Flavors and fragrances substances

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. 

Three main methods are used to concentrate plant flavor and fragrance substances ... 

Individual compounds can be isolated from essential oils containing one or only a few major components by distillation or crystallization. Examples are eugenol from clove oil, menthol from commint oil, citronellal from Eucalyptus citriodora oil and citral from Litsea cubeba oil. These compounds are used as such or serve as starting materials for the synthesis of derivatives, which are also used as flavor and fragrance substances. However, the importance of some of these oils has decreased substantially because of the development of selective synthetic processes for their components. 

Although synthetic flavor and fragrance materials are produced on industrial scales, naturally occurring raw materials continue to be essential, important ingredients in the manufacture of flavor and fragrance compositions for several reasons. First, the compositions and sensory natures of natural products are often too complex to be reproduced by combinations of synthetic fragrance substances. Second, the characteristic flavor and fragrance substances of a particular product often cannot be synthesized at a competitive price. Third, the use of natural materials in the production of certain flavor compositions is compulsory. Moreover, a continous demand for perfumes based on natural materials is still observed. 

Observing and Inferring Flowers and fruits have pleasant odors partly because they contain substances called esters. Companies make blends of synthetic esters to mimic the flavors and fragrances of esters found in nature. In this experiment, you will make an ester that has a familiar smell. 

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. 

Survey on flavouring substances currently marketed or used in Japan (summary), March 2001. flavor Committee, Japan Flavor and Fragrance Materials Association Discussion paper on the development of a Codex Guideline that establishes safe conditions of use for flavourings in foods with a reference to the evaluations completed by JECFA (2005). Codex Alimentarius Commission, Joint FAO/WHO Food Standards Programme, Rome... 

Up until now, most of the published work on the SFE of natural products has been concerned primarily with nonpolar substances such as essential oils, lipids, flavor, and fragrance ingredients. However, recent reports have shown that some polar plant constituents (e.g. flavonoid glycosides, proteins, and steroidal glycosides) can be extracted by SFE as effectively as conventional organic solvent extraction. Examples of SFE applications for natural products are well reviewed in several literature sources [19-22]. 

Turpentine. Turpentine is used directly as a solvent, thinner, or additive for paints, varnishes, enamels, waxes, polishes, disinfectants, soaps, pharmaceuticals, wood stains, sealing wax, inks, and crayons, and as a general solvent. The chemistry of its mono-terpenes offers many possibilities for conversion to other substances, as illustrated in Fig. 28.20. There is increasing use of turpentine to produce fine chemicals for flavors and fragrances. An important use of turpentine is in conversion by mineral acids to synthetic pine oil. It also is a raw material for making terpin hydrate, resins, camphene, insecticides, and other useful commodities. These uses are included in the following summary of its applications. 

This volume treats pheromones (Chapters 4.01—4.06), defensive substances and toxins (Chapters 4.08—T. 10), antifeedants (Chapters 4.11-4.12), compounds employed in plant-plant and plant-microbe interactions (Chapter 4.13), plant-insect interactions (Chapter 4.14) and microbe-microbe interactions (Chapter 4.07). Hormones of plants (Chapter 4.02) and insects (Chapter 4.03) are also treated in this volume. A unique attempt in the present volume is to regard flavor and fragrance (Chapter 4.15) and taste (Chapter 4.16) as phenomena of human-environmental interactions or human chemical ecology. 

The SLRs cover groups of substances with related chemical stmctures and, therefore, presumably, related metabolic and toxicological properties. The titles of these SLRs together with their order number are listed in Flavor and Fragrance Materials 2004 [15]. This publication contains for each GRAS substance an alpha numeric code to the SLR. The SLRs are available either in hard copy or on microfiche from the Customer Service National Technical Information Services (NTIS), 5285 Port Royal Road, Springfield, VA 22161 (USA). 

In part 5 the authorised lists of ingredients are mentioned. According to 5.1. all materials published in Flavor and Fragrance Materials [15] may be used with due consideration for restrictions of certain substances in part 7 and 8. Part 7 is identical with Annex II of the EC Flavour Directive [19]. Furthermore (5.3.) the flavouring... 

Most simple esters are pleasant-smelling substances. They are responsible for the flavors and fragrances of most fruits and flowers and many of the artificial fruit flavorings that are used in cakes, candies, and ice cream (Table 27-13). Esters of low molecular weight are excellent solvents for nonpolar compounds. Ethyl acetate is an excellent solvent that gives many nail polish removers their characteristic odor. 

The agricultural production of flavor and fragrance materials has several disadvantages, including variation in consistency and quality, and dependency on climatic, seasonal, geographic, and even political factors. The microbial production of flavor and fragrance materials may compliment or offer an alternative to traditional sources of these materials. Fermentation may be particularly suited to the production of unique, highly intense character impact components, i.e., substances that can potentiate the aroma and flavor of fruits, dairy and other flavors at low levels ( 100 ppm in the finished flavor). 

There are more than 150 natural essential oils and natural extracts from which a large number of important flne chemicals in the field of flavor and fragrances have been extracted, isolated, and sold as blends in predetermined quantities. Table 10.1 gives some details of only those natural substances containing cresols, precmsors such as cymenes, derivatives such as thymol, menthol, and other allied products. 

Extraction of Essential Oils from Plants. Essential oils are aromatic substances widely used in the perfume industry, the pharmaceutical sector, and the food and human nutrition field. They are mixtures of more than 200 compounds that can be grouped basically into two fractions a volatile fraction, which constitutes 90-95% of the whole oil, and a nonvolatile residue, which constitutes the remaining 5-10%. The isolation, concentration, and purification of essential oils have been important processes for many years, as a consequence of the widespread use of these compounds. The common methods used are mainly based on solvent extraction and steam distillation. SFE has been used for the extraction of essential oils from plants, in an attempt to avoid the drawbacks linked to conventional techniques (57). Such is the case with the extraction of flavor and fragrance compounds, such as those from rose (58), rosemary (59), peppermint (60), eucalyptus (61), and guajava (62). The on-line coupling of the extraction and separation ietermi-nation steps (by SFE-GC-FID) has been proposed successfully for the analysis of herbs (63) and for vetiver essential oil (64). 

There are no universally accepted definitions of bulk, fine, and specialty chemicals, nor are these classifications based on any intrinsic properties. A substance that is currently viewed as a bulk chemical might well have been classified as a fine chemical at an earlier stage in its development. A useful working definition of a fine chemical is one with a price of more than 10 US dollars kg and a volume of less than 10000 tons per annum on a worldwide basis. We make no distinction between fine chemicals, that are often intermediates, and specialty chemicals such as pharmaceuticals, pesticides, and flavors and fragrances. The type of technology used to manufacture these products is dictated more by volume than by product application. 

Insects communicate by releasing pheromones—chemical substances that other insects of the same species detect with their anteimae. There are sex, alarm, and trail pheromones, and many of these are alkenes. Interfering with an insect s ability to send or receive chemical signals is an environmentally safe way to control insect populations. For example, traps with synthetic sex attractants have been used to capture such crop-destroying insects as the gypsy moth and the boll weevil. Many of the flavors and fragrances produced by certain plants also belong to the alkene family. 

Use Technically important M. are geraniol, a- pi-nenes, limonene, cymenoles, 3- carenes, and cam-phor. M. alcohols usually occur in esterified form, these esters are used as fragrances, flavor, and spice substances in the perfume, cosmetic, and food industries. Some enantiomerically pure M. are used in stereospecific syntheses of certain natural products. 

Essential oil components are often found in the glands or intercellular spaces in plant tissue. They may exist in all parts of the plant but are often concentrated in the seeds or flowers. Many components of essential oils are steam-volatile and can be isolated by steam distillation. Other methods of isolating essential oils include solvent extraction and pressing (expression) methods. Esters (see the essay "Esters-Flavors and Fragrances") are frequently responsible for the characteristic odors and flavors of fruits and flowers, but other types of substances may also be important components of odor or flavor principles. Besides the esters, the ingredients of essential oils may be complex mixtures of hydrocarbons, alcohols, and carbonyl compounds. These other components usually belong to one of the two groups of natural products called terpenes or phenylpropanoids. 

In the previous chapters, the methods of RP and NP HPLC have been discussed in detail. These methods are ideally suited for qualitative and quantitative analytical investigations of complex mixtures of substances. However, they do not allow any statement about the chiral composition of the analyte. Therefore, another liquid chromatographic method is used for the determination of the enantiomeric composition of samples. Enantioselective HPLC, as the method is called, can be viewed as a complementary measurement for the characteri2ation of analytes. This is not only true for samples of pharmaceutical origin, for which monitoring of achiral and enantiomeric purity are mandatory [1], but also for agrochemical products, flavors, and fragrances. 

Flavorings—These are the substances that stimulate the senses of taste and/or smell. With the exception of the four primary sensations—sweet, bitter, salty, and sour— flavor characteristics are the result of our perception of odor the difference between flavor and fragrance is in large part only a semantic distinction. Thus, a substance that provides an odor in perfumes may also be used to add flavoring to a food. 

Aroma chemicals are an important group of organic molecules used as ingredients in flavor and fragrance composition. Aroma chemicals consist of natural, nature-identical, and artificial molecules. Natural products are obtained directly from the plant or animal sources by physical procedures. Nature-identical compounds are produced synthetically, but are chemically identical to their natural counterparts. Artificial flavor substances are compounds that have not yet been identified in plant or animal products for human consumption. 

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