Preparation method of sweet osmanthus extract with high yield and high aroma retention

Abstract

The invention discloses a preparation method of a sweet osmanthus extract with high yield and high aroma retention. The method comprises the steps of sweet-scented osmanthus picking, precooling, sorting, freeze drying and subcritical n-butane extraction. The specific aroma components, namely linalool oxide, trans-linalool oxide, beta-ionol and dihydro-beta-ionol, of the osmanthus fragrans extract obtained through vacuum freeze drying are characteristic aroma components of the osmanthus fragrans extract, and the aroma substances of the osmanthus fragrans extract obtained through subcritical extraction are the highest in retention and the most abundant in quantity. According to the method, the loss of volatile components of the sweet-scented osmanthus extract is small, the overall fragrance of the sweet-scented osmanthus is good, the obtained sweet-scented osmanthus extract is rich in fragrance and good in quality, the yield of the sweet-scented osmanthus extract is greatly increased, and the method is simple in process, convenient to operate, high in economic benefit, suitable for large-scale industrial production and application and good in market prospect.

Description

Technical Field

[0001] The invention relates to the technical field of plant extraction, and in particular to a method for preparing an osmanthus extract with high yield and high aroma retention. Background Art

[0002] Osmanthus fragrans, a member of the genus Osmanthus in the family Oleaceae, is an important economically important fragrant flower in China. Its sweet aroma and nutritious properties make it a popular commodity. Osmanthus fragrans can be used to produce extracts, essential oils, and absolutes, all of which have high value and economic benefits. Osmanthus fragrans concrete, extracted from osmanthus flowers using organic solvents, contains essential oils, waxes, pigments, and other substances. It is a natural flavoring and fragrance ingredient for foods and cosmetics, and possesses high health and medicinal value. Xianning, Hubei, is known as the hometown of osmanthus in China and its origin. Liuyang, Hunan, is the largest osmanthus distribution center in China.

[0003] The current osmanthus extract industry faces challenges: low extraction yield, high prices, and high domestic and international demand. The flowering period, variety, origin, and extraction process of osmanthus flowers all affect the yield and quality of the extract. Osmanthus flowers are delicate and prone to browning and spoilage after harvesting. Quick freezing and vacuum freeze-drying with liquid nitrogen directly after harvesting greatly preserves the flower's shape and color, minimizing aroma loss. The current national standard for extracting osmanthus extracts uses Soxhlet extraction (SE), using petroleum ether as the solvent. The resulting product has an unpleasant aroma mixed with petroleum ether, and the extract yield is low. Supercritical CO2 extraction yields a more monotonous aroma in osmanthus extracts, requires high-pressure conditions, and is expensive. Subcritical butane extraction (SBE) is a non-thermal anaerobic treatment method that uses n-butane as the extraction solvent. The target product is separated from the material under conditions below the critical temperature and pressure. It is widely used to extract active ingredients from plants, such as linseed oil, cinnamon extract, and phenolic antioxidants. It overcomes the shortcomings of Soxhlet extraction and supercritical CO2 extraction, and offers advantages such as high production efficiency, guaranteed quality, and ease of industrialization. However, there are currently no patents related to the extraction of osmanthus extract using subcritical n-butane.

[0004] Patent CN113150871A discloses a method for preparing osmanthus extract. The method involves drying the flowers with hot air, irradiating them with varying doses using an electron accelerator, and then extracting them using supercritical CO2. This method has the following drawbacks: low yield (maximum yield: 1%); the use of hot air drying and electron irradiation results in the loss of heat-sensitive components in the extract's aroma; and the high pressure of supercritical extraction poses a safety hazard. Therefore, a method for preparing osmanthus extract with high yield, good aroma preservation, and suitable production safety is needed. Summary of the Invention

[0005] The invention aims to overcome the shortcomings of the existing osmanthus extract preparation method, such as long extraction time, low yield and low aroma retention, and provides a preparation method for osmanthus extract with high yield and high aroma retention. The method comprises the steps of osmanthus picking, precooling, sorting, freeze drying and subcritical n-butane extraction, and the whole process is simple, easy to operate and highly economical. The yield of osmanthus extract is greatly improved, and aroma loss is minimized as much as possible. The obtained osmanthus extract has a rich aroma and good quality.

[0006] The preparation method of the osmanthus extract of the present invention comprises the following steps: S1. Harvest osmanthus flowers during their early flowering period, pre-cool them to 0-4°C, and sort and remove impurities. S2. The osmanthus was freeze-dried in vacuo, crushed and sieved to obtain dry osmanthus powder; S3. Extract the dried osmanthus flower powder with subcritical n-butane. The extraction conditions are as follows: a particle size of 20-30 mesh, a solid-liquid ratio of 1 g:25-30 mL, an extraction temperature of 45°C-50°C, and an extraction time of 30-40 min. The extract is evaporated to remove the solvent to obtain an osmanthus flower extract.

[0007] Preferably, the osmanthus fragrans is golden osmanthus Preferably, the osmanthus fragrans is Xianning golden osmanthus.

[0008] Preferably, the impurity removal is to use a color sorter to remove leaves, branches and gravel.

[0009] Preferably, the vacuum freeze-drying conditions are a vacuum of 30 Pa, a cold trap temperature of -80°C, freezing for 2 hours, and sublimation drying for 20 hours. Vacuum freeze-drying involves freezing a sample at low temperatures and then heating it under vacuum to sublimate and dry it, removing ice crystals and carrying away some bound water.

[0010] Preferably, the extraction conditions are: the particle size of the dry osmanthus powder is 20-20.41 mesh, the material-liquid ratio is 1 g:25.5 mL, the extraction temperature is 45°C-45.48°C, and the extraction time is 38.59 min.

[0011] The present invention also provides an osmanthus extract prepared according to the method.

[0012] The present invention provides a highly efficient extraction method and process for osmanthus extract. This method primarily optimizes the pretreatment drying step and compares different extraction yields to determine the optimal drying method and process parameters. The extract yields of the different extraction methods are then compared to determine the optimal extraction method, namely subcritical extraction. Model fitting and orthogonal experimental design are then used to determine the optimal subcritical extraction process parameters. The optimized parameters are verified by comparing the extraction yields obtained from experimental and theoretical simulations. Finally, gas chromatography-mass spectrometry (GC-MS) analysis reveals that the optimal drying method, vacuum freeze-drying, yields the specific aroma components of osmanthus extract: linalool oxide, trans-linalool oxide, β-ionol, and dihydro-β-ionol. Comparison of GC-MS total ion chromatograms (TIC) reveals that subcritical extraction results in the osmanthus extract with the highest retention and richest aroma compounds. This invention provides a new systematic approach for the application of osmanthus extract in industries such as food and daily chemical products.

[0013] The osmanthus extract prepared using the method of the present invention appears as a yellowish-brown viscous liquid, has an acid value of 42-52 mg / g, an ester value of 19-46 mg / g, and a melting point of 48°C-55°C. It exhibits a rich golden osmanthus fragrance and woody aroma. This method minimizes the loss of volatile components in the osmanthus extract and effectively preserves the overall aroma of the osmanthus. The method is simple to operate, easy to implement, and has low production costs, making it suitable for large-scale industrial production and application, and has promising market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Fig. 1 These are the response surface diagrams of the effects of various factors on the yield of osmanthus extract; among them, (a) response surface diagram of factors A and B, (b) response surface diagram of factors A and C, (c) response surface diagram of factors A and D, (d) response surface diagram of factors B and C, (e) response surface diagram of factors B and D, and (f) response surface diagram of factors C and D.

[0015] Fig. 2 VEEN diagram (a) and relative content diagram (b) of volatile components in three kinds of osmanthus extracts.

[0016] Fig. 3 This is the GC-MS total ion pattern of sample 1 (Soxhlet extraction method).

[0017] Fig. 4 This is the GC-MS total ion map of sample 2 (supercritical CO2 extraction method).

[0018] Fig. 5 This is the GC-MS total ion pattern of sample 3 (subcritical n-butane extraction method). DETAILED DESCRIPTION

[0019] The following examples are provided to further illustrate the present invention, but are not intended to limit the present invention.

[0020] Osmanthus variety screening and comparison: Select Xianning Golden Osmanthus Osmanthus fragrans var. thunbergii ), Liuyang Golden Osmanthus Osmanthus fragrans var. thunbergii ), Liuyang Silver Osmanthus Osmanthus fragrans 'Latifolius' ) and Liuyang Osmanthus fragrans Osmanthus fragrans var. aurantiacus ) Four osmanthus varieties were extracted using the Soxhlet extraction method to make extracts, and their yields were compared to provide a raw material basis for later industrial utilization.

[0021] Experimental Methods and Results: Soxhlet extraction was performed. 50 g of osmanthus powder (evenly spread on an iron plate, vacuumed to 30 Pa, cold-trap at -80°C, frozen for 2 h, sublimated and dried for 20 h, pulverized in a grinder, and passed through a 30-mesh sieve) was accurately weighed and dispensed into filter paper tubes. The powder was completely soaked in 1 L of petroleum ether and placed in a Soxhlet extractor, refluxed at 40°C for 6 h. The extract was placed in a flat-bottom flask, rotary evaporated, and dried at 40°C to obtain an osmanthus extract. Three replicates were used for each experiment. As shown in Table 1, the yield of extract from different osmanthus varieties was significantly different (P < 0.05). Xianning Jingui had the highest yield, followed by Liuyang Dangui and Liuyang Jingui, while Liuyang Yingui had the lowest yield.

[0022] Table 1 Extract yield of different osmanthus varieties Therefore, the following examples and comparative examples were all carried out using Xianning Jingui as the raw material.

[0023] The overall technical route of the preparation method of the present invention is as follows: 1. Pre-cooling: Harvest the golden osmanthus (Xianning golden osmanthus) during its early flowering period, transport it in a cold chain vehicle (set at 0~4℃) and pre-cool it at low temperature at the same time.

[0024] 2. Sorting: Use color sorter to sort and remove impurities (remove leaves, branches, gravel, etc.). Secondary color sorting and impurity removal can be carried out as needed.

[0025] 3. Drying: Four drying methods were used: vacuum freezing, infrared, hot air, and heat pump, and optimized (Example 1). After drying, the dried osmanthus flowers were crushed in a grinder and passed through a 10-30 mesh sieve to obtain dried osmanthus flower powder.

[0026] 4. Extraction: The dried osmanthus flower powder was subjected to subcritical n-butane extraction and the method was optimized (Example 2) to obtain an osmanthus flower extract.

[0027] Example 1: Optimization of drying method Osmanthus fragrans (Xiangning Jingui) was dried by hot air drying, heat pump drying, infrared drying and vacuum freeze drying. The extracts were prepared by Soxhlet extraction and the yields were compared.

[0028] 1) Hot air drying (HAD): Spread the osmanthus flowers evenly on a tray and dry them in a hot air drying oven at 70°C for 10 h.

[0029] 2) Heat pump drying (HPD): Place the material tray containing osmanthus flowers in a heat pump drying oven at 50°C for 12 h.

[0030] 3) Infrared radiation drying (IRD): Place the tray containing the osmanthus flowers in an infrared drying oven at 60°C for 6 h.

[0031] 4) Vacuum freeze drying (VFD): Spread the osmanthus flowers evenly on an iron tray, set the vacuum degree to 30 Pa, and the cold trap temperature to -80°C. Freeze the osmanthus flowers for 2 h and then sublimate and dry them for 20 h.

[0032] The results are shown in Table 2. VFD has the highest yield of 2.04%, which is significantly different from the osmanthus extracts extracted by other drying methods ( P <0.05), there was no significant difference in the yield of osmanthus extract between HAD and IRD, and the yield of HPD was the lowest, only 1.53%.

[0033] Table 2 Yields of four kinds of osmanthus extracts The volatile components of osmanthus extracts dried using four different drying methods (HAD, HPD, IRD, and VFD) were analyzed using GC-MS. The results are shown in Table 3. Thirty alcohols and four ketones were present, and their relative contents varied significantly. Alcohols were the main contributors to the volatile components of osmanthus extracts. Among the volatile components of osmanthus extracts dried using the four different drying methods, the types and relative contents of alcohols were higher than those of other substances. The relative contents of alcohols in HAD, HPD, IRD, and VFD osmanthus extracts were 35.89%, 39.62%, 37.22%, and 42.11%, respectively, with significant differences ( P<0.05), among which the relative content of alcohol in VFD osmanthus extract was the highest, followed by HPD, IRD, and HAD osmanthus extract was the lowest. Unsaturated alcohol contributed to the floral and fruity aroma, and the oxidation of linalool, trans-oxidation of linalool, β-ionone and dihydro-β-ionone were the characteristic aroma components of osmanthus extract. The oxidation of linalool contributed to the soft and sweet violet flower and beeswax aroma, the trans-oxidation of linalool contributed to the woody aroma, and the β-ionone contributed to the raspberry and violet flower aroma. The relative content of the three substances in VFD osmanthus extract was the highest, and the difference in relative content was significant (P < 0.05) compared with the other three drying methods. P <0.05). Dihydro-β-ionone contributed to the woody and floral aroma, and the relative content in IRD osmanthus extract was the highest, which was 0.24%. Linalool was only detected in VFD osmanthus extract, and the relative content was 0.29%. The relative content of geraniol, which contributed to the rose flower aroma, in VFD was the highest, which was 0.75%, and the relative contents in HAD, HPD and IRD were 0.09%, 0.08% and 0.08% respectively. This was mainly because geraniol had a low boiling point and was easy to decompose in a high-temperature environment.

[0034] The relative content of ketones in HPD osmanthus extract was the highest, followed by VFD, HPD, and HAD extract was the lowest. Long-chain ketones contributed to the floral and sweet aroma, and dihydro-β-ionone was the key aroma component of osmanthus extract. Dihydro-β-ionone contributed to the soft and sweet floral aroma, and was also known as "osmanthus king". It was detected in osmanthus extract prepared by the four drying methods, and the relative content in VFD osmanthus extract was the highest, which was 0.93%. The relative contents in HAD and IRD osmanthus extract were the same, which was 0.23%. The relative content in HPD osmanthus extract was the lowest, which was 0.19%, and the difference was significant (P < 0.05). P <0.05).

[0035] The above results showed that vacuum freeze-drying could reduce the browning and corruption of osmanthus during the drying process and the loss of heat-sensitive components in volatile components.

[0036] Table 3 Types and relative contents of volatile components in osmanthus extract prepared by different drying methods Note: - indicates not detected; different letters in the same row indicate significant difference (P < 0.05). P <0.05).

[0037] Example 2: Optimization of subcritical n-butane extraction method 1. Model fitting analysis Accurately weigh 120 g of dried osmanthus powder (prepared using the vacuum freeze-drying method described in Example 1, dried using a pulverizer, and then passed through a 10-30 mesh sieve) onto a sieve cloth and placed in the extraction vessel of a subcritical extraction apparatus. The vessel was sealed with a lid and the vacuum pump was turned on to evacuate the vessel to a vacuum state. Butane was injected into the extraction vessel as a subcritical fluid via a metering pump. Osmanthus extract was extracted using n-butane at various particle sizes, extraction temperatures, extraction times, and solid-to-liquid ratios. At the end of the extraction, the extract reached a separation tank where the solvent was removed by evaporation (the solvent evaporated and refluxed into the solvent tank). The resulting osmanthus extract was weighed and stored in a refrigerator at 4°C until ready for use. After each extraction, the extraction vessel was rinsed three times with petroleum ether to remove any residue from previous experiments.

[0038] On the basis of the single-factor experiments, particle size (10-30 mesh), extraction time (30 min-50 min), extraction temperature (40°C-50°C), and solvent volume (2.4 L-3.6 L) were selected as the four factors in the response surface design. A four-factor, three-level central composite response surface design was established, generating 29 groups of experiments in a random order (Table 3) to optimize the process flow of subcritical n-butane extraction of osmanthus extract and obtain the highest yield.

[0039] The experimental data for the response surface analysis model are shown in Table 4. The yield of osmanthus extract from subcritical extraction is 2.03%~4.52%. The variance analysis results of the quadratic model are shown in Table 5. F =63.10, P <0.0001, indicating that the model is extremely significant. F =3.84, indicating that lack of fit is not significantly correlated with pure error. R 2 The value is 0.9688, indicating a high correlation between the experimental data and the predicted values.

[0040] Table 4 Response surface experimental design and results The significance test showed that the extraction rate of osmanthus extract with subcritical n-butane was significantly affected ( P <0.05) include: linear terms of A, B, C and D; interaction terms of AB, BD and CD; and quadratic terms of the four factors. The order of influence of the linear terms on the subcritical extraction of osmanthus extract is B>A>C>D, that is, solvent volume>particle size>extraction temperature>extraction time.

[0041] The results showed that the prediction model for the yield of osmanthus extract from subcritical extraction had good fitting performance ( R 2=0.9844), the regression equation for the yield of osmanthus extract extracted by subcritical n-butane is: where Y is the yield, A, B, C and D are particle size, solvent volume, extraction temperature and extraction time, respectively.

[0042] Table 5 Analysis of variance (ANOVA) of the response surface quadratic model for osmanthus extract 2. Subcritical extraction response surface optimization analysis 3D view of response surface optimization for subcritical extraction of osmanthus extract Fig. 1 As shown in the figure, when the contour plot is elliptical, the interaction between the variables is significant, and when it is circular, the interaction between the variables is not significant. When the response surface is convex, the range of the variables is set appropriately.

[0043] like Fig. 1 As shown in (a), under constant extraction time and temperature, a 20-mesh particle size and a solvent volume of 3 L resulted in the highest yield of osmanthus extract, generating a significant interaction term. When the dried osmanthus flowers are crushed, the cell walls are disrupted, increasing the surface area for interaction between the solvent and the extract, improving the mass transfer mechanism for extract release and increasing the yield. With further refinement of the osmanthus powder particle size, leakage from the nylon bag is the primary cause of the decrease in yield. Similarly, with decreasing solid-liquid ratio, the yield initially increases and then decreases. Within the confined space of a subcritical enclosure, when the solvent cannot completely submerge the material, the osmanthus extract cannot be fully extracted. As the solid-liquid ratio decreases, the yield increases by fully soaking the material. However, when the solid-liquid ratio is too low, the active ingredients are not fully extracted due to insufficient conversion between the solid and liquid phases of the solvent, resulting in a decrease in yield.

[0044] like Fig. 1 As shown in (b), under constant solvent volume and extraction time, regardless of particle size, the yield initially increases and then stabilizes as the extraction temperature increases. Because rising temperature accelerates molecular diffusion, it enhances the contact between the butane solvent and the osmanthus extract molecules in the material, thereby improving the extract's extraction rate. Excessively high temperatures degrade the volatile components in the osmanthus extract and intensify the vaporization of butane molecules within the extraction tank, reducing the actual volume of the subcritical butane solvent, hindering the extraction of the osmanthus extract and reducing the yield. Therefore, the highest osmanthus extract yield is achieved at an extraction temperature of approximately 45°C, demonstrating a significant secondary effect.

[0045] like Fig. 1(c) As shown in Fig. 2, the yield of osmanthus extract increased at first and then decreased with the increase of extraction time at constant solvent volume and extraction temperature, regardless of the particle size of the material. In the initial stage of extraction, the active ingredients in the material were in a rapid mass transfer stage, and the butane solvent diffused rapidly to the high concentration, so the yield increased significantly with the increase of extraction time, with a significant quadratic effect. After that, the diffusion movement of the oil molecules in the butane solvent and the oil molecules in the material cells reached a dynamic balance, and the mass transfer entered a slow stage, so the yield tended to be flat. However, if the extraction time was too long, the active ingredients of osmanthus extract would be damaged, resulting in a decrease in yield.

[0046] Under the condition of fixed 20 mesh particle size and 30 min extraction time, the response surface graph of the function of solvent volume (B) and extraction temperature (C) was established, as shown in Fig. 3. Fig. 1 (d) As shown in Fig. 3, when the solvent volume was about 3 L, the yield of osmanthus extract reached a maximum as the temperature increased to 45°C. Properly increasing the solvent volume could increase the solubility of the extract, and the increase of temperature could increase the mass transfer rate, but the interaction of the two variables had no significant effect on the yield (P>0.05). The effect of extraction temperature on the yield was significant (P<0.05), and when the extraction temperature was about 45°C, the extraction system was in a stable state.

[0047] Under the condition of fixed 20 mesh particle size of osmanthus and extraction temperature of 45°C, the response surface graph of the function of solvent volume and extraction time was established. As shown in Fig. 4, Fig. 1 (e) As shown in Fig. 4, as the ratio of material to liquid decreased and the extraction time prolonged, the system tended to be stable, the mass transfer rate was fast, and the yield was high. However, the continuous increase of solvent volume and extraction time led to the decrease of active ingredients of the extract, and the interaction of the two variables had a significant effect on the yield (P<0.05). P

[0048] Under the condition of fixed 20 mesh particle size of osmanthus and solvent volume of 3 L, the response surface graph of the function of extraction temperature and time was established. The interaction of the two factors had a very significant effect on the extraction rate (P<0.01). As shown in Fig. 5, P Fig. 1 (f) As shown in Fig. 5, the yield of extract increased with the increase of extraction time, and reached a maximum around 38 min. The increase of extraction temperature increased the solubility of the extract, reduced the viscosity of the extract and the density of the solvent, thus increased the diffusion coefficient and mass transfer rate, and improved the extraction rate. However, the continuous increase of extraction time and temperature damaged the active ingredients of osmanthus extract, resulting in a decrease in yield.

[0049] ​​Regression equations and response surface analysis revealed the optimal experimental conditions: a particle size of 20.41 mesh, a solid-liquid ratio of 120 g:3.06 L (1:25.5 g / mL), an extraction temperature of 45.48°C, and an extraction time of 38.59 min. Three validation experiments under these conditions yielded an average yield of 4.43 ± 0.03%, which was comparable to the predicted yield of 4.47%, demonstrating the reliability and practicality of the extraction conditions optimized by the response surface method.

[0050] Comparative Example 1: Soxhlet extraction (SE) Accurately weigh 50 g of dried osmanthus powder (prepared using the vacuum freeze-drying method described in Example 1, crushed with a grinder, and passed through a 20-mesh sieve to obtain Xianning Jingui dried osmanthus powder). Dispense the powder into filter paper tubes and completely soak it in 1 L of petroleum ether. Place the extract in a Soxhlet extractor and reflux at 40°C for 6 h. Place the extract in a flat-bottom flask, rotary evaporate, and dry at 40°C to obtain an osmanthus extract.

[0051] Comparative Example 2: Supercritical CO2 Extraction (SFE) 100 g of dried osmanthus powder (prepared by the vacuum freeze-drying method of Example 1, dried using a grinder, and then passed through a 20-mesh sieve to obtain Xianning Jingui dried osmanthus powder) was placed in an extraction container equipped with a mesh filter. CO2 was pumped into the extractor until the desired extraction pressure value was reached, and supercritical CO2 extraction was performed. During the extraction process, the operating pressure, temperature, and time were controlled at 25 MPa, 45°C, and 4 h, respectively.

[0052] Effect evaluation: extraction conditions and yields of different extraction methods 1) Yield comparison Table 6 shows that the yields of osmanthus extract obtained using the three extraction methods, Example 2 (referring to the optimal experimental conditions of Example 2, the same below), and Comparative Examples 1 and 2, ranged from 2.33% to 4.43%, showing significant differences. The yields, from highest to lowest, were: SBE > SFE > SE. This difference is primarily due to the different extraction conditions. The higher yield of SBE is likely due to the improved permeability of n-butane under high pressure, while the lower yield of SFE is likely due to its weaker polarity and reduced ability to bind the active ingredient. SE extraction requires 6 hours, and SFE is expensive during high-pressure operation. Therefore, subcritical n-butane extraction is a suitable method for extracting osmanthus extract.

[0053] Table 6 Yields of osmanthus extracts by different extraction methods 2) Comparison of the amount of volatile components like Fig. 2As shown in (a), there are 21 volatile components in common in the osmanthus extracts extracted by three different methods, 16 volatile components unique to the SFE osmanthus extract, 18 volatile components unique to the SE osmanthus extract, and 34 volatile components unique to the SBE osmanthus extract. There are significant differences in the types of volatile components in the osmanthus extracts extracted by different methods.

[0054] Combined with Table 7 and Fig. 2 It can be seen that the types and contents of volatile components in osmanthus extracts differ significantly depending on the extraction method. A total of 115 volatile components were detected in the three control groups. The extracts extracted with SE, SFE, and SBE contained 52, 55, and 77 volatile components, respectively. Sample 1, obtained by Soxhlet extraction (SE) in Comparative Example 1, showed high relative contents of olefins and alcohols in the extract, but significant loss of aromatic components, resulting in a relatively low relative content and variety. Sample 2, obtained by supercritical CO₂ extraction (SFE) in Comparative Example 2, showed high relative contents of aromatic components such as ketones and linalool and their oxides, but with a low variety. The characteristic aromatic components of the extract were well preserved. Sample 3, obtained by subcritical n-butane extraction (SBE) in Example 2, showed a high degree of retention of the types and relative contents of specific aromatic components, resulting in a rich and natural aroma, and good preservation of the extract's overall aromatic composition.

[0055] Table 7 Relative contents of volatile components in three osmanthus extracts 3) Comparison of GC-MS components and total ion currents Depend on Fig. 3 、 Fig. 4 and Fig. 5 The GC-MS total ion current (TIC) of the three different extraction methods showed that the volatile components of the osmanthus extract obtained by SBE extraction were the largest and the richest, followed by SFE.

[0056] Olefin compounds were detected in all three osmanthus extracts obtained by different extraction methods. Among them, α-pinene, β-pinene, α-phellandrene, myrcene, terpinene, 1-caryophyllene, dextrorotatory terpenoids, valencia citronellal, β-cedrene, caryophyllene oxide, styrene, and thujopsis belong to the terpene class. These compounds have a low olfactory threshold and are the primary contributors to the aroma of the essential oil. They were primarily detected in the SBE osmanthus extract. β-pinene, α-phellandrene, myrcene, terpinene, β-cedrene, caryophyllene oxide, and thujopsis are unique aroma compounds in the SBE osmanthus extract. β-pinene, with a characteristic turpentine odor, contributes a dry, woody or resinous aroma, with a relative content of 0.03%; α-phellandrene, with a relative content of 0.01%, has a pleasant, refreshing citrus with a discrete minty note; myrcene, with a relative content of 0.01%, has a sweet, resinous aroma; terpinene, with a relative content of 0.01%, contributes a bitter, tropical, lemony aroma; β-cedrene, with a relative content of 0.53%, contributes a cypress-like, woody note; caryophyllene oxide, styrene, and thujopsis oleraceus, with relative contents of 0.05%, 0.06%, and 0.05%, respectively, contribute clove notes and sweet, floral aromas. α-pinene, 1-caryophyllene, dextrorotatory terpenes, and valencia tangerene are common substances in SBE and SFE osmanthus extracts but were not detected in SE osmanthus extract. α-Pinene, 1-caryophyllene, dextrorotatory terpenes and valencia tangerene contribute to the pine woody smell, spicy clove smell, lemon smell and citrus-like sweet smell respectively.

[0057] Alcohols were the most numerous and most abundant volatile compounds in the osmanthus extracts extracted using the three different extraction methods. Most alcohols had high olfactory thresholds and contributed little to the aroma of the extracts. SE osmanthus extract had the most diverse alcohols, with the highest relative content of 42.90%. Linalool, trans-linalool oxide, dihydro-β-ionol, β-ionol, and geraniol had low olfactory thresholds and were the primary aroma components of osmanthus extracts. These compounds were detected in all three extracts. Linalool contributes a sweet, floral aroma, with the highest relative content in SBE extract at 0.29% and the lowest in SE at 0.20%. Trans-linalool contributes a soft, sweet, and long-lasting violet and beeswax aroma, with the highest relative content in SBE at 4.52%, followed by SFE at 4.42%, and the lowest relative content in SE at 2.27%. Dihydro-β-ionol contributes a woody, floral, and camphoraceous aroma, with the same relative content of 0.16% in both SBE and SFE, and the lowest relative content in SE at 0.12%. β-ionol contributes a violet floral aroma, with the highest relative content in SBE at 4.15%, followed by SE at 3.31%, and the lowest relative content in SFE at 3.09%. Cinnamal, a component unique to SBE, possesses a cypress woody aroma and a calming effect. The relative contents of geraniol in SBE, SE, and SFE are 0.55%, 0.53%, and 0.35%, respectively.

[0058] Among ketones, dihydro-β-ionone, an aroma component of osmanthus extract, contributes a soft, sweet violet floral aroma. It was detected in all three extracts, with a relative concentration of 2.54% in the SBE extract. Menthone, a minty aroma unique to the SBE extract, was present at a relative concentration of 0.06%. Esters were found in the SBE extract at a relative concentration of 11.54% and the largest number of 14 species, followed by SFE at 8.99% and eight species. SE extract had the lowest relative concentration. Dihydroactinolactone, a slightly milky, fruity, sweet aroma, was present at a relative concentration of 0.08% in the SBE extract. Neroli acetate, a unique component of SBE, possesses sweet orange blossom and rose aromas.

Claims

1. A method for preparing osmanthus extract, characterized in that: The following steps are involved: S1. Harvest osmanthus flowers during their early flowering period, pre-cool them to 0-4°C, and sort and remove impurities. S2. The osmanthus was freeze-dried in vacuo, crushed and sieved to obtain dry osmanthus powder; S3. Extract the dried osmanthus flower powder with subcritical n-butane. The extraction conditions are as follows: a particle size of 20-30 mesh, a solid-liquid ratio of 1 g:25-30 mL, an extraction temperature of 45°C-50°C, and an extraction time of 30-40 min. The extract is evaporated to remove the solvent to obtain an osmanthus flower extract.

2. The method according to claim 1, characterized in that The osmanthus fragrans is golden osmanthus.

3. The method according to claim 2, characterized in that The osmanthus fragrans is Xianning golden osmanthus.

4. The method according to claim 1, wherein The impurity removal is to use a color sorter to remove leaves, branches and gravel.

5. The method according to claim 1, wherein The vacuum freeze-drying conditions are as follows: vacuum degree 30 Pa, cold trap temperature -80 ° C, freezing for 2 h, and sublimation drying for 20 h.

6. The method according to claim 1, wherein The extraction conditions are as follows: the particle size of the dry osmanthus powder is 20-20.41 meshes, the material-liquid ratio is 1 g:25.5 mL, the extraction temperature is 45° C.-45.48° C., and the extraction time is 38.59 min.

7. The sweet osmanthus extract prepared according to the method according to any one of claims 1 to 6.

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