Volatile compounds affecting aroma

Volatile Compounds Affecting the Aroma of Vitis vinifera L. cv. Scheurebe... 

Maarse, H., Belz, R. (Eds.) Isolation, separation and identification of volatile compounds in aroma research. Akademie-Verlag Berlin. 1981 Maier, H.G. Zur Bindung fluchtiger Aromastoffe an Proteine. Dtsch. Lebensm. Rundsch. 70,349 (1974) McNulty, RB., Karel, M. Factors affecting flavour release and uptake in OAV-emulsions. J. Food Technol, 8, 319 (1973)... 

Many factors affect the volatile composition of fruit and vegetables, e.g. genetics, maturity, growing conditions and postharvest handling. Furthermore, preparation of the fruits and vegetables for consumption and the method for isolation of volatile compounds may change the volatile profile and key aroma compounds compared to non-processed fruits and vegetables. 

The release of various aroma compounds (ethyl esters, methylketones, and alcohols), from either carrageenan-based, or carrageenan-acetylated monoglycerides emulsion-based, or acetylated-monoglycerides-based films strongly differs (Marcuzzo et al., 2010). In lipid films, the aroma compound release is more affected by factors related to diffusivity, whereas in carrageenan emulsified films, the affinity between volatile compounds and polymer preponderantly influences sorption... 

The structure of the food matrix is also known to affect the release of volatile compounds having an impact on flavors and aroma. Changes in flavor result from the interactions of lipid-derived carbonyl compounds by aldolization with the amino groups of proteins. Undesirable flavors are produced when beef or chicken are fried in oxidized fats by the interaction of secondary lipid oxidation... 

Phospholipids contribute specific aroma to heated milk, meat and other cooked foods through lipid oxidation derived volatile compounds and interaction with Maillard reaction products. Most of the aroma significant volatiles from soybean lecithin are derived from lipid decomposition and Maillard reaction products including short-chain fatty acids, 2-heptanone, hexanal, and short-chain branched aldehydes formed by Strecker degradation (reactions of a-dicarbonyl compounds with amino acids). The most odor-active volatiles identified from aqueous dispersions of phosphatidylcholine and phos-phatidylethanolamine include fra 5 -4,5-epoxy-c/5-2-decenal, fran5,fran5-2,4-decadienal, hexanal, fra 5, d5, d5 -2,4,7-tridecatrienal (Table 11.9). Upon heating, these phospholipids produced cis- and franj-2-decenal and fra 5-2-undecenal. Besides fatty acid composition, other unknown factors apparently affect the formation of carbonyl compounds from heated phospholipids. 

EOs are generally products of rather complex compositions used contemporaneously in aroma therapy and for centuries as aromatic medicinal plant species in traditional systems of medicine. Aromatic formulas are used for the treatment of a variety of illnesses, including those that affect the CNS (Almeida et al. 2004). Volatile compounds presenting sedative or stimulatory properties have been and continue to be identi ed in EOs from aromatic medicinal species spread into dif ferent families and genera. The majority of these substances have small structures with less than 12 carbons and present low-polarity chemical functions, being therefore quite volatile. Since most natural EOs are formed by complex mixtures, their bioactivity(ies) is obviously dependent on the contribution of their various components. Therefore, studies failing to characterize at least the main components of the EO studied are not discussed in this chapter. 

The formation of typical aromas takes place during the ripening of fruit. In bananas, for example, noticeable amounts of volatile compounds are formed only 24 h after the climacteric stage has passed. The aroma build-up is affected by external factors such as temperature and day/night variations. Bananas, with a day/night rhythm of 30 °C/20 °C, produce about 60% more volatiles than those kept at a constant temperature of 30 °C. The synthesis of aroma substances is discussed in section 5.3.2. 

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). 

The Maillard reaction is chiefly responsible for the desirable colors and flavors that occur when many foods are heated. A substantial amount of data has been obtained relating to the volatile aroma compounds produced during the reaction (e.g. l-3 and this is due largely to the success of gas chromatography-mass spectrometry as a technique for the separation and identification of volatile compounds. Information relating to the factors affecting the formation of these aroma compounds is also available (c.g. 4-7). 

LOXs are of agricultural significance In so far as they apparently play an Important role In the biogenesis of a number volatile flavor and aroma constituents that can affect food quality. Wheat leaves are particularly active in the generation of volatile compounds and were therefore Investigated to determine the role of LOXs In the generation of these compounds. 

Of the different types of lipids in foods, the phospholipids, being more unsaturated, are particularly important in relation to aroma formation in meat.151 The aroma of cooked meat was not affected by the prior extraction of triglycerides with hexane, but the use of a more polar solvent (chloroform-methanol), which extracts all lipids, including phospholipids, resulted, after cooking, in the replacement of the meaty aroma by a roast or biscuit-like one. This was reflected in the volatiles, the dominant aliphatic aldehydes and alcohols being replaced by alkylpyrazines. This implies that the participation of the lipids in the Maillard reactions inhibited the formation of heterocyclic compounds. 

Comparative aroma dilution analyses of the headspace of aqueous solutions, containing either the total volatiles isolated from a fresh coffee brew or these volatiles mixed with the melanoidins isolated from coffee brew, revealed drastic losses of odorous thiols, 2-furfurylthiol, 3-methyl-2-butenethiol, 3-mercapto-3-methylbutyl formate, 2-methyl-3-furanthiol, and methanethiol, in the presence of melanoidins.509 The first compound was affected most, the reduction being 16-fold, and was accompanied by an overall reduction in roasty-sulfury aroma. The rapid loss of thiols was confirmed by stable-isotope dilution analysis. [2H]-NMR and LC-MS gave strong evidence that the thiols become covalently bound via Maillard-derived pyrazinium compounds. 

While the wine contains several g/L of L-malic acid before MLR, it usually only contains between 200 mg/L and 300 mg/L of citric acid. Although the citric acid is only present in low concentrations, it is of considerable importance. On the one hand, its metabolic pathway leads to production of acetic acid, in other words, it increases the volatile acidity of the wine. However, the most important enological significance associated with fermentation of citrate is the production of diacetyl and other acetonic compounds, which affect the wine aroma. 

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