Coffee potent odorant

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). 

Semmelroch, P., Laskawy, G., Blank, I., Grosch, W., Determination of potent odorants in roasted coffee by stable isotope dilution assays, Flavour Fragrance J. 10(1), 1, 1995. 

Czerny M and Grosch W. 2000. Potent odorants of raw arabica coffee. Their changes during roasting. J Agric Food Chem 48(3) 868-872. 

Mayer, F., Czerny, M., and Grosch, W. 1999. Influence of provenance and roast degree on the composition of potents odorants in Arabica coffees. Eur. Food Res. Technol. 209 242-250. 

Blanck, I., Sen, A., and Grosch, W. (1992). Potent odorants of the roasted powder and brew of Arabica coffee. Z. Lebensm. Unters. Forsch. 195, 239-245. 

Table 6.52 Concentrations and OAV of potent odorants in ground, medium roasted Arabica coffee from Colombia yields of odorants in the production of the beverage [101,102]...

Quantification of aroma-impact components by isotope dilution assays (IDA) was introduced in food flavor research by Schieberle and Grosch (1987), when trying to take into account losses of analytes due to isolation procedures. The labeled compounds have to be synthesized, the suitable fragments have to be chosen, and calibration has to be effected. A quantitative determination of ppb levels of 3-damascenone (Section 5,D.38) in foods, particularly in roasted coffee (powder and brew), was developed by Sen et al. (1991a). Semmelroch et al. (1995) quantified the potent odorants in roasted coffee by IDA. Hawthorne et al. (1992) directly determined caffeine concentration in coffee beverages with reproducibility of about 5 % using solid-phase microextraction combined with IDA. Blank et al. (1999) applied this combined method to potent coffee odorants and found it to be a rapid and accurate quantification method. They also concluded that the efficiency of IDA could be improved by optimizing the MS conditions. 

It has a very powerful and penetrating, diffusive, acid odor, pungent when undiluted, but more unpleasant when diluted. In fact it becomes more animal- and perspiration-like in dilution. Only in extreme dilution does the odor become again more pleasant, fruity, warm. Below 10 ppm, the taste is rather fruity, but at higher concentrations, the odor develops and it becomes more unpleasant (Arctan-der, 1967). For Czerny and Grosch (2000), it is one of the potent odorants in green coffee with a sweaty odor description. 

This lactone is the flavoring compound formed by the aging of a-ketobutyric acid (Sulser et al., 1967). The flavor is described as malt, molasses, maple, burnt sugar (Chemisis, 1965), with a strong seasoninglike aroma at a concentration of 0.1 ppm and a taste threshold of 1-5 ppb for Sulser et al. (1972). Manley et al. (1980) reported a maple-like, remarkably persistent curry-like odor and wondered if the enolization or the instability of the compound could be responsible for the two notes. It is a potent odorant of roasted powder and brew of arabica coffee with odor descriptions similar to those of G.12, and an odor threshold of 2-4ng/m , air (Blank et al., 1992a,b), of 7.5 ppb in water (Semmelroch et al., 1995). 

Methoxy-3,5-dimethylpyrazine is another potent odorant of green and roasted coffee. The odor description is earthy and the odor threshold 0.006 xg/kg cellulose, lower than those of the isopropyl and isobutyl analogs 0.75 and 0.77. 

The odor is powerful, diffusive onion and meat-like, in dilution more pleasant, less onion-like, reminiscent of bouillon (Arctander, 1967). At a concentration of 2 ppm it has a typical meaty and sulfury flavor (Chemisis, 1993). An odor threshold of 0.2 ppb in water is given by Semmelroch et al. (1995) and of 9 xg/kg cellulose by Czerny and Grosch (2000), being classified among the potent odorants of green and medium-roasted arabica coffee. 

Grosch W., Semmelroch P. and Masanetz C. (1993) Quantification of potent odorants in coffee. 15th Int Colloq. Chem. Coffee (Montpellier, 6-11.6.1993) (ASIC, 1993), 2, 545-9. 

Fig. 21.2. Changes in the concentration of potent odorants in the roasting process (according to Mayer et al. 1999). Arabica coffee from Colombia was slightly ( ), moderately ( ) and strongly ( ) roasted. 1, 2,3-Butandione 2, 4-Hydroxy-2,5-dimethyl-3(2H)-furanone 3, 2-ethyl-3,5-dimethylpyrazine 4, 2-fur-furylthiol 5, guaiacol...

Aroma activities of volatile compounds obtained by GCO dilution analyses were represented as Charm values, and the relative intensities of component odorants were represented in terms of the odor spectrum value (OSV) [14]. Each Charm value was rounded off to two significant figures in order to reflect the actual resolution of the dilution analysis. Acidic, buttery-oily, green-black currant, green-earthy, nutty-roast, phenolic, smoke-roast, soy sauce, sweet-caramel, and sweet-fruity were the aroma descriptions used in all GCO experiments to describe potent odorants. These descriptions were chosen from the results of a single preliminary free choice GCO analysis using a lexicon of words commonly used for coffee evaluation. 

The TICs of the headspace volatiles of Ethiopia coffee bean (L23) adsorbed on the SPME fiber under static and dynamic conditions under the same GCMS conditions are shown in Fig. 3. The DH-SPME sampling resulted in acceptable peak intensity and a chromatographic profile, and the ratios of components adsorbed were different from those obtained by the SH-SPME sampling. The amount of peak area of 47 volatile compounds trapped under the dynamic condition was about 1.8 times that of volatiles trapped under the static condition (Table 1). Also, minor compounds reported as potent odorants of coffee, such as 4-hydroxy-2,5-dimethyl-3(2//)-furanone, 2-methoxyphenol, 4-ethenyl-2-methoxyphenol, and 2-ethyl-3,5-dimethylpyr-azine, were found to be present in higher concentrations in the dynamic headspace than in the static headspace. This chromatographic difference was considered to have resulted from additional volatilization of compounds induced by flowing inert gas above the sample [10]. 

Table 3 GC/O Results of 20 Potent Odorants Detected in the Headspace of Roasted Ethiopia Coffee Beans (L 23) Under Dynamic and Static Conditions...

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