Identification in roasted coffee

Frank O., Blumberg S., Kunert C., Zehentbauer G., Hofmann T. Structure determination and sensory analysis of bitter-tasting 4-vinylcatechol oligomers and their identification in roasted coffee by means of LC-MS/MS. Journal of Agricultural and Food Chemistry, 55 1945-1954 (2007). 

The knowledge that not all of the volatiles (e.g. more than 800 in roasted coffee) [5] that occur in a food contribute to its aroma was the rationale for changing the methodology of analysis. Since 1984, when the procedure for charm analysis was published [4], techniques have been developed that focus on the identification of compounds contributing to the aroma with higher OAV. 

Figure 4.1 illustrates the progressive identification of the nearly 850 volatile constituents discovered in roasted coffee flavor. It shows that at the advent of chromatography (1956) 60 compounds were already known thanks to the remarkable contribution of Reichstein and Staudinger (1926) (see Table 4.4). 

Fig. 5.1 Progressive identification of hydrocarbons in roasted coffee volatiles...

The y-quinide G.15, the lactone of the main quinic acid (E.52) formed during roasting was identified in roasted coffee (chlorogenic lactones have been found in green coffee, see Section 2.1.4). The identification of isomers of this lactone was described by Maier s group (Scholz and Maier, 1990 Scholz-Bottcher et al., 1991 Scholz-Bottcher and Maier, 1992). The formation of the main lactone reached a maximum with a medium roast, whereas the minor isomers increased regularly. 

Identified in roasted coffee flavor by Merritt et al. (1963) as butylfuran (same remark as for 2-propylfuran, 1.6). The identification was also confirmed in the same way by Vitzthum and Werkhoff (1976b). It was identified in green coffee volatiles by Gutmann et al. (1979). Bakes and Bochmann (1987a) found it in coffee but not in model reactions when heating serine and threonine with sucrose. 

Identified by Stoffelsma et at. (1968) in roasted coffee flavor. In fact, the authors did not specify the furanic structure but, as they referred to Stoll et al. (1967) for the m-isomer, there is little doubt about the identification. Friedel et al. (1971) confirmed the identification for the /ram-isomer in an aroma complex of coffee (method in Gianturco et al., 1963). Cantergiani et al. (2001) found it in a green Mexican arabica (1.56% of the volatiles by GC on a polar column). 

The first mention of the presence of pyridine in roasted coffee was made by Monari and Scoccianti (1895), but 18 years later Bertrand and Weisweiller (1913) continued to ignore this discovery. Hughes and Smith (1946) published an interesting study on the non-volatile nicotinic acid, but it was only after the advent of gas chromatography that the number of identifications increased, as was the case for many other classes of compounds. The main contributions were due to Vitzthum and Werkhoff (1974b) and Baltes and Bochmann (1987d,e). 

Ouweland et al., 1978) or directly by the pyrolysis of amino acids (Fujimaki et al., 1969). Another important, if not the main, precursor of pyridines in roasted coffee is trigonelline (see Section 2.1.1.2), a product isolated by Goi ter (1910), identical to the product isolated from the seeds of Trigonella foenum-graecum. Viani and Horman (1974, 1976) identified 12 pyridinic compounds after pyrolysis of trigonelline, six of which have now been identified in roasted coffee (4-methylpyridine is noted as identified in coffee, but it is not present in the lists of quoted publications, and to our knowledge its identification has not yet been reported in the literature). The presence of four other alkyl derivatives and of two N-methylnicotinamides have not yet been confirmed in the flavor. The authors have also isolated two piperidylpyridines, 3-phenylpyridine and two of its methyl derivatives, as well as four unsubstituted and dimethyl-substituted dipyridyl compounds. 

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