Chemistry of hydrocarbon compounds – Purification – separation – or recovery – By addition of extraneous agent – e.g. – solvent – etc.
Patent
1997-02-19
1998-08-04
Griffin, Walter D.
Chemistry of hydrocarbon compounds
Purification, separation, or recovery
By addition of extraneous agent, e.g., solvent, etc.
585803, 585351, 585867, C07C 700, C07C40300
Patent
active
057896470
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a process for the extraction of carotenoid dyes from natural starting materials using compressed gases.
Carotenoids are yellow to deep-red coloured polyene dyes which are widespread in the plant and animal kingdom. Their colour is based on a tetraterpenoid structure with conjugated double bonds. The carotenoids are differentiated according to their functional groups into carotenes (pure hydrocarbons) and xanthophylls (having polar substituents on the carbon skeleton). The obsolete term "lipochromes" takes into account the liposoluble properties of these dyes.
The food industry has traditionally made use of their strong colouring action and their manifold applications. Although carotenoids are widespread in nature, industry was for a long time not sufficiently able to exploit productive sources from which larger quantities of carotenoids could be obtained commercially. The methods of the synthetic chemical industry were the first to lead to the production of synthetic carotenoids in lower cost ranges.
The increasingly more critical conduct of consumers and the resulting demand for "natural" foods and dyes has now set the task for the modern food technology to provide food additives that are derived form natural sources and have furthermore been processed mildly and naturally. Fermenting processes have recently enabled carotenoids to be obtained microbiologically and thus naturally and in large amounts.
A wide variety of processes have been developed in the past for the isolation of carotenoid dyes from natural sources. Thus for example the U.S. Pat. No. 2,170,872 describes a method for the extraction of carotenoids in which the plant material is treated with sodium hydroxide solution in order to break up the fat-soluble matrix components, it is then heated with steam and finally extracted with petroleum ether or hexane. Subsequently the extract obtained in this way has to be distilled with steam and the aqueous phase has to be extracted again with an oil. The oily solution that is formed is used as a colourant.
The use of organic solvents is still widespread in order to obtain carotenoids in larger amounts starting from dried natural products. Such a method is described in the U.S. Pat. No. 1,988,031 according to which plant material, in particular carrots, is firstly admixed with lipophilic solvents such as propyl alcohol in order to precipitate the carotenoid dyes in this manner. The carrot powder obtained in this way is subsequently repeatedly extracted with petroleum ether and concentrated during which the carotenoid dyes crystallize more and more.
WO 92/18 471 offers a solvent-free process. In this process the extract derived from plant material is separated into a liquid fraction containing carotenoids and into a pulp and the liquid fraction is admixed with salts such as CaCl.sub.2 which precipitates the carotenoids.
However, in principle it has proven to be advantageous to remove accompanying fatty substances during the extraction of carotenoids which would otherwise pass into the extract and subsequently,--in particular at low carotenoid concentrations,--impair crystallization of the dyes. Due to this experience a procedure has often been used in which the interfering oils are saponified such as for example according to U.S. Pat. No. 2,032,006. The process described there utilizes the finding already described by Preston et al. (Food Chem. 5(1), 47, 1980) that high process temperatures should be avoided when isolating carotenoids, since these compounds are very thermolabile and tend to isomerize their double bonds and/or decompose at high temperatures.
The rapid development of the extraction of natural substances with the aid of for example compressed gases has enabled carotenoid dyes to be isolated under milder processing conditions than those described above. Thus in U.S. Pat. No. 4,400,398 an extraction method is described with supercritical CO.sub.2 that proceeds in several steps in which aromatic compounds (peppery substances) are firs
REFERENCES:
patent: 4345976 (1982-08-01), Peter et al.
patent: 5310554 (1994-05-01), Haigh et al.
Cully Jan
Heidlas Jurgen
Vollbrecht Heinz-Rudiger
Wiesmuller Johann
Griffin Walter D.
Preisch Nadine
SKW Trostberg Aktiengesellschaft
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