Preparation method and application of hippophae rhamnoides leaf whole powder

Abstract

The invention discloses hippophae rhamnoides leaf whole powder and a preparation method and application thereof, and belongs to the technical field of agricultural and sideline product processing, and the preparation method comprises the following steps: preparing hippophae rhamnoides leaves by combining blanching color protection treatment with vacuum freeze drying treatment to obtain the hippophae rhamnoides leaf whole powder. The invention also provides the hippophae rhamnoides leaf whole powder prepared by the preparation method and application of the hippophae rhamnoides leaf whole powder in food processing. The process provided by the invention is simple, the requirement on equipment is not high, and compared with instant powder preparation, the method is more suitable for batch production of powder.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural and sideline product processing, and in particular relates to a preparation method and application of seabuckthorn leaf whole powder. Background Art

[0002] Seabuckthorn Seabuckthorn (Hippophae rhamloides L.) is a plant of the genus Hippophae rhamnoides of the family Elaeagnaceae. It is a thorny, nitrogen-fixing, deciduous, dioecious shrub distributed in Asia, Europe and North America. Seabuckthorn leaves contain a large number of active ingredients, mainly polysaccharides, flavonoids, polyphenols, triterpenes and sterols, among which the content of flavonoids, polyphenols and vitamin C and vitamin E in some varieties are higher than that in seabuckthorn fruits. Seabuckthorn leaves have high medicinal and health value. At the same time, they also have the advantages of large reserves, long harvest period, easy picking and storage, and great potential for development into functional foods, medicines, health products, etc. The research, development and application of seabuckthorn leaves are developing rapidly. Making full use of seabuckthorn leaves can not only solve the problem of waste resources, but also promote the development of the seabuckthorn industry and create higher economic and social benefits.

[0003] At present, there are few studies on the processing and utilization of seabuckthorn leaf powder. The existing seabuckthorn leaf powder preparation methods include a seabuckthorn leaf freeze-dried instant powder and a preparation method thereof of Beijing Forestry University. The preparation method mainly prepares seabuckthorn leaf freeze-dried instant powder, which mainly involves the extraction and drying of water-soluble components in seabuckthorn leaf powder, and the obtained product is brown. The obtained product does not belong to the seabuckthorn leaf powder and full nutrition product, nor does it have good color and the original smell and sensory sense of seabuckthorn leaf. Moreover, the seabuckthorn leaf powder quick-drying powder prepared by this method has a complicated process, involves many process equipment, and has a high cost. In addition, Hangzhou Shangyi Bencao Chinese Medicine Technology Co., Ltd. discloses a deep processing method of seabuckthorn leaf, the product prepared by this method is a seabuckthorn leaf Monascus fermentation product, and the product cannot maintain the original color, smell and nutrition of seabuckthorn leaf.

[0004] In summary, in the prior art, most seabuckthorn leaf products are extraction products and fermentation products, which cannot retain all the nutrients of seabuckthorn leaves, nor have the original color, smell and tissue state of seabuckthorn leaves. In addition, they involve many types of equipment, complicated processes and high costs.

[0005] Therefore, how to provide a method for preparing a complete nutrient seabuckthorn leaf powder is a technical problem that those skilled in the art need to solve urgently. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a complete nutritional seabuckthorn leaf powder and a preparation method and application thereof.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing whole seabuckthorn leaf powder comprises the steps of blanching and color protection treatment of the seabuckthorn leaves combined with vacuum freeze drying treatment to obtain the whole seabuckthorn leaf powder.

[0009] Preferably, the seabuckthorn leaves are picked in September.

[0010] Preferably, the blanching and color protection treatment comprises the following steps: blanching the seabuckthorn leaves in a 90°C water bath for 10 seconds, removing the leaves, placing them in 15°C clean water, stirring for 10 minutes, and then cooling them to room temperature.

[0011] Beneficial effects: The blanching step can achieve the effect of inactivating chlorophyllase in seabuckthorn leaves, making the leaves green. The hot water blanching treatment in the present invention has the effects of sterilization and cleaning, and the prepared powder has a higher level of hygiene and safety. At the same time, the hot water blanching treatment has the effect of inactivating chlorophyllase, which is conducive to the stable storage of the powder. In addition, the hot water blanching treatment destroys the epidermis of the seabuckthorn leaves, which is conducive to the dissipation of water during the drying process, shortens the drying time, improves the drying efficiency, and is easier to break into uniformly dispersed powder.

[0012] Preferably, the vacuum freeze-drying process specifically comprises the following steps:

[0013] The blanched and color-protected seabuckthorn leaves were frozen at -40°C for 1 hour, and then the cold trap temperature was set to -60°C, the vacuum degree was 13Pa, and the vacuum was gradually increased to 25°C for 24 hours to complete the vacuum freeze-drying process.

[0014] The vacuum gradient temperature rise is: -30℃ for 4h; -20℃ for 1h; -10℃ for 1h; 0℃ for 2h; 10℃ for 4h; 20℃ for 4h; 25℃ for 8h.

[0015] Beneficial effects: The present invention adopts a vacuum freeze drying method, and utilizes a low temperature, oxygen-proof and light-proof drying method to improve the preservation effect of active substances (phenolic substances) and photosensitive substances (chlorophyll), and can obtain a loose and porous structure, which is easier to be broken into uniformly dispersed powders during the crushing process. The present invention uses this method to dry seabuckthorn leaves, which can maintain the heat-sensitive components and photosensitive components to the greatest extent, and the leaves prepared by vacuum freeze drying have a loose and dispersed structure, which is beneficial to the crushing process.

[0016] Preferably, the bleaching and color protection treatment further includes pretreatment of the seabuckthorn leaves.

[0017] Preferably, the pretreatment includes removing impurities and dry and seriously polluted leaves from the collected seabuckthorn leaves and then washing them with water three times.

[0018] Preferably, the vacuum freeze-drying process further includes the steps of removing loose hair and pulverizing.

[0019] Beneficial effects: There are a lot of star-shaped and umbrella-shaped floating hairs on the back of sea buckthorn leaves, which are easy to fall off after blanching and freeze-drying. The floating hairs will generate electrostatic attraction when the whole sea buckthorn leaf powder is bagged, affecting sampling and packaging, so they should be removed before crushing as much as possible.

[0020] Preferably, the removal of the floating hairs is specifically performed by placing the vacuum freeze-dried seabuckthorn leaves on a 40-mesh sieve and shaking for 10 minutes.

[0021] Preferably, the pulverization is to pulverize to a particle size of less than 40 meshes.

[0022] Beneficial effects: After crushing, the sea buckthorn leaf powder product is obtained, which has fine texture, dispersed particles, uniform coarseness and fineness, good dry fluidity, uniform color, emerald green, glossy, and rich leaf fragrance.

[0023] A method for preparing seabuckthorn leaf whole powder obtains seabuckthorn leaf whole powder.

[0024] Application of seabuckthorn leaf whole powder in food processing.

[0025] Compared with the prior art, the present invention has the following advantages and technical effects:

[0026] The invention provides a whole seabuckthorn leaf powder and a preparation method and application thereof. The whole seabuckthorn leaf powder sample prepared by the invention has a bright green color, a color similar to that of matcha powder, dispersed powder particles, uniform thickness, fine texture, good fluidity, and maintains the original nutritional quality of seabuckthorn leaves to the greatest extent, including protein content, total phenol content and chlorophyll content, and has a minimum content of moisture, uniform color, green and gloss; the leaves are fragrant and rich, and have a smell closest to seabuckthorn leaves. The invention adopts blanching and vacuum freeze drying treatment at the same time, and the white floating hair on the back of the leaves is easier to fall off, so that the powder is uniform, and the influence of static electricity can be reduced during packaging. The product obtained by the invention can be used for food additives and feed additives, which not only solves the problem of waste resources, but also promotes the development of the seabuckthorn industry and creates higher economic and social benefits. In addition, the process provided by the invention is simple, and the equipment requirements are not high. Compared with the preparation of instant powder, the method is more suitable for batch production of powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0028] Figure 1 The water content (%) of the whole seabuckthorn leaf powder obtained in Example 1 and Comparative Examples 1-4;

[0029] Figure 2 The sensory evaluation scores of the whole seabuckthorn leaf powder obtained in Example 1 and Comparative Examples 1-4;

[0030] Figure 3 The chromaticity value of the whole seabuckthorn leaf powder obtained in Example 1 and Comparative Examples 1-4;

[0031] Figure 4 The chlorophyll of the whole seabuckthorn leaf powder obtained in Example 1 and Comparative Examples 1-4;

[0032] Figure 5 The particle size distribution of the whole seabuckthorn leaf powder obtained in Example 1 and Comparative Examples 1-4;

[0033] Figure 6 The scanning electron microscope images of the whole seabuckthorn leaf powder obtained in Example 1 and Comparative Examples 1-4 are shown;

[0034] Figure 7 The total phenol content in the seabuckthorn leaves obtained in Example 1 and Comparative Examples 1-4;

[0035] Figure 8 The total protein content in the seabuckthorn leaves obtained in Example 1 and Comparative Examples 1-4;

[0036] Fig. 9 The actual photos of the whole seabuckthorn leaf powder obtained in Example 1 and Comparative Examples 1-4;

[0037] From left to right are Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Example 1;

[0038] Fig.10 The front and back of the sea buckthorn leaf;

[0039] Fig.11 The cross-sectional appearance photos of bread with different addition amounts of sea buckthorn leaf whole flour;

[0040] Fig.12 The results of sensory evaluation of bread with different addition amounts of seabuckthorn leaf flour are shown in the figure;

[0041] Fig.13 This is the result graph of total phenol content in seabuckthorn leaf whole flour bread;

[0042] Fig.14 This is the result of antioxidant activity of sea buckthorn leaf whole flour bread.

[0043] The bar graphs in the accompanying drawings of the present invention represent standard errors (±SE), and different letters represent significant differences (P<0.05). DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] The embodiment of the invention discloses a method for preparing whole seabuckthorn leaf powder. The whole seabuckthorn leaf powder is prepared by blanching and color-protecting treatment of the seabuckthorn leaves combined with vacuum freeze-drying treatment.

[0047] In a preferred embodiment, the seabuckthorn leaves are picked in September.

[0048] In a preferred embodiment, the blanching and color protection treatment comprises the following steps: blanching the seabuckthorn leaves in a 90°C water bath for 10 seconds, removing the leaves, placing them in 15°C clean water, stirring for 10 minutes, and then cooling them to room temperature.

[0049] The blanching step can achieve the effect of inactivating chlorophyllase in the seabuckthorn leaves, making the leaves green. The blanching operation can also have the effects of cleaning and sterilization. In addition, blanching can destroy the epidermis and cell wall of the seabuckthorn leaves, which is conducive to the escape of water during the drying process, shortening the drying time and improving the drying efficiency.

[0050] In a preferred embodiment, the vacuum freeze-drying process specifically comprises the following steps:

[0051] The blanched and color-protected seabuckthorn leaves were frozen at -40°C for 1 hour, and then the cold trap temperature was set to -60°C, the vacuum degree was 13Pa, and the vacuum was gradually increased to 25°C for 24 hours to complete the vacuum freeze-drying process.

[0052] The vacuum gradient temperature rise is as follows: -30℃ for 4h; -20℃ for 1h; -10℃ for 1h; 0℃ for 2h; 10℃ for 4h; 20℃ for 4h; 25℃ for 8h.

[0053] In a preferred embodiment, the bleaching and color protection treatment further includes pretreatment of the seabuckthorn leaves.

[0054] In a preferred embodiment, the pretreatment includes removing impurities and dry and seriously polluted leaves from the collected seabuckthorn leaves and then washing them with water for three times.

[0055] In a preferred embodiment, the vacuum freeze-drying process further includes the steps of removing loose hair and pulverizing.

[0056] There are a lot of star-shaped and umbrella-shaped floating hairs on the back of sea buckthorn leaves, which are easy to fall off after blanching and freeze-drying. These floating hairs will generate electrostatic attraction when the whole sea buckthorn leaf powder is subsequently bagged, affecting sampling and packaging, so they should be removed before crushing as much as possible.

[0057] In a preferred embodiment, the removal of the floating hairs is specifically as follows: placing the vacuum freeze-dried seabuckthorn leaves on a 40-mesh sieve and shaking for 10 minutes.

[0058] In a preferred embodiment, the pulverization is pulverizing to a particle size of less than 40 meshes. After pulverization, a sea buckthorn leaf powder product with fine texture, dispersed particles, uniform coarseness, good dry fluidity, uniform color, emerald green, glossy, and rich leaf fragrance is obtained.

[0059] The embodiment of the invention also discloses a method for preparing seabuckthorn leaf whole powder and the prepared seabuckthorn leaf whole powder.

[0060] The embodiment of the present invention also discloses an application of seabuckthorn leaf powder in food processing

[0061] The seabuckthorn leaves in the embodiment of the present invention are leaves of Chinese seabuckthorn (Hippophae rhamnoides subsp. sinensisRousi). The front and back sides of the seabuckthorn leaves are as follows: Fig.10 shown.

[0062] Unless otherwise specified, the room temperature described in the embodiments of the present invention is 25±3°C.

[0063] Example 1

[0064] A method for preparing seabuckthorn leaf whole powder comprises the following steps:

[0065] (1) Seabuckthorn leaf pretreatment: Seabuckthorn leaves were picked in September, and impurities (weeds, seabuckthorn stems, etc.) and dry and seriously polluted seabuckthorn leaves were removed from the samples. The seabuckthorn leaves were then washed three times with 20°C clean water to remove floating dust and impurities, thereby obtaining pretreated seabuckthorn leaves.

[0066] (2) Blanching: Place the pretreated seabuckthorn leaves in a 90°C water bath and stir for 10 seconds, then remove them and place them in 15°C clean water and stir for 10 minutes until the temperature drops to room temperature.

[0067] (3) Place the blanched sea buckthorn leaves in a vacuum freeze dryer for drying. The vacuum freeze dryer conditions are as follows: freeze the blanched and color-protected sea buckthorn leaves at -40°C for 1 hour, then set the cold trap temperature to -60°C, the vacuum degree to 13Pa, and vacuumize and gradually increase the temperature to 25°C for 24 hours, thus completing the vacuum freeze drying process.

[0068] The vacuum gradient temperature rise is as follows: -30℃ for 4h; -20℃ for 1h; -10℃ for 1h; 0℃ for 2h; 10℃ for 4h; 20℃ for 4h; 25℃ for 8h.

[0069] (4) Collect the freeze-dried seabuckthorn leaves, place them on a 40-mesh sieve and shake them for 10 minutes to remove the white floating hairs on the seabuckthorn leaves, then place them in a universal grinder and grind them for 10 seconds, and then pass them through a 40-mesh sieve to obtain the seabuckthorn leaf powder product, which is stored at -20°C in the dark.

[0070] Comparative Example 1

[0071] A method for preparing seabuckthorn leaf whole powder comprises the following steps:

[0072] (1) Seabuckthorn leaves were picked in September, and impurities (weeds, seabuckthorn stems, etc.) and dried and seriously polluted seabuckthorn leaves were removed. The seabuckthorn leaves were then washed three times with 20° C. clean water to remove floating dust and impurities, thereby obtaining pretreated seabuckthorn leaves.

[0073] (2) The leaves were placed in a ventilated and cool place indoors to dry naturally for 3 days at a room temperature of (24±2)°C and a relative humidity of (40±2)%, and were turned over and stirred twice a day to obtain dried seabuckthorn leaves.

[0074] (3) The dried seabuckthorn leaves were placed in a grinder and crushed for 10 seconds, and then passed through a 40-mesh sieve to obtain the whole seabuckthorn leaf powder, which was then stored at -20°C in the dark.

[0075] Comparative Example 1 mainly adopts the natural drying method. A large number of previous studies have found that natural drying is a drying method with high cost performance, simple operation, high processing efficiency and low cost, and the quality of the dried product is good. Therefore, natural drying is selected as the control of this example to compare the differences in powder quality.

[0076] Comparative Example 2

[0077] A method for preparing whole seabuckthorn leaf powder, which adds a blanching process on the basis of comparative example 1, is mainly used to investigate the effect of the blanching process on the quality of whole seabuckthorn leaf powder, and specifically comprises the following steps:

[0078] (1) Pick sea buckthorn leaves in September, remove impurities (weeds, sea buckthorn stems, etc.) in the sample, remove dry and seriously polluted sea buckthorn leaves, and then wash the sea buckthorn leaves three times with 20°C clean water to remove dust and impurities.

[0079] (2) Place the sea buckthorn leaves in a 90°C water bath and stir for 10 seconds, then remove them and place them in 20°C water and stir for 10 minutes until the temperature drops to room temperature.

[0080] (3) The leaves were placed in a ventilated and cool place indoors to dry naturally for 3 days at a room temperature of (24±2)°C and a relative humidity of (40±2)%, and were turned over twice a day to obtain dried seabuckthorn leaves.

[0081] (4) The dried seabuckthorn leaves were placed in a grinder and crushed for 10 seconds, and then passed through a 40-mesh sieve to obtain the whole seabuckthorn leaf powder, which was then stored at -20°C in the dark.

[0082] Comparative Example 3

[0083] A method for preparing seabuckthorn leaf whole powder mainly utilizes a vacuum freeze-drying process to investigate the effect of vacuum freeze-drying on the quality of seabuckthorn leaf whole powder, and specifically comprises the following steps:

[0084] (1) Pick sea buckthorn leaves in September, remove impurities (weeds, sea buckthorn stems, etc.) in the sample, remove dry and seriously polluted sea buckthorn leaves, and then wash the sea buckthorn leaves three times with 20°C clean water to remove dust and impurities.

[0085] (2) Place the seabuckthorn leaves on a drying tray and dry them in a vacuum freeze dryer. The vacuum freeze dryer is set as follows: freeze the blanched and color-protected seabuckthorn leaves at -40°C for 1 hour, then set the cold trap temperature to -60°C, the vacuum degree to 13Pa, and gradually increase the temperature to 25°C for 24 hours to complete the vacuum freeze drying process.

[0086] The vacuum gradient temperature rise is as follows: -30℃ for 4h; -20℃ for 1h; -10℃ for 1h; 0℃ for 2h; 10℃ for 4h; 20℃ for 4h; 25℃ for 8h.

[0087] (3) Collect the freeze-dried seabuckthorn leaves, place them on a 40-mesh sieve and shake them for 10 minutes to remove the white floating hairs that have fallen from the seabuckthorn leaves.

[0088] (4) The seabuckthorn leaves were placed in a grinder and crushed for 10 seconds, and then passed through a 40-mesh sieve to obtain a seabuckthorn leaf powder product, which was stored at -20°C in the dark.

[0089] Comparative Example 4

[0090] A method for preparing whole seabuckthorn leaf powder, wherein the technical parameters of the blanching treatment refer to the existing color protection treatment of fruits and vegetables before freeze-drying, and is used to investigate the effect of the blanching time before vacuum freeze-drying on the quality of the whole seabuckthorn leaf powder, and specifically comprises the following steps:

[0091] (1) Pick sea buckthorn leaves in September, remove impurities (weeds, sea buckthorn stems, etc.) in the sample, remove dry and seriously polluted sea buckthorn leaves, and then wash the sea buckthorn leaves three times with 20°C clean water to remove dust and impurities.

[0092] (2) Place the sea buckthorn leaves in a 95°C water bath and stir and blanch for 90 seconds. Then remove them and place them in 20°C water and stir for 10 minutes until the temperature drops to room temperature.

[0093] (3) Place the sea buckthorn leaves on a drying tray and dry them in a vacuum freeze dryer. The vacuum freeze dryer is set as follows: freeze the blanched and color-protected sea buckthorn leaves at -40°C for 1 hour, then set the cold trap temperature to -60°C, the vacuum degree to 13Pa, and vacuumize the leaves to 25°C for 24 hours, thus completing the vacuum freeze drying process.

[0094] The vacuum gradient temperature rise is as follows: -30℃ for 4h; -20℃ for 1h; -10℃ for 1h; 0℃ for 2h; 10℃ for 4h; 20℃ for 4h; 25℃ for 8h.

[0095] (4) Collect the freeze-dried seabuckthorn leaves, place them on a 40-mesh sieve and shake them for 10 minutes to remove the white floating hairs that have fallen from the seabuckthorn leaves.

[0096] (5) Place the seabuckthorn leaves in a grinder and grind them for 10 seconds. Then, pass them through a 40-mesh sieve to obtain the seabuckthorn leaf powder product, which is then stored at -20°C in the dark.

[0097] Technical effect:

[0098] 1. Water content

[0099] The water content of the products obtained in Example 1 and Comparative Examples 1-4 is as follows Figure 1 As shown by Figure 1 It can be seen that the moisture content of the whole seabuckthorn leaf powder obtained in Example 1 and Comparative Examples 1-4 is all below 8%, which meets the moisture requirement for powder storage safety. However, the moisture content of the whole seabuckthorn leaf powder obtained in Example 1 is significantly lower than that in the comparative examples, indicating that the product in Example 1 is more conducive to storage.

[0100] 2. Sensory evaluation

[0101] Evaluation and scoring were performed based on the sensory evaluation table 1.

[0102] Table 1. Sensory evaluation table

[0103]

[0104]

[0105] According to the evaluation criteria in Table 1, combined Fig. 9 The following sensory evaluation results were obtained for the whole seabuckthorn leaf powder obtained in Example 1 and Comparative Examples 1-4:

[0106] Example 1: The color is emerald green, bright and uniform, the powder particles are dispersed, the coarseness is uniform, and there is a light fragrance.

[0107] Comparative Example 1: The leaf powder is emerald green, dull and uneven in color, the powder particles are dispersed but uneven in coarseness and have a faint fragrance.

[0108] Comparative Example 2: The leaf powder is yellow-green, bright and uniform in color, the powder particles are dispersed, uniform in coarseness and fineness, and have a faint fragrance.

[0109] Comparative Example 3: The color is emerald green, bright and uniform, the powder particles are dispersed, but the coarseness is uneven, and there is a faint fragrance.

[0110] Comparative Example 4: The color is yellow-green, darker and uniform, the powder particles are dispersed, the coarseness is uniform, and there is no fragrance of sea buckthorn leaves.

[0111] Sensory evaluation scores of seabuckthorn leaf powder Figure 2 As shown, from Figure 2 It can be seen that Example 1 is significantly better than the comparative example in terms of color, texture and smell, among which Example 1 is particularly outstanding in terms of color.

[0112] 3. Chroma

[0113] The color of dried products is an important quality attribute that affects their market value. Different drying methods also have different direct effects on the color of dried products. The test results are expressed as L, a, and b, where L represents the degree of brightness and darkness. The higher the L value, the brighter the sample color. a represents the red-green color, +a represents reddish color, -a represents greenish color. b represents the yellow-blue color, +b represents yellowish color, -b represents bluish color. The results are as follows: Figure 3 As shown by Figure 3 It can be seen that the seabuckthorn leaf sample of Example 1 has the highest L value, the lowest a value, and the highest b value, indicating that the sample has the brightest brightness, the greenest color, and the best color. This result is consistent with the evaluation result of color in the sensory evaluation.

[0114] 4. Chlorophyll Content

[0115] Chlorophyll content is one of the important indicators for measuring the quality of seabuckthorn leaves. The chlorophyll content results of the products obtained in Example 1 and Comparative Examples 1-4 are as follows: Figure 4As shown, it can be seen that the chlorophyll a, chlorophyll b and total chlorophyll in Example 1 and Comparative Example 3 are significantly higher than those in Comparative Example 1 and Comparative Example 2, indicating that vacuum freeze drying has a better effect on maintaining the chlorophyll content of seabuckthorn leaves, because the vacuum freeze drying process is low temperature, light-proof and oxygen-proof, thus retaining the chlorophyll in the seabuckthorn leaves to the maximum extent. During the room temperature drying process, Comparative Examples 1 and 2 have a long contact time with heat, light and oxygen, which greatly affects the stability of chlorophyll in the seabuckthorn leaves. However, the blanching time of Comparative Example 4 is too long, and the chlorophyll is severely damaged and browned.

[0116] 5. Particle size distribution

[0117] The particle size distribution of the whole seabuckthorn leaf powder obtained in Example 1 and Comparative Examples 1-4 is shown in Figure 5 It can be seen that the particle size distribution of the product of Example 1 is narrower, and the particle size is the smallest. The reason may be that Example 1 mainly adopts vacuum freeze drying, and the shape of the leaves remains basically unchanged during the drying process, the shrinkage is small, and there is no agglomeration phenomenon. However, in the natural drying process adopted by Comparative Examples 1 and 2, due to the process of droplets from the wet surface to the dry surface, these moving droplets or particles inevitably collide and agglomerate, resulting in a wide particle size distribution of the particles. In addition, the same mass of seabuckthorn leaves, after being crushed under the same conditions, have different contact areas of particles that collide with each other during the crushing process due to different volumes. Since the water content of the whole seabuckthorn leaf powder is directly sublimated during vacuum freeze drying, a hollow porous structure is formed inside the tissue, and the heat transfer direction of natural drying is from the surface to the inside, and there is a shrinkage phenomenon. Therefore, the volume of vacuum freeze drying is significantly larger than that of other drying methods. Therefore, during the crushing process, the contact area of ​​the materials increases, and the frequency of mutual collision also increases, thereby making the crushing particle size smaller. In addition, Example 1 was blanched with hot water, and the white floating hairs on the surface of the leaves were easier to fall off and removed after drying. The epidermal structure of the leaves was also destroyed, making it easier for moisture to escape from the leaves during the drying process, and making the sample more uniform.

[0118] 6. Microstructure

[0119] The microstructure of the whole seabuckthorn leaf powder obtained in Example 1 and Comparative Examples 1-4 is as follows: Figure 6 As shown, it can be seen that Comparative Examples 1 and 2 use natural drying, which is a heat conduction heating method from the outside to the inside, causing the sample tissue to deform and shrink. Therefore, the surface of the seabuckthorn leaf powder particles dried naturally is uneven, the material shrinkage phenomenon is serious, and the tissue structure is irregular. From the microstructure of the seabuckthorn leaf powder in Example 1, because it uses vacuum freeze drying to allow the intercellular ice crystals to directly sublimate, the structural shrinkage is minimized, the density is low, and it is a larger loose particle with a relatively flat surface (loose dried materials are easy to be crushed), and the material shrinkage phenomenon is less. The seabuckthorn leaf powder in Example 1 has a loose texture, and the powder particles are small and uniform. This result is consistent with the particle size result.

[0120] 7. Nutritional quality

[0121] The total phenol content of the whole seabuckthorn leaf powder obtained in Example 1 and Comparative Examples 1-4 is as follows: Figure 7 As shown, it can be seen that the influence of different drying methods on the total phenol content of sea buckthorn leaf powder is as follows: Comparative Example 1 < Comparative Example 2 < Comparative Example 4 < Comparative Example 3 < Example 1, among which the total phenol content in the sea buckthorn leaf powder dried in Example 1 is significantly (P < 0.05) higher than that in the other four types of sea buckthorn leaf powder. This is because sea buckthorn leaves retain more heat-sensitive and antioxidant components under vacuum and low-temperature conditions.

[0122] The total protein content of the whole seabuckthorn leaf powder obtained in Example 1 and Comparative Examples 1-4 is as follows: Figure 8 As shown, it can be seen that the influence of different drying methods on the protein content of seabuckthorn leaf powder is as follows: Comparative Example 1 < Comparative Example 2 < Comparative Example 4 < Comparative Example 3 < Example 1. It can be seen that the protein content of seabuckthorn leaf powder in Example 1 is significantly (P < 0.05) higher than that of the other three drying methods.

[0123] In summary, the seabuckthorn leaf sample of Example 1 has good color, retains the fresh color very well, and has the best sensory evaluation; in terms of nutritional components, Example 1 retains the nutritional components such as chlorophyll, total phenols and total protein of the dried sample to the greatest extent; in terms of sample morphology, the sample of the example has a low particle size, the drying process does not destroy the original framework structure of the sample, and the pulverization process is easier to break into powder with uniform particles.

[0124] 8. Application of seabuckthorn leaf powder in food processing (application of seabuckthorn leaf powder in bread processing):

[0125] (1) Basic recipe of bread: 300g high-gluten flour, 6g yeast, 3g salt, 40g sugar, 50g egg, 150g milk, 20g milk powder, 15g butter. The addition amount of seabuckthorn leaf powder is 0%, 0.5%, 1%, 2%, 4% of the flour mass, respectively.

[0126] (2) Bread making steps: First, put all ingredients except butter into a blender and stir until smooth. Add butter to melt it and stir until the dough can be pulled out of the fascia. The dough is proofed in a proofing room (temperature 30°C, humidity 80%) for 60 minutes. The shaped dough is then placed in a proofing room (temperature 38°C, humidity 85%) for 60 minutes. The bread is baked in a 190°C oven for 40 minutes. The finished product is cooled at room temperature overnight for later use.

[0127] (3) Basic indicators of bread testing:

[0128] (3-1) Specific volume of bread: Determined in accordance with GB / T 20981-2021 “General Rules for Bread Quality”.

[0129] (3-2) Sensory evaluation: Refer to GB / T 20981-2021 "General Rules for Bread Quality" to conduct sensory evaluation of bread. The bread sensory scoring table is shown in Table 2:

[0130] Table 2

[0131]

[0132] (3-3) Determination of total phenolic content and antioxidant activity of bread

[0133] Total phenols were determined using the Folin phenol method, and DPPH radical scavenging rate was used to reflect the antioxidant activity of bread.

[0134] (4) Quality analysis of sea buckthorn leaf bread:

[0135] (4-1) Sensory quality of sea buckthorn leaf whole flour bread

[0136] The cross section of bread with different addition amounts of seabuckthorn leaf powder Fig.11 As shown in the figure, the sensory evaluation of bread with different addition amounts of seabuckthorn leaf flour is as follows: Fig.12 As shown, it can be seen that the scores of bread in terms of shape, color, smell and taste first increase and then decrease with the increase of the amount of sea buckthorn leaf powder added. When the amount of sea buckthorn leaf powder added is ≤1%, the taste of bread can be improved and it has a unique sea buckthorn leaf flavor.

[0137] (4-2) Specific volume of sea buckthorn leaf powder bread

[0138] It was determined that the specific volume of bread without sea buckthorn leaf powder was 4.73 mL / g, and the specific volumes of bread with addition amounts of 0.5%, 1%, 2%, and 4% were 4.92, 4.78, 4.33, and 3.96 mL / g, respectively. When the addition amount of sea buckthorn leaf powder was ≤1%, there was no significant effect on the specific volume of bread, which indicates that a lower addition amount of sea buckthorn leaf powder had no significant effect on the gas production capacity during dough fermentation. When the addition amount of sea buckthorn leaf powder was greater than 1%, the specific volume decreased significantly as the addition amount increased.

[0139] (4-3) Total phenolic content and antioxidant capacity of seabuckthorn leaf whole flour bread

[0140] like Fig.13 and Fig.14It can be seen that the total phenol content of bread is positively correlated with the amount of sea buckthorn leaf powder added. Sea buckthorn leaves are rich in phenolic substances. By adding sea buckthorn leaf powder to bread, the phenolic content in bread can be significantly increased (0.63-6.13 mg GAE / g), thereby improving the antioxidant activity of bread. When making bread, adding sea buckthorn leaf powder can prevent dough oxidation, further delay bread aging, and improve bread quality. As the amount of sea buckthorn leaf powder added increases, the DPPH free radical scavenging ability of sea buckthorn bread is significantly enhanced (17.21%-75.21%), which shows that sea buckthorn leaf powder still has an antioxidant effect in bread.

[0141] In summary, compared with the control bread, when the sea buckthorn leaf powder was added at a level of ≤1%, the bread had better quality, softer and more elastic texture. Adding sea buckthorn leaf powder can significantly increase the total phenolic content and DPPH free radical scavenging ability of bread. Therefore, adding an appropriate amount of sea buckthorn leaf powder can improve the quality of bread and enhance its antioxidant activity.

[0142] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing seabuckthorn leaf whole powder, characterized in that: The seabuckthorn leaves are prepared by a blanching and color protection treatment combined with a vacuum freeze-drying treatment to obtain the seabuckthorn leaf whole powder.

2. The method for preparing seabuckthorn leaf whole powder according to claim 1, characterized in that: The blanching and color protection treatment comprises the following steps: blanching the seabuckthorn leaves in a 90° C. water bath for 10 seconds, taking them out, placing them in 15° C. clean water, stirring them for 10 minutes, and then cooling them to room temperature.

3. The method for preparing seabuckthorn leaf whole powder according to claim 1, characterized in that: The vacuum freeze drying process specifically comprises the following steps: The blanched and color-protected seabuckthorn leaves were frozen at -40°C for 1 hour, and then the cold trap temperature was set to -60°C, the vacuum degree was 13Pa, and the vacuum was gradually increased to 25°C for 24 hours to complete the vacuum freeze-drying process.

4. The method for preparing seabuckthorn leaf whole powder according to claim 3, characterized in that: The vacuum gradient temperature rise is specifically: -30°C for 4 hours; -20°C for 1 hour; -10°C for 1 hour; 0°C for 2 hours; 10°C for 4 hours; 20°C for 4 hours; 25°C for 8 hours.

5. The method for preparing seabuckthorn leaf whole powder according to claim 1, characterized in that: The method also includes pretreatment of the seabuckthorn leaves before the bleaching and color protection treatment.

6. The method for preparing seabuckthorn leaf whole powder according to claim 5, characterized in that: The pretreatment comprises removing impurities and dry and seriously polluted leaves from the collected seabuckthorn leaves and then washing them with water for 3 times.

7. The method for preparing seabuckthorn leaf whole powder according to claim 1, characterized in that: The vacuum freeze-drying process also includes the steps of removing floating hair and crushing.

8. The method for preparing seabuckthorn leaf whole powder according to claim 7, characterized in that: The method of removing the floating hair is as follows: placing the vacuum freeze-dried seabuckthorn leaves on a 40-mesh sieve and shaking for 10 minutes; The pulverization is to pulverize to a particle size of less than 40 meshes.

9. Seabuckthorn leaf whole powder prepared by the method for preparing seabuckthorn leaf whole powder according to any one of claims 1 to 8.

10. Use of the whole seabuckthorn leaf powder as claimed in claim 9 in food processing.

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