Preparation method of ethanol-free food-grade water-soluble menthol

Abstract

The invention relates to the technical field of menthol preparation, in particular to a preparation method of ethanol-free food-grade water-soluble menthol, which comprises the following steps: raw material preparation, micronization pretreatment, constant-temperature inclusion reaction, gradient shear emulsification and low-temperature fluidized drying. The raw materials comprise food-grade L-menthol, beta-cyclodextrin, polyglycerol fatty acid ester, sucrose fatty acid ester and deionized water, and ethanol is not used in the whole process; the micronization pretreatment is to crush the L-menthol until the particle size is less than or equal to 50 microns; ethanol is not used as a cosolvent in the whole process, only food-grade L-menthol, beta-cyclodextrin, polyglycerol fatty acid ester, sucrose fatty acid ester, deionized water and other raw materials meeting the GB2760 food additive standard are adopted, the water solubility of menthol is improved through the synergistic effect of physical inclusion and emulsification, ethanol residues are not detected in a final product, and the preparation method is simple and convenient to operate. And potential safety hazards caused by a traditional ethanol hydrotropy process are thoroughly avoided.

Description

Technical Field

[0001] This invention relates to the field of menthol preparation technology, specifically to a method for preparing ethanol-free, food-grade, water-soluble menthol. Background Technology

[0002] In the field of food additives and functional food preparation, menthol is widely used in various products such as beverages, candies, and baked goods due to its unique refreshing flavor and sensory experience. However, menthol itself has the inherent characteristic of poor water solubility, which has long restricted its uniform dispersion and stable application in water-based food systems, becoming a key technical bottleneck that urgently needs to be solved in the industry.

[0003] In traditional techniques, ethanol is often used as a co-solvent to improve the water solubility of menthol. However, ethanol-co-solvent processes have significant drawbacks: firstly, ethanol residue poses a potential safety risk to food, especially failing to meet the stringent requirements for alcohol-free ingredients in children's food and non-alcoholic beverages; secondly, the volatility of ethanol causes menthol to be easily lost along with the ethanol during processing and storage, not only reducing the content of active ingredients in the product but also compromising flavor stability, leading to a significant decline in product quality over its shelf life.

[0004] To avoid the drawbacks of ethanol as a solubilizer, two ethanol-free solutions have gradually developed in existing technologies: single inclusion technology and single emulsification technology. However, both have significant shortcomings. Single inclusion technology often uses β-cyclodextrin as a carrier; however, this technology suffers from low inclusion rates, and unencapsulated free menthol easily precipitates in aqueous solutions, leading to turbidity or sedimentation after the product has stood, affecting the appearance and taste of the food. Furthermore, the choice of a single carrier limits the performance of the inclusion system, making it difficult to balance water solubility and stability. Single emulsification technology relies on emulsifiers to disperse menthol, but due to the lack of synergistic effect from a carrier, the emulsion system is prone to stratification and demulsification under high or low temperature conditions. In addition, insufficient compatibility between the emulsifier and menthol results in poor dispersion, making it difficult to meet the sensory experience and long-term stability requirements of the product.

[0005] Furthermore, existing technologies generally suffer from poor process synergy: on the one hand, the selection of inclusion carriers and emulsifiers lacks scientific matching, making it difficult for them to form effective synergy and fully leverage their respective performance advantages; on the other hand, the setting of process parameters is rather arbitrary, failing to be precisely optimized based on the characteristics of menthol, carriers, and emulsifiers, resulting in low product recovery rates and uneven particle size, further affecting the product's application effect. Simultaneously, some technologies, in pursuit of higher inclusion rates and stability, use a single, high-priced inclusion carrier, leading to persistently high raw material costs and making it difficult to meet the economic requirements of large-scale production; conversely, reducing carrier costs results in a significant decline in product performance, creating the industry pain point of "high performance inevitably leading to high cost." These combined defects of existing technologies severely limit the industrial application and market promotion of ethanol-free food-grade water-soluble menthol, necessitating a preparation method that can systematically solve the above problems. Summary of the Invention

[0006] The primary objective of this invention is to provide a method for preparing ethanol-free, food-grade, water-soluble menthol.

[0007] A further objective of this invention is to provide a method for preparing ethanol-free food-grade water-soluble menthol, comprising the following steps: raw material preparation, micronization pretreatment, isothermal inclusion reaction, gradient shear emulsification, and low-temperature fluidized bed drying; the raw materials include food-grade L-menthol, β-cyclodextrin, polyglycerol fatty acid ester, sucrose fatty acid ester, and deionized water, without using ethanol throughout the process; the micronization pretreatment involves pulverizing L-menthol to a particle size ≤50 micrometers; the isothermal inclusion reaction involves dissolving β-cyclodextrin in deionized water, adding menthol micronized powder, and stirring at a constant temperature to form an inclusion complex suspension; the gradient shear emulsification involves adding polyglycerol fatty acid ester and sucrose fatty acid ester to the inclusion complex suspension, followed by gradient speed stirring and shear treatment to form an emulsion; the low-temperature fluidized bed drying involves sequentially spray drying and low-temperature fluidized bed drying of the emulsion to obtain ethanol-free food-grade water-soluble menthol.

[0008] Preferably, the raw materials, by weight, are: 10 parts food-grade L-menthol, 50-60 parts β-cyclodextrin, 2.5-3 parts polyglycerol fatty acid ester, 2-2.5 parts sucrose fatty acid ester, and 200-220 parts deionized water.

[0009] Preferably, during the micronization pretreatment process, the temperature of the grinding chamber is controlled at 35°C.

[0010] Preferably, in the isothermal inclusion reaction, the temperature for dissolving β-cyclodextrin is 50°C, and the stirring time is 30 minutes; after adding menthol powder, the stirring speed is 500 rpm, the stirring time is 2 hours, and the temperature is maintained at 50°C.

[0011] Preferably, in the gradient shear emulsification, the temperature is raised to 60-65°C, and the mixture is stirred at 5000-6000 rpm for 10-15 minutes, followed by shearing at 10000-12000 rpm for 30-40 minutes.

[0012] Preferably, the spray dryer has an inlet temperature of 160°C, an outlet temperature of 80-85°C, and a feed rate of 15-20 ml / min; the low-temperature fluidized bed dryer uses 40°C nitrogen as the fluidizing medium and has a processing time of 20 minutes.

[0013] Preferably, the β-cyclodextrin is replaced by a complex inclusion carrier, which is composed of β-cyclodextrin and maltodextrin, and is composed of 40 parts by weight of β-cyclodextrin and 20 parts by weight of maltodextrin.

[0014] Preferably, after the micronization pretreatment, a low-temperature drying step is added, with a drying temperature of 40°C and a drying time of 30 minutes.

[0015] Preferably, after the low-temperature fluidized drying, a sieving step is added, using a 120-mesh sieve.

[0016] Preferably, the polyglycerol fatty acid ester has a degree of polymerization of 6, and the sucrose fatty acid ester has an HLB value of 11.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. This invention does not use ethanol as a co-solvent throughout the entire process. It only uses food-grade L-menthol, β-cyclodextrin, polyglycerol fatty acid esters, sucrose fatty acid esters, and deionized water, all conforming to the GB2760 food additive standard. Through physical inclusion and emulsification, the water solubility of menthol is enhanced. No ethanol residue was detected in the final product, completely avoiding the safety hazards associated with traditional ethanol-coated solubilization processes. This characteristic allows the product to be widely used in children's food, non-alcoholic beverages, health foods, and other fields with strict requirements for non-alcoholic components, significantly expanding the application scope of menthol in the food industry. Simultaneously, it avoids the interference of ethanol on the purity of food flavor and improves the sensory quality of the product.

[0019] 2. This invention constructs a highly efficient inclusion-emulsification synergistic system by optimizing the inclusion carrier ratio and process parameters, effectively solving the problems of low inclusion rate and free menthol precipitation in existing single inclusion technologies. By adjusting the type and amount of inclusion carrier, the effective contact sites between menthol molecules and the hydrophobic cavity of the carrier are increased, significantly reducing the content of free menthol. Simultaneously, precise inclusion temperature control and pretreatment processes provide favorable conditions for molecular-level inclusion, significantly improving the inclusion rate and water solubility. The final product achieves long-term stable dispersion in aqueous solution without turbidity or precipitation, meeting the requirements of component homogeneity in water-based food systems, while also improving the effective utilization rate of menthol in food.

[0020] 3. This invention addresses the problems of unstable emulsion systems and poor adaptability to high and low temperatures in existing technologies. By optimizing emulsification process parameters and emulsifier ratios, the overall stability of the product is significantly improved. Adjusting the emulsification temperature, stirring speed, and shear strength enhances the activity of emulsifier molecules, enabling them to form a uniform and dense protective film on the surface of the encapsulated particles. Simultaneously, adjusting the proportion of the composite emulsifier ensures a high degree of compatibility between the HLB value of the emulsion system and the hydrophilic and lipophilic properties of the encapsulated particles, further improving the emulsification effect. The optimized product not only exhibits excellent centrifugal stability at room temperature but also maintains good solubility and dispersibility under both high and low temperature conditions, preventing stratification and demulsification. Furthermore, the product shows minimal solubility fluctuations within a pH range of 3-7, making it suitable for processing various complex food systems such as beverages and acidic foods, providing a stable guarantee for its application in different types of foods.

[0021] 4. This invention employs a composite inclusion carrier to replace the traditional single, high-cost carrier. This reduces raw material costs while further improving product performance, effectively addressing the industry pain point of high performance inevitably leading to high costs in existing technologies. The low-cost component introduced into the composite carrier is significantly cheaper than β-cyclodextrin, and the polyhydroxyl groups in its molecular structure synergistically enhance the overall water solubility of the inclusion system. Furthermore, it prevents the escape of menthol molecules through steric hindrance, improving the product's shelf-life stability. This composite carrier design reduces the unit cost of raw materials without negatively impacting core performance characteristics such as inclusion rate, solubility, and stability. Instead, it achieves a dual optimization of cost and performance, providing economic feasibility for large-scale production and market promotion, and contributing to the widespread application of ethanol-free water-soluble menthol in the food industry.

[0022] 5. This invention further improves product quality and production efficiency through refined optimization of the entire process, including pretreatment, inclusion, emulsification, and drying. In the pretreatment stage, the combination of ultrafine grinding and low-temperature drying not only increases the contact area between menthol and the carrier but also removes trace amounts of moisture from the raw materials, preventing moisture from occupying the hydrophobic cavities of the carrier and laying the foundation for efficient inclusion. In the drying stage, the synergistic treatment of spray drying and low-temperature fluidized bed drying, along with subsequent sieving steps, effectively removes residual moisture from the product, breaks up slightly agglomerated particles, ensures uniform particle size, and improves product recovery rate. This refined process results in products that not only perform excellently in core indicators such as solubility and stability but also offer a good sensory experience and sustained-release flavor, continuously releasing a refreshing flavor throughout the food's shelf life, enhancing the consumer experience. Simultaneously, the high recovery rate reduces raw material waste during production, improves production efficiency, and further enhances the industrial application value of the technology. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1:

[0025] Raw material preparation: 10 parts food-grade L-menthol, 50 parts food-grade β-cyclodextrin, 3 parts polyglycerol fatty acid ester, 2 parts sucrose fatty acid ester, and 200 parts deionized water. All raw materials comply with GB2760 food additive standards. Among them, the polyglycerol fatty acid ester is selected as a food-grade product with a degree of polymerization of 6, and the sucrose fatty acid ester is selected as a model with an HLB value of 11. The combination of the two is adapted to the inclusion characteristics of β-cyclodextrin, solving the problem of poor compatibility between carrier and emulsifier in existing combination technologies.

[0026] Micronization pretreatment: L-menthol is fed into an ultrafine pulverizer, and the pulverization chamber temperature is controlled at 35℃ to prevent menthol volatilization. The pulverizer is pulverized to a particle size ≤50 micrometers to obtain uniformly dispersed menthol micro powder. This step increases the contact area between menthol and β-cyclodextrin, laying the foundation for molecular-level inclusion, and improving the inclusion efficiency by 12% compared to traditional pulverization methods, thus solving the problem of low inclusion rate in existing technologies.

[0027] Isothermal inclusion reaction: β-cyclodextrin is slowly added to deionized water, the stirring device is turned on, and the temperature is raised to 50°C and stirred continuously for 30 minutes until the β-cyclodextrin is completely dissolved to form a transparent solution. Menthol powder is added to the solution at a uniform rate of 5 parts per minute, maintaining a constant temperature of 50°C and stirring at 500 rpm for 2 hours, allowing menthol molecules to fully enter the hydrophobic cavities of the β-cyclodextrin, forming a stable inclusion suspension. This temperature is the optimal reaction temperature for the inclusion of menthol by β-cyclodextrin. Too high a temperature will cause menthol to volatilize, while too low a temperature will reduce the inclusion reaction rate by more than 30%, thus solving the problem of unreasonable inclusion reaction parameters in existing technologies.

[0028] Gradient shear emulsification: A predetermined ratio of polyglycerol fatty acid ester and sucrose fatty acid ester is added to the inclusion complex suspension. The mixture is heated to 60°C and stirred at 5000 rpm for 10 minutes to ensure uniform dispersion of the emulsifier. Then, a high-speed shear emulsifier is started, and the mixture is sheared at 10000 rpm for 30 minutes to form a uniform and fine emulsion. This gradient shear process avoids localized aggregation of the emulsifier, ensuring that an emulsified protective film forms on the surface of each inclusion complex particle, thus solving the problem of insufficient emulsification in existing technologies.

[0029] Low-temperature fluidized bed drying: The emulsion is fed into a spray dryer with an inlet temperature of 160°C, an outlet temperature of 80°C, and a feed rate of 20 ml / min. After drying, the primary product is collected by a cyclone separator and then fed into a low-temperature fluidized bed dryer. The primary product is treated with nitrogen at 40°C as the fluidizing medium for 20 minutes to remove residual moisture and break up slightly agglomerated particles, ultimately obtaining ethanol-free food-grade water-soluble menthol with a product recovery rate of 92%, solving the problems of easy agglomeration and low recovery rate of existing technologies.

[0030] Example 2:

[0031] Based on the test results of Example 1, it was found that the inclusion rate of 50 parts β-cyclodextrin to 10 parts menthol was 88%, but a small amount of free menthol still remained, resulting in trace precipitation after the aqueous solution was allowed to stand. This is a common defect of existing single inclusion technologies. This example specifically adjusts the raw material ratio: 10 parts food-grade L-menthol, 60 parts food-grade β-cyclodextrin, 3 parts polyglycerol fatty acid ester, 2 parts sucrose fatty acid ester, and 220 parts deionized water. The remaining process steps are completely consistent with Example 1. Increasing the amount of β-cyclodextrin increases the effective contact sites of the inclusion reaction, significantly reducing the content of free menthol. Simultaneously, adjusting the amount of deionized water allows for the dissolution of more carriers, preventing the solution from becoming viscous and affecting subsequent emulsification. This optimization increases the inclusion rate to 95%, and the solubility from 0.85 g / 100 mL to 0.92 g / 100 mL. No precipitation occurred after the aqueous solution stood for 24 hours. Compared with existing single inclusion technologies, the solubility is improved by 73.6%, completely solving the problem of free menthol precipitation.

[0032] Example 3:

[0033] The product in Example 2, after storage at 60°C, retained 95% of its solubility, indicating room for improvement. The core reason is that the emulsification temperature and shear strength were not fully adapted to the inclusion complex's characteristics, a typical problem stemming from poor synergy of process parameters in existing combined technologies. This example optimizes the emulsification process parameters: the emulsification temperature is increased to 65°C, followed by stirring at 6000 rpm for 15 minutes, and then high-speed shearing at 12000 rpm for 40 minutes. Simultaneously, the ratio of the composite emulsifier is adjusted to 2.5 parts polyglycerol fatty acid ester and 2.5 parts sucrose fatty acid ester. The remaining raw material ratios and process steps are identical to those in Example 2. 65°C enhances the activity of the emulsifier molecules, increasing their adsorption efficiency on the inclusion complex surface. The adjusted emulsifier ratio brings the HLB value closer to the hydrophilic-lipophilic balance requirement of the inclusion complex. Combined with higher shear strength, the inclusion complex is dispersed into tiny particles with a diameter ≤1 micrometer, significantly enhancing the stability of the emulsion system. This optimization improves the high-temperature solubility retention rate to 98%, ensures centrifugal stability without stratification, and raises the sensory score to 19 points. Compared with the existing simple combination technology, the high-temperature stability is improved by 18.1%, which solves the defect of easy stratification at high temperatures in the existing technology.

[0034] Example 4:

[0035] The high performance of Example 3 relies on 60 parts of a single β-cyclodextrin, resulting in high raw material costs and hindering large-scale production—a core drawback of existing single-carrier inclusion technologies. This example innovatively employs a composite inclusion carrier: 40 parts of β-cyclodextrin and 20 parts of maltodextrin, replacing the 60 parts of single β-cyclodextrin in Example 3. The remaining raw material ratios and process steps are identical to Example 3. Maltodextrin not only costs only one-third of β-cyclodextrin, but its polyhydroxyl groups in its molecular structure also synergize with β-cyclodextrin. The hydrophilic groups of maltodextrin enhance the overall water solubility of the inclusion complex, while its steric hindrance further prevents menthol molecules from escaping, achieving the dual goals of cost reduction and performance improvement. This optimization reduces raw material costs by 15%, maintains an inclusion rate of 94%, achieves a solubility of 0.95 g / 100 ml, and increases the menthol retention rate during shelf life to 94%. Compared to existing single-carrier technologies, it reduces costs by 15% while improving shelf-life retention by 18.9%, resolving the inherent trade-off between high performance and low cost in existing technologies.

[0036] Example 5:

[0037] The composite carrier system in Example 4 further optimizes the pretreatment and posttreatment processes, addressing the issues of trace moisture affecting inclusion efficiency and product particle size uniformity—details that have not been adequately addressed in existing technologies. In the pretreatment stage, a 30-minute low-temperature drying process at 40°C is added after ultrafine pulverization to thoroughly remove trace moisture from the menthol powder, preventing moisture from occupying the hydrophobic cavities of β-cyclodextrin. In the posttreatment stage, the spray drying feed rate is adjusted to 15 ml / min, and the outlet temperature is increased to 85°C to enhance moisture evaporation efficiency. Simultaneously, a 120-mesh sieving step is added after low-temperature fluidized drying to remove a very small amount of agglomerated large particles, ensuring uniform product particle size. The remaining raw material ratios and core process steps are completely consistent with Example 4. This comprehensive process improvement increases the product recovery rate to 97%, solubility exceeds 1.02 g / 100 ml, menthol retention reaches 98% during shelf life, and the clarity and flavor sustaining properties of the aqueous solution are optimized, fully meeting the stringent requirements for alcohol-free foods. Compared to traditional ethanol-assisted solubilization processes, the solubility is increased by 13.3%, with no ethanol residue; compared to existing combined technologies, the overall performance is improved by more than 15%, achieving a comprehensive surpassing of existing technologies.

[0038] Comparative Example 1:

[0039] The raw material ratio is 10 parts food-grade L-menthol and 200 parts deionized water. The process only includes micronization pretreatment and spray drying, without inclusion reaction, emulsification dispersion and low temperature fluidization steps. The menthol micron powder is directly mixed with deionized water and then spray dried, simulating the simple dispersion scheme in the existing technology that does not use any solubilization technology.

[0040] Comparative Example 2:

[0041] The raw material ratio is 10 parts food-grade L-menthol, 60 parts β-cyclodextrin, and 220 parts deionized water. The process includes micronization pretreatment, constant temperature inclusion reaction, and spray drying, without emulsification dispersion, low temperature fluidization, and sieving steps, simulating the existing technology that relies solely on cyclodextrin inclusion.

[0042] Comparative Example 3:

[0043] The raw material ratio is 10 parts food-grade L-menthol, 3 parts polyglycerol fatty acid ester, 2 parts sucrose fatty acid ester, and 200 parts deionized water. The process includes micronization pretreatment, emulsification dispersion, and spray drying. There are no inclusion reaction or low-temperature fluidization steps, which simulates the existing technology that relies solely on emulsifier dispersion.

[0044] Comparative Example 4:

[0045] The raw materials are 10 parts of food-grade L-menthol, 30 parts of edible ethanol, and 170 parts of deionized water. The process involves completely dissolving menthol in ethanol, mixing it with deionized water, and then directly spray drying it. The inlet temperature is 150℃ and the outlet temperature is 75℃. There are no inclusion carriers, emulsifiers, or low-temperature fluidization steps. This process simulates the traditional ethanol-assisted solubilization method in existing technologies.

[0046] Comparative Example 5:

[0047] The raw material ratio is the same as in Example 1. The process is to directly use ordinary stirring at 500 rpm after the inclusion reaction to replace gradient shear emulsification, without the low-temperature fluidized drying step. The remaining steps are the same as in Example 1, simulating the existing technology of simply superimposing inclusion and emulsification without optimizing process parameters.

[0048] Comparative Example 6:

[0049] The raw material ratio is 10 parts food-grade L-menthol, 50 parts β-cyclodextrin, 5 parts glyceryl monostearate, and 200 parts deionized water. The process is the same as in Example 1. Glyceryl monostearate with an HLB value of 5 is used to replace the composite emulsifier of the present invention to simulate the problem of poor compatibility between inclusion carrier and emulsifier in the prior art.

[0050] Test items and methods:

[0051] Water solubility test: Take 1 gram of sample and add it to 100 ml of 25℃ deionized water. Stir for 5 minutes and let stand for 24 hours. Use ultraviolet spectrophotometry to determine the menthol content in the supernatant and calculate the solubility. At the same time, observe the clarity of the solution and record the precipitation.

[0052] Inclusion ratio test: Free menthol in the product was extracted using Soxhlet extraction, and the inclusion ratio was calculated as the ratio of the total menthol content minus the free menthol content to the total menthol content.

[0053] Stability tests: Centrifugal stability was determined by centrifuging at 3000 rpm for 30 minutes and observing the stratification; High-temperature stability was determined by sealing and storing at 60℃ for 7 days and measuring the solubility retention rate; Cold storage stability was determined by sealing and storing at 4℃ for 30 days and observing the appearance and measuring the solubility; Shelf life stability was determined by storing at 25℃ in the dark for 6 months and measuring the menthol retention rate; Molecular dispersibility was determined by dynamic light scattering method to measure the particle size distribution of the product.

[0054] Food safety testing: Gas chromatography was used to detect ethanol residue, and atomic absorption spectrophotometry was used to detect lead and arsenic heavy metal content, both in accordance with GB2760 food additive standard.

[0055] Sensory and practical performance tests: Ten professional evaluators were invited to score the peppermint aroma intensity and refreshing taste of the aqueous solution, with a total score of 20 points; the solubility change of the product in the pH range of 3 to 7 was measured to simulate the pH adaptability of the food system; flavor sustained release was tested, and the change in peppermint aroma intensity of the aqueous solution was recorded over 2 hours.

[0056] Production performance testing: Statistical analysis of product recovery rate and calculation of raw material unit cost.

[0057] The test results are shown in Table 1 below: Table 1 Performance test results of the examples and comparative examples

[0058] Test Project Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Solubility (grams per 100 milliliters) 0.85 0.92 0.98 0.95 1.02 0.28 0.53 0.41 0.90 0.68 0.59 Inclusion rate (%) 88 95 96 94 97 - 93 - - 86 82 Centrifugal stability No layering No layering No layering No layering No layering Severe stratification Slight stratification Clearly layered No layering Slight stratification Clearly layered High-temperature solubility retention rate (%) 92 95 98 96 99 62 76 68 80 83 79 Refrigeration stability No sediment No sediment No sediment No sediment No sediment Large amount of sediment Small amount of sediment Medium sedimentation No sediment Small amount of sediment Medium sedimentation Menthol retention rate during shelf life (%) 89 93 96 94 98 58 79 71 82 85 81 Average particle size (micrometers) 1.2 1.0 0.8 0.9 0.7 5.6 2.8 3.2 1.5 2.1 2.5 Ethanol residue (mg / kg) Not detected Not detected Not detected Not detected Not detected Not detected Not detected Not detected 820 Not detected Not detected Heavy metals (lead / arsenic) Not detected Not detected Not detected Not detected Not detected Not detected Not detected Not detected Not detected Not detected Not detected Sensory rating (total score) 17 18 19 18 20 11 14 12 15 16 13 pH adaptability (solubility fluctuation %) ±3 ±2 ±1 ±1.5 ±1 ±12 ±8 ±10 ±4 ±6 ±9 Flavor sustained-release properties (2-hour retention rate %) 85 88 92 90 95 45 65 55 70 78 68 Product recovery rate (%) 92 93 94 95 97 88 90 89 91 91 90 Unit cost of raw materials (yuan per kilogram) 180 195 198 168 172 120 190 170 135 185 182

[0059] The results are analyzed as follows:

[0060] (1) Each embodiment forms a closely connected technical chain, with each optimization precisely addressing the core defects of the previous solution and the shortcomings of existing technologies. Example 1 achieves basic solubilization through molecular-level synergy, increasing solubility by 1.1 to 1.9 times compared to Comparative Examples 1 to 3; Example 2 optimizes the inclusion ratio, specifically addressing the issue of free menthol precipitation, increasing the inclusion rate by 7%; Example 3 strengthens the emulsification system, solving the problem of insufficient high-temperature stability, reducing particle size to 0.8 micrometers; Example 4 innovates the composite carrier, maintaining high performance while reducing costs by 15%; Example 5 refines the entire process, achieving comprehensive optimization of solubility, stability, and recovery rate, with overall performance improvement of over 15% compared to Example 1. This progressive optimization forms a closed loop of problem-solution-performance improvement, reflecting the integrity of the technical solution and the systematic overcoming of the defects of existing technologies.

[0061] (2) The solubility of Example 5 is 3.6 times that of Comparative Example 1, the shelf life retention rate is 1.7 times that of Comparative Example 1, and the centrifugal stability achieves no stratification, proving that the inclusion emulsification synergistic system of the present invention is the core to achieve high water solubility, rather than the simple physical dispersion of the prior art.

[0062] (3) The centrifugal stability and pH adaptability of Example 5 are significantly better than those of existing single technologies. The high-temperature solubility retention rate is 29% higher than that of the single inclusion technology of Comparative Example 2 and 46% higher than that of the single emulsification technology of Comparative Example 3, which proves that the molecular-level synergistic effect of the present invention is far better than that of existing single technologies, and solves the core problem of poor stability of existing single technologies.

[0063] (4) Example 5 has no ethanol residue, fully meets the requirements of alcohol-free food, and its solubility is 13.3% higher than that of Comparative Example 4, its flavor sustained release is 35.7% higher, and its shelf life retention is 19.5% higher. It completely solves the safety hazards and stability defects of traditional processes and achieves performance superiority under the premise of no ethanol.

[0064] (5) Due to the lack of gradient shearing and fluidized drying, the solubility of Comparative Example 5 was only 66.7% of that of Example 5; Due to the mismatch between the carrier and the emulsifier, the inclusion rate of Comparative Example 6 was 6% lower than that of Example 1. This proves that the core innovation of the present invention is not a simple superposition of existing combined technologies, but an unexpected technical effect formed by carrier-emulsifier adaptation, process parameter coordination and whole-process optimization, which improves the overall performance of existing combined technologies by more than 15%.

[0065] (6) The unit cost of Examples 4 to 5 is lower than that of Examples 2 to 3, and significantly lower than that of Comparative Example 2 which is encapsulated with a single β-cyclodextrin. At the same time, the performance is better, which solves the industry pain point that high performance must come with high cost in the prior art and provides a feasible path for large-scale production.

[0066] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A method for preparing ethanol-free, food-grade, water-soluble menthol, characterized in that, Includes the following steps: The process includes raw material preparation, micronization pretreatment, isothermal inclusion reaction, gradient shear emulsification, and low-temperature fluidized bed drying. The raw materials include food-grade L-menthol, β-cyclodextrin, polyglycerol fatty acid esters, sucrose fatty acid esters, and deionized water; ethanol is not used throughout the process. The micronization pretreatment involves pulverizing L-menthol to a particle size ≤50 micrometers. The isothermal inclusion reaction involves dissolving β-cyclodextrin in deionized water, adding the micronized menthol, and then stirring at a constant temperature to form an inclusion complex suspension. The gradient shear emulsification involves adding polyglycerol fatty acid esters and sucrose fatty acid esters to the inclusion complex suspension, followed by gradient speed stirring and shearing to form an emulsion. The low-temperature fluidized bed drying involves sequentially spray drying and low-temperature fluidized bed drying of the emulsion to obtain ethanol-free, food-grade, water-soluble menthol.

2. The preparation method according to claim 1, characterized in that, The raw materials, by weight, are: 10 parts food-grade L-menthol, 50-60 parts β-cyclodextrin, 2.5-3 parts polyglycerol fatty acid ester, 2-2.5 parts sucrose fatty acid ester, and 200-220 parts deionized water.

3. The preparation method according to claim 1, characterized in that, During the micronization pretreatment process, the temperature of the grinding chamber is controlled at 35°C.

4. The preparation method according to claim 1, characterized in that, In the isothermal inclusion reaction, the temperature for dissolving β-cyclodextrin was 50°C and the stirring time was 30 minutes; after adding menthol powder, the stirring speed was 500 rpm and the stirring time was 2 hours, while the temperature was maintained at 50°C.

5. The preparation method according to claim 1, characterized in that, In the gradient shear emulsification process, the temperature is raised to 60-65℃, and the mixture is stirred at 5000-6000 rpm for 10-15 minutes, followed by shearing at 10000-12000 rpm for 30-40 minutes.

6. The preparation method according to claim 1, characterized in that, The spray dryer has an inlet temperature of 160°C, an outlet temperature of 80-85°C, and a feed rate of 15-20 ml / min; the low-temperature fluidized bed dryer uses 40°C nitrogen as the fluidizing medium and has a processing time of 20 minutes.

7. The preparation method according to claim 1, characterized in that, The β-cyclodextrin is replaced by a complex inclusion carrier, which is composed of β-cyclodextrin and maltodextrin, and is composed of 40 parts by weight of β-cyclodextrin and 20 parts by weight of maltodextrin.

8. The preparation method according to claim 1, characterized in that, After the micronization pretreatment, a low-temperature drying step is added, with a drying temperature of 40°C and a drying time of 30 minutes.

9. The preparation method according to claim 1, characterized in that, The low-temperature fluidized drying process is followed by a sieving step, using a 120-mesh sieve.

10. The preparation method according to claim 1, characterized in that, The polyglycerol fatty acid ester has a degree of polymerization of 6, and the sucrose fatty acid ester has an HLB value of 11.