Ethers flavoring from

Whereas the glucose ester 9 has been identified for the first time as a natural wine constituent, glycoconjugates of its reduced form, i.e. of the monoterpene diol 11, are known Riesling wine constituents (2). Under acidic conditions, diol 11 was partially converted into the bicyclic ether 12, the so-called dillether (2). In analogy to the formation of ether 12 from terpene diol 11, a likely formation of lactone 10 from acid 9A could be be expected (cf. Fig. 5). This so-called wine-lactone 10, first identified as an essential oil metabolite in the Koala (55), has recently been established by Guth (34) as a major aroma contributor in two white wine varieties. The 35,3a5,7aR-configured isomer of 10, which has been identified in wine, is reported to possess an unusual low flavor threshold of 0.01-0.04 pg/L of air and a sweet, coconut-like aroma (55). 

It is a yellowish-brown liquor of sweet, smooth ethereal flavor and of fine bouquet. Alcoholic content is usually from 45 to 55 per cent by volume. 

The flavors and scents of nature include many examples of alcohols and ethers. Menthol, found in peppermint oil, is an alcohol used both for flavoring and for medicinal purposes. Vanillin, isolated from vanilla beans, contains an ether functional group, as does anethole, the licorice flavor associated with fennel. Ethanol, the alcohol produced by fermentation, is, of course, another flavor of nature. Borneol, which can be isolated from artemesia, is an alcohol with a fascinating molecular architecture. And eucalyptol, which shares the ending of its name with other alcohols but is actually an ether, comes from eucalyptus leaves (shown in the left photo above) and is used as a flavoring, scent, and medicinal agent Nature is an abundant source of alcohols and ethers, and we study the chemistry of these important functional groups in this chapter. 

Hydroxybenzaldehyde has an agreeable aromatic odor, but is not itself a fragrance. It is, however, a useful intermediate in the synthesis of fragrances. The methyl ether of -hydroxybenzaldehyde, ie, -anisaldehyde, is a commercially important fragrance. Anisaldehyde can be made in a simple one-step synthesis from hydroxybenzaldehyde and methyl chloride. Another important fragrance, 4-(p-hydroxyphenyl)butanone, commonly referred to as raspberry ketone, can be prepared from the reaction of -hydroxybenzaldehyde and acetone, followed by reduction (see Flavors and spices). 

Benzophenone. Benzophenone [119-61-9] (diphenyl ketone) exists in a stable form as colorless orthorhombic bisphenoidal prisms when crystallized from alcohol or ether. Other labile forms of lower melting point exist. Benzophenone has been identified as a flavor component of wine grapes and has a geranium-like odor. It is soluble in most organic solvents, and is insoluble in water. 

Although most consumers appreciate the fieriness of chile, capsaicinoids are not perceived through odor or taste receptors but through the nociceptive pain receptors described earlier. The compounds in chile fruit that create the flavor and aroma are produced in the fruit wall. Buttery et al. [90] generated vacuum steam distilled oil from green bell pepper macerate, with well over 40 peaks on subsequent GC/MS analysis. Of these peaks, the major flavor compound associated with bell pepper aroma was 2-methoxy-3-isobutylpyrazine (Fig. 8.1). They also reported several monoterpenoids in abundance, limonene, trans- 3-ocimene, and linalool as well as other aliphatic aldehydes and ketones. The flavor composition of dried red bell pepper powder (sweet paprika) extracted with ether identified 44 key peaks by GC/MS [91]. In these dried samples the key compounds were P-ionone and several furanones. The post-harvest processing and the different fruit maturities as well as possible varietal differences are all causes for the different aromatic profiles. 

The aromatic, warm, and sweetish odor and taste of the seed, leaves, and stem arises from the presence of a volatile oil that contains anethole p-propenyl phenylmethyl ether, C3H5C6H4OCH3), the derivatives of which (anisole and anisaldehyde) are used in food flavoring, particularly bakery, liqueur, and candy products, as well as ingredients for perfumes. For commercial production of anise oil, the seeds and the dried, ripe fruit of the plant are used. Anise oil. a colorless to pale-yellow, strongly refractive liquid of characteristic odor and taste, is prepared by steam distillation of the seed and fruit. The oil contains choline, which finds use in medicine as a carminative and expectorant. 

The odor of a freshly crushed mint leaf, like many plant odors, is due to the presence in the plant of volatile C10 and Ci5 compounds, which are called terpenes. Isolation of these substances from the various parts of plants, even from the wood in some cases, by steam distillation or ether extraction gives what are known as essential oils. These are widely used in perfumery, as food flavorings and medicines, and as solvents. Among the typical essential oils are those obtained from cloves, roses, lavender, citronella, eucalyptus, peppermint, camphor, sandalwood, cedar, and turpentine. Such substances are of interest to us here because, as was pointed out by Wallach in 1887 and reemphasized by Ruzicka in 1935, the components of the essential oils can be regarded as derived from isoprene ... 

A first approach to analyze such volatiles is the application of the AEDA on extracts prepared by dynamic headspace extraction. An apparatus used for the extraction especially of solid foods is shown in Figure 5 [55]. The powdered material is placed into a rotating cylinder and the volatiles are continuously flushed onto a polymer material (Tenax( )) by using a stream of helium (1 L/min). After 3 hr the volatiles are desorbed from the polymer by elution with a small amount of diethyl ether and evaluated by AEDA after concentration. Since different yields may change the composition of the volatiles during headspace extraction [7], it is essential to sensorially evaluate the flavor of the extracts in comparison with the food flavor itself. The following examples show applications of this method on fresh and stored wheat bread crust [55] and on fresh rye bread crust [P. Schieberle and W. Grosch, unpublished results]. 

Sample preparation. For the study of trace compounds we used two different sample preparation procedures SPI and SPII for wine no. 1 and wine no. 2, respectively. The first flavor extract SP I was obtained by liquid-liquid extraction with fluorochloromethane and dichloromethane (9+1) from 45 L Scheurebe wine. For further analysis a portion of 1/3 was used. After separation on silica gel (pentane/diethyl ether) 6 fractions were analyzed. For the second flavor extract SP II we started from 200 L wine stripping off volatile compounds with vapour in a spinning cone column (SCC) system (5). The condensate was sequentially collected in two main portions of 8 and 2 L, respectively. The first condensate was discarded. The second condensate (2 L) was subjected to liquid-liquid extration with fluorochloromethane and dichloromethane (9+1). After separation on silica gel (pentane/diethyl ether) using medium pressure chromatography (MPLC) 4 fractions were analyzed. 

Nearly 1000 compounds have so far been identified in the volatile constituents of meat from beef, chicken, mutton and pork (6). The largest number of volatiles has been determined in beef and these were representative of most classes of organic compounds. Hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, esters, lactones, ethers, sulfur and halogenated compounds as well as different classes of heterocyclic substances (Figure 1) namely furans, pyrldlnes, pyrazines, pyrroles, oxazol(in)es, thiazol(in)es, thiophenes were present in cooked meat flavor volatiles as shown in Table I. Many of these compounds are unimportant to the flavor of meat and some may have been artifacts (16). 

Certain phenols and their ethers are isolated from the essential oils of various plants (so called because they contain the essence—odor or flavor—of the plants). A few of these are ... 

When the word ether is mentioned, most people think of the well-known anesthetic, diethyl ether. There are many ethers. Their uses range from artificial flavorings to refrigerants and solvents. An ether is a compound in which an O atom is bonded to two organic groups. 

Simultaneous Steam Distillation/Extraction An elegant apparatus was described by Nickerson and Likens ( 5) for the simultaneous steam distillation and extraction (SDE) of volatile components. This device has become one of the mainstays in the flavor field. In this apparatus, both the aqueous sample and water-immiscible solvent are simultaneously distilled. The steam which contains the aroma chemicals and the organic solvent are condensed together, and the aroma compounds are transferred from the aqueous phase to the organic phase. Typical solvents used are diethyl ether, pentane or a mixture thereof normal extraction times are one to two hours. 

Vanillin and veratraldehyde are two fine examples of flavor and fragrance chemicals which have been successfully synthesized from p-cresol. A number of low volume synthetic perfume materials based on p-cresol esters and ethers have also been introduced. Following are some of the important products. 

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