Isolating flavouring materials

It should be no surprise that the methods used to produce most flavourings from plant sources are based on similar principles as those used in the isolation of aroma compounds from foods. However, economics and scale play major roles in dictating methods. Additionally, the physical characteristics of the plant material, and concentrations and properties of flavouring materials also... 

Isolation of Flavouring Materials from Waste Streams... 

H. Surburg and J. Panten, Common Fragrance and Flavour Materials, 5th Edition, Wiley-VCH, Weinheim, 2006, ISBN 3-527-31315-X. P.Z. Bedoukian, Perfumery Synthetics and Isolates, D van Nostrand, 1951. 

Soya Proteins. Early attempts to make albumen substitutes from soya protein also ran into problems. A bean flavour tended to appear in the finished product. A solution to these problems has been found. Whipping agents based on enzyme modified soy proteins are now available. The advantage of enzymatic modification is that by appropriate choice of enzymes the protein can be modified in a very controlled way. Chemical treatment would be far less specific. In making these materials the manufacturer has control of the substrate and the enzyme, allowing the final product to be almost made to order. The substrates used are oil-free soy flakes or flour or soy protein concentrate or isolate. The enzymes to use are chosen from a combination of pepsin, papain, ficin, trypsin or bacterial proteases. The substrate will be treated with one or more enzymes under carefully controlled conditions. The finished product is then spray dried. 

In the legal sense a flavouring substance must comply with certain criteria if referred to as natural . For example, it must be obtained from material of vegetable or animal origin, isolated by physical, enzymatic or microbiological processes. 

Isolation of Flavour from Plant Materials for Commercial Use... 

Natural raw materials are of high importance in flavour development. Natural isolates (Table 21.2) serve as a basis for most natural flavourings which can be blended with single natural aroma chemicals. The performance of nature-identical flavourings will be supported by using extracts and oils as they significantly enhance the complexity of flavourings and increase their authenticity. 

Valencene (5), a sesquiterpene hydrocarbon isolated from orange oils is used as starting material for the synthesis of nootkatone (6), which is used for flavouring beverages [26] and which is a much sought-after aromatic substance [131]. 

Nature-identical flavouring substances. These are substances chemically isolated from aromatic raw materials or obtained synthetically. They are chemically identical to substances present in natural products intended for human consumption, whether processed or not. 

The synthesis of nootkatone occupied many chemists for some years and has given us some excellent examples of fragmentation reactions. However, the synthetic samples of nootkatone failed to deliver the intense grapefruit taste and smell of the material from grapefruits. The reason is simply that nootkatone is not the flavour principle of grapefruit The samples of nootkatone isolated from grapefruit contained minute traces of the true flavour principle—-a simple thiol. Humans can detect 2 x 10-5 p.p.b. (yes, parts per billion) of this compound, so even the tiniest trace is veiy powerful. At least the syntheses allowed chemists to correct an error. 

Table 2.10 shows that the isolation and purification of naturally occurring flavour chemicals and extracts from animal and plant raw materials is most important for the preparation of natural flavours. About 75% of the commercially used flavours come from such natural sources. Physico-chemical reactions of typical flavour precursors may also lead to natural flavouring substances when mild conditions ( kitchen technology ) are applied. In addition, natural flavour chemicals may be prepared by biotechnological processes. This chapter outlines the most important biotechnical manufacturing techniques. 

It is the role of technical bioreactors in such advanced systems to create a specifically defined environment for the biochemical reaction system producing or modifying flavour substances. The most important purpose of such bioreactors is the well controlled combination of food raw material and flavour precursor, respectively, with the biological reaction centres. It also provides the means for survival and maintenance of the centre s metabolic activity. Presently there is laboratory and partially also industrial experience with mostly all kinds of different micro-organisms and isolated biocatalysts ... 

The first raw materials for the flavour industry included extracts, tinctures, oleoresins, juice concentrates, essential oils, and a few synthetic chemicals (Tab. 3.1). Up to the 1950s, flavour research was concentrated on the isolation, stmcmral analysis, and synthesis of just a few quantitatively outstanding natural materials (Tab. 3.1). The situation changed dramatically with the advent of gas chromatography as a means of analysis, especially in conjunction with mass spectrometry. 

Flavouring substance obtained by synthesis or isolated through chemical processes from a natural aromatic raw material and chemically identical to a substance present in natural products intended for human consumption, either processed or not... 

Flavouring substance obtained by chemical synthesis or isolated by chemical processes and which is chemically identical to a substance naturally present in material of vegetable or animal origin... 

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. 

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