Importance for flavor

Robles and Bochet showed that nitrotoluene derivatives 106 (Scheme 50) can be used as a photoremovable protecting group for aldehydes. Irradiation of 106 released aldehydes in good yields, and the authors demonstrated that aldehydes such as phenylacetalaldehyde and citronellal, which are important for flavor and fragrances, are released efficiently from 106. 

In search for the key intermediates to meat flavor development in heated cysteine-sugar systems, it was found that in addition to thiazolidine derivatives also the tetrahydro-l,4-thiazine derivatives are being formed. These tetrahydro-l,4-thiazines, which are the cyclic form of Amadori compounds of cysteine, have excellent meat flavor precursor properties and are likely to play a prominent part in meat flavor development. Another major pathway to meat flavor development is the reaction of cysteine with the Amadori compounds of other amino acids. Model experiments showed that both pathways are probably of about equal importance for flavor development in boiled meat and process flavorings, this in spite of the low reactivity of cysteine with sugars. It seems that the first pathway is general-acid-catalyzed by the other amino acids, whereas the second pathway is inhibited by cysteine. 

A comparison with the yield obtained with a mineral acid, HCl, showed high performance of the TPA-PVA-PEG catalyst. Moreover, it has the advantages of an easy catalyst separation from the reaction medium and lesser problems of corrosion. As a consequence, it leads to an ecofriendly technology for the preparation of isoamyl acetate, which is important for flavor and fragrance industries and another fine chemical products. 

Farmingdale, USA) combined with glass beads. Supernatants from lysed cells are examined for enzyme activities believed to be of importance for flavor development in cheese. These include a variety of aminopeptidase and aminotransferase activities that are involved in the conversion of the peptides and amino acids derived from the breakdown of casein to a variety of flavor compounds. 

Acid content calculated as tartaric acid is about 6—7 g/L for best flavor and stabiUty. It is higher for tart low Brix musts and less important for sweet high Brix musts. High acid levels coiacide with a higher level of the second acid of grapes, malic acid. 

A food must have the expected or proper appearance and color before it will be readily consumed (7). There are many prepared foods in which artificial flavors and colors are used whose flavor is sufticientiy bland to make color essential for flavor identification, eg, margarine. The preservation of color in natural food during processing or the development of color by processing are aspects of primary importance in food acceptance. 

Citral reacts in an aldol condensation using excess acetone and a basic catalyst, usually sodium hydroxide. The excess acetone can be recovered for recycle. The resulting intermediate pseudoionone [141-10-6] (83) after cyclization with phosphoric acid gives predominantly a-ionone [127-41 -3] (84), which is the isomer commercially important in flavors and fragrances. A hydrocarbon solvent is generally necessary in order to get high yields. P-Ionone [14901-07-6] (85) is the predominant isomer if sulfuric acid is used as the catalyst but lower temperature than that for cyclization to a-ionone is required. y-Ionone [79-6-5] (86) is also produced. 

Maturity. With the harvesting of the crop comes the first opportunity for application of objective measures of quality. The stage of maturity at which the crop is harvested is of great importance, for it is capable of having a marked effect upon the color, flavor, and texture of the finished product. 

While the above reactions are responsible for meaty flavors, animal fat plays an important role in the formation of the characteristic spedes flavor of cooked meat (14). More than 100 compounds have been identified in heated beef fat, including aldehydes, n-alkanes,n-alkenes, fatty adds, ketones, lactones and heterocyclics (15-18). Of these compounds, the lactones, metltyl ketones and free fatty adds appear to be the most important for desirable meat flavor. 

Chemical signals are indispensable for the survival of many organisms which use chemoreceptors to find their way, to hunt for and inspect food, to detect enemies and harmful objects, and to find members of the opposite sex (pheromones). These functions are no longer vitally important for humans. The importance of flavor and fragrance substances in humans has evolved to become quantitatively and qualitatively different from that in other mammals this is because humans depend to a greater extent on acoustic and optical signals for orientation. However, humans have retained the ability to detect odors and human behavior can undoubtedly be affected by fragrances and aromas. 

Although food acceptance in humans is determined mainly by appearance and texture, flavor is nevertheless also important. For example, spices are added to food not for their nutritional value, but for their taste and flavor. Furthermore, aromas that develop during frying and baking enhance the enjoyment of food. 

Fatty aldehydes are generally produced by dehydrogenation of alcohols in the presence of suitable catalysts. The alcohols are often cheap and available in good purity. Aldehyde synthesis via the oxo process is less suitable since the resultant products are often not pure enough for flavor and perfume purposes. Specific syntheses for the branched-chain and unsaturated aldehydes that are important in perfumery and flavoring techniques are described under the individual compounds. 

Uses. Because of its strong lemon odor, citral is very important for aroma compositions such as citrus flavors. In perfumery it can be used only in neutral media due to its tendency to undergo discoloration, oxidation, and polymerization. It is used as a starting material in the synthesis of ionones and methylionones, particularly /3-ionone, which is an intermediate in vitamin A synthesis. 

Uses. Most essential oils are used directly as starting materials in the production of flavor and fragrance compositions. However, some essential oils are fractionated or concentrated by distillation, partitioning, or adsorption. Substances that are important for the desired characteristic odor and taste are thus concentrated, and other components, which possess either an unpleasant or very faint odor or are unsuitable for the application in question, are removed. 

Schmidt H-L, Werner RA, Eisenreich W (2003) Systematics of patterns in natural compounds and its importance for the elucidation of biosynthetic pathways. Phytochem Rev 2 61 Culp RA, Noakes JE (1992) Determination of synthetic components in flavor by deuterium/ hydrogen isotopic ratios. J Agric Food Chem 40 1892... 

Certain aroma components from fruits are responsible for the characteristic odor of many wines. An example is the typical aroma of many V. labrusca grapes which often gives their wines a distinctive aroma and flavor. Furthermore, some volatile constituents are characteristic of certain varieties and their wines are recognized by these distinctive aromas. This is significantly important for varietal wines (grape) where their distinct aromas are a prerequisite in rating the quality at the highest level. In addition to the importance of variety in the aroma and flavor of wines, other variables known to influence the volatile components within the fruit variety are maturity, location, climatic conditions, and cultural practices. 

Fermentation of lactic acid to yield propionic acid, carbon dioxide, acetic acid, and succinic acid is important for proper eye formation and flavor development in Emmental, Gruyere, and Swiss-type cheese varieties. This fermentation is associated with Propionibacterium spp. subspecies of Propionibacterium freudenreichii are of greatest significance. These organisms can also be used for industrial production of vitamin Bi2 and propionic acid. 

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