Green note

For all the processes cited, the overall yield from the natural sources and the productivity are too low for commercially interesting applications. Nevertheless, the very low threshold of this flavor ingredient implies that it can be used in very low concentrations, making even these low-yield processes still appealing, provided that they are developed further. 

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. 

An efficient biocatalytic reaction [173] was developed to synthesize (2 )-hexenal at large scale, based on the conversion of 13-HPOT by means of sugar beet HPL extracted from leaves or expressed by recombinant E. coli strains. With the adaptation of fed-batch substrate addition and continuous extraction of volatiles, 3.46 and 1.37 mM of C6-aldehydes were produced with the native HPL at, respectively, 2 and 1001 scale. Furthermore, higher molar productivity of green leaf volatiles was reached with recombinant HPL (5.5 mM at 2-1 scale), while no other side-products from the LOX pathway were formed. 

In soybean seeds, three distinct isoforms of LOXs (LOXl-3) were described in particular [174], isozyme LOX3 was reported not only to produce less 

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Men s Fragrances. Earlier ia the twentieth century, men s fragrances were expected to have a masculine direction, such as tobacco, leather, fougere, or citms, even if only in name. This is no longer tme, however since the 1970s, men s perfumes have become less conservative and have allowed much more creative use of rich woody, ambery, and green notes. 

Equal amounts of the two crowns were also formed when BU4NOH was used as base, but both rate and yield were considerably reduced. Greene noted that such a template effect would actually involve binding between the open-chained intermediates and cations and these interactions are known to be weak relative to crown-cation interactions. Nevertheless, evidence for such interactions exists (see also Chap. 7) ... 

Fig. 13.1 Triple immunostaining of a normal duct epithelium for K14 (Ckl4, pink), K5 (Ck5/6, red), and K8/18 8 (Ckl8, green). Note that few progenitor cells are stained only for K5 and/or K14 (1), whereas most are stained both for basal (usually K5) and glandular keratins K8/18. These cells represent intermediary glandular cells. Few cells stained only for K8/18 are differentiated glandu lar cells...

Fig. 13.5 Double immunostaining of the nipple epidermis for K5 (pink) and K10 (green). Note that with increasing differentiation, K5 is lost and the cells express K10...

Fig. 9.9 (a) Structure of the salicylic acid fragment covalently bound to caspase-3 (gray), superimposed on a tetrapeptide-based inhibitor (green). Note the collapse of the S2 pocket and the widening of the S4 pocket to accommodate the salicylic acid moiety, (b) Structure of a second fragment covalently bound to caspase-3 (blue) superimposed on... 

It can be synthesized by reaction of a 1 1 molar ratio of ethyl vinyl ether and phenethyl alcohol in the presence of cation exchange resin [141]. It imparts fresh, floral, green notes and is used in fine fragrances as well as in soap, cosmetics and detergents. 

Uses. Coumarin is one of the most widely used fragrance materials. It is used in fine fragrances as well as in soap perfumes for spicy green notes. It is also used in galvanization as a brightener. 

Coumarin 162 (Structure 4.49) is a naturally occurring lactone in crystal form found in hay and tonka beans. It is one of the most used fragrance materials and is responsible for spicy green notes. Dihydrocoumarine 163 is also present in various essential oils with a characteristic sweet herbal odour. Umbellif-erone 164, scopoletin 165, bergaptene 166 and coumarin are found in Rutaceae, Apiaceae, Lamiaceae and Asteraceae oils. Nepetalactones 167 are confined to the oils of Nepeta species [1,3, 21-23, 63]. 

Scheme 7.2 Pathway for the enzymatic degradation of linoleic acid and linolenic acid via the lipoxygenase (LOX) pathway to Ce key aroma compounds in fruits and vegetables responsible for green notes. HPL hydroperoxide lyase, ADH alcohol dehydrogenase...

Elderberry (Sambucus nigra) is cultivated on small scale in Europe. The fruits have a high concentration of red and purple anthocyanins and a relatively low concentration of sugars, organic acids and aroma compounds, which make this juice attractive as a natural colour ingredient in other red fruit products [126-129]. The fresh green odour of elderberry juice is associated with volatile compounds with typical green notes such as 1-hexanol, 1-octanol, (Z)-3-hexen-l-ol, ( )-2-hexen-l-ol, hexanal and ( )-2-hexenal, whereas the floral aroma is mainly due to the presence of hotrienol and nonanal [127-130]. 

Large-scale synthesis of (Z)-3-hexenyl acetate in hexane with lipase, (Z)-3-hexenol and acetic acid was described by several authors [40-42]. (Z)-3-Hex-enyl acetate has a fruity odour and shows a significant green note flavour. It can be produced using lipase from Candida antarctica immobilised on an acrylic resin [40, 41] or using immobilised lipase from Mucor miehei [42]. The conversion was reported to be about 90%. 

LOX is an important factor in the large-scale use of plant enzymes for the production of natural green note aroma compounds, a group of isomeric C6 aldehydes and alcohols [66]. 

In nature, the green notes are produced after the destruction of the plants tissue (leaves, fruits or vegetables). Destruction of the cell wall leads to a cascade of enzyme-catalysed reactions polyunsaturated fatty acids with the diene system described before are converted into hydroperoxides by LOX catalysis. The hydroperoxide lyase cleaves the hydroperoxides in the whole cascade, oxireduc-tases are involved too. The biotechnological large-scale production of natural green notes follows the natural pathway. 

A patented process for the production of green notes applying bakers yeast for in situ reduction of enzymatically produced aldehydes [67, 68] has been called into question regarding the effective production of (Z)-3-hexenol. According to Gatfield s report [69] the isomerisation of (Z)-3-hexenol to (E)-2-hexenal is a very fast process. The latter undergoes facile conversion to hexanol. Beside this, baker s yeast can add activated acetaldehyde to ( )-2-hexenal, forming 4-octen-2,3-diol. 

At present, there are some patents concerning the production of green notes by recombinant guava 13-hydroperoxide lyase expressed in Escherichia coli [70, 71] and Cucumis melo hydroperoxide lyase the latter yields a mixture of C6 and C9 compounds [72]. 

Scheme 233 Formation of aliphatic flavour aldehydes and alcohols, a Biotechnological reaction sequence mimicking plant biosynthesis of C6 compounds (green notes ), b HomologoiK reaction sequence in fimgi leading to mushroom-like C8 compounds. The stoichiometric formation of w-oxo-carboxylic acids during hydroperoxide lyase cleavage is not depicted...

The cloning, characterisation and expression of many lipoxygenase (TOX) [17] and hydroperoxide lyase (HPL) [18] genes has led researchers to propose new processes for the production of green note flavours. HPT specifically produces the highly demanded compound ds-3-hexenal from the 13-hydroperoxide of linolenic acid and hexanal from the hydroperoxide of linoleic acid, both of which are formed by TOXs (Scheme 26.2). 

Schematic diagram comparing some anatomic and neurotransmitter features of autonomic and somatic motor nerves. Only the primary transmitter substances are shown. Parasympathetic ganglia are not shown because most are in or near the wall of the organ innervated. Cholinergic nerves are shown in blue noradrenergic in red and dopaminergic in green. Note that some sympathetic postganglionic fibers release acetylcholine or dopamine rather than norepinephrine. The adrenal medulla, a modified sympathetic ganglion, receives sympathetic preganglionic fibers and releases epinephrine and norepinephrine into the blood. ACh, acetylcholine D, dopamine Epi, epinephrine M, muscarinic receptors N, nicotinic receptors NE, norepinephrine.

Fig. 4 Immunofluorescence microscopy of Giardia intestinalis showing segregation of mi-tosomes during mitosis. A Interphase, prophase, and C telophase cells. Nuclei were stained by DAPI (blue), mitosomes were detected by an antibody raised against GiiscU (red), and axonemes were visualized by the antibody AXO 49 recognizing polyglycylated carboxy-terminal peptides of a- and fl-tubulin (green). Note the proximity of mitosomes (white arrows) to axonemes...

FIGURE 22-20 Biosynthesis of histidine in bacteria and plants. Atoms derived from PRPP and ATP are shaded red and blue, respectively. Two of the histidine nitrogens are derived from glutamine and glutamate (green). Note that the derivative of ATP remaining after step (AICAR) is an intermediate in purine biosynthesis (see Fig. 22-33, step ), so ATP is rapidly regenerated. 

B. Ethyl N-nitroso-N-benzylcarbamate (Note 2). In a 12-1. three-necked flask fitted with a thermometer, a 2-1. addition funnel (Note 3), and a gas outlet tube are placed a solution of 360 g. (2.0 moles) of ethyl N-benzylcarbamate in 2 1. of ether and a solution of 1.2 kg. (17.4 moles) of sodium nitrite in 2 1. of water. A stirrer is not used. The reaction mixture is cooled by means of a water bath to 20° and treated with a solution of 1 1. each of concentrated nitric acid and water, contained in the addition funnel. Enough of this solution is added to impart a permanent green color to the aqueous layer, and the remainder is then added over a period of 5 hours at such a rate as to keep the aqueous phase green (Note 4) and the temperature at 25-30°. The reaction mixture is allowed to stand an additional 30 minutes, and the layers are separated. The ether layer is washed with 200-ml. portions of 10% potassium carbonate solution (Note 5) until the evolution of gas ceases and is then dried over anhydrous potassium carbonate. The ether is removed under vacuum on a water bath kept below 50° (Note 6), a residue of 400-415 g. (95-100%) of a bright orange oil (Note 7) being left. 

On the basis of high FD-factors (Table 3) the sensory significance of 3-methylbutanal and 2-acetyI-l-pyrroIine with malty, roasty odors previously identified as the key odorants in fresh wheat bread crust [21] was established. During storage for 4 days the FD-factors of both odorants decreased significantly, while especially butanoic acid (rancid) and (E)-2-nonenaI remained unchanged. The fatty, green note of the latter odorant especially contributes to the stale note detectable in the overall crust flavor of the stored wheat bread. 

Leaving out one or both of these letters signifies lack of such information, for example green note, characteristic. 

Godshall et al. (57) have concluded that typical molasses aroma is composed of two fractions. One is a sweet component that can arise from compounds such as diacetyl and other aldehydes while the other is a strong grassy or green note which they attribute to... 

Green notes Floral cinnamic derivatives Eugenol cA-3-Hexenyl acetate Violet leaf absolute c/.s-3-Hexenyl benzoate Isoeugenol... 

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