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Supercritical Fluid Extraction in Natural Pigments

     Food coloring is an important part of food additives, not only widely used in food industry to improve the color of food, but also widely used in medicine and cosmetics.


     Before the middle of 19th century, people used natural pigment to color. Since 1856, W.H. Perkins invented the first synthetic organic pigment aniline violet, many organic pigments have been synthesized one after another. Due to their bright color, stable properties and low cost, these pigments quickly replace natural pigments. With the development of science, many synthetic pigments have been found to be harmful to the human body. In addition to its own chemical properties endanger human health, but also in the synthesis process, may also be arsenic, aluminum and other harmful substances. Therefore, many countries in the world have banned the use of many synthetic pigments. According to statistics, there are 90 kinds of synthetic pigment varieties that have been used as food in various countries in the world. However, there are only a dozen or so kinds of synthetic pigment varieties widely used in various countries at present. Some countries, such as Norway, have completely banned the use of any synthetic pigment. China approved the use of synthetic pigments only carmine, amaranth, lemon yellow, indigo, Japan East yellow and so on. In this case, people's interest in natural pigments has greatly increased, and recent studies have found that most natural pigments have certain physiological functions, such as natural β-carotene in the prevention of cancer, cancer and prevention of cardiovascular disease Has a significant effect; α-carotene on adrenal cancer, gastric cancer, uterine cancer has a good anti-cancer effect, and its role than β-carotene much greater; lycopene in carotenoid antioxidant the strongest, its Disease prevention, disease resistance is better than β and α-carotene. Anthocyanins can treat circulatory disorders and angina. Functional natural pigments not only give food bright, lifelike luster, but also have health care functions to the human body, in line with the trend of the development of modern functional foods, is the new trend of development of natural pigments.


     Supercritical fluid extraction is a new emerging extraction and separation technology in the food industry. Compared with the traditional chemical solvent extraction method, its superiority is no chemical solvent consumption and residue, no pollution, avoid heat degradation of the extract at high temperature, protect the activity of the physiologically active substance and maintain the natural flavor of the extract and so on. The following describes the application of supercritical fluid extraction in natural pigments.


Second, the supercritical fluid extraction

     Supercritical fluid extraction is the extraction process using fluids above the critical temperature and critical pressure as the solvent. The fluid near the critical point not only has a very high solubility of the substance, but also the solubility of the substance varies with the pressure or the temperature of the system, so that the selective extraction of the separated substance can be easily carried out by adjusting the pressure or the temperature of the system .

The application of supercritical fluid extraction in food, mainly for nearly 20 years. In 1974, Zosel first studied the extraction of caffeine from coffee by supercritical fluid extraction. For the first time in 1978, Hag AG established an industrialized process and equipment for removing caffeine from coffee beans. It is a supercritical fluid extraction applied to the food industry Important milestone. At present, supercritical fluid extraction has been widely used in the extraction and separation of oils, cholesterol, flavors, fragrances and pigments. Supercritical fluid extraction In food processing, almost all use of CO2 as an extractant. CO2 is not only a very strong solvent, it can extract a wide range of compounds in food processing. In contrast, CO2 is stable, inexpensive, non-toxic, non-flammable and recyclable. CO2 preparation costs low, available high purity gas, no residue. The lower critical point of CO2, the criticality of 31.1 ℃, the critical pressure of 7.38MPa, it is particularly suitable for extraction of volatile and heat-sensitive substances. Compared with the traditional solvents n-hexane, methylene chloride, has significant advantages.


Third, the application of supercritical fluid extraction in natural pigments

     The nature of supercritical CO2 is similar to that of n-hexane and is therefore particularly suitable for the extraction of fat-soluble ingredients. Such as β-carotene, capsanthin, Cigar orange, lutein and so on. In addition, by using different entrainer, you can change the polarity of CO2, so that the extraction range to expand, can extract more polar pigments such as tea polyphenols, ginkgo flavonoids.

1. Extraction of carotene by supercritical CO2 In the past, carotenoids were mainly extracted with organic solvents such as n-hexane, which not only consumed a large amount of solvent, but also eliminated all the solvents and avoided the toxicity caused by solvent residue. Supercritical CO2 extraction can replace the traditional solvent method, effectively extract carotene. Yu Enping and other supercritical CO2 extraction of seaweed carotene. With acetone as entrainer, can improve the extraction rate.

Lyophilized alfalfa leaf protein concentrate

Carotene and lutein

Extraction temperature 40 ℃, CO2 flow 5 ~ 6Lmin, extraction pressure> 30MPa can be extracted β-carotene; 70MPa can extract 70% of lutein.



The β-carotene extracted by supercritical CO2 from cold-dried potato tissue increased by 5-fold and 3-fold, respectively, compared with the high-temperature drying and fresh tissue extraction. The supercritical CO2 extraction at 20 Mpa and 48 ℃ resulted in 93.6% β- carotene.

Freeze dried carrots

β- and α-carotene

The optimum conditions of supercritical CO2 extraction temperature 50 ℃, pressure 300atm, 10% ethanol as entrainer, extraction time 1hr, β-carotene 475ug / g, α-carotene 600ug / g. M. Margare. Bartn et al. (1995)

Carrot press cake

β- and α-carotene

99.2% of β-carotene can be obtained by using 10% ethanol as the entrainer. The extraction temperature and entraining agent play a major role, and the pressure has little effect. The response surface model of β-carotene is obtained.

2. Supercritical fluid extraction of capsanthin Capsanthin Industrial use of ethanol or n-hexane and other extracted from paprika pepper oil resin, and then after the separation of the hot pepper capsaicin-free resin, and then separated by hot pepper Su-hot red-hot liquid - red pepper. Due to the oily nature of capsanthin, the removal of residues (solvents such as n-hexane, etc.) in the solvent-extracted products can hardly reach the standards of FAO and WHO, which greatly affects their use and export earnings. Extraction of capsanthin from ground chilli by supercritical CO2. The optimum extraction conditions were particle size <1.2mm, pressure 15MPa, extraction temperature 50 ℃, flow 6M3 / hr. Wu Lianzeng, etc. extracted from the red chilli pepper capsanthin (including solvent 10000mg / kg or more) for purification. The best extraction conditions for 18Mpa, 25 ℃, flow 2.0L / min. Residual solvents up to 20mg / kg or less.

3. The maximum solubility of pure annatto in CO2 is 0.003 mg / g, while the maximum solubility of the rouge seed pigment is 0.026 mg / g. Increasing the solubility of the pigment in CO2 increases the solubility, but does not increase the pressure solubility at the same temperature. Vegetable oil as entrainer can increase the extraction rate of rouge orange.

 Supercritical CO2 natural pigment extracted from the birch tree seed, the results show that the extraction of pigments are mainly rouge orange and nocturnal orange. Nocturnal orange is more extractable than nocturnal orange. The rouge orange is easier to extract than the rouge orange, the extraction temperature is 50 ℃ and the pressure is 310bar, the higher total pigment yield can be obtained.