A functional asparagus powder with high saponin content and its preparation method

Abstract

This invention relates to the field of functional food processing technology, specifically disclosing a functional asparagus powder with high saponin content and its preparation method. The method includes the following steps: asparagus is sliced ​​and microwaved to deactivate enzyme activity; after pulping, a composite regulator aqueous dispersion is added; the pH is adjusted and a cellulose complex enzyme is added for enzymatic hydrolysis; then, it is pre-frozen and vacuum freeze-dried; finally, it is pulverized, sieved, and packaged under a nitrogen atmosphere. The composite regulator can dynamically stabilize and protect saponin molecules through temperature-responsive behavior during processing, significantly reducing thermal degradation. The resulting asparagus powder has a saponin content of 72-85 mg / g and is rich in flavonoids, phenols, and soluble dietary fiber. This product can be used in functional foods that improve sleep. When added at a 4% level to bread, noodles, or meal replacement porridge, animal experiments have verified that it can significantly prolong sleep time and increase the incidence of sleep in mice, exhibiting high nutrient retention and good stability.

Description

Technical Field

[0001] This invention relates to the field of functional food processing technology, and in particular to a functional asparagus powder with high saponin content and its preparation method. Background Technology

[0002] Functional asparagus powder, as a high-value nutritional food ingredient, has garnered significant attention in the health food sector. Asparagus is rich in various bioactive components, such as saponins, flavonoids, phenolic substances, and polysaccharides. These components endow it with physiological functions such as antioxidation, anti-inflammation, immune regulation, and sleep improvement, making it widely used in meal replacement foods, nutritional supplements, and functional beverages. Traditional asparagus powder processing mainly relies on hot air drying or vacuum drying technologies. While these methods achieve basic dehydration and preservation, they often lead to significant degradation of heat-sensitive components such as saponins, thus limiting the product's nutritional value and functional properties. With the increasing consumer demand for natural, healthy, and convenient foods, and the advancement of sustainable development concepts, the development of asparagus powder is trending towards retaining higher levels of active ingredients and improving processing efficiency.

[0003] High-saponin functional asparagus powder aims to maximize the retention of active substances such as saponins in asparagus to meet market demand for efficient nutrient carriers. Currently, optimizing processing techniques such as microwave blanching, enzymatic hydrolysis, and vacuum freeze-drying can improve saponin retention to some extent. However, existing technologies still have many limitations: for example, in traditional heat processing, high temperatures easily trigger the thermal oxidative degradation of saponins, leading to unstable saponin content in the final product; the addition of chemical modifiers or stabilizers can introduce off-flavors or affect taste, such as metal residue issues; at the same time, processing costs are high and processes are complex, making it difficult to achieve economic efficiency and consistency in large-scale production. These shortcomings restrict the widespread application of high-saponin asparagus powder, necessitating the development of more efficient and gentle processing methods to balance the multifunctional needs of high nutrient retention, low cost, and good sensory quality. Summary of the Invention

[0004] To address the problems mentioned in the background section, this invention provides a functional asparagus powder with high saponin content and its preparation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing functional asparagus powder with high saponin content includes the following steps: S1. Wash and slice the asparagus scraps or whole asparagus, and then microwave them to completely deactivate the peroxidase activity. S2. Place the blanched asparagus into a pulping machine and pulp it. Add the aqueous dispersion of the compound regulator and stir for 30 minutes to obtain the pulp. S3. Add cellulosic complex enzyme to the slurry, adjust the pH to 5.4±0.2 with 1mol / L hydrochloric acid or sodium hydroxide, and enzymatically hydrolyze at 60±2℃ for 1.8h. After enzymatic hydrolysis, inactivate the enzyme by boiling water bath for 10min. S4. Pre-freeze the enzymatically hydrolyzed slurry at -45℃ for 12 hours, and then perform vacuum freeze drying until the moisture content is ≤6% to obtain the dried material. S5. Use a pulverizer to pulverize the dried material to pass through a 100-mesh sieve, and seal and package it under a nitrogen atmosphere to obtain the functional asparagus powder product.

[0006] Furthermore, the asparagus powder has a saponin content of 72-85 mg / g and contains a compound regulator.

[0007] Furthermore, the asparagus powder also contains the following functional components: total flavonoids content of 3.5-4.2 mg / g, total phenol content of 2.8-3.5 mg / g, soluble dietary fiber content of 65-75 mg / g, and moisture content ≤6%.

[0008] Furthermore, the composite regulator is prepared through the following steps: A1. N-vinylcaprolactam and octadecyl acrylate were dissolved in anhydrous toluene at a molar ratio of 7:3. Azobisisobutyronitrile (AIBN) of 1% of the total monomer mass was added as an initiator. The reaction was carried out at 70±1℃ under nitrogen protection for 12 hours to synthesize a composite copolymer. A2. Mix the above composite copolymer with maleic anhydride at a weight ratio of 10:1, add benzoyl peroxide as an initiator accounting for 1.5% of the total mass of the composite copolymer and maleic anhydride, and react in xylene solvent at 80±1℃ for 6 hours. A3. The composite regulator powder was obtained by precipitation with ether, washing three times, and vacuum drying at 50±1℃ for 24 hours.

[0009] Furthermore, in step S1, the asparagus slices are 2-3 mm thick, the microwave power is 560 W, and the blanching time is 90 ± 10 s.

[0010] Further, in step S2, the concentration of the aqueous dispersion is 1.5% w / v, the amount of the composite regulator added is 0.8% of the mass of the asparagus pulp, the stirring temperature is 35±5℃, the stirring speed is 200 rpm, and the preparation method of the aqueous dispersion of the composite regulator is as follows: the composite regulator powder is dispersed in deionized water, heated to 40℃ and stirred at 500 rpm for 1 hour until completely dispersed, and finally the aqueous dispersion of the composite regulator is obtained.

[0011] Further, in step S3, the cellulose complex enzyme is composed of pectinase and cellulase in a mass ratio of 1:1, and the amount of enzyme added is 0.11% of the mass of asparagus pulp. The enzymatic hydrolysis reaction is carried out in a constant temperature stirring water bath at a stirring speed of 150 rpm. After the enzymatic hydrolysis is completed, the enzyme is inactivated by boiling water for 10 min.

[0012] Furthermore, in step S4, the process conditions for vacuum freeze drying are: cold trap temperature ≤ -50℃, drying chamber pressure ≤ 15Pa, and drying time 24-36h.

[0013] Furthermore, after step S5, the asparagus powder is sterilized by cobalt-60 irradiation at a dose of 5 kGy and stored at 4 ± 2 °C to maintain saponin stability for at least 12 months.

[0014] Furthermore, when the asparagus powder is added at a rate of 4% to bread, noodles, or meal replacement porridge, animal experiments have verified that it can significantly prolong the sleep time of mice and increase the incidence of sleep.

[0015] 1. In the technical solution of this invention, the composite regulator has temperature-responsive characteristics. Its molecular chains extend at low temperatures, exposing hydrophobic regions, and bind to the steroidal core of the saponin molecule through hydrophobic interactions. Simultaneously, the maleic anhydride-derived carboxyl groups are linked to the glycosyl groups of the saponin via hydrogen bonds. During processing heating, the polymer chains contract to form protective microcapsules, encapsulating the saponin and physically isolating it from high temperatures and oxygen, thereby reducing thermal oxidative degradation and providing stability and protection for the saponin.

[0016] 2. From a microstructural perspective, the amphiphilic design of this polymer allows it to disperse uniformly in the aqueous phase, ensuring sufficient contact with saponins. The temperature response behavior, based on the low critical dissolution temperature of the N-vinylcaprolactam unit, dynamically adapts the protective effect to changes in processing temperature. This structure, obtained through controlled polymerization, results in uniform component distribution, avoiding performance fluctuations caused by localized unevenness. From a physicochemical perspective, this structure helps maintain saponin stability during blanching and drying, improving retention rates while reducing off-flavor or taste problems associated with traditional additives.

[0017] 3. In the technical solution of this invention, the thermal stability of saponins is improved, reducing nutrient loss during processing; enhancing the functionality and nutritional value of the product; due to its protective effect, it may reduce dependence on high-temperature processing, thereby saving energy; in addition, the biocompatibility of the regulator helps to maintain the natural taste of the product, avoid metal residues or chemical off-flavors, and improve the overall eating experience.

[0018] 4. In the technical solution of this invention, the polymer structure is obtained through a mild polymerization process, ensuring component uniformity and reducing performance fluctuations. From structure to effect, this design achieves efficient protection of saponins, reduces the need for additional chemical stabilizers, lowers processing complexity, and optimizes cost-effectiveness by increasing yield. Overall, this invention may help produce more stable and healthier functional asparagus powder, meeting market demand for high-quality nutritional foods while promoting sustainable resource utilization. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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.

[0020] Unless otherwise specified, the raw materials used in this invention are all from commercially available conventional products.

[0021] Example 1 Raw material pretreatment: Steps: Wash the asparagus scraps or whole asparagus plants to remove impurities, then slice them to a thickness of 2-3mm.

[0022] Parameters: Microwave rinsing was performed using a household microwave oven (560W) for 90 seconds to ensure complete inactivation of peroxidase (POD) activity (test standard: no browning in 1.5% guaiacol solution).

[0023] Equipment: A ceramic tray is used to lay asparagus slices, with a single layer thickness not exceeding 2 cm.

[0024] Pulping and Conditioner Addition: Steps: Place the blanched asparagus in a pulping machine and pulp it until the particle size of the pulp is ≤100μm.

[0025] Parameters: Aqueous dispersion of compound regulator (concentration 1.5% w / v), the amount of regulator added is 0.8% of the asparagus pulp mass. Stir at 200 rpm for 30 min at 35℃ to ensure uniform mixing.

[0026] Equipment: Constant temperature stirring water bath, temperature control accuracy ±1℃.

[0027] Enzymatic hydrolysis: Step: Add cellulase complex enzyme (pectinase and cellulase are mixed in a 1:1 mass ratio) to the slurry.

[0028] Parameters: The enzyme addition amount is 0.11% of the asparagus pulp mass; the pH is adjusted to 5.4 with 1 mol / L hydrochloric acid or sodium hydroxide; enzymatic hydrolysis is carried out at 60℃ for 1.8 h with a stirring speed of 150 rpm. After enzymatic hydrolysis, the enzyme is inactivated by boiling in a water bath for 10 min.

[0029] Equipment: constant temperature stirred water bath, pH meter for monitoring pH value.

[0030] dry: Steps: Pre-freeze the enzymatically hydrolyzed slurry, and then perform vacuum freeze-drying.

[0031] Parameters: Pre-freezing temperature below -45℃, pre-freezing time 12h; during vacuum freeze drying, cold trap temperature ≤ -50℃, drying chamber pressure ≤ 15Pa, drying time 24h, until moisture content ≤ 6%.

[0032] Equipment: Scientz-10N vacuum freeze dryer, with partition temperature set at 25℃ and material thickness ≤10mm.

[0033] Crushing and Packaging: Steps: Use a universal pulverizer to pulverize the dried material, pass it through a 100-mesh sieve, and seal it in a nitrogen atmosphere.

[0034] Parameters: Particle size ≤150μm, packaged in aluminum foil bags, protected by nitrogen.

[0035] Equipment: Universal pulverizer, nitrogen packaging machine.

[0036] Example 2 The process of Example 2 is basically the same as that of Example 1, but the grafting rate of the composite regulator is 10%, and other parameters are the same: Addition of regulator: The grafting rate of the compound regulator is 10%, and the addition amount is still 0.8% of the mass of asparagus pulp.

[0037] All other steps and parameters are the same as in Example 1, including microwave blanching (560W, 90s), pulping, enzymatic hydrolysis (0.11% enzyme added, pH 5.4, 60℃, 1.8h), drying (pre-freezing -45℃, vacuum freeze drying -50℃, ≤15Pa, 24h), and pulverization and packaging.

[0038] Example 3 The process of Example 3 is similar to that of Examples 1 and 2, but the grafting rate of the composite regulator is 12%, and other parameters are the same: Addition of regulator: The grafting rate of the compound regulator is 12%, and the addition amount is still 0.8% of the mass of asparagus pulp.

[0039] All other steps and parameters are the same as in Example 1, ensuring process consistency.

[0040] Comparative Example 1 Raw material pretreatment: Steps: Wash and slice the asparagus (2-3mm thick), then microwave blanching (560W, 90s) to deactivate POD activity.

[0041] Parameters: Same as in the example, ensuring consistent preprocessing.

[0042] Equipment: Household microwave oven, ceramic plate.

[0043] Pulping: Steps: After blanching, the asparagus is pulped, and the pulp particle size is ≤100μm.

[0044] Parameters: No modifiers are added; the pulp is directly beaten and then dried.

[0045] Equipment: Pulping machine.

[0046] dry: Steps: Dry using a hot air dryer.

[0047] Parameters: Drying temperature 60℃, drying time 8h, until moisture content ≤6%.

[0048] Equipment: Hot air drying oven, temperature control accuracy ±2℃.

[0049] Crushing and Packaging: Steps: Grind through a 100-mesh sieve and package as usual (without nitrogen protection).

[0050] Parameters: Particle size ≤150μm.

[0051] Equipment: Universal pulverizer.

[0052] Comparative Example 2 The process for Comparative Example 2 is similar to that of Comparative Example 1, but the drying method is changed to vacuum drying: Drying: Use a vacuum dryer at a drying temperature of 60℃, a drying chamber pressure of 20Pa, and a drying time of 8 hours until the moisture content is ≤6%.

[0053] All other steps are the same as in Comparative Example 1, including pretreatment and pulping.

[0054] Equipment: Vacuum drying oven.

[0055] Comparative Example 3 Raw material pretreatment: Same as in the example (microwave rinsing 560W, 90s).

[0056] Pulping and Additives: After pulping, add citric acid as a sintering aid at a rate of 1% of the asparagus pulp mass and stir for 30 minutes (35℃, 200 rpm).

[0057] Enzymatic hydrolysis: Same as in the example (enzyme added at 0.11% of the mass of asparagus pulp, pH 5.4, 60℃, 1.8h).

[0058] Drying: Vacuum freeze drying was used, with the same parameters as in the example (pre-freezing -45°C, drying -50°C, ≤15Pa, 24h).

[0059] Crushing and packaging: Same as in the example.

[0060] Test metrics and methods: Saponin content: determined by phenol-sulfuric acid method, using smilax saponin as standard, and absorbance measured at a wavelength of 535 nm.

[0061] Total flavonoid content: measured at a wavelength of 510 nm using the aluminum nitrate colorimetric method with rutin as the standard.

[0062] Total phenol content: measured at a wavelength of 765 nm using the Folin-Ciocalteu method with gallic acid as the standard.

[0063] Soluble dietary fiber (SDF) content: measured by enzymatic gravimetric method (AOAC 991.43).

[0064] Moisture content: Oven drying method (105℃ to constant weight).

[0065] All measurements were repeated three times, and the average value was taken to ensure data accuracy. The experiment was conducted in a temperature and humidity controlled laboratory (25℃, 50%RH). The results are shown in Table 1. Table 1. Experimental results of Examples 1-3 and Comparative Examples 1-3

[0066] This invention introduces an innovative composite polymer regulator that demonstrates significant potential in asparagus processing. The regulator's molecular design is based on temperature responsiveness and amphiphilic properties. Its mechanism is as follows: at low temperatures, the polymer chains extend, exposing hydrophobic regions that bind to the steroidal core of the saponin molecule through hydrophobic interactions, while the carboxyl groups connect to the glycosyl groups via hydrogen bonds. During heating, the polymer chains contract to form microcapsule structures, stabilizing and protecting the saponins, effectively isolating them from high temperatures and oxygen, thereby reducing thermal oxidative degradation. This intelligent protection mechanism ensures the stability of saponins during heat processing steps such as blanching and drying.

[0067] As shown in Table 1, the composite regulator provided by this invention, combined with vacuum freeze-drying, significantly improves the retention of asparagus active ingredients, especially saponins, compared to traditional processing methods. Compared to Comparative Example 1 (hot air drying) and Comparative Example 2 (vacuum drying), the saponin content (72–85 mg / g) in each example increased by approximately 25%–30%, demonstrating that the regulator effectively isolates heat and oxygen through temperature-sensitive stability and a protective mechanism, inhibiting saponin degradation. Simultaneously, the retention rates of total flavonoids, total phenols, and soluble dietary fiber were also significantly improved, indicating that this protection strategy has broad-spectrum benefits. The composite regulator with a grafting rate of 12% (Example 3) performed best, indicating that its molecular structure design and functional synergy have a significant impact on the protective effect. In summary, this invention not only significantly improves the retention rate of active ingredients but also helps improve product functionality and stability, demonstrating significant technological advancement and application potential.

[0068] From a microstructural perspective, the uniform dispersion and controllable polymerization process of the composite polymer regulator avoid the problem of uneven local distribution of components, reducing the performance fluctuations common in traditional additives. Its pH-responsive behavior (swelling ratio 4.0-6.0 under acidic conditions, 16.0-20.0 under neutral conditions) adapts to different processing environments, enhancing product consistency. Furthermore, the regulator's biocompatibility helps maintain the natural flavor of asparagus, avoids metallic odors or chemical residues, and improves the taste and sensory quality of the final product.

[0069] At the application level, this asparagus powder is widely used in the health food field, such as meal replacement porridge, nutritional bread, and functional beverages. Its high saponin content (72–85 mg / g) enhances the product's antioxidant and immunomodulatory functions, meeting consumers' demand for natural and convenient diets. Simultaneously, optimized processes, such as the synergistic use of microwave blanching and vacuum freeze-drying, retain other active ingredients such as flavonoids (3.5–4.2 mg / g), phenols (2.8–3.5 mg / g), and soluble dietary fiber (65–75 mg / g), improving overall nutritional value. Experimental data shows that compared to traditional methods, this invention increases saponin retention by 25%–30% and improves processing efficiency.

[0070] Overall, this invention not only solves the common problem of saponin degradation in asparagus processing but also supports sustainable resource utilization by reducing waste through the use of asparagus by-products. Future research requires further toxicological evaluation and large-scale production validation to promote industrial application. This technology provides a new approach to developing high-quality functional foods and is expected to play a significant role in the fields of nutritional supplementation and health promotion.

[0071] In the description of this specification, the terms "preparation example," "example," "various examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that example or preparation example, which are included in at least one example or preparation example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same example or preparation example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more examples or preparation examples.

[0072] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing functional asparagus powder with high saponin content, characterized in that, Includes the following steps: S1. Wash and slice the asparagus scraps or whole asparagus, and then blanch them in microwave to completely deactivate the peroxidase activity. S2. Place the blanched asparagus into a pulping machine and pulp it. Add the aqueous dispersion of the composite regulator and stir for 30 minutes to obtain the pulp. The composite regulator is prepared through the following steps: A1. N-vinylcaprolactam and octadecyl acrylate were dissolved in anhydrous toluene at a molar ratio of 7:

3. Azobisisobutyronitrile (AIBN) of 1% of the total monomer mass was added as an initiator. The reaction was carried out at 70±1℃ under nitrogen protection for 12 hours to synthesize a composite copolymer. A2. Mix the above composite copolymer with maleic anhydride at a weight ratio of 10:1, add benzoyl peroxide as an initiator accounting for 1.5% of the total mass of the composite copolymer and maleic anhydride, and react in xylene solvent at 80±1℃ for 6 hours. A3. After precipitation with diethyl ether, washing three times, and vacuum drying at 50±1℃ for 24h, a composite regulator powder was obtained. S3. Add cellulose complex enzyme to the slurry, adjust the pH to 5.4±0.2 with 1mol / L hydrochloric acid or sodium hydroxide, and enzymatically hydrolyze at 60±2℃ for 1.8h. After enzymatic hydrolysis, inactivate the enzyme by boiling water bath for 10min. S4. Pre-freeze the enzymatically hydrolyzed slurry at -45℃ for 12 hours, and then perform vacuum freeze drying until the moisture content is ≤6% to obtain the dried material. S5. Use a pulverizer to pulverize the dried material to pass through a 100-mesh sieve, and seal and package it under a nitrogen atmosphere to obtain the functional asparagus powder product.

2. The functional asparagus powder with high saponin content according to claim 1, characterized in that, The asparagus powder contains 72-85 mg / g of saponins and also contains a compound regulator.

3. The functional asparagus powder with high saponin content according to claim 1, characterized in that, The asparagus powder also contains the following functional components: total flavonoids of 3.5-4.2 mg / g, total phenols of 2.8-3.5 mg / g, soluble dietary fiber of 65-75 mg / g, and moisture content ≤6%.

4. The method for preparing a functional asparagus powder with high saponin content according to claim 1, characterized in that, In step S1, the asparagus slices are 2-3 mm thick, the microwave power is 560W, and the blanching time is 90±10s.

5. The method for preparing a functional asparagus powder with high saponin content according to claim 1, characterized in that, In step S2, the concentration of the aqueous dispersion is 1.5% w / v, the amount of the composite regulator added is 0.8% of the mass of the asparagus pulp, the stirring temperature is 35±5℃, the stirring speed is 200 rpm, and the preparation method of the aqueous dispersion of the composite regulator is as follows: the composite regulator powder is dispersed in deionized water, heated to 40℃ and stirred at 500 rpm for 1 hour until completely dispersed, and finally the aqueous dispersion of the composite regulator is obtained.

6. The method for preparing a functional asparagus powder with high saponin content according to claim 1, characterized in that, In step S3, the cellulose complex enzyme is composed of pectinase and cellulase in a mass ratio of 1:

1. The amount of enzyme added is 0.11% of the mass of asparagus pulp. The enzymatic hydrolysis reaction is carried out in a constant temperature stirred water bath at a stirring speed of 150 rpm. After the enzymatic hydrolysis is completed, the enzyme is inactivated by boiling water for 10 minutes.

7. The method for preparing a functional asparagus powder with high saponin content according to claim 1, characterized in that, In step S4, the drying time for vacuum freeze drying is 24-36 hours.

8. The method for preparing a functional asparagus powder with high saponin content according to claim 1, characterized in that, After step S5, the asparagus powder was sterilized by cobalt-60 irradiation at a dose of 5 kGy and stored at 4 ± 2 °C to maintain saponin stability for at least 12 months.

9. The application of a functional asparagus powder with high saponin content as described in any one of claims 1 to 3 in the preparation of sleep-improving functional foods, characterized in that, The asparagus powder, when added at a 4% concentration to bread, noodles, or meal replacement porridge, has been shown in animal experiments to significantly prolong sleep time and increase the incidence of sleep in mice.

Images