Apple esters

Natural fruit aromas are mixtures of certain organic compounds and esters. Synthetic aromas prepared in laboratories are simple mixtures of these same esters and organic compounds. They are used in perfumes, foods and drinks to give taste and pleasant smells. Ethyl acetate, for example, is a colorless liquid with an apple flavour it is known as apple ester and is used in perfumery as a fruit essence. Propyl acetate has the smell of pears, isopentyl acetate that of bananas and ethyl butyrate smells of pineapples. All are colorless liquids. Higher molar mass esters are odorless. 

The combination of ethyl 2-methyl butyrate, P-damascenone, and hexanal is important for the characteristic flavor note of the Delicious apple (22,23a). The blend of character impact flavors combines apple ester and green apple notes, which fluctuate with apple ripeness and seasonality. p-Damascenone is an unusually potent aroma compound with a threshold of 2 pg/g in water, and it also occurs in natural grape and tomato flavors (23a). 

As a general guide, however, it may be noted that the following have fairly easily recognisable odours methyl and ethyl formate methyl and ethyl acetate (apples) methyl and ethyl benzoate methyl salicylate (oil of winter-green) and ethyl salicylate methyl and ethyl cinnamate. (It is however usually impracticable to distinguish by odour alone between the methyl and ethyl esters of a particular acid.) Methyl and ethyl o. alate, and methyl and ethyl phthalate are almost odourless. Succinic and tartaric esters have faint odours. 

It has been found that the flavor of fmit can be increased by a process called precursor atmosphere (PA) (77). When apples were stored in a controlled atmosphere containing butyl alcohol [71-36-3] the butyl alcohol levels increase by a factor of two, and the polar products, butyl ester, and some sesquiterpene products increase significantly. The process offers the possibiUty of compensating for loss of flavor in fmit handling and processing due to improper transportation conditions or excessive heat. 

Stereoanalysis of 2-alkyl-branched acids, esters and alcohols in apple aroma concentrate... 

K. Rettinger, V. Karl, H.-G. Schmarx, E. Dettmar, U. Hener and A. Mosandl, Chirospeciflc analysis of 2-alkyl-branched alcohols, acids and esters chirality evaluation of 2-methylbutanoates from apples and pineapples , Phytochem. Anal. 2 184-188 (1991). 

Ethyl Malonate.—Ethyl malonate is not a member of the parafiinoid acid esters, but is sufficiently nearly related to this series to be included here as a matter of convenience. It is of considerable value in modifying flower odours, having a more or less characteristic apple odour, but of a much sweeter type than the valerianic ester perfume. It is an oil of specific gravity 1 068, and boils at 198°. 

Amyl Valerianate,—This ester is an oil of strong apple odour, and is used for the preparation of cider essence. Its formula is CgHjj. CgH O.. ... 

See the lUPAC rules Guthrie, R.D. Pure Appl. Chem., 1989, 61, 23. As given here, the lUPAC designations for BacI and BalI are the same, but Rule A.2 adds further symbols so that they can be distinguished Su-AL for BalI and Su-AC for BacI- por reviews of the mechanisms of ester hydrolysis and formation, see Kirby, A.J. in Bamford Tipper, Ref 193, vol. 10, 1972, p. 57 Euranto, E.K. in Patai, Ref 216, p. 505. This is an Sn 1 mechanism with OR as leaving group, which does not happen. 

Diene alcohol (38) is the pheromone of the codling moth, tlie creature responsible for the grubs in apples, and of the various possible disconnections (a) is best as it gives most simplification and a stabilised ylid (39) which will produce the requi red trans double bond. Allylic bromide (40) and aldehyde-ester (41) are available,... 

Contrary to PAE, RGAE removed at random the acetyl esters from apple pectic hairy ramified regions (MHR), to a maximum of 70 %. RGAE was essential for the activity of rhamnogalacturonase (RG), and as such comparable with A. aculeatus RGAE. 

Paris DF, NL Wolfe, WC Steen (1984) Microbial transformation of esters of chlorinated carboxylic acids. Appl Environ Microbiol 47 7-11. 

Taylor BF, RW Curry, EF Corcoran (1981) Potential for biodegradation of phthalic acid esters in marine regions. Appl Environ Microbiol 42 590-595. 

N. Ragendran, O. Matsuda. N. Imamura, and Y. Urushigawa, Variation in microbial biomass and community structure in sediments of eutrophic bays as determined by phospholipid ester-linked fatty acids, Appl. Environ. Microbiol. 58 562 (1992). 

J. B. Guckert, M. A. Hood, and D. C. White, Phospholipid ester-linked fatty acid profile changes during nutrient deprivation of Vibrio cholerae increases in the irans/cis ratio and the proportions of cyclopropyl fatty acids, Appl. Environ. Microbiol. 52 794 (1986). 

Johannsen FR, Wright PL, Gordon DE, et al. 1977. Evaluation of Delayed Neurotoxicity and Dose-Response Relationships of Phosphate Esters in the Adult Hen. Toxicol Appl Pharmacol, 41 291-304. 

Robinson EC, Hammond BG, Johannsen FR, et al. 1986. Teratogenicity studies of alkylaryl phosphate ester plasticizers in rats. Fundam Appl Toxicol 7 138-143. 

Schwab BW, Richardson RJ. 1986. Lymphocyte and brain neurotoxic esterase Dose and time dependence of inhibition in the hen examined with three organophosphorus esters. Toxicol Appl Pharmacol 83 1-9. 

Basile, F. Voorhees, K. J. I Iadfield.T. L. Microorganism Gram-type differentiation based on pyrolysis mass-spectrometry of bacterial fatty-acid methyl-ester extracts. Appl. Environ. Microbiol. 1995, 61,1534-1539. 

Figure 11.1 Py/methylation GC/MS chromatograms of lead white pigmented linseed oil paint after 610 °C Curie point pyrolysis assisted with on line methylation using 2.5% methanolic TMAH (the sample and TMAH solution was applied onto a rotating Curie point wire pyrolysis time 6 s, interface 180°C). 1, heptenoic acid, methyl ester 2, heptanoic acid, methyl ester 3, butenedioic acid, dimethyl ester 4, butanedioic acid, dimethyl ester 5, octenoic acid, methyl ester 6, octanoic acid, methyl ester 7, pentenedioic acid, dimethyl ester 8, pentanedioic acid, dimethyl ester 9, nonanoic acid, methyl ester 10, hexanedioic acid, dimethyl ester 11, decanoic acid, methyl ester 12, heptanedioic acid, dimethyl ester 13, octanedioic acid, dimethyl ester 14, 1,2 benzenedicarboxylic acid, dimethyl ester 15, a methyl octanedioic acid, dimethyl ester 16, nonanedioic acid, dimethyl ester 17, a methoxy octanedioic acid, dimethyl ester 18, a methyl nonanedioic acid, dimethyl ester 19, a,a dimethyl nonenedioic acid, dimethyl ester 20a, a methyl nonenedioic acid, dimethyl ester 20b, a,a dimethyl nonanedioic acid, dimethyl ester 21, decanedioic acid, dimethyl ester 22, a methoxy nonanedioic acid, dimethyl ester 23, a methyl decan edioic acid, dimethyl ester 24, undecanedioic acid, dimethyl ester 25, a methoxy decan edioic acid, dimethyl ester 26, pentadecanoic acid, methyl ester 27, dodecanedioic acid, dimethyl ester 28, hexadecanoic acid, methyl ester 29, heptadecanoic acid, methyl ester 30, octadecanoic acid, methyl ester 31,8 methoxy 9 octadecenoic acid, methyl ester 32, 11 methoxy 9 octadecenoic acid, methyl ester 33, 9 methoxy 10 octadecenoic acid and 10 methoxy 8 octadecenoic acid 34, 9 oxo octadecanoic acid, 10 oxo octadecanoic acid 35, 9 epoxy octadecanoic acid 36, eicosanoic acid, methyl ester 37, 9,10 dimethoxy octadecanoic acid, methyl ester 38, docosanoic acid, methyl ester. Reprinted from J. Anal. Appl. Pyrol., 61, 1 2, van den Berg and Boon, 19, Copyright 2001, with permission from Elsevier...

Figure 11.8 THM GC trace of bleached beeswax. FAME, fatty acid methyl ester obtained with a resistively heated filament pyrolyser at 550°C MeO FAME, methyl ester of methoxy fatty acid ME, alkyl methyl ether DiME, dimethoxyalkane EtC, hydrocarbon X Y, carbon chain length number of double bonds. Reprinted from J. Anal. Appl. Pyrol., 52, Asperger et al., 1, 13, Copyright 1999 with permission from Elsevier...

C. Schwarzinger, I. Tanczos and H. Schmidt, Pyrolysis gas chromatography/mass spectrometry and thermally assisted hydrolysis and methylation (THM) analysis of various cellulose esters, J. Anal. Appl. Pyrol., 58 59, 513 523 (2001). 

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