Process for extracting carotenes from carotene-containing...

Chemistry of hydrocarbon compounds – Purification – separation – or recovery – By addition of extraneous agent – e.g. – solvent – etc.

Reexamination Certificate

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C585S862000, C585S860000, C585S864000, C585S351000

Reexamination Certificate

active

06407306

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims benefit of priority under 35 U.S.C. §120 to International Application PCT/EP99/03219, filed May 11, 1999, and under 35 U.S.C. §119 to DE19821009.4, filed May 11, 1993.
The present invention relates to a process for extracting carotenes from carotene-containing materials, in particular from fats and oils of biological origin. though the invention shall chiefly be explained through the example of carotene, the term “carotenes” encompasses not only the isomers of carotene but also carotenoids.
According to a definition by IUPAC, carotenoids are chemical compounds of aliphatic or aliphatic-alicyclic structure having conjugated double bonds and comprising 3 to 8 (or even more) isoprene moieties.
The carotenoids are the most important group of natural colouring materials most widely occurring in plants and animals. They are fat-soluble, nitrogen-free, yellow to violet materials, wherein the uninterrupted sequence of isoprene moieties and thus the chromophoric accumulation of conjugated double bonds gives rise to colouring. All carotenoids being polyenes, they exhibit a blue solution color in concentrated sulphuric acid.
Carotene is the carotenoid which has been known for the longest time. It was isolated for the first time by H. Wackenroder (in 1831) from carrots. About 100 years after its discovery, Kuhn found in 1931 that the naturally occurring carotene is composed of three isomers which he named &agr; carotene, &bgr;-carotene and &ggr;-carotene. In the untreated carotene of carrots, they are contained at proportions of about 15, 85, and 0.1%, respectively. Ever since the first carotenoid syntheses by P. Karrer and H. H. Inhoffen (1950), a rapid development commenced in the field of commercial syntheses of carotenoids.
All three carotene isomers possess the same fundamental structure, comprising one &bgr;-ionone ring structure at one molecule end, 9 conjugated double bonds and 8 branchings. They differ only in the structure of the other molecule end.
Depending on its origin, carotene is a varying mixture of the structurally isomeric polyene hydrocarbons C
40
H
56
: all-trans-&agr;-carotene, all-trans-&bgr;-carotene, all-trans-&ggr;-carotene. Depending on processing and starting material, cis isomers may also occur.
Carotene occurs not only in carrots but also in numerous other plants, and particularly accompanying chlorophyll it counts among the most frequently occurring plant coloring materials. Carotenes are present in vegetable oils at moreor less elevated concentrations. The carotene contents are particularly high in palm oil, in the ranging from 0.05 to 0.2%.
Raw carotene is a dark coppery to cinnabar-colored crystal powder of wax-like consistency. Its solution color is yellow to orange.
&bgr;-Carotene is the carotene occurring most frequently in animals and vegetables. It forms deeply violet prisms (crystallised from benzene/methanol) or polyhedra (from petroleum ether). Its solubility in grams per 100 cm
3
of solvent at 19° C. is 5.5 in carbon disulfide; 0.35 in benzene; 0.1 in petroleum ether; 0.008 in ethanol. It is optically inactive. &agr;-Carotene forms deeply violet prisms (from benzene/methanol) or polyhedra (from petroleum ether). It is optically active and more readily soluble than &bgr;-carotene. &ggr;-Carotene forms dark red prisms (from benzene/methanol). It is optically inactive and also more readily soluble than &bgr;-carotene.
Carotene is merchandised in the form of the following preparations: crystallised &bgr;-carotene in vacuum ampoules; technically crystallised at about 80%; carotene concentrates in powder form at about 3%; carotene solutions in vegetable oils at about 0.3 to 0.5%.
Carotenes, being polyene hydrocarbons, exhibit good solubility in tetrahydrofuran, carbon disulfide, benzene, chloroform and oils, low solubility in ether and petroleum ether. All carotenes are insoluble in water. In fats and oils of biological origin, their solubility typically is 2 to 3%. Almost all carotenes have high melting points (e.g., &bgr;-carotene 183° C.). They are sensitive to acids, oxygen and exposure to light.
The carotenes, have gained importance in nutrient technology as antioxidants and as natural colouring materials. They predominantly serve for coloring fats and oils, for vitamin enrichment of margarine, nutrient preparations, and pharmaceuticals, as an addition to concentrated feed in rearing young animals and to ice creams or sherbets and milk preparations.
The carotenoids, being hydrocarbons or compounds closely related to hydrocarbons, are markedly lipophilic. (Carotenoids of the polyene alcohol type dissolve well in alcohol and acetone.) All-trans forms do not dissolve as well as corresponding cis compounds. Carotenoids occur in nature almost exclusively in solution in the lipoid particles of the cell, for which reason they are at times referred to as lipochrome colouring materials. From the dried cell substance they can be extracted only by means of lipophilic solvents. The commonly known fact that the carotenoids of our nutrient plants, e.g., the lycopene of the tomato, enrich in the fat globules of the foods prepared from them, is founded in this lipophilic character.
H. V. Euler realised (in 1928) the property of carotene being provitamin A. &bgr;-Carotene is related to vitamin A, which latter one may be conceived to be formed by cleavage of the central C═C double bond of the carotene with concomitant incorporation of two molecules of water. Biosynthesis of vitamin A also appears to unfold in this way. At least the animal body is capable of transforming in most cases carotene, especially &bgr;-carotene, into vitamin A. This is of interest inasmuch as a vitamin A deficiency may be remedied through easily obtained foods which contain carotene.
For obtaining the carotene, the natural material is dried mostly at temperatures below 50° C., and the carotenes are extracted with lipophilic solvents. Jointly dissolved accompanying substances are separated out either by saponification or by freezing out. Crystallised raw carotene (75-90%) or oil-based carotene concentrates (1-20%) are obtained. Of the isomers, only &bgr;-carotene is obtained pure. Starting products are either such having a high carotene content, like carrots (1 g of raw carotene/kg of dry substance), raw palm oil (up to 3 g/kg), pumpkin seeds or green plants such as lucerne (alfalfa), stinging nettle or broccoli (Brassica), from which xanthophyll and chlorophyll are furthermore obtained besides carotenes.
For the extraction of carotenes from dry plants, petroleum ether, naphtha, less frequently benzene, fatty oils are used, or also trichloroethylene in the case of red palm oil. For obtaining them from carrots, autumn carrots [Herbstmöhren] are suited best, which should contain at least 10 mg % [mg/100 ml] of carotene for 10-15% dry substance. One starts out from dried carrots (dry processing method) or from material processed in the autoclave and pressed hydraulically (wet processing method). The dry method procures a yield of 67 g of carotene/1000 kg of carrots. In the wet method, extraction is performed with tetrahydrofuran and provides a yield of 62-72 g of carotene from 1000 kg of carrots having a carotene content of 90-100 g.
The most important cultivation areas for oil palms are Africa, Indonesia, Malaysia and Brazil. Depending on their origin and freshness condition, palm oils have a bright yellow (predominantly &agr;-carotene), red (lycopene), orange (predominantly &bgr;-carotene) or reddish brown (presence of chlorophyll) coloration. In general, the raw oil is processed with alkali into low-water soaps from which the carotenoids are extracted with benzene, trichloroethylene or petroleum ether. The yield is approximately 80-90% of the overall carotenoids of the oil. From 1000 kg of palm oil, one obtains about 3-4 kg of carotene extract (containing 20% carotene, 6.5% lycopene and 6% volatile oils).
The recovery of the carotenes present in oils and fats by way of saponification of the glycerides

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