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Supercritical CO2 extraction of rice bran sterol oil

Rice Bran Sterol Oil

Rice bran and rice bran oil

Rice bran is a by-product of rice processing, accounting for about 6% of the total grain quality, with an annual output of about 14 million tons. In recent years, research on the utilization of high value-added rice bran has been extensive.

Supercritical CO2 extraction of rice bran sterol oil
Supercritical CO2 extraction of rice bran sterol oil


Rice bran is rich in a variety of nutrients, of which the fat content is about 20%, which is a good oil crop.

Rice bran oil

Rice bran oil is a semi-dry oil. The fatty acid ratio is reasonable and the content of unsaturated fatty acids is relatively high. Among them, oleic acid and linoleic acid are the main ones, accounting for about 80%.

Phytosterols in rice bran account for about 81% of the unsaponifiables of oils. Rice bran oil is one of the oils with the most abundant phytosterols. It is rich in vitamin E, oryzanol, squalene and other biologically active substances, and has a variety of physiological health functions for the human body. .

Therefore, rice bran oil is known as “healthy fat”.

Phytosterol

Phytosterols are a class of active substances with cyclopentane perhydrophenanthrene as the skeleton. It has a variety of physiological functions and mainly exists in the roots, stems, leaves and seeds of plants.

It is generally believed that vegetable oils and deodorized distillates contain the most phytosterols.

Phytosterols have a variety of physiological functions such as promoting cholesterol metabolism, reducing cholesterol content, reducing the incidence of coronary heart disease, inhibiting tumors, and regulating immunity. The human body cannot synthesize by itself and must be ingested from external foods. Therefore, it has received widespread attention.

Supercritical CO2 extraction of rice bran oil

Supercritical CO2 extraction

Supercritical CO2 fluid (abbreviated as SCF) is a special state fluid with dual properties of gas and liquid.

Supercritical CO2 fluid extraction technology is a separation method that uses CO2 as an extractant to extract the required components from the material.

Supercritical CO2 fluid extraction technology belongs to low-temperature preparation technology, has good solvent characteristics, and is widely used in the field of oil extraction. It is a new, efficient and green separation technology.

Traditional rice bran oil extraction method

China’s industrial production of rice bran oil mainly uses mechanical squeezing and solvent extraction.

  • Squeezed rice bran oil has good quality and light color, but the oil yield is low;
  • Solvent leaching method, although the oil yield is obviously improved, but the solvent recovery is difficult, there is solvent residue in the oil, and the nutrients in the rice bran meal are destroyed.

Supercritical CO2 extraction

Supercritical CO2 extraction of rice bran oil is to extract oil from the oil by adjusting the solubility of the fluid.

Rice bran oil supercritical CO2 extraction equipment
Rice bran oil supercritical CO2 extraction equipment
Rice bran oil supercritical CO2 extraction equipment
Rice bran oil supercritical CO2 extraction equipment

Compared with the traditional process, the oil yield is high, the quality is good, there is no solvent residue, the nutrients in the rice bran meal are destroyed, the process operation is simple, the safety is high, the fluid selectivity is good, the dissolving ability is strong, and there is no waste discharge. It is called “Efficient and green” process technology.

At present, many researches have been conducted on the supercritical CO2 extraction method to produce rice bran oil.

Supercritical CO2 Extraction of Rice Bran Oil Process 1

Using supercritical CO2 fluid to extract rice bran oil, the best process is as follows: CO2 flow rate 60kg/h, extraction temperature 42°C, extraction pressure 30MPa, time 60min, rice bran oil extraction rate is 94%, unsaturated fatty acid content is 71 % Above.

Supercritical CO2 Extraction of Rice Bran Oil Process 2

Supercritical CO2 fluid was used to extract rice bran oil, and the extraction rate of rice bran oil reached 97.1%. The optimal conditions were determined as follows: extraction temperature 45°C, extraction pressure 30MPa, time 80min, and material water content about 5%~6%.

Supercritical CO2 Extraction of Rice Bran Oil Process 3

Using fresh rice bran as raw material, supercritical CO2 fluid extraction technology is used to prepare rice bran oil. Through response surface regression analysis, it is concluded that the order of influence on the yield of rice bran oil is: extraction pressure>extraction time>extraction temperature, and the extraction rate of rice bran oil is 95.12 %.
The free fatty acid content of the prepared rice bran oil is less than 1%.

Supercritical CO2 fluid extraction of rice bran sterol oil

Phytosterol

The industrial production of plant sterols has a history of more than forty years. The deodorizing distillate of plant oils and fats is used to extract plant sterols and various health products have been developed.

Refining Rice Bran Oil by Supercritical CO2 Fractionation Technology

The supercritical CO2 fractionation technology is used to refine the rice bran oil, and the material in the fractionation column I is used as the raw material, and the rice bran sterol is extracted and purified by the molecular distillation technology, and the sterol content is 63.85%.

Traditional method to prepare rice bran oil

  • Using traditional methods to prepare rice bran oil cannot selectively extract phytosterols in rice bran.
  • In addition, in the process of oil alkali refining and deodorization, a large amount of plant sterols flows into the waste and deodorizing distillate, resulting in a very low content of plant sterols in the finished oil.

Supercritical CO2 Fractional Distillation for Extraction of Rice Bran Sterol Oil

The use of supercritical CO2 extraction method to prepare rice bran oil can not only increase the oil yield and improve the quality of oil, but also can selectively extract plant sterols, combined with supercritical CO2 fractionation technology, using two-extraction four-rectification supercritical CO2 fluid The extraction device refines rice bran oil, which not only can directly obtain food-grade rice bran oil, reduces the refining process, but also reduces the loss of sterols in the rice bran oil.

Sterol content

In the supercritical CO2 extraction method to prepare rice bran oil, the extraction temperature and extraction pressure affect the extraction rate of rice bran oil. It is found that with the increase of pressure and temperature, the extraction rate of rice bran oil increases greatly, and the content of sterols in rice bran oil also increases.

CO2 extraction VS solvent extraction

The experiment shows that the 2L supercritical CO2 extraction equipment of BIT is used to prepare rice bran sterol oil. The extraction rate of rice bran oil is 18.4g/100g, and the sterol content is 2.2%, which is significantly higher than the 1.5% sterol content in the solvent-extracted rice bran oil.

Summary

After refining by supercritical CO2 extraction-fractionation technology, the acid value of rice bran sterol oil is 2.2KOH mg/g, the content of moisture and volatile matter is 0.08%, the total content of gum and wax is 0.37%, and the content of sterol in the oil is 1.69 %, which is significantly higher than the 0.5% sterol content in the commercially available oils and fats.

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