Aroma roasted coffee

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... 

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... 

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. 

Holscher, W., Steinhart, H., Formation pathways for primary roasted coffee aroma compounds, in ACS Symposium Series 543, Thermally Generated Flavors, 1994, 206. (CA120 105189t)... 

Vitzthum, O. G., Werkhoff, P., Measurable changes of roasted coffee aroma in oxygen permeable bag packs, Chem. Mikrobiol. Technol. Lebensm., 6, 25, 1979. (CA91 54812p)... 

Vitzthum, O. G., Werkoff, P., Steam volatile aroma constituents of roasted coffee, Z. Lebensm.-Unters. Forsch., 160, 277, 1976. (CA84 178488n)... 

Tressl, R., Gruenewald. K. G., Kamperschroer, H., Silwar, R., Formation of pyrroles and aroma contributing sulfur components in malt and roasted coffee, Prog. Food Nutr. Sci., 5, 71, 1981. 

As these examples indicate, the characteristic flavor of a food, fruit, etc., usually derives from a complex mixture of components. In a few cases, one unique sulfur compound is a character-impact compound, a material recognized as having the same organoleptic character as the material itself. Although some 670 compounds, of which more than 100 are sulfur-containing, have been identified in roast coffee, one material, furfurylmercaptan (2-furylmethanethiol) is considered to be a character-impact compound.43,44 The threshold level for detection of 2-furylmethanethiol in water is 0.005 ppb, and at levels of 0.01-0.5 ppb, it has the very characteristic aroma of freshly roasted coffee. However, as in many other cases, there is a concentration effect. At levels from 1-10 ppb the aroma is that of staled coffee with a sulfury note .43 Hence, 2-furylmethanethiol has a two headed property - at low concentrations it is a character impact compound and at higher levels it is an off-flavor component. 

Phenols. See also Phenol Phenolic entries achiral derivatizing agents, 6 96t alkylation, 2 196-197, 212-214 aroma chemicals, 3 243-246 aroma compounds in roasted coffee, 7 256ts... 

Steam volatile aroma constituents of CA094 roasted coffee-neutral fraction. Z Lebe-nsm-Unters Forsch 1976 160 277. 

C7H10O3, Mr 142.16, has been found in, e.g., lovage and roast coffee. It has a bouillon-like, coffee and lovage aroma, depending on its concentration. It can be... 

Tominaga, T., Blanchard, L., Darriet, P., and Dubourdieu, D. (2000). A powerful aromatic volatile thiol, 2-furanmethanethiol, exhibiting roast coffee aroma in wines made from several Vitis vinifera grape varieties. ]. Agric. Food Chem. 48,1799-1802. 

More than 700 constituents have been identified in aroma extracts of roasted coffee. Heterocyclic aroma components represent the greatest amount of the steam volatile aroma complex (80 - 85 %) which amounts to 700 -900 ppm in medium roasted Arabica coffees. The concentration of individual components varies depending on coffee varieties and roasting conditions. Typical components are formed by thermal degradation of free and bound amino acid and chlorogenic acid precursors. Compared to other roasted foodstuffs, sulfur containing constituents and phenols are formed in high amounts and contribute to desirable coffee flavor or off-flavor. 

Aroma and flavor components of roasted coffee were investigated by numerous authors. In 1926 Reichstein and Staudinger (J 8) characterized furfurylmercaptan (2-furyl-methanthiol) as an important aroma constituent of roasted coffee which is a character impact component. 

Furans and reductones are major components in roasted coffee as shown in Figure 3. Arabicas possess higher amounts of furanaldehydes and Furaneol than Robustas, when roasted under comparable conditions. The aldehydes and reductones are Strecker-active components and further transformed into typical aroma and flavor compounds as demonstrated in model experiments. 

The concentrations of furfurylsulfides and -disulfides wich possess toasted, bread- and meat-like aromas do not change during storage of roasted coffee. Sulfur containing furans are formed by heating furanaldehydes with cysteine and methionine, respectively (24). 

---