Process for extracting sandalwood essential oil and sandalwood hydrolat through multi-stage variable-temperature distillation

Abstract

The invention discloses a process for extracting sandalwood essential oil and sandalwood hydrolat through multi-stage variable-temperature distillation, and belongs to the technical field of natural perfume extraction. The process comprises the steps of raw material treatment, multi-stage variable-temperature distillation, essential oil post-treatment and hydrolat post-treatment. The raw material treatment comprises selecting old sandalwood tree core materials, processing the old sandalwood tree core materials into particles and soaking; according to the multi-stage variable-temperature distillation, different components are extracted through first-stage to fourth-stage distillation by gradually refining wood and matching with parameters such as steam pressure and temperature which are adjusted in a gradient manner; in the post-treatment step, the essential oil and the hydrolat are respectively subjected to operations such as filtration, alcoholization and sterilization. According to the technology, wood grading treatment and multi-stage variable-temperature distillation are cooperated, the problems of wall sticking, charring and essential oil volatilization caused by crushing in advance in a traditional technology are avoided, sufficient extraction is achieved, and the obtained essential oil and hydrolat are rich in component, pure in fragrance, stable in quality and suitable for high-end market requirements.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of natural perfume extraction, and particularly relates to a process for extracting sandalwood essential oil and sandalwood hydrolat through multi-stage variable-temperature distillation. BACKGROUND

[0002] Sandalwood essential oil is a natural perfume extracted from sandalwood, has a unique sweet woody fragrance, and is widely used in high-end perfumes, cosmetics, aromatherapy and medicine fields; sandalwood hydrolat is a solution of water-soluble aromatic components produced in the distillation process, and is often used for skin care products, fragrances and beverage flavoring due to its mild fragrance and natural ingredients.

[0003] At present, traditional extraction processes for sandalwood essential oil and hydrolat mainly include water distillation and water-over distillation. In the water distillation method, sandalwood logs are directly crushed and immersed in water for heating and distillation, and in the water-over distillation method, the logs are placed on a sieve plate on the water surface and extracted by steam heating. However, these two processes have significant defects. In order to pursue extraction efficiency, the traditional process often completely crushes the sandalwood logs into powder in advance, which causes the wood powder to easily stick to the wall and form clumps during distillation, and even causes local overheating and charring. This not only reduces the yield of essential oil, but also damages the natural fragrance of hydrolat. In addition, the frictional heat generated during the crushing process causes some volatile sandalwood essential oil to be lost in advance, resulting in low content of key effective components such as alpha-santalol and beta-santalol in the extracted essential oil, and weak fragrance of hydrolat, which cannot meet the needs of the high-end market. SUMMARY

[0004] The purpose of the present application is to provide a process for extracting sandalwood essential oil and sandalwood hydrolat through multi-stage variable-temperature distillation, which aims to solve the problems of wall sticking, clumping and charring caused by the traditional water distillation method and water-over distillation method due to the advance of completely crushing sandalwood logs, as well as the problems of volatile loss, low yield, few effective components and poor fragrance quality of essential oil.

[0005] The purpose of the present application is achieved by the following technical solution: A process for extracting sandalwood essential oil and sandalwood hydrolat through multi-stage variable-temperature distillation, comprising the following steps: S1. Raw material processing: selecting sandalwood old tree core material, processing into particles and then soaking; S2. Multi-stage variable-temperature distillation: S21. First-stage distillation: adding the soaked sandalwood particles and soaking liquid into a distillation kettle, controlling the steam pressure to be less than or equal to 0.03 MPa, the heating temperature to be less than or equal to 98 DEG C, the cooling water inlet temperature to be less than 25 DEG C, the condensate oil-water separation temperature to be 15-25 DEG C, the evaporation flow rate to be 700-800 ml / min, and the extraction time to be 22-26 hours; collecting sandalwood oil, sandalwood hydrolat and sandalwood wood residue after distillation; S22. Secondary distillation: The sandalwood residue after the first distillation is coarsely crushed to 20-30 mesh, and is put into the distillation kettle according to the mass ratio of pure water:wood residue = (2.5-3.5):1, the steam pressure is controlled at 0.03-0.05 MPa, the heating temperature is ≤98℃, the cooling water inlet temperature is <25℃, the condensate oil-water separation temperature is 25-30℃, and the extraction is carried out for 22-26 hours; the sandalwood oil, sandalwood hydrolate and sandalwood residue after distillation are collected; S23. Tertiary distillation: The sandalwood residue after the secondary distillation is crushed to 100-120 mesh, and is put into the distillation kettle according to the mass ratio of pure water:wood residue = (3.5-4.5):1, the steam pressure is controlled at 0.05-0.1 MPa, the heating temperature is 105-120℃, the cooling water inlet temperature is 25-30℃, the condensate oil-water separation temperature is 30-40℃, and the extraction is carried out for 10-14 hours; the sandalwood oil, sandalwood hydrolate and sandalwood residue after distillation are collected; S24. Quaternary distillation: The sandalwood residue after the tertiary distillation is dried, and is extracted with double-dealcoholized alcohol, and after salting out, dealcoholization and filtration, is put into a molecular distillation device, the material heating temperature is controlled at 40-50℃, the vacuum degree is 1-2 mbar, the heating evaporation temperature is 70-80℃, and the condensation temperature is 5-10℃, and the sandalwood essential oil is collected; S3. Essential oil post-treatment: The sandalwood essential oils collected after the first to fourth distillation are mixed, and after vacuum filtration, centrifugal dewatering and low-temperature alcoholization, the sandalwood oil product is obtained; S4. Hydrolate post-treatment: The sandalwood hydrolates collected after the first to third distillation are mixed, and after microporous membrane filtration and cool alcoholization, and after sterilization treatment, the sandalwood hydrolate product is obtained.

[0006] The process realizes efficient extraction of sandalwood essential oil and hydrolate through the synergy of "wood grading treatment" and "multi-stage variable-temperature distillation", as follows: Wood grading treatment: The process breaks the traditional one-time crushing mode, and gradually refines according to the extraction stage —— the granular wood is used for the first distillation, and the steam uniformly penetrates through the gaps between the particles; the wood residue is coarsely crushed to 20-30 mesh before the secondary distillation, and the middle structure of the wood is exposed; the wood residue is further crushed to 100-120 mesh before the tertiary distillation, and the core components are released; finally, the wood residue is dried and extracted, and the residual essential oil is extracted. The whole process avoids the problems of wall sticking and clumping caused by premature crushing of wood powder.

[0007] Multi-stage temperature-variable distillation: adjust the distillation parameters according to the degree of wood refinement - the first stage uses low pressure and low temperature (steam pressure ≤0.03 MPa, heating temperature ≤98℃), to extract the surface volatile components; the second stage increases the steam pressure (0.03-0.05 MPa), to extract the middle components; the third stage increases the temperature and pressure (steam pressure 0.05-0.1 MPa, heating temperature 105-120℃), to extract the core high-boiling-point components; the fourth stage uses molecular distillation (material heating temperature 40-50℃, vacuum degree 1-2 mbar), to separate the residual essential oil from the extract, realizing the whole-process extraction.

[0008] As some embodiments of the present application, in step S1, the particle size is 1-2 mesh; the soaking uses pure water, the material-water mass ratio is 1:(1.5-2.5), and the soaking time is 20-28h.

[0009] The sandalwood core material has a hard texture, and the particle size of 1-2 mesh can ensure the formation of stable gaps between the particles, facilitating the flow of steam; the material-water ratio of 1:(1.5-2.5) and the soaking time of 20-28h can allow the wood to fully absorb water and soften, making the wood fibers expand and facilitating the release of aromatic substances with steam.

[0010] As some embodiments of the present application, in step S24, the sandalwood residue after the third-stage distillation is dried at a temperature of 30-40℃ for 5-7h. The ratio of sandalwood powder to double-dealcohol alcohol during extraction is 1:(2.5-3.5), and the extraction time is 10-14h.

[0011] In the present application, by limiting relevant parameters, alcohol can be quickly removed without damaging the components of essential oil, solving the problem of alcohol residue affecting the purity of essential oil.

[0012] As some embodiments of the present application, in step S24, during the dealcoholization process, the material heating temperature is 78-79℃, the cooling water inlet temperature is 10-15℃, the evaporation flow rate is 40-50ml / min, and the extraction time is 0.5-1h.

[0013] As some embodiments of the present application, in step S24, the feeding speed of the molecular distillation equipment is 200-300rpm / min, the scraper speed is 120-130rpm / min, and liquid nitrogen is used for cold condensation.

[0014] As some embodiments of the present application, in step S3, vacuum filtration uses 800 mesh filter cloth with glass sand filter element; during centrifugal dewatering, the centrifugal equipment has a rotation speed of 18000-20000rpm / min; the low-temperature aging temperature is 2-8℃, and the aging period is 1.5-2.5 months.

[0015] As some embodiments of the present application, in step S4, the pore size of the microporous membrane is 0.2-0.25 μm; the temperature of the cool alcoholization is <20℃, and the alcoholization period is 1.5-2.5 months.

[0016] In the present application, the 0.2-0.25 μm microporous membrane can filter microorganisms and suspended impurities in the pure distillate; cool alcoholization at <20℃ for 1.5-2.5 months can promote the fusion of water-soluble aromatic ingredients and avoid the decomposition of ingredients caused by high temperature.

[0017] As some embodiments of the present application, in step S4, the sterilization method is low-temperature pasteurization, the sterilization temperature is 60-65℃, the sterilization time is 25-30 min, and sterile nitrogen is introduced to replace the air in the container immediately after sterilization.

[0018] The heat-sensitive aromatic ingredients (such as benzyl-4-hydroxyphenone) in the pure distillate are prone to decomposition at >65℃. Low-temperature pasteurization at 60-65℃ for 25-30 min can kill 99.9% of microorganisms (such as molds and yeasts) and significantly reduce the damage rate to heat-sensitive ingredients.

[0019] According to the present application, the beneficial effects are: The present application realizes efficient extraction of sandalwood essential oil and pure distillate through the synergistic process of "wood grading treatment" and "multi-stage variable-temperature distillation", and can solve the defects of traditional processes: Firstly, the traditional water-in / water-over distillation causes wood powder to stick to the wall, form clumps, and become scorched due to the premature crushing of wood, and the essential oil is prone to loss during crushing. In the present process, the wood is treated by particles→ coarse crushing (20-30 mesh) → crushing (100-120 mesh) in a step-by-step manner, and the distillation parameters (such as ≤98℃ for the first stage and 105-120℃ for the third stage) are adjusted at each stage, so that there is no clumping and scorching of wood powder throughout the process, and the loss of essential oil due to volatilization is reduced.

[0020] Secondly, the multi-stage variable-temperature distillation matches the characteristics of wood at different stages (particles→ coarse crushing→ crushing), adjusts the steam pressure (≤0.03 MPa→ 0.03-0.05 MPa→ 0.05-0.1 MPa) and temperature (≤98℃→ ≤98℃→ 105-120℃) by gradient, and extracts the components at each part in a targeted manner, so that the essential oil and aromatic ingredients in sandalwood are fully extracted.

[0021] Thirdly, the extracted sandalwood essential oil has a clear appearance and pure aroma; the sandalwood pure distillate has a mellow woody aroma without a scorched taste, and the quality is more stable.

[0022] Fourthly, the parameters at each step (such as soaking time, distillation temperature, and alcoholization period) are clear and can be stably reproduced from raw material treatment to product alcoholization, solving the batch difference problem in traditional processes. DETAILED DESCRIPTION

[0023] Example 1 S1. Raw material processing: Select old sandalwood tree cores with an age of more than 30 years, process into rectangular particles with a length of 1-2 cm, a width of 0.2-1 cm, and a mesh size of 1-2 (appearance dry, no mildew, no odor, pure wood fragrance); soak the particles in pure water at a material-to-water mass ratio of 1:2 for 24 hours to ensure that the pure water completely submerges the particles.

[0024] S2. Multi-stage variable-temperature distillation S21. First-stage distillation: Add the soaked sandalwood particles and soaking liquid to a distillation kettle, control the distillation vapor pressure at 0.02 MPa, the heating temperature at 95°C, the cooling water inlet temperature at 20°C, the condensate oil-water separation temperature at 20°C, the evaporation flow rate at 750 ml / min, and extract for 24 hours (counting from the time when the condensate is collected); collect the sandalwood oil, sandalwood hydrolate, and sandalwood wood residue after distillation.

[0025] S22. Second-stage distillation: Coarsely crush the sandalwood wood residue after the first-stage distillation to 25 mesh, add pure water and wood residue at a mass ratio of 3:1 to the distillation kettle, control the vapor pressure at 0.04 MPa, the heating temperature at 96°C, the cooling water inlet temperature at 22°C, the condensate oil-water separation temperature at 28°C, the evaporation flow rate at 750 ml / min (referring to the flow rate of the evaporated aromatic extract after cooling to become a condensate, the same below), and extract for 24 hours; collect the sandalwood oil, sandalwood hydrolate, and sandalwood wood residue after distillation.

[0026] S23. Third-stage distillation: Crush the sandalwood wood residue after the second-stage distillation to 110 mesh, add pure water and wood residue at a mass ratio of 4:1 to the distillation kettle, control the vapor pressure at 0.08 MPa, the heating temperature at 110°C, the cooling water inlet temperature at 28°C, the condensate oil-water separation temperature at 35°C, the evaporation flow rate at 1100 ml / min, and extract for 12 hours; collect the sandalwood oil, sandalwood hydrolate, and sandalwood wood residue after distillation.

[0027] S24. Quaternary distillation: The sandalwood residue after tertiary distillation is placed in a 300-mesh nylon membrane filter bag and dried in an oven at 35℃ for 6 hours (dehumidifying fan frequency 50Hz); it is then extracted for 12 hours with 96% (v / v) acetaldehyde-removed ethanol (i.e., acetaldehyde-removed ethanol refers to food-grade ethanol with formaldehyde and acetaldehyde removed; here, the sandalwood powder:acetaldehyde-removed ethanol = 1:3 mass ratio), followed by salting out with 20% (v / v) of the total extract. The ethanol and impurities are removed using a separatory funnel. The extract is then fed into a 5L small distillation apparatus, with the material heating temperature controlled at 78.5℃, the cooling water inlet temperature at 12℃, and the evaporation flow rate at 45ml / min. The ethanol is extracted for 40 minutes to recover the alcohol. After cooling, it is distilled using 800... Vacuum filtration is performed using a mesh filter cloth and a glass sand filter element. The extracted material after impurity removal is then fed into a molecular distillation apparatus. The material heating temperature is controlled at 45℃, the vacuum degree at 1.5mbar, the feed rate at 250rpm / min, the scraper speed at 125rpm / min, the heating and evaporation temperature at 75℃, and the condensation temperature at 8℃. Liquid nitrogen and hydrazine are used for condensation to collect sandalwood essential oil.

[0028] S3. Essential oil post-processing: Mix the sandalwood essential oils collected from first to fourth stage distillation, and vacuum filter them using an 800-mesh filter cloth and a glass sand filter element; put them into a centrifuge and centrifuge at a speed of 19,000 rpm / min to dehydrate them; put the centrifuged sandalwood oil into an aluminum can and seal it, and aging it in a 5℃ cold storage for 2 months to obtain the finished sandalwood oil.

[0029] S4. Post-processing of the hydrosol: Mix the sandalwood hydrosols collected from the first to third distillation stages, filter through a 0.22μm microporous membrane; seal in a tonne container and aging in a cool, dark warehouse at 15℃ for 2 months; pasteurize at low temperature (62℃, 30min), and immediately after sterilization, purge the air in the container with sterile nitrogen to obtain the finished sandalwood hydrosol.

[0030] Example 2 S1. Raw material processing: Select sandalwood heartwood from trees over 30 years old and process it into rectangular particles with a length of 1-2cm, a width of 0.2-1cm, and a mesh size of 1-2 (dry appearance, no mold, no odor, and pure wood fragrance); soak the particles in pure water at a material-to-water mass ratio of 1:1.8 for 22 hours, ensuring that the particles are completely submerged in pure water.

[0031] S2. Multi-stage variable temperature distillation: S21. First-stage distillation: Add the soaked sandalwood granules and soaking liquid to the distillation vessel, control the distillation steam pressure to 0.03 MPa, heating temperature to 97℃, cooling water inlet temperature to 23℃, condensate oil-water separation temperature to 22℃, evaporation flow rate to 720 ml / min, and extract for 23 hours (starting from the time the condensate is discharged); collect sandalwood oil, sandalwood hydrosol and sandalwood residue after distillation.

[0032] S22. Secondary distillation: The sandalwood residue after primary distillation is coarsely crushed to 22 mesh and added to the distillation vessel at a mass ratio of pure water to wood residue of 2.8:1. The steam pressure is controlled at 0.035 MPa, the heating temperature at 95℃, the cooling water inlet temperature at 21℃, the oil-water separation temperature of the condensate at 26℃, the evaporation flow rate at 730 ml / min, and the extraction is carried out for 25 h. The sandalwood oil, sandalwood hydrosol, and sandalwood residue after distillation are collected.

[0033] S23. Tertiary distillation: The sandalwood residue after secondary distillation is crushed to 105 mesh and added to the distillation vessel at a mass ratio of pure water to wood residue of 3.8:1. The steam pressure is controlled at 0.06 MPa, the heating temperature at 115℃, the cooling water inlet temperature at 27℃, the oil-water separation temperature of the condensate at 33℃, the evaporation flow rate at 1050 ml / min, and the extraction is carried out for 13 hours. The sandalwood oil, sandalwood hydrosol, and sandalwood residue after distillation are collected.

[0034] S24. Quaternary distillation: The sandalwood residue after tertiary distillation is placed in a 300-mesh nylon membrane filter bag and dried in an oven at 38℃ for 5.5 hours (dehumidifying fan frequency 50Hz); it is then extracted with 95% (v / v) dialdehyde-free ethanol (sandalwood powder: dialdehyde-free ethanol = 1:2.8 mass ratio) for 11 hours, followed by salting out with 19% (w / v) of the total extract mass, and removing ethanol and impurities using a separatory funnel; the extract is then fed into a 5L small distillation apparatus, with the material heating temperature controlled at 78℃, the cooling water inlet temperature at 13℃, and the evaporation flow rate at 42ml / min, for 50 minutes. Alcohol is recovered; after cooling, it is vacuum filtered using an 800-mesh filter cloth and a glass sand filter element; the impurity-removed extract is fed into a molecular distillation apparatus, with the material heating temperature controlled at 48℃, vacuum degree at 1.2mbar, feed rate at 220rpm / min, scraper speed at 122rpm / min, heating and evaporation temperature at 78℃, condensation temperature at 7℃, and liquid nitrogen and hydrazine are used for condensation to collect sandalwood essential oil.

[0035] S3. Essential oil post-processing: Mix the sandalwood essential oils collected from first to fourth stage distillation, and vacuum filter them using an 800-mesh filter cloth and a glass sand filter element; put them into a centrifuge and centrifuge at a speed of 18,500 rpm / min to dehydrate them; put the centrifuged sandalwood oil into an aluminum can and seal it, and aging it in a 6℃ cold storage for 2.2 months to obtain the finished sandalwood oil.

[0036] S4. Post-processing of the hydrosol: Mix the sandalwood hydrosols collected from the first to third distillation stages, filter through a 0.24μm microporous membrane; seal in a tonne container and aging in a cool, dark warehouse at 18℃ for 1.8 months; pasteurize at low temperature (63℃, 28min), and immediately after sterilization, purge the air in the container with sterile nitrogen to obtain the finished sandalwood hydrosol.

[0037] Example 3 In Example 1, during multi-stage distillation, the lignin and minerals from sandalwood residue easily form scale on the inner wall of the distillation vessel. Essential oils (especially α-santalol) are adsorbed onto the scale surface due to hydrophobicity, forming a "scaling-adsorption" cycle. After approximately 10 batches, each batch loses 0.5-1 wt% of essential oil. Conventional acid washing easily corrodes equipment and residual acid affects quality. Therefore, based on Example 1, a "superhydrophilic-superhydrophobic alternating coating" is introduced onto the inner wall of the distillation vessel. The coating preparation method is as follows: Superhydrophilic coating (chitosan-nano silica composite coating): Natural chitosan (deacetylation degree ≥90%) is used as the base material. 12% of the base material mass of nano silica (particle size 70nm) is added, and 2.5% of the base material mass of glutaraldehyde is added as a crosslinking agent. During preparation, chitosan is first dissolved in 1% acetic acid solution (mass concentration) until completely dissolved. After adding nano silica, it is ultrasonically dispersed for 30min. Then, glutaraldehyde is added and stirred evenly to form a coating liquid. The coating liquid is evenly sprayed onto a preset area (5cm wide) on the inner wall of the distillation vessel using a high-pressure spraying device. It is dried at 80℃ for 2h to cure into a film with a water contact angle <5°.

[0038] Superhydrophobic coating (fluorine-modified lignin-graphene composite coating): Using lignin extracted from papermaking waste as the base material, 6% of the base material mass is modified with perfluorooctyltrichlorosilane, and then 2.5% of the base material mass is added with graphene (3μm sheet diameter). During preparation, lignin is dissolved in 30% ethanol solution (mass concentration), perfluorooctyltrichlorosilane is added, and the mixture is stirred at 60℃ for 2 hours to complete the modification. Graphene is added and ultrasonically dispersed for 20 minutes to form a coating liquid. The coating liquid is then sprayed onto a predetermined area (5cm wide) on the inner wall of a distillation vessel using a thermal spraying device, and cured into a film by hot pressing at 90℃ for 1 hour. The water contact angle is >150°.

[0039] Coating arrangement: The above-mentioned superhydrophilic coating and superhydrophobic coating are alternately sprayed at 20cm intervals along the inner wall of the distillation vessel to form a circulating protective structure.

[0040] The above coatings function as follows: the superhydrophilic coating forms hydrogen bonds with water molecules through chitosan hydroxyl groups, promoting the formation of a continuous water film from condensate to flush away scale; the superhydrophobic coating reduces essential oil adsorption due to the compatibility of lignin and sandalwood components and the electrostatic repulsion of graphene.

[0041] Coating maintenance: After every 5 batches, introduce 50°C deionized water (containing 0.1wt% food-grade sodium citrate) into the distillation vessel and circulate for 30 minutes to chelate mineral scale.

[0042] Comparison of this embodiment with Example 1: After 10 batches of Example 1, there was obvious scaling on the inner wall of the distillation vessel, with an essential oil loss of about 0.7 wt% per batch; after 10 batches of this embodiment, there was no obvious scaling on the vessel wall, the essential oil adsorption loss was reduced to 0.1 wt%, and the yield stability was improved by 3.2 wt% compared with Example 1; moreover, the coating did not introduce new impurities, and the appearance, aroma, and hydrosol quality of the essential oil were consistent with those of Example 1, meeting the standards for high-end fragrances.

[0043] Comparative Example 1 (Existing Traditional Water Distillation Method) Sandalwood is completely crushed into 100-120 mesh powder and added to a distillation vessel at a material-to-water mass ratio of 1:3. The vessel is then directly immersed in water and heated for distillation. The steam pressure is controlled at 0.05-0.1 MPa, the heating temperature at 95-100℃, and the extraction time at 36 hours. The sandalwood oil and hydrosol are collected and then simply filtered to obtain the final product.

[0044] Comparative Example 2 (Existing Traditional Water Distillation Method) Sandalwood is crushed into 20-30 mesh particles and placed on a sieve plate in a distillation kettle (without direct contact with water). Steam is generated by bottom heating for distillation, with the steam pressure controlled at 0.03-0.05 MPa, the heating temperature at 98-102℃, and the extraction time at 40 hours. The sandalwood oil and hydrosol are collected and then simply filtered to obtain the finished product.

[0045] Comparative Example 3 Differences from Example 1: The "fourth-stage distillation" step is omitted (i.e., the drying, extraction, and molecular distillation of the wood chips are not performed). The essential oil is extracted only through first- to third-stage distillation. The remaining steps and parameters are the same as in Example 1.

[0046] Comparative Example 4 Differences from Example 1: The "gradual refinement" grading process is omitted, and the sandalwood is completely crushed to 100-120 mesh before the first distillation. The remaining steps and parameters are the same as in Example 1.

[0047] Comparative Example 5 Differences from Example 1: The first to third stage distillation were all carried out at a constant temperature of 95°C without temperature gradient adjustment, and the remaining steps and parameters were the same as in Example 1.

[0048] Comparative Example 6 Differences from Example 1: The first to third stage distillation uses a constant steam pressure of 0.04 MPa, without pressure gradient adjustment, and the remaining steps and parameters are the same as in Example 1.

[0049] Experimental Example The quality of the hydrosols and essential oils collected in Examples 1-3 and Comparative Examples 1-6 was tested using the following methods: Sandalwood hydrosol component test (test results are shown in Table 1): The content of the main aromatic components in the hydrosol was determined by gas chromatography-mass spectrometry (unit: %).

[0050] Sandalwood essential oil quality test (test results are shown in Table 2): In accordance with the ISO 3518-2022 international standard for plant essential oils, the appearance, aroma, relative density, optical rotation, refractive index and content of key components (Z-α-santalol, Z-β-santalol) of the essential oil were tested (unit: %).

[0051] Table 1: Table 2: From Table 1 and Table 2, we can see that: Examples 1-3 achieve efficient extraction through the synergistic effect of "wood grading" and "multi-stage variable temperature distillation": Grading gradually refines the wood from granules to powder, avoiding the wood powder sticking to the wall, clumping, and loss of essential oil due to premature crushing in traditional processes; Multi-stage variable temperature distillation adjusts the pressure and temperature according to the degree of wood refinement, and selectively extracts volatile components on the surface, components in the middle and high-boiling-point components in the core. At the same time, residual essential oil is recovered through four-stage distillation, so that aromatic components are fully released and preserved.

[0052] Comparative Examples 1-2 used traditional distillation processes. Because the wood was completely crushed in advance, the wood powder stuck to the walls and was locally scorched. Furthermore, the volatile essential oils were lost during the crushing stage, resulting in insufficient effective components in the hydrosols and essential oils, and thus poor quality.

[0053] Comparative Example 3 omits the fourth stage of distillation, making it impossible to recover the essential oil remaining in the wood residue after the third stage of distillation, resulting in insufficient extraction of effective components and a thin aroma profile.

[0054] Comparative Example 4 directly pulverized the wood before the first distillation, which reproduced the defects of the traditional process. The wood powder stuck to the wall and local overheating caused the essential oil to have a burnt taste and the integrity of the components was damaged.

[0055] Comparative Examples 5-6, due to the fixed distillation temperature or pressure, could not match the boiling point characteristics of components in wood with different degrees of refinement. High-boiling-point components were difficult to extract fully, resulting in a decrease in the content of key components and insufficient aroma intensity.

[0056] In summary, this invention effectively solves the problems of sticking to the wall, scorching, and essential oil volatilization caused by pre-crushing in traditional distillation by using a synergistic process of "wood grading treatment" and "multi-stage temperature distillation". By adjusting the process parameters in a gradient manner, the aromatic components in sandalwood are fully extracted. The sandalwood essential oil and hydrosol obtained are significantly better than the comparative scheme in terms of component richness, aroma quality and stability.

Claims

1. A process for extracting sandalwood essential oil and sandalwood hydrosol through multi-stage variable temperature distillation, characterized in that, Includes the following steps: S1. Raw material processing: Select old sandalwood heartwood, process it into granules, and then soak it; S2. Multi-stage variable temperature distillation: S21. First-stage distillation: Add the soaked sandalwood granules and soaking liquid to the distillation vessel, control the steam pressure ≤0.03MPa, the heating temperature ≤98℃, and extract for 22-26h; collect sandalwood oil, sandalwood hydrosol and sandalwood residue after distillation; S22. Secondary distillation: The sandalwood residue after primary distillation is coarsely crushed to 20-30 mesh and added to the distillation vessel at a mass ratio of pure water: wood residue = (2.5-3.5):

1. The steam pressure is controlled at 0.03-0.05 MPa, the heating temperature is ≤98℃, the cooling water inlet temperature is <25℃, the oil-water separation temperature of the condensate is 25-30℃, and the extraction is carried out for 22-26 hours. The sandalwood oil, sandalwood hydrosol, and sandalwood residue after distillation are collected. S23. Tertiary distillation: Crush the sandalwood residue after secondary distillation to 100-120 mesh, and add it to the distillation vessel at a mass ratio of pure water: wood residue = (3.5-4.5):

1. Control the steam pressure at 0.05-0.1 MPa, the heating temperature at 105-120℃, the cooling water inlet temperature at 25-30℃, and the oil-water separation temperature of the condensate at 30-40℃. Extract for 10-14 hours; collect the sandalwood oil, sandalwood hydrosol, and sandalwood residue after distillation. S24. Quaternary distillation: The sandalwood residue after tertiary distillation is dried, extracted with double-dealdehyde alcohol, and after salting out, de-alcoholization, and filtration, it is fed into a molecular distillation apparatus. The material heating temperature is controlled at 40-50℃, the vacuum degree is 1-2mbar, the heating evaporation temperature is 70-80℃, and the condensation temperature is 5-10℃. The sandalwood essential oil is collected. S3. Essential oil post-processing: The sandalwood essential oils collected from first to fourth stage distillation are mixed, vacuum filtered, centrifuged and dehydrated, and then ethanolified at low temperature to obtain the finished sandalwood oil; S4. Post-processing of hydrosol: The sandalwood hydrosols collected from first- to third-stage distillation are mixed, filtered through a microporous membrane, aged in a cool place, and then sterilized to obtain the finished sandalwood hydrosol.

2. The process for extracting sandalwood essential oil and sandalwood hydrosol through multi-stage variable temperature distillation according to claim 1, characterized in that, In step S1, the particle size is 1-2 mesh; pure water is used for soaking, the material-to-water mass ratio is 1:(1.5-2.5), and the soaking time is 20-28 hours.

3. The process for extracting sandalwood essential oil and sandalwood hydrosol through multi-stage variable temperature distillation according to claim 1, characterized in that, In step S24, the drying temperature of the sandalwood residue after three-stage distillation is 30-40℃, and the drying time is 5-7h. The ratio of sandalwood powder to dialdehyde-free alcohol during extraction is 1:(2.5-3.5), and the extraction time is 10-14 hours.

4. The process for extracting sandalwood essential oil and sandalwood hydrosol through multi-stage variable temperature distillation according to claim 1, characterized in that, In step S24, during the de-alcoholization process, the material heating temperature is 78-79℃, the cooling water inlet temperature is 10-15℃, the evaporation flow rate is 40-50ml / min, and the extraction time is 0.5-1h.

5. The process for extracting sandalwood essential oil and sandalwood hydrosol through multi-stage variable temperature distillation according to claim 1, characterized in that, In step S24, the feed rate of the molecular distillation equipment is 200-300 rpm / min, the scraper speed is 120-130 rpm / min, and liquid nitrogen is used for cold hydrazine condensation.

6. The process for extracting sandalwood essential oil and sandalwood hydrosol through multi-stage variable temperature distillation according to claim 1, characterized in that, In step S3, vacuum filtration uses an 800-mesh filter cloth in conjunction with a glass sand filter element; during centrifugal dehydration, the speed of the centrifuge is 18,000-20,000 rpm / min; the temperature for low-temperature alcoholization is 2-8℃, and the alcoholization cycle is 1.5-2.5 months.

7. The process for extracting sandalwood essential oil and sandalwood hydrosol through multi-stage variable temperature distillation according to claim 1, characterized in that, In step S4, the pore size of the microporous membrane is 0.2-0.25 μm; the temperature for cool aging is < 20℃, and the aging cycle is 1.5-2.5 months.

8. The process for extracting sandalwood essential oil and sandalwood hydrosol through multi-stage variable temperature distillation according to claim 1, characterized in that, In step S4, the sterilization method is low-temperature pasteurization, the sterilization temperature is 60-65℃, the sterilization time is 25-30 minutes, and sterile nitrogen gas is immediately introduced to replace the air in the container after sterilization.

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