Tomato volatile compounds

Xu Y Barringer S. Comparison of tomatillo and tomato volatile compounds in the head-space by selected ion flow fube mass speetrometiy (SIFT-MS). J Food Sci. 2010 75 C268-C73. 

Kanasawud and Crouzet have studied the mechanism for formation of volatile compounds by thermal degradation of p-carotene and lycopene in aqueous medium (Kanasawud and Crouzet 1990a,b). Such a model system is considered by the authors to be representative of the conditions found during the treatment of vegetable products. In the case of lycopene, two of the compounds identified, 2-methyl-2-hepten-6-one and citral, have already been found in the volatile fraction of tomato and tomato products. New compounds have been identified 5-hexen-2-one, hexane-2,5-dione, and 6-methyl-3,5-heptadien-2-one, possibly formed from transient pseudoionone and geranyl acetate. According to the kinetics of their formation, the authors concluded that most of these products are formed mainly from all-(E) -lycopene and not (Z)-isomers of lycopene, which are also found as minor products in the reaction mixture. 

Rios, J. J. et al. (2008). Description of volatile compounds generated by the degradation of carotenoids in paprika, tomato and marigold oleoresins. Food Chem. 106(3) 1145-1153. 

The central question that I want to approach here is the possible relationship between flavor preferences and nutritional value. There are a lot of data to work with. More than 70(X) volatile flavor substances have been identilied in foods and beverages. The situation may not be quite as complex as this would suggest. While it is true that any single fruit or vegetable may synthesize a few hundred volatile compounds, only a modest subset of these will contribute to its flavor profile. So the task is to sort out what these are, identify their sources, and link, where possible, these sources to nutritional value. Studies with the tomato provide a great example. The bottom line is Virtually all of the major tomato volatiles can be linked to compounds providing health benefits to humans. ... 

The fruit of the tomato plant Lycoperskon esculentum) is eaten raw, boiled, baked or fried. Tomato is also canned whole or pureed. More than 400 volatile compounds have been identified in tomato [190,191], of which 16 or so have odour-... 

Sucan, M.K. and Russell, G.F. 1997. A novel system for purge-and-trap with thermal desorption Optimization using tomato juice volatile compounds. J. High. Resol. Chromatogr. 20 310-314. 

Alliaceous plants release characteristic volatile compounds. The most well-known compound is the allylthio-sulfinate allicin (169), which is produced from alliin (170) by alliinase and exhibits strong antibacterial and antifungal activities. For this reason, alliaceous plants are used as companion plants of tomato, cucumber,... 

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. 

Studies with model systems of standard solutions of components in water using the same isolation procedure outlined by the authors for the tomato (2) showed satisfactory recoveries of most tomato volatiles. A few compounds gave unacceptable recoveries for the 1 hour sweeping period used. These were 2-phenylethanol which gave a 3 recovery (relative to anethole) and eugenol which gave a 0.55S recovery (relative to anethole) for the 1 hour sweep period. ... 

Tomato volatiles are important to both aroma and flavor and their concentration increases with ripening (1061. Because many of the volatile aroma compounds of tomatoes apparently result from enzymatic breakdown of carotene pigments (1071. CA, which delays pigment synthesis, can be expected to delay volatile production. 

Among a large number of volatile compounds, (Z)-3-hexenal, 3-ionone, hexanal, P-damasce-none, l-penten-3-one, and 3-methylbutanal are of special importance for the aroma of tomatoes (cf. Table 17.12). 

Tandon K.S., Baldwin E.A., Shewfelt R.L. Aroma perception of individual volatile compounds in fresh tomatoes Lycopersicon esculentum, Mill.) as affected by the medium of evaluation. Postharvest Biology and Technology, 20 261-268 (2000). 

Table III shows that the concentrations of all listed volatile compounds are far above the sensory threshold values (determined in water) thus strongly contributing to flav(M they may contribute to off-flavor, if th exceed certain concentrations. Therefore the Strecker aldehydes and dimethyl sulfide listed in Table III can be used as very sensitive marker substances for sensory changes during heat processing of tomatoes, espedally 2- and 3-methylbutanal, since their concentrations are more than hundredfold higher in tomato flakes than in tomato paste.

Table IH Determination of Volatile Compounds in Tomato Paste and Tomato Flakes by Static Head-Space-Gas Chromatography...

Table V shows thermally generated Maillard reaction products with medium and low volatility isolated from the tomato products by extraction with methylene chloride and cleaned up by gel chromatography. They were separated on a 60 m fused silica capillary (conditions as for the volatile compounds listed in Table IV).

Monitoring Volatile Compounds Released from Macerated Tomato... 

Cucumber fruits were studied by using the same analytical approach as they contain only five key volatiles and their concentration in cucumber tissue seems to be less variable than in tomato (see, for example. Ref. 12). Table 4 shows the El and API correlations for the five compounds each one could be attributed to a single ion mass on the API, and calibration with authentic standards allowed conversion of the ion signal into concentration units (parts per billion by volume). The amount of the Cg volatiles present in the macerated tissue was estimated by microwaving a sample of cucumber to inactivate the enzyme system that produces Cg and Cg volatile compounds. Inactivation was confirmed by APIMS analysis of the headspace above the treated samples. Microwaved samples were macerated after spiking them with known amounts of the Cg volatiles, then measuring volatile compound release in the blender apparatus. The values obtained from the spiked standards were then compared with the release traces from cucumber samples and the amounts of nonenal and nona-2,4-dienal estimated as 5 and 8mg/kg fresh tissue, respectively. These values compare well with the... 

Of the 400 volatiles detected in the tomato, only 17 have a positive impact on the flavor profile. Two of the most important ones are also key players in the aroma of roses p-ionone and p-damascenone. Another player is methyl salicylate, a compound we previously encountered in oil of wintergreen. Some of the most important flavor elements are present in very small concentrations but can be perceived by us at these extremely small concentrations. 

Finally, carotenoids are the metabolic precursors for three more of the flavor volatiles of the tomato. Although the role of carotenoids, light-harvesting pigments in plants, in human nutrition is the subject of debate, these compounds are antioxidants and P-carotene is the principal source of the visual pigments of the eye. 

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