Aroma preparation

Natural fruit aromas are mixtures of certain organic compounds and esters. Synthetic aromas prepared in laboratories are simple mixtures of these same esters and organic compounds. They are used in perfumes, foods and drinks to give taste and pleasant smells. Ethyl acetate, for example, is a colorless liquid with an apple flavour it is known as apple ester and is used in perfumery as a fruit essence. Propyl acetate has the smell of pears, isopentyl acetate that of bananas and ethyl butyrate smells of pineapples. All are colorless liquids. Higher molar mass esters are odorless. 

Furfural was first isolated in the eady nineteenth century. Dobereiner is credited with the discovery. He obtained a small amount of a yellow "oil" (too Htde to characterize) as a by-product in the preparation of formic acid (8). Other chemists found that the same "oil" having a charactedstic aroma could be obtained by boiling finely divided vegetable materials such as oats, com, sawdust, bran, etc, with aqueous sulfuric acid or other acids (9,10). The oil was present in the Hquid resulting from condensation of the vapors produced during heating. The empirical formula was determined by Stenhouse... 

Mustard is marketed in three forms, ie, as a seed as a prepared blend of ground mustard seed, vinegar, salt, sugar, and other spices and as powdered dry mustard, also known as ground mustard or mustard flour. The seeds of the white or yellow mustard add pungency to any preparation, and that of the black mustard is required for aroma. Mustard is the largest volume spice imported into the United States and its use covers almost every flavor category except dessert items. 

By the thirteenth century AD, essential oils were being produced along with medicinal and herbal preparations in pharmacies. Around this time improvements in distillation techniques were made, in particular the development of the alembic apparatus, which would eventually estabUsh the quaUty of such matenals. As a result, many of the essential oils in use today are denved from those produced in the sixteenth and seventeenth centunes in terms of odor character, even though production methods have continued to evolve. The current practice of aroma therapy is an indication of this common root of medicinal and fragrance chemistry. 

Synthesis. Exploratory research has produced a wide variety of odorants based on natural stmctures, chemicals analogous to naturals, and synthetic materials derived from available raw materials and economical processing. As in most areas of the chemical industry, the search for new and useful substances is made difficult by the many materials that have been patented and successfully commercialized (4). In the search for new aroma chemicals, many new materials are prepared for screening each year. Chemists who perform this work are involved in a creative exercise that takes its direction from the commercial sector in terms of desirable odor types and specific performance needs. Because of economic limitations, considerations of raw material costs and available processing methods may play a role eady in the exploratory work. 

Linalool has been used to prepare a mixture of terpenes useful for enhancing the aroma or taste of foodstuffs, chewing gums, and perfume compositions. Aqueous citric acid reaction at 100°C converts the linalool (3) to a complex mixture. A few of the components include a-terpineol (34%) (9), Bois de Rose oxide (5.1%) (64), ocimene quintoxide (0.5%) (65), linalool oxide (0.3%) (66), tij -ocimenol (3.28%) (67), and many other alcohols and hydrocarbons (131). 

Garyophyllene. (-)-CaryophyUene can be isolated from Indian turpentine and has been used to prepare a number of woody aroma products. The epoxides are produced by reaction with peracids. Acetylation of caryophyUene also gives a usehil methyl ketone (180) (Fig. 8). Acid-catalyzed rearrangement of caryophyUene in the presence of acetic acid gives a mixture of esters, which are related to caryolan-l-ol and clovan-2-ol (181). 

Cinnamaldehyde has been efficiently isolated in high purity by fractional distillation from cassia and cinnamon bark essential oils. This material has been utili2ed in several manufacturing protocols (39—41) for the preparation of natural ben2aldehyde through a retro-aldol process. Since the late 1970s the demand for natural flavors has increased dramatically. This demand has led to a corresponding requirement for a more extensive line of readily available natural aroma chemicals for flavor creation. 

GUILLEN M D, MANZANOS M J and IBARGOITIA M L (1996) Smoking of food products. Preparation, use, study methods, and composition of smoke aromas , Alimentaria, 274 45-53. 

The coffee beans with the most desirable flavor to many tastes are the highest grown Arabicas prepared by the wet method. Coffee beverages need to be prepared within 8 h of grinding the freshly roasted coffee beans if the volatile flavor and aroma compounds are to be retained. Brew... 

In liquid preparations containing organic solvents, drug concentration changes can occur through loss of solvent to the atmosphere. Similarly, flavors and aromas in formulations may diminish in strength as volatile components pass out of the preparation. 

Soluble solids uptake due to osmotic dehydration, in addition to improving color, aroma, and vitamin stability during both air drying and frozen storage, could also play a very important role in the preparation of new types of ingredients at reduced water activity (Torreggiani et al., 1988). Due to the... 

Optically pure trans- and czs-linalool oxides, constituents of several plants and fruits, are among the main aroma components of oolong and black tea. These compounds were prepared from 2,3-epoxylinalyl acetate (9) (Scheme 17) [102]. The key step consist of a separation of the diastereomeric mixture of 9 by employing an epoxide hydrolase preparation derived from Rhodococcus sp. NCIMB 11216, yielding the product diol and remaining epoxide in excellent diastereomeric excess (de>98%). Further follow-up chemistry gave both linalool... 

Mikami, Y., Fukunaga, Y., Arita, M., Obi, Y., and Kisaki, T. Preparation of aroma compounds by microbial transformation of isophorone by Aspergillusnlger, Agric. Biol Chem., 45(3) 791-793, 1981. 

Soy sauce is a uniquely Japanese seasoning prepared from soy beans and wheat. Aldiough soy sauce is made from soy beans, it has a highly desirable flavor without the beany aroma. Soy sauce is currently used not only in the preparation of many Japanese cuisines but also in the preparation of many popular western dishes such as l f steaks, poultry, and stews. Japan has more than 2,300 soy sauce producing firms. Soy sauce production in Japan is l,200,000kL per year at a cost of about 239.4 billion yen ( 1,840 million U.S.). The per capita consumption of soy sauce in Japan is 2,947 yen ( 22.70 U.S.) per year. By comparison, the per capita yearly consumption of sugar in Japan is 2,318 yen ( 17.80 U.S.). This indicates the relative impact of soy sauce as a fo adjuvant for the Japanese consumer. 

Uq 1.4378, may occur in the optically active form. It is found, for example, in lavender oil and is a steam-volatile component of mushrooms. l-Octen-3-ol is a liquid with an intense mushroom, forest-earthy odor that can be prepared by a Grignard reaction from vinylmagnesium bromide and hexanal. It is used in lavender compositions and in mushroom aromas. 

CH3(CH2)4CH = CHCH = CHC00CH2CH3, C12H20O2, Mr 196.29, bp6i> 70-72 °C, has been identified in pears and has the typical aroma of Williams pears. Synthesis of ethyl 2-trans-4-cw-decadienoate starts from cis-l-heptenyl bromide, which is converted into a 1-heptenyllithium cuprate complex with lithium and copper iodide. Reaction with ethyl propiolate yields a mixture of 95% ethyl 2-trans-A-cis- and 5% ethyl 2-tranx-4-tranx-decadienoate. Pure ethyl 2-trans-A-cis-decadienoate is obtained by fractional distillation [25]. A biotechnological process for its preparation has been developed [26]. 

Chemical Properties. Hydrogenation of menthols yields / -menthane oxidation with chromic acid or catalytic dehydrogenation yields menthones. Dehydration under mild conditions yields 3-/ -menthene as the main product. Reaction with carboxylic acids or their derivatives yields menthyl esters, which are used mainly as aroma substances and in pharmaceutical preparations and formulations. The esterification of menthols with benzoic acid is used on an industrial scale in the resolution of racemic menthol. 

CgHioO, Mr 122.17, mp 20°C, Z pioi.skPa 203°C, df 1.0135, ng 1.5275, has been identified as a volatile component of food (e.g., in tea aroma and mushrooms). The alcohol is a colorless liquid with a dry, roselike odor, slightly reminiscent of hawthorn. It can be prepared by catalytic hydrogenation of acetophenone. 1-Phenylethyl alcohol is used in small quantities in perfumery and in larger amounts for the production of its esters, which are more important as fragrance materials. 

Methyl cinnamate is a colorless crystalline solid mp 36.5 °C) with a fruity, sweet-balsamic odor. In addition to the common esterification methods, it can be prepared by Claisen condensation of benzaldehyde and methyl acetate in the presence of sodium. Methyl cinnamate is used in soap perfumes, as well as in blossom and oriental perfumes, and is sometimes added to aromas. 

C6Hg03, Mr 128.13, is a constituent of pineapple and strawberry aroma and is also found in other foods. It forms colorless crystals (mp 77-79 °C) with a relatively weak, nonspecific odor. Dilute solutions develop a pineapple, strawberry-like odor. It can be prepared by cyclization of hexane-2,5-diol-3,4-dione in the presence of an acidic catalyst [186]. The dione is the ozonization product of 2,5-hexynediol, which is obtained by ethynylation of acetaldehyde. 

A cis trans-mixture can be prepared by radical addition reaction of pentanal with crotonic acid followed by reductive cyclization of the resulting 7-0x0 acid with sodium boron hydride/sulfuric acid [198]. It is used in aroma compositions, e.g., for beverages. 

CeHgOs, Mr 128.13, was found in, e.g., fenugreek, coffee, sake, and flor-sherry. Its aroma characteristic changes from caramel-like at low concentrations to currylike at high concentrations. A method described for its preparation comprises condensation of ethyl propionate with diethyl oxalate and reaction of the intermediately formed diethyl oxalylpropionate with acetaldehyde. Acidic decarboxylation of the ethyl 4,5-dimethyl-2,3-dioxodihydrofuran-4-carboxylate gives the title compound [199]. 

The resinoids described above should be distinguished from prepared oleoresins (e.g., pepper, ginger, and vanilla oleoresins), which are concentrates prepared from spices by solvent extraction. The solvent that is used depends on the spice currently, these products are often obtained by extraction with supercritical carbon dioxide [223a]. Pepper and ginger oleoresins contain not only volatile aroma compounds, but also substances responsible for pungency. 

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