Chemically Defined Flavouring Substances

A flavouring substance is a defined chemical component or substance with flavouring properties (Tab. 3.3). Various synonyms are in use, e.g. flavour substance, flavour chemical, flavour(ing) component, flavour(ing) compound, flavouring agent, aroma compound, aroma chemical, and others. Since flavour includes both taste and odour, a flavouring substance may be a substance that causes either taste or odour impressions, or both. 

Flavouring substances that cause only taste impressions are defined as substances that are usually non-volatile at room temperature. Therefore, they are only perceived by the taste receptors [7]. Examples are sucrose (sweet) or caffeine (bitter). Flavouring substances causing odour impressions are volatiles that are perceived by the odour receptors [7]. Examples are ethyl butyrate or dimethyl sulfide. Some flavouring substances are perceived by taste and odour receptors (e.g. acetic acid, butyric acid). 

Elavouring substances may be classified into natural, nature-identical, and artificial flavouring substances (Tab. 3.3). These will be discussed below in detail. 

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CE. 2000b. Chemically-defined Flavouring Substances. Council of Europe, Strasbourg, Cedex, France. 

In amending the Flavour Directive, Article 5, the Commission has prepared a draft Proposal for a council directive establishing a list of flavouring substances used in foodstuffs following the SCF guidelines for the evaluation of flavourings for use in foodstuffs I. Chemically defined flavouring substances [16],... 

Commission Regulation (EC) No. 622/2002 of 11 April 2002 establishing deadlines for the submission of information for the evaluation of chemical defined flavouring substances used in or on foodstuffs, Official Journal of the European Communities L 95/10-11 of 12.4.2002 Regulation (EC) No. 2065/2003 of the European Parliament and of the Council of 10 November 2003 on smoke flavourings used or intended for use in or on foods, Official Journal of the European Communities L 309 of 26.11.2003... 

Chapter 3 deals with the raw materials which are of interest for the flavour sector. The topics range from chemically defined flavouring substances, both of natural and synthetic origin, to flavouring preparations and source materials, such as complex natural extracts, essential oils and juices. Eurthermore, process flavourings and nonflavouring compounds which are important for food technology are also presented. 

Contrary to microbial flavour generation directly in the food by starter cultures, the technical bioreactions for flavour production with micro-organisms do not use the complete food raw material as substrate. Isolated and purified single components of food are used as substrates for the micro-organisms. Examples are butterfat from butter, proteins from meat, carbohydrates from plant food materials. Microbial material syntheses may lead to chemically defined pure substances (cf. chapter 3.2.1.1.2). It is also possible to obtain complex mixtures of different compounds. Polysaccharides, natural colours and also complex flavour extracts belong to this category. Figure 3.17 outlines the principle of such processes. 

Flavouring substances are chemically defined substances with flavouring properties. There are three different categories of flavouring substances defined in the definitions of the lOFI Code of Practice and EU Flavour Directive 88/388/ EEC [1,2] ... 

In Europe chemically defined substances with flavouring properties, which are obtained by chemical synthesis, are defined in the European Union Flavouring Directive 88/388/EEC [6], article 1 No. 2(b) (ii) and (iii) in two categories (see 7.1 and 7.4.2) ... 

These flavouring substances are defined by the criterion that the flavouring substance is not chemically identical to a substance naturally present in materials of vegetable or animal origin. 

Micro-organisms also have a potential to form fruity components like alcohols, esters, lactones, ketones and terpenes. These substances are, however, also obtainable by chemical syntheses as well as by relatively simple extraction from the natural fruit. Additionally, fermented fruit flavours in many cases are not very typical for a certain fruit species and therefore may be used only as raw materials for compounded flavours. Presumably this is the reason why the corresponding processes have not yet been transferred onto an industrial scale. This is not true for the fermentative generation of well defined single substances which may serve as natural flavour raw materials for compounded flavours (cf. chapter 3.2.1.1.2). 

Smoke flavourings are either smoke condensates or smoke preparations. Smoke flavouring blends produced by mixing chemically defined substances are not on the market because they would be more expensive than the products made from traditional smoke. 

Natural flavouring Consisting of simple substances, chemically defined, or of compounds extracted from vegetables, or sometimes animal substances, natural or manufactured, suitable for human consumption, exclusively by physical means. 

Artificial flavourings Aromatic substances, chemically defined which are not found in natural products, and which are obtained by organic synthesis, and compounded or not with natural flavourings or nature-identical flavourings. 

In flavourings that are not chemically defined compounds, but mixtures of many substances, the following can be distinguished ... 

Defined chemical substance with flavouring properties... 

Regardless of this problem biotechnically produced flavour extracts are very attractive. Under properly defined conditions biotechnical reactions allow a significant increase of yield or strength of the flavours compared to purely natural flavours. It is also practised to run biotechnical reactions in such a way that the purity of the produced flavours is increased and undesired side products are suppressed. In comparison to the complicated chemical syntheses of pure isomers of flavours chemicals, the biotechnically manufactured substances are generally homogeneously composed by nature . 

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