- Crystallization method: The freezing crystallization method uses the low-temperature freezing method to crystallize certain compounds in the essential oil as a solid, and then separate the solid from other liquid components to obtain a purer product. The crystallization extraction and separation technology has low pollution but requires multiple purifications to meet the requirements of the desired product, and the production efficiency is low.
- Supercritical extraction: Supercritical fluid extraction (SFE) technology is a separation technology that emerged in the 1960s. It uses high-pressure gas above the critical temperature as a solvent to separate, extract, and refine organic matter. Effectively overcome the shortcomings of traditional separation methods. In recent years, the liquid and supercritical fluid extraction technology is a fast-developing extraction process, which is widely used in the extraction of plant aroma components, the extraction and concentration of fruit and vegetable aroma components, and the extraction of flower aroma components. In the process, it shows a strong vitality. Supercritical extraction technology has the advantages of high extraction yield, good selectivity, low extraction temperature, complete top note retention, suitable for heat-sensitive fragrances, and no solvent residues. It also has the advantages of low energy consumption, good product quality, and a non-toxic and pollution-free production process. The extraction effect of supercritical extraction on volatile and polar components is not as good as steam distillation, and the one-time investment in equipment is relatively large. Currently, hops, ginger, celery seed, cardamom, vetiver, cumin, nutmeg, angelica, vanilla, rosemary, marjoram, and star anise are used in the processing of aromatic plants. , Coriander seeds, mint, allspice, and other 30 varieties. Due to its non-polar characteristics, its application range is greatly limited. When extracting polar substances, it is necessary to call an entertainer. The entrainer affects the solubility and selectivity of the solvent. It is necessary to find out the appropriate entrainer and its dosage on the basis of a large number of experiments. In addition, operating temperature and pressure are the two main factors that affect the extraction effect. At present, the practical application of supercritical fluid extraction is still very limited, mainly due to the large equipment investment cost, lack of data on the design basis, and insufficient design experience. This requires strengthening the basic research of supercritical fluid extraction and establishing a more reliable and more general analysis model in order to give full play to its advantages.
- Molecular distillation technology: It is a new technology for effective separation of high boiling point and heat-sensitive raw materials that appeared in the 1930s. In the late 1980s, due to the successful development of centrifugal membrane and rotor molecular distillation machinery, molecular distillation technology was put into production and application in developed countries. Molecular distillation is an effective method to separate high boiling points and heat-sensitive materials under high vacuum conditions. It has the advantages of low operating temperature, high vacuum, short heating time, high separation degree, and high product yield. It is suitable for heat-sensitive materials. Aromatic plant raw materials. Molecular distillation can effectively remove light molecular substances in heat-sensitive substances, remove heavy substances and colors in products, and reduce the probability of heat-sensitive substances being damaged by heat; compared with traditional kettle distillation, molecular distillation not only has a higher product yield but also product quality Great. Most natural fragrances are heat-sensitive substances, which are suitable for purification by molecular distillation technology. The application of molecular distillation in the field of natural fragrance extraction is mainly to process natural essential oils to achieve the purpose of deodorization, decolorization, and improvement of purity. A large number of experimental results show that molecular distillation technology is an effective method to purify essential oils. It can concentrate a certain main component in aromatic oils, remove odors and colored impurities, improve its purity, and reduce pollution. As a result, many new composite mass transfer separation technologies based on distillation have been developed, mainly including additive distillation, coupled distillation, and heat-sensitive material distillation. Industrialized molecular distillation equipment can be divided into three types: free-falling film type, rotating wiped film type, and mechanical centrifugal type. Due to its high vacuum operation, molecular distillation consumes a lot of energy and is suitable for the separation of heat-sensitive and high value-added substances, which limits the application field.
