Green note compounds, flavors

Another example is the production of green note compounds using lipoxygenase pathway enzymes. Lipoxygenase and hydroperoxide lyase are the determinant enzymes for the conversion of fatty acids into natural food flavor components. However, these compounds present in natural sources at very low levels and because of their instable nature it has been difficult to purify these compounds. As a result, considerable efforts have been made to clone these two enzymes for commercial uses in the production of natural flavor components. Many plant lipoxygenase from different plants have been cloned and expressed in E. coli or yeast [5],... 

Green-note compounds are responsible of the fresh, green odor of cut leaves and are important components of the flavor of fruits and vegetables, such as apples, cherries, kiwifruits, raspberries, strawberries, and tomatoes. They include six-carbon aldehydes and alcohols, such as (2 )-hexenal (leaf aldehyde) and (3Z)-hexenol (leaf alcohol). Nine-carbon aldehydes and alcohols, which are found in the aroma of cucumbers and melons, are also considered green-note compounds. 

HPL cleaves the bond between C-12 and C-13 of these hydroperoxides to form C6 aldehydes. The aldehydes can be further enzymatically isomerized and reduced by alcohol dehydrogenase, to afford the corresponding alcohols. These green-note compounds find extensive applications, especially in the cosmetic and beverages sectors, to convey freshness to final products and to sharpen fruit flavors. 

From French cider the cis/trans-isomeric 2-methyl-4-pentyl- (52a, 53a) and 2-methyl-4-(2 )(Z)-pentenyl- 1,3-dioxanes (52b, 53b) were identified by NMR, NOE, H,H-decoupling and various chromatographic techniques (cf. Scheme 16) as the compounds exhibit a weak green note they may contribute to the flavor of cider (97JAFC3178). 

Whitehead, I.M., Muller, B.L., and Dean, C., Industrial use of soybean lipoxygenase for the production of natural green note flavor compounds, Cereal Foods World, 40, 193, 1995. 

F F compounds are usually not a significant part of plants. Typically they comprise <1%, sometimes much less than 1%, of the plant s total weight. They form from precursors that may constitute a large proportion of the plant. Maltol, a burnt sugar note, has carbohydrates as its precursor, vanillin has lignin as its precursor, beta-ionone, used in berry flavors, has carotenoids as its precursor, and the green notes, hexanal and (E)-2-hexenal, have the fatty acids, linoleic acid and linolenic acid, respectively, as their precursors. 

Tea flavor. Primary and secondary flavor compounds (more than 300) contribute to the flavor of black tea, which is otherwise strongly influenced by its origin or production procedures (withering, fermentation, roasting). A major contribution is made by components with flowery notes such as geraniol, linalool, citronel-lol, 2-phenylethanol, and a-//3- ionones, as well as (Z)-jasmone, methyl jasmonate, d- jasmin(c) lactone, and methyl anthranilate as trace components. Green notes such as 2- and 3- hexen-l-ols, (E)-2-... 

Coffee flavor is a complex mixture of compounds belonging to many classes in distinct concentration ratios. Flament (2 ) listed 1 7 typical constituents of coffee aroma with buttery, woody, green, earthy caramel, burnt, smoky, roasted and sulfury notes, aroma and flavor qualities. 

The pH of the steam distillate was 6.2 in all cases. The total flavor isolate (by SDE) of plain cashews had, on the whole, a strong pungent and green aroma, reminiscent of the cashew nut testa and cashew shell, whereas the flavor isolates from roasted samples had the characteristic mildly nutty aroma also. The flavor fractions obtained by selective extraction method gave some information about the chemical nature of compounds responsible for the characteristic flavor notes. Accordingly, the basic fraction of roasted nuts, (both oven-and oil-roasted), had the typical nutty aroma associated with pyrazine. compounds. The basic fraction of plain cashews did not have any characteristic flavor in particular. 

The development of characterizing fish aromas and flavors Involve both enzymic and nonenzymlc oxidative reactions. Llpoxygenase-derlved carbonyls and alcohols contribute the distinctive planty-green aroma notes to fresh fish that vary with species with regards to compounds and concentrations. 

Its ability to more effectively direct toward the t, , -lsomer Is seen by an elevated Isomer ratio of 3.08 In the presence of Trolox C (Table II). As noted earlier, low concentrations of the , , -lsomer of 2,4,7-decatrlenal exhibit a more pronounced flshy/burnt flavor quality In oxidizing fish oils while the , , -lsomer causes more green-fishy, burnt character notes (28). Although substantial concentrations of the Cg unsaturated compounds were produced In the fish oils containing Trolox C or alpha-tocopherol (Table I), the production of 2,4,7-decatrlenals provided the underlying unpleasant, characterizing fish flavor notes. 

In 1976 Winter et al. (22) identified 3-methylthio-hexanol and a mixture of (Z)- and (E)-2-methyl-1,3-oxa-thiane in yellow passion fruit. 3-Methylthiohexanol possesses a green fatty and sulfury note and imparts the character of fresh fruit to the juice of passion fruits. The oxathianes were described as key compounds for the typical aroma of passion fruit and the (Z)-isomer had a stronger flavor. Pickenhagen and Bronner-Schindler (23) synthesized the enantiomers of (+)- and (-)-(Z)-2-methyl-... 

Although more than 280 compounds have been identified in the volatile fiction of wheat bread, only a small number is responsible for the flavor notes in the crust and the crumb. Schieberle and Grosch (73) used aroma extract dilution analysis (AEDA) to select 32 odorants in wheat. Among the odorants, 2-acetyl-pyrroline (roasly, bread crust-like) was the most potent aroma, followed by E-2-nonenal (green, tallowy), 3-methylbutanal (malty, nutty), diacetyl (buttery) and Z-2-nonenal (green, fiitty). 

Spadone et al. (1990) also identified aliphatic unsaturated aldehydes, long-chain 2-alkanones, lactones and esters which are only present in green coffee and would give the beans the characteristic soapy, fatty and fruity (coconut, peach, apricot) notes. They were the first authors to find (3-damascenone (Section 5,D.38) in raw coffee, a compound that resists roasting and contributes highly to the tea-like and fruity flavor of the beverage,... 

Bade-Wegner et al. (1998) studied the volatile compounds associated with the over-fermented flavor defect, considered to be one of the most objectionable organoleptic defects in coffee. They examined two defective samples of arabica and one sample of robusta green coffees, comparing them to reference products with a neutral flavor. As the off-flavor can be due to overfermentation of green coffee or to the presence of so-called stinker beans, the authors considered that the previous studies and identifications were more indicative than causative. By GC-olfactometry, three fruity odor notes were perceived, at different intensities, that were attributed to ethyl 2-methylbutanoate (Section 5,F.40), ethyl 3-methyl-butanoate (Section 5,F.41) and ethyl cyclohexanecarboxylate (Section 5,F.46). The three esters were considered to be the most important contributors to the over-fermented flavor defect. 

Strawberry flavor The strawberry aroma is made up of caramel-like [ impact compounds Furaneol, mesifuran (see Furaneol )], fruity [ fruit esters, 4-decanolide (see alkanolides)], green [( )-2- hexen-l-ols, ( )-2- hexenals, 2-hexenyl acetate (see fruit esters)], and flowery notes ( linalool, methyl anthran-ilate). Particularly important fruit esters are ethyl butanoate and hexanoate as well as the corresponding methyl esters. Free acids such as 2-methylbutanoic acid (C5H,o02, Mr 102.13, CAS [116-53-0]) and trace substances, e.g., dimethyl sulfide and vanillin, round off the aroma. 

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