According to the production needs of different grades of camellia oil, camellia oil industrial extraction and preparation methods mainly include the production of the more mature mechanical pressing method, solvent extraction method, supercritical fluid extraction method. China's camellia oil production generally take the mechanical pressing method and solvent extraction method.
Mechanical pressing method
Mechanical pressing method is the basic way of extracting camellia oil, camellia oil pressing has gone through several stages, such as earth pressing (mainly wedge pressing), hydraulic oil pressing and screw oil pressing. According to the different temperatures of the tea seeds in the press chamber during the pressing process, the first two are usually called low-temperature pressing process, and the latter is called high-temperature pressing process.
Low-temperature pressing method
At present, in the rural areas of the oil tea production areas are often used in the hydraulic oil extraction process to extract camellia oil, the process of obtaining less impurities in the tea oil, light color, is now the mainstream of the extraction of camellia oil preparation process. Hydraulic oil press has vertical and horizontal two structures, the actual production of horizontal hydraulic oil press mostly.
Commonly used low-temperature extraction of camellia oil process: tea seed → low-temperature storage → cleaning and grading → magnetic separation of a shell → rolling → cold pressing → dregs separation → gross tea oil → low-temperature crystallization of crystalline → low-temperature filtration → tea seed cake → leaching Cold pressed oil
Low-temperature cold pressing of the key process quality control points for the low-temperature storage, cleanup and grading, cold pressing, dregs separation. In the low-temperature storage process, the temperature is controlled at 0-7°C, which is conducive to the maturing of camellia seeds; in the cleaning and grading process, grading is carried out according to the different particle sizes, and then the raw materials with more uniform particles are threshed to ensure the efficiency of hulling; a special cold press is used in the cold pressing process, and the cold pressing temperature is at 70-80°C, which can avoid the high temperature caused by the darkening of the color of the oil, the loss of active ingredients, etc. In the cold press, the oil is extracted by the cold press, and the residues are separated from the residues, and the residues are separated from the oil. In the oil residue separation process, the separation time and retention time should be controlled, and the oil need not pass through the sedimentation tank when filtering.
High-temperature pressing method
The high-temperature pressing method mainly adopts the screw oil press for dynamic pressing. The instantaneous pressing temperature of the oil in the press chamber is high, which has an effect on both the oil and the press cake, such as more impurities and dark color of the gross tea oil, which reduces the refining rate of camellia oil. Therefore, screw press oil in the process requires shelling of tea seeds.
The key process quality control points of high temperature pressing method are shelling, steaming and pressing. In the shelling process, after drying the tea seeds (moisture content of 12% -14%), into the tea seed shelling machine to break the shell, followed by wind sorting, kernel and shell separation; in the steaming and frying process, the tea seed kernel should be moisture and temperature regulation, control of the moisture of the tea seeds in the press at about 3%, into the pressing temperature of 110-120 ° C; in the pressing process, the continuous dynamic pressing, the gross tea oil from the press uninterruptedly released. In the pressing process, through continuous dynamic pressing, the gross tea oil is uninterruptedly released from the press.
Mechanical pressing method has the advantages of simple and flexible process, adaptability, low cost, investment, no solvent residue in the pressed oil, but its oil yield is not high, the data show that the yield of about 80%, and because of the high content of reducing sugar, total sugar, starch in the kernel of the camellia seed, the oil is easy to press the method of meladic reaction, so that the color of the fat is deepened, thus increasing the amount of activated clay in the process of decolorization. The dosage of activated white clay in the decolorization process will be increased. In addition, due to the mechanical pressing method of raw materials need to be stir-fried or baked heat treatment, proteins will be denatured, the comprehensive utilization value of oil extraction cake meal decreased, and residual oil in the residue rate is high, still need to be solvent leaching.
Solvent leaching method
Solvent leaching method is the 1970s after the rise of an oil method. Solvent leaching is the use of some organic solvents (such as hexane, petroleum ether, anhydrous ethanol) to dissolve the properties of oil and grease, the material billet or pre-press cake in the oil extraction method. The basic process of pre-press leaching, direct leaching and 2 times leaching 3 ways.
Solvent extraction to get rid of the oil process: oil → billet (or billet pre-pressing) → solvent leaching → mixed oil separation → oil refining → finished meal ← meal desolvation
Scientific researchers compared the effect of several different solvents on the extraction of camellia oil, the results show that, with petroleum ether as the solvent for the extraction of the material-liquid ratio of 1:10, the extraction temperature of 50 ° C, the extraction of two, each time, 3 hours, the extraction of camellia oil, the extraction of the oil, the extraction of the oil and the extraction of the oil. The results showed that with petroleum ether as the extraction solvent, at the material-liquid ratio of 1:10 and the extraction temperature of 50°C for 2 times, each time for 3 hours, the extraction rate of camellia oil reached more than 93%, and the obtained tea seed oil was light yellow.
Solvent extraction method of higher oil yield (production yield can reach 90% or so), extraction is more thorough, the solvent can be recovered, reducing the cost, easy to operate, easy to laboratory research; but in the process of solvent recovery is easy to cause the decomposition of unsaturated fatty acids, so that the resulting saponification of the gross oil value of the high, and the product of the solvent residue, the solvent is extremely flammable, the operation of the higher safety requirements. Recently, it was reported in the news that the benzo(a)pyrene of camellia oil produced by a company exceeded the standard. The company said that benzo(a)pyrene exceeded the standard is mainly leaching oil, benzene content exceeded the standard is mainly because farmers in the extraction of camellia oil, in order to improve the oil yield, the tea seeds for repeated baking, steaming and frying, resulting in the phenomenon of charring, this charred tea cake is prone to produce benzo(a)pyrene, and in the extraction process there is a benzene material and solvent oil at high temperatures in a chemical reaction phenomenon, which further improves the benzo(a)pyrene in the content of camellia oil. Therefore, when extracting camellia oil by solvent extraction, attention should be paid to the temperature control of tea seed roasting and steaming process to prevent overheating and safety problems.
Water enzyme method
Water enzyme method is in recent years the research and utilization of a new method of oil extraction, it is mechanically and enzymatically as a means of degradation of the cellulose skeleton of the plant cell wall, so that wrapped in the cell wall within the oil free, but also to destroy the other molecules with carbohydrates and proteins combined together with the oil complex, so as to make the release of oil.
Water enzyme extraction of camellia oil process:
Camellia seeds → crushing → weighing → adding buffer → steam treatment → cooling → adding enzyme preparations → enzyme → enzyme digestion → inactivation → filtration → take out the residue → drying in the oven → petroleum ether extraction → filtration → vacuum drying → drying to a constant weight → camellia oil
Researchers using different enzymes to extract camellia oil, found that Alcalase 2.0L protease is the most favorable for oil extraction, and its dosage is 0.02ml/g, the oil extraction rate reaches the highest. At the same time, the effects of temperature, pH and solid-liquid ratio on the oil extraction rate and protein hydrolysis were investigated, and the optimal conditions for the enzymatic oil extraction were optimized and determined by response surface method: temperature 55°C, pH 8, and solid-liquid ratio of 1:6 (g/ml), and under this condition of enzymatic hydrolysis for 4 hours, the oil extraction rate reached 78.25%, which was higher than that of the ordinary pressing method.
Compared with the traditional process of water enzyme method has the following advantages: mild conditions, high oil yield, light color, easy to refine; degreasing cake meal protein denaturation is low, good availability; oil and cake meal is easy to separate, simplify the process, improve the processing capacity of the equipment, reduce production costs; reduce energy consumption, wastewater in the biochemical oxygen demand (BOD) and chemical oxygen demand (COD) value is greatly reduced (about 35% ~ 75%), reduce energy consumption, waste water biochemical oxygen demand (BOD) and chemical oxygen demand (COD) value is greatly reduced (about 35% ~ 75%), and reduce energy consumption, waste water in the biochemical oxygen demand (BOD) and chemical oxygen demand (COD) value is greatly reduced (about 35% ~ 75%), and reduce energy consumption. 75%), easy to handle, in favor of energy saving, environmental protection, in line with the principle of sustainable development.
Supercritical carbon dioxide (CO2) extraction method
Supercritical fluid extraction is in the supercritical state, the supercritical fluid {generally using CO2) and the material to be separated from the contact, control the pressure and temperature of the system, so that it is selective extraction of one of the components, and then through the change in temperature or pressure, reduce the density of the supercritical fluid, the extracted material for Then the density of the supercritical fluid is reduced by changes in temperature or pressure, the extracted material is separated, and the supercritical fluid is recycled.
Researchers proposed a method of extracting camellia oil with supercritical CO2, examined the effect of pressure and temperature on the solubility of camellia oil in CO2, analyzed the relationship between extraction conditions and oil quality, and came up with the optimal process conditions: pressure of 30MPa, temperature of 35°C, and flow rate of CO2 of 6L/min. Fang Fang et al. explored the effects of supercritical CO2 extraction on the extraction of camellia oil by the factors such as pressure, temperature, flow rate, time, and so on, Fang Fang et al. explored the effect of supercritical CO2 extraction pressure, temperature, flow rate, time and other factors on the extraction rate of camellia oil, and determined the optimal process conditions for supercritical CO2 extraction of camellia oil (in the raw material particle size of 40 mesh) as follows: extraction pressure of 35MPa, temperature of 50°C, CO2 flow rate of 20kg/h, extraction time of 150min, at this time, the extraction rate of up to 33.5%, and compared with conventional solvent extraction (6h, 30.3%), the extraction time was shortened. Compared with the conventional solvent extraction method (6h, 30.3%), the extraction time is shortened, and the yield and utilization rate of raw materials are greatly improved.
Han Weiyan et al. investigated the optimal process parameters for supercritical CO2 extraction of Eshi camellia oil and the relationship between oil yield and extraction pressure, temperature and time. The results of orthogonal test showed that the extraction pressure of 35MPa, temperature of 45°C and time of 2.5h were the optimal process parameters; the factors affecting the extraction yield were pressure, time and temperature in order. The one-way test showed that the extraction rate increased with the increase of extraction pressure and temperature. The supercritical CO2-extracted Eshi camellia oil retained the tea aroma, and the acid value was low, the color was relatively light, there was no residual solvent, and it did not need further refining.
Supercritical CO2 extraction of camellia oil, its operating temperature is low, will not affect the natural activity of heat-sensitive substances, the aroma of the tea seed oil obtained is closer to the natural flavor, and can be omitted from the refining process of the oil, the oil yield is more than 90%. However, the process equipment requirements are high, expensive, large-scale production of poor operability, now only in the laboratory research stage.