Cumin, also known as Cuminum cyminum L., is an annual herb of Cuminum L., which belongs to Umbelliferae. Its flavor substance mainly exists in the volatile oil of fruit.
Cumin seeds contain 2% – 5% volatile oil, mainly terpenes, aromatic aldehydes, ketones and ethers. Cumin aldehyde, one of its main components, has many physiological functions.
At present, there are many researches on extraction technology and components of cumin oil at home and abroad, including steam distillation, simultaneous distillation extraction, supercritical extraction and organic solvent extraction.
However, the above-mentioned extraction methods have different effects on the product quality.
For example, in the water vapor method, due to the long-term contact between raw materials and water vapor, some fragile aroma components are easy to be destroyed and decomposed; in the solvent method, the residual solvent will affect the product safety; in the supercritical method, due to its special extraction system, some oils and pigments in the seeds will be obtained at the same time as the essential oil. And so on.
The area normalization method is the most widely used method in the quantitative analysis of cumin essential oil, but it is only suitable for all components that can flow out of the chromatographic column and have response on the detector. As the composition of cumin oil is very complex, it is difficult to fully meet the above conditions, so the area normalization method for quantitative analysis may cause significant errors.
Molecular distillation (MD) is a new high-tech used in liquid-liquid separation.
According to the difference of average free path of molecular movement, MD can separate the mixed components. Because MD is a pure physical method and it is carried out under high vacuum, and the separation temperature is very low, it is especially suitable for separation of high volatility, high relative molecular weight, high boiling point, high viscosity and thermal sensitivity.
For example, octacosanol is extracted from rice bran, fatty acids and VE are extracted from grape seed oil, and VE is extracted from rape seed oil. Molecular distillation has carried out a wide range of research on spices, such as the purification of patchouli oil, Litsea cubeba oil, star anise oil, garlic oil, pepper essential oil and so on.
SFE & MD
In this study, cumin essential oil was extracted and purified by supercritical co2 fluid extraction combined with molecular distillation to ensure the natural characteristics of the product to the greatest extent.
The main aroma components were screened repeatedly by GC-MS combined with double column qualitative method. The main aromatic substances β – pinene, Cymene, γ – Terpinene and cumin aldehyde in cumin oil were quantitatively analyzed by internal standard curve method.
Through comparing the content of cumin aldehyde before and after purification, the purification effect of molecular distillation on cumin essential oil was evaluated.
Extraction of cumin Oleoresin by supercritical co2 extraction
First, 1 kg of cumin powder is crushed to 40 mesh and evenly filled in the extraction kettle.
After purification, CO2 enters the condensation tank and condenses to the fluid.
After pressurized to 35 MPa by high pressure metering pump and heated to 40 ℃ by heater, it enters the extraction kettle for 2.5 h.
The CO2 dissolved with cumin oil resin enters the separator through pressure reducing valve, and the pressure drops to 6 MPa. CO2 vaporizes, and cumin oil resin is separated and deposited in the separation kettle.
The bottom is discharged and collected by the oil drain valve, and the CO2 gas enters the storage tank and merges with the CO2 from the steel cylinder, which is closed and recycled in the whole device.
The product is a dark brown viscous liquid with a yield of 13.56%. It can be used for the next step of molecular distillation and purification.
Experimental conclusion on Extraction of cumin Oleoresin by supercritical co2 extraction
The essential oil of cumin was extracted and purified by supercritical combined molecular distillation.
The volatile components of cumin essential oil were qualitatively analyzed by GC-MS and double column retest.
44 components were identified on DB-5 column and 39 components were identified on inno-wax column, 20 of which existed on both columns. A method for the simultaneous determination of the main aromatic compounds (β – pinene, paracymene, γ – Terpinene, cumin aldehyde) in cumin oil by capillary gas chromatography with n-dodecane as internal standard was established.
The results showed that there was a good linear relationship between the peak area of four aromatic substances and their mass concentration under the selected chromatographic conditions, and R2 was greater than 0.9996. After molecular distillation and purification, the content of cumin aldehyde, the main component of cumin essential oil, increased from 11.48% to 30.30% before purification.
Pulverization degree: 40 mesh
Extraction pressure: 35 MPa
Extraction temperature: 40°C
Extraction time: 150 min
Yield ： 13.56%