Carotene, an orange fat-soluble compound, contains a large amount of β-carotene (C40H56).
It is widely found in carrots, papayas, mangoes, sweet potatoes and green vegetables. It is an important natural pigment and antioxidant. Beta-carotene is an important source of vitamin A.
It can prevent or delay cancer, prevent cardiovascular disease, and improve the body’s immune function. Carotene has a wide range of applications in the food industry, medicine, health care, cosmetics and other industries.
Among them, natural carotene products with high nutritional content and no toxic and side effects are most popular.
Extraction of natural carotene
At present, the extraction of natural carotene in the world is mainly divided into organic solvent extraction, molecular distillation, supercritical carbon dioxide extraction, ultrasonic assisted extraction, microblog assisted extraction, enzymatic hydrolysis assisted extraction, etc.
C.K. Ooi et al. Used a combination of transesterification and molecular distillation to extract carotene from palm oil to obtain a carotene extract with a content of 80,000 ppm. The carotene recovery rate was 75%.
Harrison et al found through research that the solubility of carotene in supercritical carbon dioxide increased significantly with the increase of pressure, and the method of high pressure (30Mpa) extraction after removing triglyceride with low pressure (10-20MPa) was used to obtain The carotene extract with a content of 3942mg / kg has a recovery rate of 90%.
Supercritical extraction and separation of concentrated carotene samples
In the traditional molecular distillation extraction process, there are organic solvent residues, and too high evaporation temperature will destroy the structure of carotene, and it is difficult to increase the carotene content of the resulting sample. In view of these shortcomings, it is conceivable to use supercritical extraction to carry out supercritical extraction and separation of carotene samples with higher concentrations.
The nature of the solubility of carotene and impurities in supercritical CO2 changes with pressure. The carotene content is further increased during the pressure increase.
Cyclohexane, analytical grade; carbon dioxide, purity ≥99.9%; carotene sample, content 10%.
Supercritical extraction and concentration experiment under fixed pressure
The supercritical CO2 extraction of 10% carotene raw materials was carried out at pressures of 20 MPa and 30 MPa, respectively. Separator and raffinate were collected under different extraction pressures.
Gradient boost supercritical extraction and concentration experiment
Gradient pressure increase method was adopted to gradually increase the extraction pressure and collect the separated substances at pressures of 18 MPa, 24 MPa, 28 MPa, 32 MPa and 36 MPa.
The raw materials were detected by ultraviolet-visible spectrophotometer, the composition of components was detected by liquid chromatography tandem quadrupole time-of-flight mass spectrometer, and the chemical bond type was detected by Fourier transform infrared spectrometer. Spectrophotometer to detect the content of carotene.
Results and discussion
The raw materials were analyzed by liquid chromatography tandem quadrupole time-of-flight mass spectrometer. In addition to β-carotene, there are other carotenoids in the raw materials. The characteristic peaks of 3.62min, 4.34min and 4.58min appearing at the wavelength of 295nm indicate that the raw materials contain natural vitamin E with different configurations.
Infrared detection results
There may be ester compounds such as triglycerides in the sample; the absorption peaks of POC and P = O bonds appear at 1087.41 cm-1 and 1194.71 cm-1, indicating the presence of phosphorus compounds in the sample, considering the source of the sample (palm (Extracted from oil), presumably phospholipid;
Meanwhile, absorption peaks of C = C appear at 964.31 cm-1 and 888.16 cm-1, and may also be absorption peaks of hydroxyl groups at 1087.41 cm-1, presumably containing sterols and vitamins E and other hydroxyl-containing components.
Prompt the raw material composition is complex.
Effect of fixed extraction pressure on the content of carotene in extract and raffinate
The extraction experiments were conducted at 20 MPa and 30 MPa, and the extract and raffinate were collected. At 20 MPa, the extract content was 4.04% and the raffinate content was 13.40%;
When the extraction pressure increased to 30MPa, the extract content increased to 9.74% and the raffinate content increased to 13.64%. Although the content of raffinate has increased, the increase in content is not obvious. Therefore, it is difficult to concentrate the carotene content by direct extraction.
Gradient boost extraction experiment
To this end, we designed a gradient boost extraction experiment on this basis.
In the gradient pressure extraction, after putting a certain amount of raw materials, the extraction pressure is gradually increased from 18MPa to 36MPa, and the extract under each pressure is collected.
With the gradual increase in extraction pressure, the content of carotene in the isolate increases High, reaching the highest at 24MPa, which is 20.14%. The content of carotene in the isolate is higher than that under the corresponding fixed pressure, which may be due to the solubility of triglyceride, vitamin E and other impurities in the sample in CO2 at low pressure. High, caused by the first removal during the gradient boost.
The decrease of carotene content in the isolates with the increase of pressure in the later period may be due to the limitation of the total carotene content in the samples.
The composition of 10% carotene raw materials is complex, and it is difficult to increase the content of carotene by supercritical CO2 extraction at a fixed pressure.
Use of supercritical CO2 gradient pressure extraction method can concentrate 10% of natural carotene samples to 20.14%, optimized Later, the concentration is expected to increase further.