A jade green superfine bamboo leaf powder and its preparation and application

Abstract

The present application relates to a kind of jade green superfine bamboo leaf powder and its preparation and application. Specifically, a kind of preparation method of jade green superfine bamboo leaf powder is disclosed, and the bamboo leaf powder obtained using the method has the advantages of jade green color, fine granularity and safe edible ingredients, which can advantageously promote the popularization and application of bamboo leaf powder in the food field.

Description

Technical Field

[0001] This invention relates to the field of materials, specifically to a bright green ultrafine bamboo leaf powder and its preparation and application. Background Technology

[0002] Bamboo leaves contain a large number of bioactive substances beneficial to the human body, such as flavonoids, phenolic acids, terpenes, polysaccharides, adenosine, as well as trace elements and minerals such as organic germanium and organic silicon. These substances can play a role in fighting free radicals, anti-oxidation, anti-fatigue, enhancing immunity, regulating lipid metabolism, and preventing cardiovascular and cerebrovascular diseases. For example, the ancient Chinese medical text *Qianjin Yueling* states, "Bamboo leaf porridge in July is suitable for those suffering from heatstroke"; *Ben Cao Qiu Zhen* says, "Bamboo leaves cool the heart and soothe the spleen, clear phlegm and quench thirst." Antioxidants extracted from bamboo leaves were included in the national standard GB 2760 for use as food additives in 2004, and bamboo leaf flavonoids are also recognized as "new food raw materials." Currently, several types of bamboo leaf tea and instant health tea made from bamboo leaves are available on the market.

[0003] Currently reported bamboo leaf powders may have issues such as insufficient green color, inadequate fineness, or substandard ingredients, making it difficult to meet the growing market demand.

[0004] Therefore, there is an urgent need in this field to develop a bamboo leaf powder that is bright green in color, has a fine particle size, and is safe and edible in terms of ingredients, as well as a method for its preparation. Summary of the Invention

[0005] The purpose of this invention is to provide a bamboo leaf powder that is bright green in color, has a fine particle size, and is safe and edible in terms of ingredients, as well as a method for preparing the same.

[0006] In a first aspect, the present invention provides a method for preparing ultrafine green bamboo leaf powder, the method comprising the following steps:

[0007] 1) Place the bamboo leaves in a bleaching and color-protecting solution at 70-85℃ for 0.5-1.5 minutes at a material-to-liquid ratio of 1:70-80g / mL for bleaching and color protection treatment;

[0008] The bleaching and color-protecting solution is a sodium carbonate aqueous solution or a sodium bicarbonate aqueous solution with a concentration of 0.2-2g / 100mL;

[0009] The bleaching and color-protecting treatment is performed with ultrasonic assistance;

[0010] 2) Drying process: The bamboo leaves obtained from step 1) after bleaching and color protection treatment are dried bamboo leaves.

[0011] 3) The dried bamboo leaves obtained in step 2) are subjected to a first low-temperature pretreatment to obtain bamboo leaves that have undergone the first low-temperature pretreatment;

[0012] 4) The bamboo leaves obtained in step 3) after the first low-temperature pretreatment are coarsely crushed to obtain coarsely crushed bamboo leaves;

[0013] 5) The coarsely crushed bamboo leaves obtained in step 4) are subjected to a second low-temperature pretreatment to obtain bamboo leaves that have undergone a second low-temperature pretreatment.

[0014] 6) The bamboo leaves obtained in step 5) after two low-temperature pretreatments are subjected to ultrafine pulverization to obtain ultrafine pulverized bamboo leaf powder.

[0015] 7) The ultrafine bamboo leaf powder obtained in step 6) is subjected to air classification to obtain air classified bamboo leaf powder, namely the emerald green ultrafine bamboo leaf powder.

[0016] In another preferred embodiment, the following steps are included before step 1):

[0017] 1-1) Select a suitable bamboo leaf variety;

[0018] 1-2) Harvest and select bamboo leaves, removing inferior bamboo leaves such as branches, yellow leaves, and insect-damaged leaves, leaving fresh, bright green, high-quality tender bamboo leaves for later use;

[0019] 1-3) Wash the selected bamboo leaves with water.

[0020] In another preferred embodiment, the bamboo leaves are selected from the following group: Liangshan Cizhu and Arrow Bamboo.

[0021] In another preferred embodiment, in step 1), the material-to-liquid ratio is 1:75-80 g / mL, more preferably 1:80 g / mL.

[0022] In another preferred embodiment, in step 1), the temperature of the bleaching and color-protecting liquid is 75-80°C.

[0023] In another preferred embodiment, in step 1), the bleaching and color-protecting treatment takes 0.8-1.2 minutes, preferably 1 minute.

[0024] In another preferred embodiment, in step 1), the concentration of the bleaching and color-protecting liquid is 0.3-1.8 g / 100 mL, preferably 0.5-1.5 g / 100 mL.

[0025] In another preferred embodiment, in step 1), the pH of the bleaching and color-protecting solution is 4-9, preferably 5-8, more preferably 6-8, and most preferably 7-8.

[0026] In another preferred embodiment, in step 1), the bleaching and color-protecting liquid is an aqueous solution of sodium carbonate or an aqueous solution of sodium bicarbonate.

[0027] In another preferred embodiment, in step 1), the bleaching and color-protecting solution is an aqueous solution of sodium carbonate.

[0028] In another preferred embodiment, in step 1), the bleaching and color-protecting solution is an aqueous solution of sodium bicarbonate.

[0029] In another preferred embodiment, in step 1), the power of the ultrasound assistance is 200-350W (preferably 250-300W).

[0030] In another preferred embodiment, in step 1), the total volume of the mixture of bamboo leaves and the bleaching and color-protecting liquid is 40-80L (preferably 45-70L, more preferably 50-60L).

[0031] In another preferred embodiment, in step 2), the drying process is performed using a method selected from the group consisting of hot air drying, microwave drying, or a combination thereof.

[0032] In another preferred embodiment, in step 2), the drying process is first hot air drying followed by microwave drying.

[0033] In another preferred embodiment, the hot air drying process is carried out at a temperature of 50-70°C (more preferably 55-65°C, even more preferably 55-60°C).

[0034] In another preferred embodiment, the hot air drying process takes 1-6 hours (preferably 1-4 hours, more preferably 1-2 hours).

[0035] In another preferred embodiment, the microwave drying process has a power of 300-500W.

[0036] In another preferred embodiment, the microwave drying process takes 5-10 minutes.

[0037] In another preferred embodiment, in step 3), the initial low-temperature pretreatment is performed at a temperature of -30 to -5°C (preferably -25 to -10°C, more preferably -20 to -15°C); and / or

[0038] The initial low-temperature pretreatment time is 0.3-6 hours (preferably 0.5-4 hours, more preferably 1-3 hours).

[0039] In another preferred embodiment, the cryogenic pretreatment is performed using a method selected from the group consisting of liquid nitrogen treatment, cryogenic storage treatment, dry ice treatment, or a combination thereof.

[0040] In another preferred embodiment, in step 4), the coarse crushing is a cyclic crushing to obtain crushed bamboo leaves with a particle size of 40-100 mesh (preferably 60-90 mesh (160-250 μm), more preferably 70-80 mesh (180-212 μm)).

[0041] In another preferred embodiment, the number of cycles of cyclic pulverization is 2-4.

[0042] In another preferred embodiment, in step 5), the secondary low-temperature pretreatment is performed at a temperature of -30 to -5°C (preferably -25 to -10°C, more preferably -20 to -15°C); and / or

[0043] The secondary low-temperature pretreatment takes 0.3-4 hours (preferably 0.5-2 hours, more preferably 1-2 hours).

[0044] In another preferred embodiment, the cryogenic pretreatment is performed using a method selected from the group consisting of liquid nitrogen treatment, cryogenic storage treatment, dry ice treatment, or a combination thereof.

[0045] In another preferred embodiment, in step 6), the ultrafine pulverization is performed by ball milling combined with ultrasonic assistance.

[0046] In another preferred embodiment, the ball milling has one or more features selected from the group consisting of:

[0047] 1) The ball-to-material ratio is 5-10:1 (preferably 6-7:1);

[0048] 2) The ball milling temperature is 40-50℃;

[0049] 3) The ball grinding time is 30-60 minutes.

[0050] In another preferred embodiment, in step 6), the power of the ultrasound assistance is 200-400W (preferably 200-300W); and / or

[0051] The duration of ultrasound assistance is 3-10 minutes.

[0052] In another preferred embodiment, the particle size of the ultrafinely pulverized bamboo leaf powder is 1-8 μm, more preferably 2-6 μm, and even more preferably 2-4 μm.

[0053] In another preferred embodiment, in step 7), the airflow separation has one or more features selected from the group consisting of:

[0054] 1) The airflow velocity is 10-30 m / s (preferably 15-25 m / s, more preferably 18-23 m / s);

[0055] 2) The speed of the grading wheel is 1000-3000 r / min (preferably 1500-2500 r / min, more preferably 1800-2000 r / min);

[0056] 3) The air separation time is 10-30 minutes (preferably 15-25 minutes, even better 18-23 minutes).

[0057] In a second aspect, the present invention provides an ultrafine green bamboo leaf powder, wherein the color value a* of the bamboo leaf powder is -12 to -10 (preferably -11.8 to -10.5, more preferably -11.7 to -11.2);

[0058] After being treated with white light for 180 minutes, the Δa* value of the bamboo leaf powder was 2-5 (preferably 2.1-4.5, more preferably 2.2-3.5, even more preferably 2.3-3);

[0059] The bamboo leaf powder has a D50 of 2-4 μm (preferably 2.5-3.8 μm, more preferably 3-3.7 μm);

[0060] The Span value of the bamboo leaf powder is 1.01-1.3 (preferably 1.05-1.2, more preferably 1.1-1.2).

[0061] In another preferred embodiment, the bamboo leaf powder has a D90 of 4-8 μm, more preferably 5-7 μm, and even more preferably 6-6.5 μm.

[0062] In another preferred embodiment, the bamboo leaf powder is prepared using the method described in the first aspect of the present invention.

[0063] In a third aspect, the present invention provides a health product or medicine comprising the bamboo leaf powder described in the second aspect of the present invention.

[0064] It should be understood that, within the scope of this invention, the above-described technical features of this invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here. Attached Figure Description

[0065] Figure 1 The results show the color value changes for samples A, B, C, and D. Figure 1 A represents the a* value at 0 min for different samples. Figure 1 B represents the color difference value a* between different samples after 180 min of illumination and after 0 min. Figure 1 C is a comparison image of different samples before and after illumination.

[0066] Figure 2 The particle size distribution results are for samples 1, 2, and 3. Figure 2 A shows the particle size distribution of different samples. Figure 2 B shows images of different samples under a microscope.

[0067] Figure 3 The results show the color value changes for samples 1, 2, and 3. Figure 3 A represents the a* value at 0 min for different samples. Figure 3B represents the color difference value a* between different samples after 180 min of illumination and after 0 min. Figure 3 C is a comparison image of different samples before and after illumination. Detailed Implementation

[0068] Through long-term and in-depth research, the inventors unexpectedly prepared a bamboo leaf powder that is both bright green in color and fine in particle size, and whose ingredients are safe and edible. Based on this, the inventors completed this invention.

[0069] The basic process for preparing bamboo leaf powder is as follows:

[0070] Bamboo selection → Harvesting → Sorting → Washing → Blanching → Drying → Crushing → Sterilization → Grading and impurity removal → Foreign matter detection → Packaging → Warehousing

[0071] The best bamboo leaf powder should be bright green in color and have a fine texture, and the preparation process should be stable and efficient.

[0072] Compared with the prior art, the present invention has the following main advantages:

[0073] (1) The bamboo leaf powder of the present invention has the advantages of being bright green in color, fine in particle size and safe and edible in ingredients;

[0074] (2) The bamboo leaf powder prepared by the method of the present invention has a more emerald green color and a bamboo leaf powder value a* can reach -12 to -10. The ingredients are safer. The weak alkali used replaces zinc sulfate / magnesium sulfate for bleaching and color protection, which is safer and conducive to its vigorous promotion in the food field.

[0075] (3) The bamboo leaf powder of the present invention has a smaller particle size, a D50 value of up to 3.193 μm, a uniform distribution, and a Span value of up to 1.183.

[0076] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise stated, percentages and parts are by weight.

[0077] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0078] Preparation process research

[0079] 1. Bleaching and color protection

[0080] Bamboo leaves are prone to discoloration during the processing into powder, so bleaching and heat treatment is necessary to ensure their green color remains stable.

[0081] 1. Bleaching liquid

[0082] (1) There are many types of bleaching and color-protecting solutions, including weak alkaline solutions, organic acid solutions and salt solutions. Based on the relevant characteristics of bamboo leaves, the inventors chose a weak alkaline solution with higher compatibility.

[0083] ① Prevent pigment degradation

[0084] A weakly alkaline solution can adjust the pH level in bamboo leaves, reducing the damage to pigments caused by an acidic environment. Some pigments are easily degraded under acidic conditions, while they are relatively stable in a weakly alkaline environment. For example, chlorophyll easily undergoes magnesium loss and discoloration under acidic conditions, but is relatively stable in a weakly alkaline environment.

[0085] ② Inhibit enzymatic browning

[0086] Enzymatic browning is one of the important causes of discoloration in bamboo leaves. A weakly alkaline solution can alter the active sites of enzymes in bamboo leaves, reducing or even inactivating the activity of enzymes involved in the browning reaction (such as polyphenol oxidase). This effectively inhibits the occurrence of enzymatic browning.

[0087] ③ Prevent oxidation reaction

[0088] Under slightly alkaline conditions, a thin protective film may form on the surface of bamboo leaves, preventing oxygen from contacting the internal components of the bamboo leaves, thereby reducing the occurrence of oxidation reactions.

[0089] ④ Edible safety

[0090] Compared to traditional zinc sulfate / magnesium sulfate bleaching and color protection, using a weak alkali as a bleaching solution for color protection has the advantages of being edible and having high safety.

[0091] (2) The process parameters are proposed as follows:

[0092] ① Weakly alkaline solution: sodium carbonate aqueous solution or sodium bicarbonate aqueous solution.

[0093] ②Concentration: 0.3-2g / 100mL.

[0094] ③ pH value: 4.0-9.0.

[0095] ④ Material-to-liquid ratio: 1:70-80 (g / mL)

[0096] 2. Ultrasonic-assisted bleaching

[0097] This involves using ultrasound to assist in the blanching process. Ultrasound can promote the penetration of the color-protecting solution, allowing the color-protecting components to be evenly distributed in the bamboo leaf tissue, accelerating the reaction between pigments and the color-protecting solution components, and making pigment molecules more stable. It also enhances heat and mass transfer, allowing heat to be transferred to the interior of the bamboo leaves more quickly, shortening the blanching time, promoting the diffusion of moisture and impurities, and improving uniformity. Furthermore, it disrupts the active structure of enzymes, accelerating enzyme inactivation and inhibiting enzymatic browning at relatively low temperatures.

[0098] The process parameters are proposed as follows (for a mixture of 40-80L bamboo leaves and bleaching and color-protecting solution):

[0099] Ultrasonic power: Generally, 200-350W can be selected.

[0100] 3. Light Illumination Experiment

[0101] The photostability experiment was conducted to observe its destructive effect on the color of the samples. Four samples were illuminated with three 12W LED white light tubes (FSL6500K), with the samples placed 30cm below the tubes. After 180 minutes of illumination, the color difference before and after illumination was compared.

[0102] Color difference analysis: Testing instrument: CM-600d colorimeter (manufactured by KNICA MTNOLTA, Japan). Experimental method: First, the colorimeter was zeroed and calibrated. Then, a certain amount of bamboo leaf powder sample was placed on a standard white board and spread evenly. The light inlet of the colorimeter was aligned with the sample, and then the test button was pressed to perform the test.

[0103] Colorimeter working principle: The Lab value of a colorimeter analyzes color differences using X, Y, and Z color values. X, Y, and Z are the three axes in the three-dimensional Lab color space coordinate system, representing the red (L*), green (a*), and blue (b*) components, respectively. The L* value represents lightness / darkness, with 0 representing black and 100 representing white; the a* value represents red / green, with positive values ​​for red and negative values ​​for green; and the b* value represents yellow / blue, with positive values ​​for yellow and negative values ​​for blue.

[0104] Sample preparation: Four samples, A, B, C, and D, were treated with different bleaching and color-protecting methods while keeping other conditions constant to obtain bamboo leaf powder. The color-protecting effect and photostability were compared through a light exposure experiment.

[0105] Specific examples of bleaching and color-protecting treatments are as follows:

[0106] Sample A: According to the material-liquid ratio of 1:80 (g / mL), place the bamboo leaves in gently boiling hot water (i.e., hot water at 75-85℃), stir slightly to disperse the leaves evenly, blanch for 1 minute, and then remove and drain.

[0107] Sample B: Bamboo leaves were placed in a slightly boiling blanching and color-protecting solution (i.e., 1.5g / 100mL zinc sulfate aqueous solution at 75-85℃) at a material-to-liquid ratio of 1:80 (g / mL). The leaves were stirred slightly to disperse them evenly. After blanching for 1 minute, the leaves were removed and drained.

[0108] Sample C: Bamboo leaves were placed in a slightly boiling blanching and color-protecting solution (i.e., 1.5g / 100mL sodium bicarbonate aqueous solution at 75-85℃) at a material-to-liquid ratio of 1:80 (g / mL). The leaves were stirred slightly to disperse them evenly. After blanching for 1 minute, the leaves were removed and drained.

[0109] Sample D: Bamboo leaves were placed in a gently boiling blanching and color-protecting solution (i.e., a sodium bicarbonate aqueous solution of 1.5g / 100mL at 75-85℃) at a material-to-liquid ratio of 1:80. The leaves were gently stirred to ensure even distribution and blanched for 1 minute before being removed and drained. Ultrasonic assistance (250-300W) was applied during the blanching process.

[0110] Figure 1 The results show the color value changes for samples A, B, C, and D. Figure 1 A represents the a* value at 0 min for different samples. Figure 1 B represents the color difference value a* between different samples after 180 min of illumination and after 0 min. Figure 1 C is a comparison graph of different samples before and after light exposure. In the graph, a, b, c, and d indicate that the values ​​between different groups have significant differences (P < 0.05).

[0111] Table 1 shows... Figure 1 A, Figure 1 B and Figure 1 The color value changes of samples A, B, C, and D corresponding to C.

[0112] Table 1 Color values ​​of samples A, B, C, and D

[0113] a* value (0min) a* value (180min) Δa* value (0→180min) Sample A -10.88±0.11 -4.72±0.08 6.09±0.14 Sample B -11.35±0.18 -6.13±0.13 5.22±0.28 Sample C -11.69±0.16 -7.55±0.12 4.14±0.28 Sample D -11.53±0.19 -9.03±0.01 2.50±0.19

[0114] from Figure 1 As shown in A, among the four samples A, B, C, and D, sample A has the lightest green color of bamboo leaves, while samples B, C, and D have slightly darker green colors with slight differences, but these differences are not significant (P > 0.05).

[0115] from Figure 1As shown in B and 1C, after 180 minutes of light exposure on different samples, the degree of green fading of different samples after light exposure was compared by calculating the Δa* value with that at 0 minutes. It was found that after 180 minutes of light exposure, the Δa* values ​​of bamboo leaf powder in different groups were in descending order as A > B > C > D. This indicates that different bleaching and color-protecting treatments have different effects on the photostability of bamboo leaf powder. Among them, the color-protecting effect of bamboo leaf powder bleached and protected with ultrasonic-assisted sodium bicarbonate was the best.

[0116] Experiments have shown that weak alkaline bleaching solution has a better color-protecting effect on bamboo leaf powder than zinc sulfate bleaching solution, and ultrasonic-assisted weak alkaline bleaching solution has a better color-protecting effect than using weak alkaline bleaching solution alone. Therefore, ultrasonic-assisted weak alkaline bleaching solution was ultimately selected to protect the color of bamboo leaf powder.

[0117] II. Low-temperature pretreatment and airflow separation to prevent bamboo leaf powder agglomeration

[0118] Low-temperature pretreatment and air classification processes can help improve the efficiency and fineness of bamboo leaf powder pulverization, and effectively solve the agglomeration phenomenon caused by bamboo leaf powder pulverization.

[0119] 1. Low-temperature pretreatment

[0120] Freezing bamboo leaves makes them more brittle, allowing them to be broken into smaller particles more easily during the grinding process. This helps improve grinding efficiency and fineness, resulting in more uniform particle size in the bamboo leaf powder. Furthermore, low-temperature freezing reduces damage to heat-sensitive components in the bamboo leaves, such as some bioactive substances and vitamins. This helps preserve the nutritional and functional properties of the bamboo leaf powder.

[0121] Therefore, before bamboo leaves are pulverized, they can be pre-treated at low temperatures using liquid nitrogen, freezers, or dry ice, which helps to improve the efficiency of bamboo leaf pulverization and the quality of bamboo leaf powder.

[0122] Preferably, the low-temperature pretreatment temperature is -30 to -5°C, more preferably -25 to -10°C, and even more preferably -20 to -15°C.

[0123] Preferably, the low-temperature pretreatment time is 0.3-6 hours, more preferably 0.5-4 hours, and even more preferably 1-3 hours.

[0124] The low-temperature pretreatment ensures that the bamboo leaves are completely frozen.

[0125] The low-temperature pretreatment results in a liquid water content of ≤5wt% in the bamboo leaves, preferably ≤4wt%, and more preferably ≤3wt%.

[0126] 2. Airflow separation

[0127] After ultrafine grinding of bamboo leaves, the extremely fine bamboo leaf powder tends to agglomerate after being left for a period of time. This is because as the grinding time increases, the particle size of the bamboo leaf powder gradually decreases, and the degree of cell breakage increases significantly, but the functional group structure of the main components of the bamboo leaf powder remains unchanged. When the particle size is refined to a certain extent, the specific surface area and surface energy increase, and the particles are in an energy unstable state, making them prone to adhesion and agglomeration.

[0128] The inventors have found that air classifiers can avoid particle agglomeration and performance degradation caused by over-grinding, while also removing larger particles and impurities, thus improving the purity and quality of bamboo leaf powder.

[0129] The proposed process parameters are as follows:

[0130] The typical airflow velocity of an air classifier is between 10-30 m / s, the classifying wheel speed is between 1000-3000 r / min, and the air classification time is set to 10-30 minutes.

[0131] 3. Particle size analysis

[0132] Low-temperature pretreatment and air classification can effectively prevent the agglomeration of bamboo leaf powder, resulting in high-quality bamboo leaf powder with more uniform particle size distribution and smaller particle size.

[0133] The quality of bamboo leaf powder was evaluated by comparing the particle size distribution of bamboo leaf powder that had not undergone low-temperature pretreatment and air classification with that that had undergone low-temperature pretreatment and air classification.

[0134] Particle size analysis: The particle size distribution of the powder was determined using an Omec LS-909 laser particle size analyzer. A dry method was used, where 2.0g of bamboo leaf powder was weighed and placed in the feed hopper of an Omec DPF-110 dry sampler. The particle size distribution of the bamboo leaf powder was characterized by D10, D50, D90, specific surface area, and span. D10, D50, and D90 represent the particle sizes corresponding to 10%, 50%, and 90% of the cumulative particle size distribution of the sample, respectively. D50 is usually taken as the average particle size of the sample. Span is calculated using the formula: Span = (D90 - D10) / D50.

[0135] Samples 1, 2, and 3 are the products obtained after processing the aforementioned sample D as follows:

[0136] 1) Drying treatment: The drying temperature is 50-60℃, and the drying time is 1-4 hours. The product obtained after drying treatment is basically free of moisture.

[0137] 2) Optional first low temperature pretreatment: The product obtained in the previous step is subjected to low temperature pretreatment at a temperature of -20 to -15℃ for 1-4 hours.

[0138] 3) Coarse grinding treatment: The product obtained in the previous step is subjected to coarse grinding treatment, one or more (2-4 times) grinding treatment, so that the mesh size of the obtained product is 40-100 mesh (150-380μm).

[0139] 4) Optional secondary low-temperature pretreatment: The product obtained in the previous step is subjected to low-temperature pretreatment at a temperature of -20 to -15°C for 1-2 hours.

[0140] 5) Ultrafine grinding treatment: The product obtained in the previous step is ground in a ball mill (ball-to-material ratio 5:1, ball milling temperature 40-50℃, ball milling time 30-45 minutes) with ultrasonic assistance (ultrasonic power 200-300W) to obtain a particle size of 1-8μm.

[0141] 6) Optional airflow sorting: The product obtained in the previous step is subjected to airflow sorting. The airflow velocity is between 15-25 m / s, the grading wheel speed is between 1500-2000 r / min, and the air sorting time is set to 15-25 minutes.

[0142] Sample 1: Bamboo leaf powder obtained without low-temperature pretreatment and air classification;

[0143] Sample 2: Bamboo leaf powder obtained after initial and secondary low-temperature pretreatment, without air classification;

[0144] Sample 3: Bamboo leaf powder obtained after initial and secondary low-temperature pretreatment and airflow separation.

[0145] Figure 2 The particle size distribution results are for samples 1, 2, and 3. Figure 2 A shows the particle size distribution of different samples. Figure 2 B shows images of different samples under a microscope.

[0146] The Span values ​​for samples 1, 2, and 3 are calculated as shown in Table 2.

[0147] Table 2

[0148] sample D10 / μm D50 / μm D90 / μm Span Sample 1 2.287 6.484 19.175 2.605 Sample 2 1.224 3.193 7.289 1.899 Sample 3 1.894 3.568 6.115 1.183

[0149] Span is generally used to characterize the width of particle size distribution. Table 2 shows that the span values ​​of different sample groups, from largest to smallest, are: Sample 1 > Sample 2 > Sample 3. Figure 2 The particle size distribution diagram of sample A further validated this result, indicating that the uniformity of the bamboo leaf powder particle size distribution was improved after low-temperature pretreatment and airflow classification. Microscopic observation of the bamboo leaf powder particles in each sample revealed that... Figure 2 As shown in B, after low-temperature pretreatment and airflow separation, the agglomeration of bamboo leaf powder was significantly improved, indicating that the quality of bamboo leaf powder was significantly enhanced.

[0150] Furthermore, in terms of particle size, by Figure 2 As shown in Table 2, the D50 value of sample 1 is greater than that of sample 2, which indicates that low-temperature pretreatment can improve the fineness of bamboo leaf powder to a certain extent and reduce its particle size.

[0151] Experiments have shown that both low-temperature pretreatment and air classification can improve the agglomeration of bamboo leaf powder, and low-temperature pretreatment can improve the fineness of bamboo leaf powder. Therefore, by sequentially subjecting bamboo leaves to low-temperature pretreatment and air classification, high-quality bamboo leaf powder with small particle size and uniform distribution can be obtained.

[0152] Samples 1-3 were tested according to the color difference analysis method described above, and the results are shown in Table 3.

[0153] Table 3 Color values ​​of samples 1, 2, and 3

[0154] a* value (0min) a* value (180min) Δa* value (0→180min) Sample 1 -11.35±0.18 -9.03±0.04 2.32±0.15 Sample 2 -11.69±0.16 -9.00±0.08 2.70±0.18 Sample 3 -11.53±0.19 -9.03±0.01 2.50±0.19

[0155] In addition, from Table 3 and Figure 3 It can be seen that when the color values ​​of each sample were measured at different times, there was no significant difference in the color value a* and color difference value Δa* of samples 1, 2 and 3 (P>0.05). This indicates that low temperature pretreatment and air separation can not only improve the agglomeration of bamboo leaf powder and obtain smaller particle size bamboo leaf powder, but also will not affect the color value of bamboo leaf powder, thus ensuring its emerald green color and color stability.

[0156] The results of the determination of relevant active ingredients in bamboo leaf powder (sample 3) are shown in Table 4.

[0157] Table 4. Determination of total phenols, total flavonoids, total sugars, and protein content in bamboo leaf powder.

[0158] Group Total phenols (mg / g) Total flavonoids (mg / g) Total sugar (mg / g) protein(%) Liangshan Cizhu 5.55±0.08 1.86±0.03 1.47±0.04 22.07±0.03 Arrow bamboo 5.21±0.03 1.27±0.03 1.05±0.04 18.05±0.04

[0159] As shown in Table 4, the final bamboo leaf powder is rich in bioactive content and high in nutritional value, and has high edible value.

[0160] III. Summary

[0161] Based on the optimization and innovation of the above production process, the bamboo leaf powder preparation process is summarized as follows:

[0162] Bamboo species selection → Harvesting → Sorting → Washing → Blanching (blanching solution, ultrasonic-assisted blanching) → Drying → Low-temperature pretreatment → Circulating grinding (coarse) → Low-temperature pretreatment → Ultrafine grinding (fine) → Air classifier → Foreign matter detection → Packaging → Warehousing

[0163] The specific production process is as follows:

[0164] 1. Choose a suitable bamboo leaf variety.

[0165] 2. Harvest the bamboo leaves.

[0166] 3. Select bamboo leaves. Remove branches, yellow leaves, and leaves with insect spots, leaving fresh, bright green tender bamboo leaves for later use.

[0167] 4. Wash the selected bamboo leaves with water.

[0168] 5. Immerse the bamboo leaves (as raw material) in a color-protecting solution at 75-85℃ for 0.5-1.5 minutes. Use a weakly alkaline solution (sodium carbonate, sodium bicarbonate, etc.) with a concentration of 0.3-2g / 100mL, and a material-to-liquid ratio of 1:70-80 (g / mL). Ultrasonic assistance can be used during the blanching process, with an ultrasonic power of 200-350W.

[0169] 6. Dry the blanched bamboo leaves by combining hot air drying and microwave drying.

[0170] 7. After drying, the bamboo leaves are subjected to low-temperature pretreatment by placing them in liquid nitrogen, a freezer, or dry ice.

[0171] 8. Place the frozen bamboo leaves into a grinder for coarse grinding to obtain bamboo leaf powder with a larger particle size. Set up multiple grinding cycles, with each grinding cycle lasting between 5 and 15 minutes. The number of cycles is determined according to actual needs, generally 3 to 4 times.

[0172] 9. The crushed (coarse) bamboo leaf powder is subjected to low-temperature pretreatment again.

[0173] 10. Further pulverize the bamboo leaf powder into ultrafine powder to obtain bamboo leaf powder with smaller particle size. A ball mill is selected for ultrafine pulverization, with a ball-to-material ratio of 5-10:1, a ball milling temperature of 40-50℃, and a ball milling time of 30-60 minutes.

[0174] 10. The obtained bamboo leaf powder is subjected to air separation. The air velocity of the air separator is generally between 10-30 m / s, the rotation speed of the classifying wheel is between 1000-3000 r / min, and the air separation time is set to 10-30 minutes.

[0175] 11. Perform foreign object detection on bamboo leaf powder.

[0176] 12. After completing the foreign object detection, package the bamboo leaf powder.

[0177] All documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference. Furthermore, it should be understood that after reading the foregoing teachings of this invention, those skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing ultrafine green bamboo leaf powder, characterized in that, The method includes the following steps: 1) Place the bamboo leaves in a bleaching and color-protecting solution at 70-85℃ for 0.5-1.5 minutes at a material-to-liquid ratio of 1:70-80g / mL for bleaching and color protection treatment; The bleaching and color-protecting solution is a sodium carbonate aqueous solution or a sodium bicarbonate aqueous solution with a concentration of 0.2-2g / 100mL; The bleaching and color-protecting treatment is performed with ultrasonic assistance; 2) Drying process: The bamboo leaves obtained from step 1) after bleaching and color protection treatment are dried bamboo leaves. 3) The dried bamboo leaves obtained in step 2) are subjected to a first low-temperature pretreatment to obtain bamboo leaves that have undergone the first low-temperature pretreatment; 4) The bamboo leaves obtained in step 3) after the first low-temperature pretreatment are coarsely crushed to obtain coarsely crushed bamboo leaves; 5) The coarsely crushed bamboo leaves obtained in step 4) are subjected to a second low-temperature pretreatment to obtain bamboo leaves that have undergone a second low-temperature pretreatment. 6) The bamboo leaves obtained in step 5) after two low-temperature pretreatments are subjected to ultrafine pulverization to obtain ultrafine pulverized bamboo leaf powder. 7) The ultrafine bamboo leaf powder obtained in step 6) is subjected to air classification to obtain air classified bamboo leaf powder, namely the emerald green ultrafine bamboo leaf powder.

2. The method as described in claim 1, characterized in that, In step 1), the power of the ultrasound assistance is 200-350W.

3. The method as described in claim 1, characterized in that, In step 3), the initial low-temperature pretreatment is performed at a temperature of -30 to -5°C; and / or The initial low-temperature pretreatment takes 0.3-6 hours.

4. The method as described in claim 1, characterized in that, In step 4), the coarse crushing is a circulating crushing process to obtain bamboo leaves with a particle size of 40-100 mesh.

5. The method as described in claim 1, characterized in that, In step 5), the secondary low-temperature pretreatment is performed at a temperature of -30 to -5°C; and / or The secondary low-temperature pretreatment takes 0.3-4 hours.

6. The method as described in claim 1, characterized in that, In step 6), the ultrafine pulverization is carried out by ball milling combined with ultrasonic assistance.

7. The method as described in claim 1, characterized in that, In step 7), the airflow separation has one or more features selected from the group below: 1) The airflow velocity is 10-30 m / s; 2) The grading wheel speed is 1000-3000 r / min; 3) The air separation time is 10-30 minutes.

8. A bright green ultrafine bamboo leaf powder, characterized in that, The color value a* of the bamboo leaf powder is -12 to -10; After being treated with white light for 180 minutes, the Δa* value of the bamboo leaf powder was 2-5; The D50 of the bamboo leaf powder is 2-4 μm; The Span value of the bamboo leaf powder is 1.01-1.

3.

9. The bamboo leaf powder as described in claim 8, characterized in that, The bamboo leaf powder is prepared using the method described in claim 1.

10. A health product or medicine, characterized in that, It contains the bamboo leaf powder as described in claim 8.

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