Walnut Oil CAS 8024-09-7

The pressing method is the main method of producing walnut oil. It uses the principle of mechanical pressing to squeeze out the oil in the material at one time. The commonly used ones are screw oil press and hydraulic oil press. According to whether the material is heat-treated before pressing, it is divided into two types: cold pressing and hot pressing. The cold pressing method is carried out in an environment below 65°C, which is a physical method. The material is not fried and roasted, and has no effect on the quality of oil and nutrients. The nutritional components remain intact, the color is good, but the smell is poor; abroad, Germany The cold pressing technology of oilseeds has developed rapidly. For example, the CA59GKOMET laboratory cold press developed by IBGmonforts in Germany is widely used in laboratory cold pressing oil production experiments because of its simple operation, good performance, and relatively small volume. The hot pressing method is to fry and roast the seeds of oil crops to extract the oil plants. The smell is special, the color is darker, the yield is higher, and the residue is less, but the loss of nutrients is greater. Both pressing methods leave no solvent residue. The oil yield rate of the pressing method is 50% to 60%, and there are disadvantages such as high residual oil rate in the cake, protein variability, high labor intensity, and high cost. However, this method has simple equipment and is easy to operate. Because the oil yield of the cold pressing method is lower than that of the hot pressing method, but the nutrients are well preserved, the price of the cold pressed oil is generally about 50% higher than that of the hot pressed oil. The cold pressing method is more suitable for the extraction of walnut oil.

The leaching method is a method in which the oil in the oil is extracted by selecting an organic solvent that can dissolve the oil and contacting with the oil (soaking or spraying). At present, n-hexane leaching is mostly used in my country, which is suitable for large-scale continuous production and has a high oil yield, but it is easy to cause walnut protein denaturation, and has problems such as flammable, explosive and residual solvents. The butane and propane leaching method is a kind of oil production process with mild conditions, especially suitable for the extraction of valuable oils and the development and utilization of low-denatured vegetable protein. This method is more suitable for the large-scale production of walnut oil. High utilization rate. In 1989, my country started the research on this technology, and put it into practice soon, and it has been applied to large-scale production now. The pre-pressing-extraction method is a method that combines the pressing method and the solvent leaching method, that is, during the pre-pressing process, the pressing conditions are eased, and part of the oil is squeezed out first, and then solvent leaching is performed to fully dissolve the oil in the oil. It also makes adipoproteins readily available. This method combines the advantages of the pressing method and the solvent method, and is widely used in the modern oil industry. In recent years, a lot of attempts have been made to combine the solvent method with other auxiliary techniques. For example, the combination of solvent method and auxiliary methods such as microwave and ultrasonic can significantly improve the oil yield and oil quality, but these methods are still in the stage of laboratory research and have not yet been applied to large-scale production.

The water substitution method is the method of “substituting water for oil”, which is a unique traditional oil production process in my country. Hot water is added to the oil slurry to make the protein particles absorb water and expand, and the oil is separated by means of vibration by means of the difference in specific gravity. The method is simple in process, safe and reliable, but there are problems such as difficult separation, protein denaturation, low oil yield and subsequent treatment of wastewater. In recent years, enzyme preparations have been introduced into the water substitution method in order to improve oil yield and protein utilization. Preliminary selection of enzymes for extracting walnut oil by aqueous enzymatic method, it is considered that neutral protease has the best effect when single enzyme is used, and the effect of compound enzyme is obviously higher than that of single enzyme. Studies have shown that adding enzymes and ultrasonic treatment can improve the extraction rate of traditional water substitution methods. As a new technology of oil extraction, the aqueous enzymatic method has the advantages of high oil yield, good oil quality, light color, low production energy consumption, and is not easy to cause environmental pollution, so it has been valued by scholars at home and abroad. As the research continues to deepen, it is expected to create a new situation in walnut oil processing.

Supercritical fluid extraction technology is a modern food processing high-tech separation technology that uses supercritical fluid (mostly CO2) as a solvent, and uses the fluid in this state to have high permeability and high solubility to extract and separate non-polar mixtures. According to the quality characteristics of walnut oil, the process conditions of walnut oil extracted by supercritical CO2 fluid were studied, and the obtained walnut oil reached the first-class edible oil standard and met the requirements of the European Economic Community (EEC) for walnut oil. Wu Cai’e, Yan Shijie et al. [42] proposed that the optimum process parameters for supercritical CO2 fluid extraction of walnut oil are: particle size 30 mesh, extraction pressure 30 MPa, extraction temperature 45 °C, separation temperature 50 °C, separation pressure 8 MPa, extraction time 5 h, CO2 flow rate 40 L /h, under this condition, the extraction rate of walnut oil can reach 93.98%. The walnut oil produced is clear and transparent, light yellow in color and has no solvent residue. It does not need further refining and is a high-quality edible oil product. The supercritical extraction method overcomes the shortcomings of the solvent extraction method such as heating and distillation during the separation process, easy oxidation and rancidity of oil, and solvent residues. It also solves the problems of low oil yield, cumbersome refining process, and unsatisfactory color in the pressing method. However, this technology is limited by many factors such as equipment, energy consumption, food safety, etc. It is still in the laboratory stage, and its application in actual production is extremely limited.