Volatile coffee

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. 

A stable instant coffee powder can be produced which retains the volatile coffee-flavored components [15-18]. 

In 2003, the HLCs for six volatile coffee flavor compounds in pure water and in liquid coffee were measured with dynamic measurements [145]. The partition coefficients in pure water and coffee were significantly different for ethyl-2-methylbutyrate and barely different for 2-methylpropanal. For 2-methyIbutanal, 3-methylbutanal, dimethyl sulfide, and dimethyl disulfide, however, the values were indistinguishable in pure water and coffee within the experimental precision. Moreover, this method was first used to measure acetone concentrations in the surface seawater by Holzinger et al. [194]. At present, the detailed description about the quantification of dissolved dimethyl sulfide in seawater using HLC was reported in 2009, and the HLC of dimethyl sulfide and its temperature dependence were considered [196] ... 

Many instant coffee producers in the United States incorporate natural coffee aroma in coffee oil into the powder. These highly volatile and chemically unstable flavor components necessitate inert-gas packing to prevent aroma deterioration and stating from exposure to oxygen. 

In outline, a percolation process is used to produce an aqueous coffee extract, which in turn is dehydrated to yield water-soluble solids. Instant and soluble coffees are synonymous for these water-soluble coffee extract solids. Usually some of the volatile aroma and flavor compounds, which are lost during the processing, are added back immediately before packaging. 

Both solvent-extracted and expelled coffee oils can be sprayed directly onto soluble coffee solids. The oil is adsorbed without degradation, provided moisture and oxygen are absent. However, the most volatile compounds do tend to leave the coffee powder and fill the head space of the container. 

Methods of fixing the volatile aroma and flavor compounds separately from the instant coffee powder have been developed. The volatile mixture can be mixed with aqueous gelatin or gum arabic and spray dried. The oily droplets of the flavor and aroma compounds are coated with gelatin or gum arabic in a dry lattice. This powder can be mixed in with instant coffee powder and is relatively stable in the presence of air. Emulsification with sugar is also a highly effective way of trapping and preserving coffee volatiles, but is of limited use for instant coffees. 

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... 

One of the most significant differences between Arabica and Robusta coffees is in the caffeine content. Robusta coffees contain almost twice the caffeine found in Arabica coffees. There are some other differences recognized thus far Robustas contain almost no sucrose and only very small amounts of the kaurane and furokaurane-type diterpenes they contain higher proportions of phenols, complex carbohydrates (both soluble and hydrolyzable), volatile fatty acids on roasting, and sulfur compounds, all in comparison with Arabicas. References to these distinctions can be found in Chapter 6 of this book. 

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. 

The compounds given off during the roasting of coffee are not necessarily found in the finally roasted bean, and so only a few such compounds are included. In a list of volatile components in foods which is regularly brought up to date4 more than 800 volatile compounds are listed for coffee when it is roasted, and of these 60 to 80 contribute to coffee aroma.5 Comparison of the 14 most potent odorants from roasted Arabica and Robusta coffees, revealed significant differences,6 (see Table 2). 

The most volatile aliphatic compounds are largely lost at some stage of the roasting process. For example, acetaldehyde was among 12 volatile compounds evolved after an 8-min roast of coffee beans at 220°C.23 Waste... 

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 of the more volatile heterocyclic compounds in ground roasted coffee are substantially lost after 2 weeks for example, thiophene-3-alde-hyde is 80 to 90% lost in this time.21... 

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)... 

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

Another challenge is to develop methods to replace the volatile organic solvents that are used in many industrial procedures. One choice is water as a solvent it is easily repurified, and has a harmless vapor. Another choice is supercritical carbon dioxide, a good solvent for many organic substances. It is not as innocuous as is water, but carbon dioxide can be easily recovered and reused. It is currently used to remove caffeine from coffee, and is being developed as a dry-cleaning solvent to replace organic solvents (Chapter 9). 

Flink [4.17] described the relative retention of volatile components in coffee extracts as a function of the freezing speed and the operation pressure ... 

Coffee, for example, itself does not evaporate even at low pressure, since it is a solid. Solids are generally much less volatile than liquids, owing to the stronger interactions between the particles. In consequence, the vapour pressure of a solid is several orders of magnitude smaller than that above a liquid. 

Secondly, solid CO2 is relatively cheap. Finally, after caffeine removal, any occluded CO2 will vaporize from the coffee without the need to heat it or employ expensive vacuum technology. Again, we retain the volatile essential oils of the coffee. Even if some CO2 were to persist within the coffee granules, it is chemically inert, has no taste and would be released rapidly as soon as boiling water was added to the solid, decaffeinated coffee. 

Expandable PS beads are a material devised to accommodate the transportation drawbacks of foams. Foams take up a lot of room, but not much weight, so a truck or boxcar cannot be used very efficiently. Expandable PS beads can be readily turned into foam at their destination. The beads are impregnated with a volatile liquid like pentane as they are extruded, chopped, and cooled. Later, on site, the beads are heated in small batches with steam. The vaporization temperature of the pentane is just below the melting point of the PS beads. As the beads soften, the pentane flashes (volatilizes) and causes the PS to foam. The polymer is then ready for molding. Coffee cups, ice chests, life preservers, buoys, and floats are often fabricated this way. 

Source Identified as a volatile constituent released by fresh coffee beans Coffea canephora variety Robusta) at different stages of ripeness (Mathieu et ah, 1998). Also identified among 139 volatile compounds identified in cantaloupe [Cucumis melo var. reticulates cv. Sol Real) using an automated rapid headspace solid phase microextraction method (Beaulieu and Grimm, 2001). 

Mathieu, F., Malosse, C., and Frerot, B. Identification of the volatile components released by fresh coffee berries at different stages of ripeness, J. Agric. Food Chem., 46 (3) 1106-1110, 1998. 

---