed by sterols, free terpenes, tocopherols, and as yet unknown... 

The presence of tocopherols,114 as well as caffeic acid,108 accounts for the remarkable stability of green coffee bean oils toward oxidation. In coffee beans from different origins, a-tocopherol concentrations are in the range 89 to 188 pg/kg and (p + y)-tocopherol concentrations are in the range 252 to 530 pg/kg.114 Since p- and y-tocopherols have better antioxidant properties than a-tocopherol,114 it is not surprising to see coffee oil patented as an antioxidant material.115117... 

Several diterpenes, free, as their esters or as their glycosides, have been recognized in green coffee beans. Cafestol (a furokaurane) and kahweol (a furokaurene) are the predominant diterpenes. They have been recog-... 

Some sterols found in green coffee beans.111 112... 

Theobromine and theophylline concentrations are relatively low in coffee the values in green coffee beans are, respectively, 20 and 5 mg/kg.3... 

Several vitamins have been recognized in green coffee beans, as might be expected in a plant seed. A relatively high ascorbic acid content is associated with fine-grade coffee beans to be used as seeds.162 Vitamin E has already been mentioned as a component of coffee oil.114... 

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