Flavors 2-phenylethanol

Free amino acids are further catabolized into several volatile flavor compounds. However, the pathways involved are not fully known. A detailed summary of the various studies on the role of the catabolism of amino acids in cheese flavor development was published by Curtin and McSweeney (2004). Two major pathways have been suggested (1) aminotransferase or lyase activity and (2) deamination or decarboxylation. Aminotransferase activity results in the formation of a-ketoacids and glutamic acid. The a-ketoacids are further degraded to flavor compounds such as hydroxy acids, aldehydes, and carboxylic acids. a-Ketoacids from methionine, branched-chain amino acids (leucine, isoleucine, and valine), or aromatic amino acids (phenylalanine, tyrosine, and tryptophan) serve as the precursors to volatile flavor compounds (Yvon and Rijnen, 2001). Volatile sulfur compounds are primarily formed from methionine. Methanethiol, which at low concentrations, contributes to the characteristic flavor of Cheddar cheese, is formed from the catabolism of methionine (Curtin and McSweeney, 2004 Weimer et al., 1999). Furthermore, bacterial lyases also metabolize methionine to a-ketobutyrate, methanethiol, and ammonia (Tanaka et al., 1985). On catabolism by aminotransferase, aromatic amino acids yield volatile flavor compounds such as benzalde-hyde, phenylacetate, phenylethanol, phenyllactate, etc. Deamination reactions also result in a-ketoacids and ammonia, which add to the flavor of... 

Ethyl hexanoate and octanoate were the predominant FA esters found in Tinta Negra wines, whereas diethyl succinate and ethyl lactate were the most abundant diprotic acid ethyl esters. According to the authors, the most sensory important flavors seem to be attributed to 3-methylbutan-l-ol, 2-phenylethanol, isoamyl acetate, diethyl succinate, 2-phenylethylace-tate, phenylacetaldehyde, y-nonalactone, ethyl hexanoate, ethyl octanoate, hexanoic acid, and octanoic acid. 

Alcohols occur widely in nature. Methanol is also known as wood alcohol because it can be obtained by distilling wood in the absence of air. It is very poisonous and can cause blindness or death if ingested. Ethanol is consumed in alcoholic beverages. Other simple alcohols, such as 2-phenylethanol from roses and menthol from peppermint, are constituents of natural flavors and fragrances. Alcohols are important intermediates in chemical synthesis. They are also commonly used as solvents for various chemical processes. Ethylene glycol is used in antifreeze and in the preparation of polymers such as Dacron. 

Recently, AEDA and SHA-0 yielded 41 and 45 odor active compounds for Scheurebe and Gewurztraminer wines, respectively (P). Ethyl 2-methylbutyrate, ethyl isobutyrate, 2-phenylethanol, 3-methylbutanol, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, 3-ethylphenol and one unknown compound, named wine lactone, showed high flavor dilution (FD)- factors (Table I) in Gewurztraminer and Scheurebe wines. 4-Mercapto-4-methylpentan-2-one belongs to the most potent odorants only in the variety Scheurebe whereas cis-rose oxide was perceived only in Gewurztraminer (Table I). 4-Mercapto-4-methylpentan-2-one was identified for the first time in Sauvignon blanc wines (JO). The unknown compound with coconut, woody and sweet odor quality, which has not yet been detected in wine or a food, was identified as 3a,4,5,7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one (wine lactone) (JJ). 

L-Phenylalanine,which is derived via the shikimic acid pathway,is an important precursor for aromatic aroma components. This amino acid can be transformed into phe-nylpyruvate by transamination and by subsequent decarboxylation to 2-phenylacetyl-CoA in an analogous reaction as discussed for leucine and valine. 2-Phenylacetyl-CoA is converted into esters of a variety of alcohols or reduced to 2-phenylethanol and transformed into 2-phenyl-ethyl esters. The end products of phenylalanine catabolism are fumaric acid and acetoacetate which are further metabolized by the TCA-cycle. Phenylalanine ammonia lyase converts the amino acid into cinnamic acid, the key intermediate of phenylpropanoid metabolism. By a series of enzymes (cinnamate-4-hydroxylase, p-coumarate 3-hydroxylase, catechol O-methyltransferase and ferulate 5-hydroxylase) cinnamic acid is transformed into p-couma-ric-, caffeic-, ferulic-, 5-hydroxyferulic- and sinapic acids,which act as precursors for flavor components and are important intermediates in the biosynthesis of fla-vonoides, lignins, etc. Reduction of cinnamic acids to aldehydes and alcohols by cinnamoyl-CoA NADPH-oxido-reductase and cinnamoyl-alcohol-dehydrogenase form important flavor compounds such as cinnamic aldehyde, cin-namyl alcohol and esters. Further reduction of cinnamyl alcohols lead to propenyl- and allylphenols such as... 

The main volatiles in wines are the higher aliphatic alcohols, ethyl esters, and acetates formed from yeasts during fermentation. Acetates are very important flavors characterized by fruity notes, C4-Ci0 fatty acid ethyl esters manly confer fruity scents to the wine. Other wine aroma compounds are C6 alcohols, such as 1-hexanol and cis- and trans-3-hexen-l-ol, 2-phenylethanol, and 2-phenylethyl acetate. Contents of these compounds in wine are linked to the winemaking processes used fermentation temperature, yeast strain type, nitrogen level in must available for yeasts during fermentation, clarification of wine (Rapp and Versini, 1991). Much literature on the wine aroma compounds was reported in reviews by Schreier (1979) and Rapp (1988). 

Taste and flavor of bread can be improved with optimal use of sourdough (Seibel and Briimmer, 1991). The flavor of sourdough wheat bread is richer and more aromatic than in wheat bread, a factor that can be attributed to the long fermentation time of sourdough (Briimmer and Lorenz, 1991). Studies on the influence of lactic acid bacteria on the aroma of wheat bread revealed a positive influence, particularly on the crumb aroma (Hansen and Hansen, 1996). The concentration of 2-phenylethanol, one of the most potent odorants of wheat bread crumb (Grosch and Schieberle,... 

Figure 1 Effect of the use of the immobilized and free 13-glucosidase of Candida molischiana 35M5N on the level of flavor compounds in apricot fruit juice. (1) a-pinene, (2) a-terpinene, (3) y-terpinene, (4) a-terpineol, (5) linalool, (6) 2-phenylethanol.

The authors assessed the relative importance of these components using gas chromatographic effluent sniffing. B-phenylethanol seems to be the component most like the muscadine flavor with benzyl acetate and one or two unknowns also contributing a grapey flavor or aroma. 

The most pronounced decreases occurred early in the storage period. Using objective and subjective techniques, Sistrunk (25) determined that ethyl acetate, benzyl acetate and B-phenylethanol are probably of primary importance to the typical flavor of muscadines. Ethyl acetate comprised 25%... 

Cocoa flavor. Some of the over 500 known volatile components of C. f. are already present in raw cocoa, but most are formed after diying and roasting (at 110-130 °C), mainly by Maillard or Strecker reactions from amino acids, peptides, and sugars resulting from anaerobic fermentation. C. f. is not determined by one impact compound but is rather a composition of various aromas caramel-like ( maltol, Furaneol , and 2-hydroxy-3-methy 1-2-cyclopenten-1 -one), flowery ( linalool, 2-phenylethanol, phenylacetaldehyde). 

Natural and natural-identical F. c. are used in the commercial production of aromas. The latter are F. c. that have been identified as components of foods and then produced synthetically. For the biotechnical production of natural F. c., see Lit.. The world m et of aroma and flavor substances in 1994 amounted to 9.7 billion US, the most important individual compounds being (consumption in t per year) 2-phenylethanol and its esters (7000), musk aromas (62()0), linalool or its esters (6()00), ester of lower fatty acids (5800) and vanilla (see 3,4-dihydroxybenzaldehydes) (5500) . Using tools of molecular biology, scientists are beginning to figure out how the olfactory sense works and how flavor impression is formed. ... 

Plum flavor An important factor is the correct quantitative ratio of a few major components such as linalool, benzaldehyde, methyl cinnamate (see cinnamic acid), 2-phenylethanol, and 4-decanolide (see alkanolides), in addition to green notes such as (Z)-3- -hexen-l-ols and 2- hexenals, as well as fruit esters, e. g., ethyl octanoate. 

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-... 

Tieman, D., et al. (2006) Tomato aromatic amino acid decarboxylases participate in synthesis of the flavor volatiles 2-phenylethanol and 2-phenylacetaldehyde. Proc. Natl. Acad. Sci. USA 103, 8287-8292... 

Phenylethanol Sweet and fruit flavors High demand - simple flavor Product cytotoxicity... 

The chromatograms of tomato volatiles obtained by the three methods are shown in Fig. 3. SPME was unable to detect the highly volatile flavor components l-penten-3-one and 3-methyl butanol. All important aroma volatiles were detected by liquid-liquid extraction. Phenylacetaldehyde and 2-phenylethanol were... 

Urbach (78) recently discussed the formation of volatile flavor compounds in different varieties of cheeses and provided a compilation of important aroma compounds. A recent qualitative assessment by Sable and Cottenceau (79) surveys the significant flavor volatiles that have been identified in soft mold-ripened cheeses, including Camembert, Brie, blue, Gorgonzola, Muenster, and Limburger, among others. Octen-3-ol, 2-phenylethanol, and 2-phenylethyl acetate are character impact... 

---