Aroma quantitative analysis

The highest OAVs were found for 4-hydroxy-2,5-dimethyl-3(2H)-fura-none, followed by ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, methyl 2-methylbutanoate and ( ,Z)-l,3,5-undecatriene. It is assumed that these odorants contribute strongly to the aroma of pineapples [50]. However, FD factors and OAVs are functions of the odorants concentrations in the extract, and are not psychophysical measures for perceived odour intensity [71,72]. To take this criticism into account, aroma models are prepared on the basis of the results of the quantitative analysis (reviewed in [9]) and in addition omission experiments are performed [9]. 

Schieberle, P. and Grosch, W. 1987. Quantitative analysis of aroma compounds in wheat and rye bread crusts using stable isotope dilution assay. J. Agric. Food Chem. 35 252-257. 

Femandez-Garcia, E. (1996). Use of headspace sampling in the quantitative analysis of artisanal Spanish cheese aroma. J. Agric. Food chem. 44,1833-1939. 

Analysis of the vacuum volatile constituents of fresh tomatoes was carried out using capillary GLC-MS and packed column GLC separation with Infrared, NMR and CI-MS analysis. Evidence was obtained for the presence of the unusual components 3-damascenone, 1-nltro-2--phenylethane, 1-nltro-3-methylbutane, 3-cyclocltral and epoxy-3-1onone. A method for the quantitative analysis of the volatile aroma components In fresh tomato has been Improved and applied to fresh tomato samples. The quantitative data obtained have been combined with odor threshold data to calculate odor unit values (ratio of concentration / threshold) for 30 major tomato components. These calculations Indicate that the major contributors to fresh tomato aroma Include (Z)-3-hexenal, 3-lonone, hexanal, 3-damascenone, 1-penten-3-one, 3-methylbutanal, (E)-2-hexenal, 2-lso-butylthlazole, 1-nltrophenylethane and (E)-2-heptenal. 

Three main approaches were applied to fresh tomatoes. The first approach was a qualitative one. It was aimed at the further identification of important aroma compounds. The second approach was designed to develop better methods for the quantitative analysis of important tomato aroma compounds and to apply the methods to various samples of tomatoes. The third approach involved the sensory evaluation of identified tomato volatiles to determine their probable importance to fresh tomato aroma. 

The three compounds presented in Table 6.34 are the key odorants of butter [63]. A comparison of the odour profiles of five samples of butter (Table 6.35) with the results of quantitative analysis (Table 6.34) show that the concentrations of these three odorants, which were found in samples 1 and 2, produce an intensive butter aroma. In samples 3 and 5, the concentration of 2,3-butanedione is too low and, therefore, the buttery odour quality is weak. In sample 4, the excessively high butyric acid concentration stimulates a rancid off-flavour. 

The aroma substances consist of highly diversified classes of compounds, some of them being highly reactive and are present in food in extremely low concentrations. The difficulties usually encountered in qualitative and quantitative analysis of aroma compounds are based on these features. Other difficulties are associated with identification of aroma compounds, elucidation of their chemical structure and characterization of sensory properties. 

The quantitative analysis of aroma substances using conventional methods often gives incorrect values. The high vapor pressure, the poor ex-tractability especially of polar aroma substances from hydrous foods and the instability of important aroma substances, e. g., thiols, can cause unforeseeable losses in the purification of the samples and in gas chromatography. 

Only the three compounds listed in Table 10.40 make an appreciable contribution to the aroma of butter. A comparison of the aroma profiles of five samples of butter (Table 10.41) with the results of a quantitative analysis (Table 10.40) show that... 

Table 1 lists volatiles identified in white and black truffle aromas by head-space SPME (lOO-pm PDMS) GC/MS, and Table 2 lists results by purge-and-trap (Tenax) GC/MS. Results obtained by HS-SPME-GC/MS agreed well with those obtained by headspace Tenax adsorption GC/MS for the volatile organic sulfur compounds, and the expected discrimination of the polar or very volatile compounds by HS-SPME was confirmed. Pelusio et al. concluded that HS-SPME-GC/MS is a powerful technique for analysis of volatile organic sulfur compounds in truffle aromas, but because HS-SPME (with PDMS fibers) strongly discriminates more polar and very volatile compounds, it is less suited for quantitative analysis. 

F. Ullrich and W. Grosch, Identification of the most intense odor compounds formed during autoxidation of linoleic acid, Z. Lebensm. Unters. Forsch. 184 277 (1987). W. Grosch and P. Schieberle, Bread flavour qualitative and quantitative analysis, Characterization, production and application of food flavours, Proceedings of 2nd Wartburg Aroma Symp., Akademie-Verlag, Berlin, 1987, p. 139. 

Preininger, M. 1998. Quantitation of potent food aroma compounds by using stable isotope labeled and unlabeled standard methods. In Food Flavors Formation, Analysis and Packaging Influences (E.T. Contis, C.T. Ho, C.J. Mussinan, T.H. Parliament, R. Shahidi, and A.M. Spanier, eds.) pp. 87-97. Elsevier, Amsterdam. 

Ferreira, V., Ortin, N., Escudero, A., Lopez, R., and Cacho, J. (2002b). Chemical characterization of the aroma of Grenache rose wines. Aroma extract dilution analysis, quantitative determination and sensory reconstitution studies. J. Agri. Food Chem. 50,4048—4054. 

If more exact data are desired, the results obtained by aroma extract dilution analysis must be complemented by quantitative measurements. Quantification of odorants is a difficult task, since the concentration of the odorants showing high FD-factors can be extraordinarily low. 

Quantitative chromatographic analysis of the composition of distilled essential oil was reported previously by Nigam and Purohit (1960) and by Lawrence (1970). The major constituent of large cardamom essential oil is 1,8-cineole (65-80%), while the content of a-terpenyl acetate is low (traces to 5%). The monoterpene hydrocarbon content is in the range of 5-7%, of which limonene, sabinene, terpinene and pinene are significant components. The terpinols comprise approximately 5-7% of the oil. The high cineole and low terpenyl acetate probably account for the very harsh aroma of this spice in comparison with that of true cardamom (Pruthi, 1993). 

In a recent study, using multivariate statistical analysis of quantitative sensory descriptive analysis and precise chemical compositional data, Smyth et al. (2005) found that the importance of individual yeast esters to the aroma profile of wine can vary with the type of wine. In the case of unwooded Chardonnay wines, for... 

Beltran, J., Serrano, E., Lopez, F.J., Pemga, A., Valcarcel, M., Rosello, S. Comparison of two quantitative GC-MS methods for analysis of tomato aroma based on purge-and-trap and on solid-phase microextraction. Anal. Bioanal. Chem. 385, 1255-1264 (2006)... 

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