Aroma compounds volatiles

Partitioning of volatile substances between the liquid and gas phases is mainly governed by aroma compound volatility and solubility. These physicochemical properties are expected to be influenced by wine constituents present in the medium, for instance polysaccharides, polyphenols, proteins among others. Consideration of the physicochemical interactions that occur between aroma compounds and wine constituents is necessary to understand the perception of wine aroma during consumption. The binding that occurs at a molecular level reflects changes at a macroscopic level of the thermodynamic equilibrium, such as volatility and solubility, or changes in kinetic phenomena. Thus, thermodynamic and dynamic approaches can be used to study the behaviour of aroma compounds in simple (model) or complex (foods) media. 

The surrounding medium of encapsulated aroma such as polysaccharides, proteins, lipids, and salts could play an important role in release in liquid media and then on aroma compound retention by the film matrix. Different behaviors have been observed in the presence of salt or sucrose molecules of aroma compound volatility in food products, observing that some of them presented a salting out effect (favored release by volatilization), others an opposite salting in effect, and for some others no modification (Lubbers et al., 1998 Van Ruth et al., 2002). Similar effects could be observed in the release of the aroma compounds encapsulated in films. While the salting out effect should accelerate the release, the salting in could decrease the rate of the release. 

Volatile and semivolatile compounds are present in honeys and are attributed to aroma qualities. Aroma compoimds can indicate floral and geographical origins and processing treatments. Aroma compounds come from nectar or honeydew. Aroma components can be also formed during fhermal processing and sforage (Bonvehi and Coll, 2003 Soria et ah, 2003). More than 400 components have been detected in the volatile flavor fraction of honey... 

Bianchi, F., Careri, M., and Musci, M. (2005). Volatile norisoprenoids as markers of botanical origin of Sardinian strawberry-tree (Arbutus unedo L.) honey Characterisation of aroma compounds by dynamic headspace extraction and gas chromatography-mass spectrometry. Food Chem. 89,527-532. 

Methods of fixing the volatile aroma and flavor compounds separately from the instant coffee powder have been developed. The volatile mixture can be mixed with aqueous gelatin or gum arabic and spray dried. The oily droplets of the flavor and aroma compounds are coated with gelatin or gum arabic in a dry lattice. This powder can be mixed in with instant coffee powder and is relatively stable in the presence of air. Emulsification with sugar is also a highly effective way of trapping and preserving coffee volatiles, but is of limited use for instant coffees. 

The coffee beans with the most desirable flavor to many tastes are the highest grown Arabicas prepared by the wet method. Coffee beverages need to be prepared within 8 h of grinding the freshly roasted coffee beans if the volatile flavor and aroma compounds are to be retained. Brew... 

Tandy, P., Courthaudon, J.-L., Dubois, C., and Voilley, A. Effect of interface in model food emulsions on the volatility of aroma compounds, / Agric. Food Chem., 44(2) 526-530, 1996. 

Solid phase microextraction (SPME) is an ideal approach to monitor volatile flavor components. This approach has been used to identify the volatile compounds in the headspace of fresh fruit during maturation [92], Using SPME fibers and GC/MS, the key flavor components are hexanal, 2-isobutyl-3-methoxypyrazine, 2,3-butanedione, 3-carene, trans-2-hexenal, and linalool (Fig. 8.1). In this study, the principal aroma compounds whose abundance varied during fruit development were specifically identified. 

Mazidaa MM, SaUehb MM, Osman H (2005) Analysis of volatile aroma compounds of fresh chilli (Capsicum annuum) during stages of maturity using solid phase microextraction (SPME). J Food Comp Anal 18 427 37... 

The symmetrical compounds (17, R = R = R ) are formed from an aldehyde and ammonium sulfide (2,29,35) or hydrogen sulfide and ammonia (33), Thialdine (17, R - R - R = Me) is an important aroma compound found in the volatiles of beef broth (48), pressure-cooked meat (49), and fried chicken (50), It is also obtained from acetaldehyde (2,29,37) or from B-mercaptoacetaldehyde and ammonium sulfide (37), In our experiments, it was synthesized as a white powder from a reaction of acetaldehyde with ammonium sulfide in 60% yield. 

The resinoids described above should be distinguished from prepared oleoresins (e.g., pepper, ginger, and vanilla oleoresins), which are concentrates prepared from spices by solvent extraction. The solvent that is used depends on the spice currently, these products are often obtained by extraction with supercritical carbon dioxide [223a]. Pepper and ginger oleoresins contain not only volatile aroma compounds, but also substances responsible for pungency. 

With methods in place to measure volatile aroma compounds within the olfactory space of individuals in real time, and to couple these to subjective reports of preference, it then becomes possible to combine these with more comprehensive measures of acute metabolism and physiology within an individual during the period when a novel food is being first perceived and olfactory preferences are being developed. 

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. 

A large number of volatile phenols and related compounds occur in vegetables and fruits, and some of them are potent aroma compounds. The majority of volatile phenols and related compounds in plants are formed mainly through the shikimic acid pathway, and are present in intact plant tissue either as free... 

Sugars, acids and aroma compounds contribute to the characteristic strawberry flavour [85]. Over 360 different volatile compounds have been identified in strawberry fruit [35]. Strawberry aroma is composed predominately of esters (25-90% of the total volatile mass in ripe strawberry fruit) with alcohols, ketones, lactones and aldehydes being present in smaller quantities [85]. Esters provide a fruity and floral characteristic to the aroma [35,86], but aldehydes and furanones also contribute to the strawberry aroma [85, 87]. Terpenoids and sulfur compounds may also have a significant impact on the characteristic strawberry fruit aroma although they normally only make up a small portion of the strawberry volatile compounds [88, 89]. Sulfur compounds, e.g. methanethiol. 

Important aroma compounds of black currant berries have been identified mainly by GC-O techniques by Latrasse et al. [119], Mikkelsen and Poll [115] and Varming et al. [7] and those of black currant nectar and juice by Iversen et al. [113]. The most important volatile compounds for black currant berry and juice aroma include esters such as 2-methylbutyl acetate, methyl butanoate, ethyl butanoate and ethyl hexanoate with fruity and sweet notes, nonanal, /I-damascenone and several monoterpenes (a-pinene, 1,8-cineole, linalool, ter-pinen-4-ol and a-terpineol) as well as aliphatic ketones (e.g. l-octen-3-one) and sulfur compounds such as 4-methoxy-2-methyl-butanethiol (Table 7.3, Figs. 7.3, 7.4, 7.6). 4-Methoxy-2-methylbutanethiol has a characteristic catty note and is very important to blackcurrant flavour [119]. 

Elderberry (Sambucus nigra) is cultivated on small scale in Europe. The fruits have a high concentration of red and purple anthocyanins and a relatively low concentration of sugars, organic acids and aroma compounds, which make this juice attractive as a natural colour ingredient in other red fruit products [126-129]. The fresh green odour of elderberry juice is associated with volatile compounds with typical green notes such as 1-hexanol, 1-octanol, (Z)-3-hexen-l-ol, ( )-2-hexen-l-ol, hexanal and ( )-2-hexenal, whereas the floral aroma is mainly due to the presence of hotrienol and nonanal [127-130]. 

The kiwi fruit is a cultivar group of the species Actinidia deliciosa. More than 80 compounds have been identified in fresh and processed kiwi [137]. Methyl acetate, methyl butanoate, ethyl butanoate, methyl hexanoate and ( )-2-hexenal have the most prominent effect on consumer acceptability of kiwi fruit flavour [137-140]. The volatile composition of kiwi fruit is very sensitive to ripeness, maturity and storage period [138, 139]. Bartley and Schwede [140] found that ( )-2-hexenal was the major aroma compound in mature kiwi fruits, but on further ripening ethyl butanoate began to dominate. Ripe fruits had sweet and fruity flavours, which were attributed to butanoate esters, while unripe fruits had a green grassy note due to ( )-2-hexenal [140]. The most important character-impact compounds of kiwi fruits are summarised in Table 7.4. 

The edible portion of broccoli Brassica oleracea var. italica) is the inflorescence, and it is normally eaten cooked, with the main meal. Over 40 volatile compounds have been identified from raw or cooked broccoli. The most influential aroma compounds found in broccoli are sulfides, isothiocyanates, aliphatic aldehydes, alcohols and aromatic compounds [35, 166-169]. Broccoli is mainly characterised by sulfurous aroma compounds, which are formed from gluco-sinolates and amino acid precursors (Sects. 7.2.2, 7.2.3) [170-173]. The strong off-odours produced by broccoli have mainly been associated with volatile sulfur compounds, such as methanethiol, hydrogen sulfide, dimethyl disulfide and trimethyl disulfide [169,171, 174, 175]. Other volatile compounds that also have been reported as important to broccoli aroma and odour are dimethyl sulfide, hexanal, (Z)-3-hexen-l-ol, nonanal, ethanol, methyl thiocyanate, butyl isothiocyanate, 2-methylbutyl isothiocyanate and 3-isopropyl-2-methoxypyrazine... 

Raw potato possesses little aroma. Approximately 50 compounds have been reported to contribute to raw potato aroma. Raw potatoes have a high content of LOX, which catalyses the oxidation of unsaturated fatty acids into volatile degradation products (Scheme 7.2) [187]. These reactions occur as the cells are disrupted, e.g. during peeling or cutting. Freshly cut, raw potatoes contain ( ,Z)-2,4-decadienal, ( ,Z)-2,6-nonadienal, ( )-2-octenal and hexanal, which are all products of LOX-initiated reactions of unsaturated fatty acids [188,189]. It is reported that two compounds represent typical potato aroma in raw potato methional and ( ,Z)-2,6-nonadienal [189]. Other important volatiles in raw potatoes produced via the LOX pathway are l-penten-3-one, heptanal, 2-pen-tyl furan, 1-pentanol and ( , )-2,4-heptadienal [189]. Pyrazines such as 3-iso-propyl-2-methoxypyrazine could be responsible for the earthy aroma of potato [35]. Some of the most important character-impact compounds of raw potatoes are summarised in Table 7.8. Aroma compounds from cooked, fried and baked potatoes have previously been reviewed [35]. 

The flavour of fruits and vegetables is a very important aspect of quality. This review has focused on the most important aroma compounds in fruits and vegetables of moderate climate and demonstrated that a wide variety of volatile compounds are formed naturally in the products or after processing that influence the aroma and flavour of fresh and processed fruits and vegetables. 

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