Aroma tomato

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)... 

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. 

Studies to develop and apply quantitative methods to the analysis of fresh tomato volatiles have been recently carried out by some of the authors (J.,2). Besides the known major compounds a number of compounds were detected In the gas liquid chromatography (GLC) analysis which had spectral data unlike that of any of the 400 compounds previously reported as tomato volatiles (cf. 3 ). As these compounds occurred In reasonable amounts In fresh tomato It seemed necessary to determine their Identities In order to give a satisfactory quantitative picture of fresh tomato volatiles. It also seemed desirable to determine the odor threshold of these compounds to have a better understanding of their probable contribution to tomato aroma. 

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 identification of 1-nitro-3-methylbutane in tomato had been reported previously by Wobben et al. (5) although they had not published any GLC or mass spectral data. None of the other numerous studies of tomato volatiles (of. 3.) had reported finding this compound. It is a relatively prominent component of fresh tomato occurring at a concentration as much as 200 ppb in some varieties such as Ace and related varieties but in other varieties it occurs at lower levels (10-50 ppb). However, it does not seem to be important to fresh tomato aroma because it is a relatively weak odorant with an odor threshold of 150 ppb. 

Nitro-2-phenylethane bears a similar relationship to phenylalanine and phenylacetonitrile. The nitro compounds are possibly formed by oxidation of these amino acids. Stone et al., ( ) had previously presented evidence (using radioactive isotopes) that leucine was one of the precursors of 2-isobutylthiazole. 1-Nitro-2-phenylethane is a moderately potent odorant with an odor threshold of 2 ppb and as later discussed probably contributes to the tomato aroma. 

However, its concentration in blended tomatoes is usually below this concentration and it seems unlikely that it can make a significant contribution to fresh tomato aroma. 

Epoxy-P-ionone had been reported previously by Viani et al.,(13), Schreler et al., (J 4) and V/obben et al., ( ). In the present study besides the mass spectrum an infrared absorption spectrum was also obtained and was found to be identical to that of an authentic sample. An odor threshold was determined in water solution to be 100 ppb. It is, therefore, a relatively weak odorant and as its concentration, in all fresh tomato samples examined, is well below this figure it seems unlikely that it can contribute to fresh tomato aroma. 

Ling, L. C. "Fresh Tomato Aroma J. Agric. Food Chem. 1987, 35,... 

Berna, A.Z., Lammertyn, J., Saevels, S.,Di Natale, C., Nicolai, B.M. 2004. Electronic nose systems to study shelf life and cultivar effect on tomato aroma profile. Sens. Actuators, B97, 324-333. 

Baldwin, E.A., J.W. Scott, C.K. Shewmaker, W. Schuch, Flavor trivia and tomato aroma biochemistry and possible mechanisms for control of important aroma components, Hort. ScL, 35(6), p. 1013, 2000. 

Buttery, R.G., et al. (1987) Fresh tomato aroma volatiles - a quantitative study. J. Agric. Food Chem. 35,540-544... 

Thiazole IV (Table 5.22) can occur in milk when it is heated, and is responsible for a stale off-fiavor. Thiazole V (Table 5.22) is a constituent of tomato aroma. The aroma of tomato products is usually enhanced by the addition of 20-50 ppb of thiazole V (for the biosynthesis of the compound, see Section 5.3.2.5). 

Isobutylthiazole (compound V, Table 5.22) contributes to tomato aroma (cf. 17.1.2.6.13). It is probably obtained as a product of the secondary metabolism of leucine and cysteine (cf. postulated Reaction 5.30). 

Buttery R.G., Takeoka G.R., Ling L.C. Furaneol odor tlmeshold and importance to tomato aroma. Journal of Agricultural and Food Chemistry, 43 1638-1640(1995). 

In summary, we may conclude that the basic fresh tomato aroma is composed of the same compounds in all four cultivars, especially (Z)-3-hexenal and tra 5-4,5-epoxy-( )-2-decenal, and that the aroma differences between the cultivars that are responsible for differences in preference are caused by concentration differences of odorants with less impact, i.e., lower odor units. The more preferred tomatoes contained more l-penten-3-one, (E,E)- and (ii,Z)-2,4-decadienal, and 4-hydroxy-2,5-dimethyl-3(2F/)-fura-none (Furaneol). High concentrations of phenylacetaldehyde and 2-phenylethanol (as in the R 144 cultivar) or 3-methylbutanal and 2-isobutylthiazole (as in the R 175 tomato) had a negative influence on preference. 

Sensory evaluation of the aroma model confirmed the results of our instrumental analyses. All important odorants of fresh tomato aroma could be identified and their concentrations determined. The differences in preference ranking among the four cultivars under the experimental conditions were due to variations in the concentrations of certain flavor compounds. Higher amounts of the E,E)- and ( , Z)-2,4-decadienal... 

RG Buttery, R Teranishi, LC Ling. Fresh tomato aroma volatiles A quantitative study. J Agric Food Chem 35 540 544, 1987. 

A. Krumbein and D. Ulrich, Comparison of three sample preparation techniques for the determination of fresh tomato aroma volatiles. Flavour Science. Recent Developments (A. J. Taylor and D. S. Mottram, eds.), Hartnolls Ltd., Bodmin, UK, 1996, p. 289. 

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