Esters fruity odours

Pleasant often fruity) odour. Esters, ethers. 

Fatty Acid Esters of Methyl Alcohol.—The following esters of methyl alcohol are commercial products, and all have fruity odours, and are very suitable for blending with flower oils to impart distinctive secondary odours to them. They are, generally speaking, very expensive, some of them costing as much as 12 per lb., but, as only minute quantities... 

Methyl Malonate.—This ester is an artificially prepared body, having a fruity odour, somewhat similar to the above-described esters of the fatty acids. It has the formula CH2(C02CHg)2, and boils at 181°. It may be prepared by treating potassium cyan-acetate with methyl alcohol and hydrochloric acid. On saponification with alcoholic potash it yields malonic acid, which melts at 132°, and serves well for the identification of the ester. 

Ethyl Acetate.—This ester does not play a very important role in synthetic perfumery, but its intensely fruity odour, together with the fact that it is found naturally in the perfume of the magnolia gives it certain possibilities, if used in very minute quantities. It is an oil of the formula CH3COO. C2H5. It boils at 76°, and has a specific gravity 0-908. It is easily soluble in the usual organic solvents, and fairly soluble in water. 

Ethyl Laurinate.—The laurinic ester of ethyl alcohol has also, quite recently, come into KOgue in synthetic perfumery. It is an oil of peculiar fruity odour, intensely strong, having the constitution... 

Amyl Heptylate.—This ester is one of the newest synthetic odours, and is also one of the very expensive ones. It has the formula CH3(CH2)r,COOCjHjj, and is an oil of powerful fruity odour. It can be identified by saponifying it and examining the resulting fatty acid, which should melt at — 10° and boil at 223°. 

Hexyl Acetate.—Hexyl acetate, CH3(CH2)500C. CHj is an ester found naturally in the oil of Heracleum giganteum. It has a fruity odour, and boils at 169° to 170°. Its specific gravity is 0-890 at 10°. 

Linalyl Propionate.—This ester is also produced by condensing the free alcohol and the free acid by means of sulphuric acid. It has a somewhat fruity odour recalling that of bergamot, and is especially suitable for perfumes of the lily of the valley type. It is a colourless oil, boiling at 115° at 10 mm. pressure. 

Linalyl Butyrate.—The butyric ester of linalol has the formula, CiflHjjOOC, CH2. CHjCHj. It resembles geranyl butyrate in odour, but is somewhat heavier. It is most useful for imparting fruity odours to flower perfumes. It is prepared by condensing the alcohol and the acid by means of sulphuric acid. 

Pinoglycyl Acetate.—This ester can be prepared by the direct acetylation of pinoglycol, C,gH,.0(0H)g, an alcohol resulting from the oxida-.tion of pinol with permanganate of potassium. It can also be prepared from pinol dibromide and acetate of silver. It is an ester with an excellent fruity odour, of the formula C,gH, 0(CgHg0.2).2, melting at 97° to 98°, and boiling at 155° at 20 mm. pressure, or at 127° at 13 mm. 

Pinolglycyl Propionate.—This ester, of the formula C,gH,( 0(C3H50.2).2, is a quite similar ester, prepared in a similar manner. It also has a fine fruity odour. 

Fig. 7.1 Some aliphatic esters that are important flavour compounds in fruits and vegetables that mainly contribute with fruity odours...

Et ester Ethyl propionate. Water scavenger for alkoxide-catalysed condensations. Liq. with fruity odour. Mod. sol. H2O. d20 0.891. Fp -73 . Bp 99 . nxp 1.3844. 

The lower fatty acid most frequently bound in esters is acetic acid, while formic, propionic, butyric and isobutyric adds occur less often. The common alcohol bound in esters is ethanol. However, esters of methanol, aUyl alcohol, butan-l-ol higher alcohols and very often esters of monoterpenic and aromatic alcohols also occur in foods, and esters of sulfur-containing alcohols are also common. Esters of low molecular weight acids and alcohols usually have a fruity odour esters of terpenic alcohols with low molecular weight adds tend to have fragrant odours resembling flowers. Esters of aromatic adds and aromatic alcohols generally have heavy balsamic odours. 

A s/cr.s possess a fruity smell and usually distil without decomposition. Boil with refltiK for 5 minutes on the water-btith a few c.c. of the licpiid with 3 to 4 volumes of a ten pei cent, solution of ctLListic potash in methyl alcohol and pour into water. Notice if the liquid dissolves and has lost the odour of the ester. An ester will be completely hydrolysed, and if the alcohol is soluble in water a clear solution will be obtained. If the alcohol is vol.atile and the solution neiitialised w ith sulphuric acid. and evaporated on the water-bath, the alkali salt of the organic acid mixed with pottissium sulphate will be left and the acid may be investigated as desciibed under 1. If it is required to. ascertain the nature of the alcohol in the ester, hydrolysis must fig effected with a strong aqueous solution of caustic potash... 

Ethyl Nonylate.—This ester has, during the past year or two, been recognised as having a most useful odour for modifying flower bouquets. It is a fruity oil boiling at 227° to 228°, and having the constitution... 

Amyl Acetate.—This is, with the exception of amyl formate, which is not of practical importance, the simplest possible ester of amyl alcohol, and has the formula CHj. COO. CsHjj. It is a fruity oil, with a strong odour resembling that of the pear, and is known as art ficial oil of pear. It is prepared on a very large scale by, for example, treating 100 parts of dry sodium acetate, 100 parts of amyl alcohol, and 130 parts of sulphuric acid for twelve hours at ordinary temperature, and then distilling off the ester. It has a specific gravity 0-876, and boils at 138°. The alcohol in this ester is not normal amyl alcohol, but isoamyl alcohol. 

The functional group names can be used in characterizing and describing the odours of many perfumes and some of the essential oils. Aldehydic smelling oils are due to compounds with functional groups called aldehydes, and sweet and fruity smelling oils are due to compounds with functional groups called esters. 

Group 6 shows additional terpene alcohols like linalool (Flavis 02.013, FEMA 3045) with flowery profile and a-terpineol (Flavis 02.014, FEMA 3045) with sweet, fruity aroma. In addition, numerous esters are listed like a-terpinyl acetate (Elavis 09.065, FEMA 3047), which is characterised by a strong herbaceous odour. 

Alkylcarbonic acids have been separated into their enantiomers without any deriva-tization and their sequence of elution was assigned by co-injection with enantio pure references [17]. Latest results on stereoselective flavour evaluation revealed characteristic sensory properties for all the enantiomers of 2-alkylbranched acids, esters and corresponding alcohols. Tremendous differences between the mirror images of 2-methylbutanoic acid have been found. While the R-enantiomer exhibits a penetrating, cheesy-sweaty odour, the S-enantiomer emits a pleasant sweet and fine fruity note [87, 88]. All commercially available homologues of 2-methylbutanoic acid esters and 2-methylbutyl acetate are simultaneously stereoanalyzed, using heptakis (2,3-di-O-methyl-6-0-tert-butyldimethylsilyl)-P-cyclodextrin (DIME-P-CD) in PS 268 as the chiral stationary phase [88] (Eig. 6.33, Table 6.19). 

The odour intensities of volatiles showing similar odour qualities are partially additive [68]. To substantiate such additive effects, three groups of odorants (terpene hydrocarbons, esters or aldehydes) were omitted from the aroma model for orange juice. For all groups, a significant difference from the complete model was observed (Table 6.39). Omission of esters nos. 12,14 and 15 with ethyl butanoate (no. 13) still present was clearly detectable. This indicates that the fruity quality in the odour profile is enhanced by additive effects. In contrast, no difference was perceivable when (R)-a-pinene (no. 17) and myrcene (no. 18) were omitted. The concentration of the odorants in juice differs depending on the variety. Thus, the weaker citrus note of Navel oranges compared with the above discussed variety Valencia late is due to a 70% lower content of (R)-limonene [67]. 

The potent odorants identified in two apple varieties with fruity/green (Elstar) and fruity/sweet/aromatic (Cox Orange) odour are shown in Table 6.40. The fruity note in the aroma profile of both varieties is produced by acetic acid esters nos. 4-6. Ethyl esters, which on molar basis are more aroma-active than acetates [72, 73[ and which predominate in some other fmits, e.g. olives (Table 6.37) and orange (Table 6.38), are of minor importance for the aroma of apples. Hexanal (no. 7), (Z)-3-hexenal (no. 9) and (Z)-2-nonenal (no. 10) are responsible for the green/apple-like note. (E)-p-damas-... 

Boelens has also used this approach to derive QSAR equations for musk, jasmine, fruit and bitter almond odorants (Boelens, 1976 Boelens and Punter, 1978 Boelens et al., 1983). In the case of bitter almond and musk, he concluded that hydrophobic and steric parameters were important. For the jasmine materials, he found that molecular connectivity indices were useful parameters. Molecular connectivity indices were also used by their inventors, Kier et al. (1977), to analyse anosmia to fatty acids and the odour similarities of ethereal, floral and benzaldehyde-like odorants. Dearden (1994) also developed a QSAR equation relating the odour similarity of bitter almond odorants to two connectivity indices. Greenberg (1979) found that the odour intensity of a series of homologous compounds was correlated to their hydrophobic properties and not to steric or polar properties, while Rossiter (1996b) found that the fruitiness of aliphatic esters was related to steric hindrance of the ester group and either molecular length or log P. 

The relative peak area of esters found in the pea cultivars is shown in Fig. 5. No differences (P > 0.05) were found between the cultivars grown in different locations (Tables 2 4). Ethyl acetate was the most abundant ester in all the pea cultivars studied (Tables 2 4). This compound has an ether and brandy odour and a fruity, sweet taste and has also been reported in soybeans and beans (Burdock, 2002 del Rosario et al., 1984). Hexanoic acid, methyl ester also identified in the peas reportedly has an ether and pineapple odour (Burdock, 2002). 

An important sulfide is methional (8-37). Methional in beer and wine is formed by the activity of microorganisms. It is partly reduced to the corresponding alcohol methionol (8-13) and reaction with acetyl-CoA yields 3-methylthiopropyl acetate (8-129), which is an important component of various fermented foods. Another ester of acetic acid 3-(methylthio)hexyl acetate is a component that posseses attractive tropical fruity notes on dilution. The less odoriferous (-)-(J )-enantiomer (8-130) is reminiscent of passion fruit, while the (-l-)-(S)-form has a more herbaceous odour. The odour thresholds of these thiols in air are 0.10 ng/1 and 0.03 ng/1, respectively. Both isomers have been found in passion fruit (Passiflora edulis, Passifloraceae), guava Psidium guajava, Myrtaceae) and aromatic white wines. Methyl-3-(methylthio)propionate, or pineapple mercaptan (8-131), has a flavour reminiscent of pineapple. S-Methylthiohexanoate (8-132) is a component of the durian fruit smell. Condensation of methional with ethanol yields (Z)-2-(methylthio)methylbut-2-enal also known as 2-ethylidenemethional (8-133), which is an important component of potato chips aroma. It also occurs in... 

The characteristic aroma components of bananas Musa x para-disiaca, Musaceae) are esters. Important components are largely acetic acid esters, and the most significant compound is isopentyl acetate. The typical banana odour comes from esters ofpentan-l-ol with acetic, propionic and butyric acids, while esters of butanols and hexanols with acetic and butyric acids generally show a fruity aroma. Other compounds also contribute to the full fine aroma. 

Alcohols, ethers and esters frequently have quite pleasant odours, those of the last class often being described as fruity . Simple halogeno-hydrocarbons of low molecular weight possess not unattractive odours, e.g. chloroform. 

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