Flavours and Fragrances

Multidimensional Chromatography Foods, Flavours and Fragrances Applications... 

Food, flavour and fragrance products are a good example of natural complex mixtures. The analysis of these matrices may be carried out to ... 

GC using chiral columns coated with derivatized cyclodextrin is the analytical technique most frequently employed for the determination of the enantiomeric ratio of volatile compounds. Food products, as well as flavours and fragrances, are usually very complex matrices, so direct GC analysis of the enantiomeric ratio of certain components is usually difficult. Often, the components of interest are present in trace amounts and problems of peak overlap may occur. The literature reports many examples of the use of multidimensional gas chromatography with a combination of a non-chiral pre-column and a chiral analytical column for this type of analysis. 

Supercritical fluid extraction (SFE) has been extensively used for the extraction of volatile components such as essential oils, flavours and aromas from plant materials on an industrial as well as an analytical scale (61). The extract thus obtained is usually analysed by GC. Off-line SFE-GC is frequently employed, but on-line SEE-GC has also been used. The direct coupling of SEE with supercritical fluid chromatography (SEC) has also been successfully caried out. Coupling SEE with SEC provides several advantages for the separation and detection of organic substances low temperatures can be used for both SEE and SEC, so they are well suited for the analysis of natural materials that contain compounds which are temperature-sensitive, such as flavours and fragrances. 

Replacement of organic solvents by water may be done for environmental, cost e.g. reduction in raw materials and VOC containment costs) or technical reasons. In the flavour and fragrance industry, where the presence of even trace amounts of volatile impurities can be detected by the expert nose , significant process costs are entailed in ensuring complete removal of solvent. If reactions can be carried out in water then these additional costs can be saved. As an example geraniol can be isomerized to the important fragrance intermediates a-terpinol and linalol in water at 220 °C (Scheme 5.9). 

Similarly, low volume chemicals are classified according to whether they are sold primarily on the basis of specification or performance. Specialties are generally formulations that are sold on the basis of their performance and their prices reflect their value rather than cost of production. Producers of specialty chemicals often provide extensive technical service to their customers. Examples of specialty chemicals include pharmaceuticals, pesticides, flavours and fragrances, specialty polymers, etc. Fine chemicals, on the other hand, are produced to customer specifications and are often intermediates or active ingredients for specialty chemicals, e.g. pharmaceutical and agrochemical intermediates and bulk actives. 

In the case of chiral molecules that are biologically active the desired activity almost always resides in only one of the enantiomers. The other enantiomer constitutes isomeric ballast that does not contribute towards the desired activity and may even exhibit unwanted side effects. Hence, there is a marked trend in pharmaceuticals, agrochemicals and flavours and fragrances towards the marketing of products as enantiomerically pure compounds. This, in turn, has generated a demand for economical methods for the synthesis of pure enantiomers (Sheldon, 1993a). 

Mukhopadhyay, Natural Extracts Using Supercritical Carbon Dioxide, CRC Press, Boca Raton, Fla., 2000 Moyler, Extraction of flavours and fragrances with compressed CO2, in Extraction of Natural Products Using Near-Critical Solvents, King and Bott (eds.), Blackie Academic Professional, London, 1993. 

Supercritical C02 extraction coupled with a fractional separation technique is used by producers of flavours and fragrances to separate and purify volatile flavour and fragrance concentrates. Like any solvent, supercritical C02, it allows processing chemicals by predpita-tion or recrystallisation, obtaining partides of controlled size and shape, without excessive fines without thermal stresses and controlling the shape of a polymorphic substance. 

Asymmetric catalysis involving metal catalysed hydrogenations and isomerisations is becoming increasingly important in the production of pharmaceuticals, agrochemicals and flavours and fragrances. More examples of... 

Mosandl A, Capillary gas chromatography in quaflty assessment of flavours and fragrances J Chromatogr 62A-.267—232, 1992. 

Werkhoff P, Brennecke S, Bretschneider W, Progress in the chirospecific analysis of naturally occurring flavour and fragrance compounds, Chem Mikrobiol Technol Lebebsm 13 129-152, 1991. 

K. A. D. Swift, Current Topics in Flavours and Fragrances, Kluwer Academic Publishers,... 

The Flavour and Fragrance Industry-Past, Present, and Future... 

Obviously, these first perfumes were all natural, since the introduction of synthetic aroma chemicals happened only at the end of the nineteenth century. Along with the invention of certain aroma chemicals, the flavour and fragrance... 

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