L,5 -Octadien-3-one

Fig. 16.2 Flavour dilution (FD) chromatogram obtained by application of aroma extract dilution analysis on an extract prepared from parsley leaves. The odorants were identified as 1 methyl 2-methylbutanoate, 2 myrcene, 3 l-octen-3-one, 4 (2)-l,5-octadien-3-one, 5 2-isopropyl-3-me-thoxypyrazine, 6p-mentha-l,3,8-triene, 71inalool, 8 2-sec-butyl-3-methoxypyrazine, 9 (.Z)-6-dece-nal, 10 / -citronellol, 11 ( , )-2,4-decadienal, 12 / -ionone, 13 myristicin, 14 unknown. RI retention index. [30, 31]...

By using aroma extract dilution analysis (AEDA) of the volatile fractions of fresh and stored butter oil, Widder et al. (29) determined diacetyl, butanoic acid, 8-octalactone, skatole, 8-decalactone, cw-6-dodeceno-8-decalactone, l-octen-3-one, and l-hexen-3-one as potent contributors to the flavor of butter oil. The concentration of l-octen-3-one, trani-2-nonenal, and i-l,5-octadien-3-one increased during the storage of the butter oil at room temperature. 

Acetyl- 1-pyrroline (Z)- l,5-Octadien-3-one (Popcorn-like) (Metallic)... 

FIGU RE 17.19 Proposed precursors of (Z)-l,5-octadien-3-one and 2-isobutyl-3-methoxypyrazine. 

Z)-l,5-Octadien-3-one 3-Methylnonane-2,4-dione Bis(2-methyl-3-furyl)disulfide (Z)-4-Heptenal... 

Melon flavor The typical M. f. of the various sorts are due to secondary flavor compounds from the degradation of linolic and linolenic acids, e.g., hexenals, (Z)-6-nonenal (see alkenals), (Z,Z)-3,6-nonadien-I-ol (C9H16O, Mr 140.23, CAS [53046-97-2], water melon odor), (Z,Z)-3,6-nonadienyl acetate (C, H,g02, Mr 182.26, CAS [130049-88-2]), and (Z)-l,5-octadien-3-one (see tea flavor). Sweet melon (muskmelon Cu-cumis melo) also contains fruit esters, especially 2-methylbutanoates, alkanolides, anisaldehyde, eugenol, and some (methylthio)carboxylates with sensory relevance. ... 

Cucumbers The impact compound is ( ,Z)-2,6- nona-dienal, together with ( )- and (Z)-2-nonenal (see alkenals), hexanal (see alkanals), and (Z)-l,5-octadien-3-one (see tea flavor). 

Oxidized fish oils, rich in n-3 polyunsaturated fatty acids, produced volatile compounds more readily than oxidized vegetable oils, rich in linoleic acid. Activation energy for the formation of propanal from fish oils was lower than for the formation of hexanal from vegetable oils. A mixture of aldehydes contributed to the characteristic odors and flavors of oxidized fish, described as rancid, painty, fishy and cod liver oil-like (Table 11.21). Oxidation of unsaturated fatty acids in fish was related to the formation of 2-pentenal, 2-hexenal, 4-heptenal, 2,4-heptadienal and 2,4,7-decatrienal. The fishy or trainy characteristic of fish oil was attributed to 2,4,7-decatrienal. Studies of volatiles from boiled trout after storage showed significant increases in potent volatiles by aroma extraction dilution analysis (Table 11.22). Volatiles with the highest odor impact included l,5-octadien-3-one, 2,6-nonadienal, 3-hexenal, and 3,6-nonadienal. 3,6-Nonadienal and 3-hexenal were considered to contribute most to the fatty, fishy flavor in stored boiled fish. 

The rapid deterioration of food containing linolenic acid should not be ascribed solely to the preferential oxidation of this acid but also to the low odor threshold values of the carbonyl compounds formed, such as (Z)-3-hexenal, (E,Z)-2,6-nonadienal and (Z)-l,5-octadien-3-one (Table 3.32). Aldehydes with exceptionally strong aromas can be released in food by the autoxidation of some fatty acids, even if they are present in low amounts. An example is octadeca-(Z,Z)-11, 15-dienoic acid (the precursor for... 

Aroma substances are formed by the enzymatic oxidative degradation of the highly unsaturated fatty acids with the participation of lipoxygenases of varying specificity. These aroma substances contribute to the iruld green-metaUic-mushroom aroma of fresh fish. Dilution analyses have shown that these substances are acetaldehyde, propanal, l-octen-3-one, (Z)-l,5-octadien-3-one, (E,Z)-2,6-nonadienal, (Z,Z)-3,6-nonadienal and (E,E)-2,4-decadienal. 

Trimethylamine also has a fishy odor. However, its odor threshold at the pH of fish meat is very much higher than that of the potent lipid peroxidation products, e. g., (Z)-l,5-octadien-3-one (cf. 3.7.2.1.8 and 11.2.4.4.4). Therefore, it plays a role as an off-flavor substance only on stronger bacterial infection of fish at temperatures >0 °C. 

Preparation and storage of products from both oilseeds is often inhibited by rancidity and bitter aroma defects caused mostly by volatile aroma active carbonyl compounds, e. g., (Z)-3-hexenal, (Z)-l,5-octadien-3-one and 3-methyl-2,4-nonan-dione. The rancidity-causing compounds are formed through peroxidation of linolenic acid, accelerated by the enzyme lipoxygenase and/or by hem(in) proteins (cf. 3.T.2.2). Furan fatty acids are the precursors in the case of the dione (cf. 14.3.2.2.5). Lipid peroxidation is also involved in the formation of another very potent odorant, 2-pentylpyridine, which produces grassy aroma defects in soybean products. Defatted soybean protein isolates contained 60-510 pg/kg of this compound, which with an odor threshold... 

The compounds (Z)-3-hexenal, methanethiol, (Z)-l,5-octadien-3-one, dimethyltrisulfide, 3-iso-propyl-2-methoxypyrazine and 3-5 c-butyl-2-methoxypyrazine contribute to the aroma of the fresh vegetable. In cooked spinach, (Z)-3-hexenal decreases and dimethylsulfide, methanethiol, methional and 2-acetyl-1-pyrroline are dominant. 

Carbowax 20M (Union Carbide, Danbury, CT, U.S.A.) on 120-140 mesh Chromosorb G (Johns Manville, NY, U.S.A.)). Trans- and c -4,5-epoxy-(ii)-2-decenal were synthesized by epoxidation of (E,E)- and E,7)-2,4-decadienal, respectively, using 3-chloroperoxybenzoic acid [3]. (Z)-l,5-Octadien-3-one was synthesized, following procedures described by Swoboda and Peers [4]. Diethyl ether was freshly distilled every 4wk and stored in the dark after addition of antioxidant 330 (l,3,5-trimethyl-2,4,6-tris-[3,5-di-tert-butyl-4-hydroxybenzyl]-benzene). 

The fishy aroma of seafood is incorrectly attributed to trimethyl amine. Flavor formation in fresh and saltwater fish results from complex enzymatic, oxidative, and microbial reactions of n-3 polyunsaturated fatty acid precursors (e.g., eicosapentaenoic acid) (69,70). Hence, fish flavor is mostly composed of non-characterizing planty or melon-like aromas from lipid-derived unsaturated carbonyl compounds. Examples are (Z)-l,5-octadien-3-one ( geranium-like ) in boiled cod (71) and (7i,Z)-2,6-nonadienal ( cucumber-like ) in boiled trout (72). 

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