Aldehydes 2,4-decadienal

Model systems indicate that aldehydes may also be produced by the action of polyphenoloxidases on amino acids in the presence of catechin, all of which are present in coffee beans at some stage between green and roasted. For example, valine yields isobutanal, leucine yields isopentanal, and isoleucine yields 2-methyl-butanal.14 Some of these aldehydes probably undergo condensation reactions in the acidic medium of the roasted bean when moisture is present.15 Some dienals in green coffee beans have recently been identified as (E,E)-2,4- and (E,Z)-2,4-nonadienal and (E,E)-2,4- and (E,Z)-2,4-decadienal.18... 

Detailed investigation of T. rotula and other diatom species revealed that 2,4-decadienal (24) and 2,4,7-decatrienal (27) represent only members of a structurally diverse class of oc, 3,y,6-unsaturated aldehydes found in several... 

The effects of decadienal (24) as well as of diatom extracts are not restricted to the reduction of copepod success. Low, micromolar concentrations of this compound also inhibits fertilization, embryogenesis, and hatching success in polychaetes and echinoderms. Crude diatom extracts as well as purified aldehydes inhibited these processes in a dose-dependent manner [80]. 

In addition to the straight-chain saturated aldehydes, a number of branched-chain and unsaturated aliphatic aldehydes are important as fragrance and flavoring materials. The double unsaturated 2-trviolet leaf aldehyde (the dominant component of cucumber aroma), is one of the most potent fragrance and flavoring substances it is, therefore, only used in very small amounts. 2-frfatty odor character is indispensible in chicken meat flavor compositions. 

The overwhelming consideration in regard to lipid deterioration is the resulting off-flavors. Aldehydes, both saturated and unsaturated, impart characteristic off-flavors in minute concentrations. Terms such as painty, nutty, melon-like, grassy, tallowy, oily, cardboard, fishy, cucumber, and others have been used to characterize the flavors imparted by individual saturated and unsaturated aldehydes, as well as by mixtures of these compounds. Moreover, the concentration necessary to impart off-flavors is so low that oxidative deterioration need not progress substantially before the off-flavors are detectable. For example, Patton et al (1959) reported that 2,4-decadienal, which imparts a deep-fried fat or oily flavor, is detectable in aqueous solution at levels approaching 0.5 ppb. 

Aldehyde Formation. Several investigators observed a marked dominance of hexanal in the volatile products of low-temperature oxidation. At the higher temperatures, however, 2,4-decadienal was the major aldehyde formed (19,20,21). Both aldehydes are typical scission products of linoleate hydroperoxides. Swoboda and Lea (20) explained this difference on the basis of a selective further oxidation of the dienal at the higher temperature, while Kimoto and Gaddis (19) speculated that the carbon-carbon bond between the carbonyl group and the double bond (Type B) is the most vulnerable to cleavage under moderate conditions of autoxidation, while scission at the carbon-carbon bond away from the olefinic linkage (Type A) is favored under stress such as heat or alkali. 

N-Heterocyclics. The reaction of primary amines with the carbonyl products derived from lipid oxidation is a major pathway in lipid-protein interactions. Formation of Schiff s base intermediates followed by cyclization and rearrangement can yield imines, pyridines and pyrroles (5,15,30,31). For example, 2-pentylpyridine may result from the reaction of ammonia with 2,4-decadienal, one of the principle aldehydes from the autoxidation of linoleate (5). 

Aldehydes Hexanal, 2,4-Decadienal (EZ) Heptanal, 2,4-Decadienal (EE) 2-Nonenal, 2-Ethylhexenal 2-Hexenal, 2,4-Heptadienal 2-Undecenal, 2,4-Nonadienal 2-Heptenal, Nonanal, Decenal Decanal. 2-Octenal. Octanal CORC ++ Decadienal (EZDe) (RV = 0.991)... 

Linoleic acid is the most abundant fatty acid in fresh corn oil (6), and its primary oxidation products, hexanal and 2,4-decadienal, were identified in both the extruded and the baked samples. However, the total number of aldehydes identified in the extruded samples is considerably smaller than the number identified by Snyder et al. (6) in the headspace volatiles of corn oil oxidized at 60°C for eight days. It is possible that aldehydes produced by lipid oxidation will form Schiff base complexes with primary amino groups in zein. 

The concentration of a specific aldehyde in a given system should then depend on the rate at which it is produced by lipid oxidation and the rate at which it is bound in the model system. For example, lipid oxidation favors the production of specific aldehydes such as hexanal and 2,4-decadienal, but the rate at which aldehdyes are bound to the zein should be fairly uniform for any straight-chain aldehydes present in the system. 

One possible mechanism for the degradation of 2,4-decadienal is the retro-aldol mechanism proposed by Josephson and Lindsay (8) for the oxidation of a,B-unsaturated fatty aldehydes. In their investigation of the degradation products of 2,4-decadienal, Josephson and Lindsay (9) identified 2-octenal and hexanal as primary products. Both 2-octenal and hexanal were identified in the present systems. 

Polyunsaturated aliphatic alkohols, aldehydes, ketones, and esters occur as fragrance components in fats, oils, fruits and plants 158). As an example the synthesis of ethyl (2 ,4Z)-2,4-decadienoate (232, pear ester ), which is responsible for the aroma of bartlett pears 161) is given. 2,4-Diunsaturated ester 232 may be obtained by a number of highly stereoselective syntheses, a lot of them making use of the Wittig reaction. Ohloff and Pawlak condensed 4,5-epoxy-( )-2-pentenal 228 with the ylide generated from 229 (butyllithium/ether) to the alkadiene epoxide 230 which was oxidized with periodic acid to the 2,4-decadienal 231. 231 is subsequently converted with MnOj/NaCN in ethanol to the pear ester 232162) [75 % (Z)-amount of the C-4 double bond] (Scheme 44). 

Creamy flavors in butter have been associated with 4-cis heptenal produced for autoxidation of isolinoleic acid (Begeman and Koster, 1964). Drier flavor in foam spray-dried milk has been associated with 6-rra x-nonenal, which has a flavor threshold in fresh milk of 0.07 pg/kg (Parks et al., 1969). Bassette and Keeney (1960) implicated a homologous series of autoxidation-derived saturated aldehydes, together with products of Maillard browning, in cereal-type off-flavors in powdered skim milk. Staleness in dry whole milk may be associated with saturated and unsaturated aldehydes (Parks and Patton, 1961). 2,4-Decadienal has been reported to be the principal compound responsible for the off-flavor associated with spontaneously oxidized milk (Parks et al., 1963). Oxidized flavors in sunlight-exposed milk are commonly related to C6 to Cn alk-2-enals... 

Casotti, R., Mazza, S., Bnmet, C., Vantrepotte, V., lanora. A., and Miralto, A. (2005). Growth inhihition and toxicity of the diatom aldehyde 2-trans, 4-trans-decadienal on Thalassiosira weissjlogii (BaciUariophyceae).y. Phycol. 41, 1—20. 

Linoleic acid has two non-conjugated double bonds and consequently the theoretical number of hydroperoxides is higher. The main hydroperoxy-octadienoic acids are 9-HPOD, lO-HPOD, 12-HPOD and 13-HPOD (cf. Fig. 3.29). Further reaction produces among others the odorant aldehydes hexanal (35), 2( )-heptanal (36), 2( )-octenal (37), 2(Z)-octenal (38), 2( )-nonenal (39), 3(Z)-nonenal (40), 2,4( , )-decadienal (41) and 2,4( , Z)-decadienal (42). The potent odorant 41 (odour threshold 0.2 mg/kg... 

The oxidation products of lipids include volatile aldehydes and acids. Therefore, lipids are one of the major sources of flavors in foods. For example, much of the desirable flavors of vegetables such as tomatoes, cucumbers, mushrooms, and peas (Ho and Chen, 1994) fresh fish (Hsieh and Kinsella, 1989), fish oil (Hu and Pan, 2000) and cooked shrimp (Kuo and Pan, 1991 Kuo et al., 1994), as well as many deep-fat fried foods such as French-fried potatoes (Salinas et al., 1994) and fried chicken (Shi and Ho, 1994), are contributed by lipid oxidation. LOX-catalyzed lipid oxidation produces secondary derivatives, e.g., tetradecatrienone, which is a key compound of shrimp (Kuo and Pan, 1991). The major difference between the flavors of chicken broth and beef broth is the abundance of 2,4-decadienal and y-dodeca-lactone in chicken broth (Shi and Ho, 1994). Both compounds are well-known lipid oxidation products. A total of 193 compounds has been reported in the flavor of chicken. Forty-one of them are lipid-derived aldehydes. 

Aldehydes, such as acetaldehyde, hexanal, 2,4-decadienal, citral, and vanillin... 

Lipid-derived volatile compoimds dominate the flavor profile of pork cooked at temperatures below 100°C. The large numbers of heterocyclic compounds reported in the aroma volatiles of pork are associated with roasted meat rather than boiled meat where the temperature does not exceed 100 C (34,35). Of flie volatiles produced by lipid oxidation, aldehydes are the most significant flavor compounds (35,36). Octanal, nonanal, and 2-undecenal are oxidation products from oleic acid, and hexanal, 2-nonenal, and 2,4-decadienal are major volatile oxidation products of linoleic acid. 

In Colombian green coffee, Boosfeld et al. (1994) and Boosfeld and Vitzthum (1995) elucidated the structure of two pairs of unsaturated aldehydes, (E,E)-2,4- and (2F,4Z)-2,4-nonadienal as well as (E,E)-2,4- and (2 , 4Z)-2,4-decadienal, probably generated via autoxidation of unsaturated fatty acids and contributing particularly to the typical green-coffee odor. The products were identified by mass spectrometry, GC-FTIR and NMR spectroscopy. The authors used particularly mild extraction techniques in order to avoid artifact formation and isomerization of the conjugated double bonds. The sensory impressions of these aldehydes at the sniffing port varied from metallic, fried, and flowery to oily notes. 

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