Tartary buckwheat instant powder and preparation method thereof

Abstract

The present application relates to the technical field of food processing, in particular to a kind of tartary buckwheat instant powder and a preparation method thereof, by the synergistic adaptation of multiple process steps, to a large extent reduce the loss of rutin and other active ingredients, while making the instant powder particles fine and easy to disperse, making the instant powder flavor more full, while ensuring product quality, reducing energy consumption, and taking into account product taste and production efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food processing, in particular to a tartary buckwheat instant powder and a preparation method thereof. BACKGROUND

[0002] As a characteristic crop with medicinal and edible properties, tartary buckwheat is rich in flavonoids such as rutin and quercetin, and dietary fiber, and has significant health benefits in terms of metabolic regulation and antioxidant activity. With the advantages of convenient brewing and uniform taste, tartary buckwheat instant powder has become a highly potential sub-category in the fast-consumption beverage market.

[0003] Currently, the preparation of tartary buckwheat instant tea in the industry generally adopts the traditional process of high-temperature baking, crushing, hot water extraction, and spray drying. Although this process can achieve large-scale production, it faces multiple bottlenecks in product quality due to the technical design flaws in the key steps. One of the core problems is the high-temperature baking step, which is far beyond the tolerance threshold of heat-sensitive components such as rutin and quercetin. High temperature also promotes the caramelization of proteins and polysaccharides in tartary buckwheat, resulting in a noticeable burnt taste and destroying the original aroma flavor. Although low-temperature baking can reduce the loss of some active ingredients, it may result in insufficient generation of tartary buckwheat's unique roasted aroma, making the product taste even more bland.

[0004] Moreover, after conventional crushing of the baked tartary buckwheat, the active ingredients and flavor substances in the cells are difficult to dissolve during subsequent hot water extraction, and the final product is prone to form hard agglomerates, with a reconstitution time exceeding 15 seconds and poor solubility, which seriously affects the consumer experience. More importantly, the porous structure inside the tartary buckwheat cannot be effectively formed, and characteristic flavor substances such as terpenes and phenolic acids cannot be fully released, further exacerbating the defect of single product flavor. In addition, another technology uses freeze-drying instead of traditional spray drying, which can reduce the damage to components caused by high temperature, but the viscosity of the concentrated liquid is high due to the lack of pretreatment of the material, the freeze-drying period is long, and the production efficiency is extremely low, which cannot meet the demand for mass production.

[0005] In summary, the existing preparation process of tartary buckwheat instant tea cannot simultaneously meet the three core demands of high retention of active ingredients, good solubility, and rich flavor levels, resulting in obvious shortcomings in market competition. Therefore, it is urgent to develop a new preparation method to break through the above technical bottlenecks and improve the overall quality and industrial application value of tartary buckwheat instant tea. SUMMARY

[0006] To solve the above technical problems, the present application provides a tartary buckwheat instant powder and a preparation method thereof, to reduce the loss of active ingredients, improve solubility, and fully release flavors, and obtain high-quality tartary buckwheat instant powder.

[0007] The present application provides the following technical solutions.

[0008] A preparation method of tartary buckwheat instant powder, characterized in that it comprises the following steps:

[0009] Screening, impurity removal, and washing of tartary buckwheat to obtain a crude product;

[0010] Mixing the crude product with water and performing drum soaking to obtain high water-absorbing and swelling tartary buckwheat;

[0011] Performing high-temperature and high-pressure puffing on the high water-absorbing and swelling tartary buckwheat to obtain puffed particles;

[0012] Performing ultra-micro grinding on the puffed particles to obtain micro-powder;

[0013] Mixing the micro-powder with water and performing high-pressure cooking to obtain cooked material;

[0014] Performing pressure filtration on the cooked material and taking the filtrate;

[0015] Pre-freezing the filtrate at -35℃ to -45℃ and then performing vacuum freeze-drying concentration to obtain concentrated liquid;

[0016] Performing freeze spray drying on the concentrated liquid;

[0017] The conditions for drum soaking include a temperature of 35℃ to 45℃, a time of 120min to 180min, and a rotation speed of 3r / min to 7r / min.

[0018] The present technical solution realizes multiple advantages through the synergistic effect of each process step: drum soaking can ensure uniform water absorption of tartary buckwheat and stability of endogenous enzyme activity, laying a foundation for subsequent puffing; high-temperature and high-pressure puffing forms a porous structure, which, in combination with ultra-micro grinding, improves the extraction contact area and further promotes the dissolution of active ingredients and flavor substances during high-pressure cooking; the subsequent -35℃ to -45℃ pre-freezing, vacuum freeze-drying concentration, and freeze spray drying steps avoid high-temperature damage throughout the process, which not only makes the rutin retention rate reach 92%, which is 20% higher than that of traditional methods, but also shortens the dissolution time of the prepared instant powder to 3 seconds, while reducing microbial contamination and material waste, and taking into account the nutritional, solubility, and flavor quality.

[0019] Further, the application limits the rotation speed in the rotating cage soaking process to 3r / min~7r / min, which can ensure sufficient contact and uniform stirring of the tartary buckwheat crude product with water, and avoid the water gradient penetration problem caused by material sinking to the bottom in static soaking, so that the water absorption rate of tartary buckwheat is stably improved to 130%~150%, and the water absorption uniformity is significantly optimized, the number of particles that do not expand sufficiently during subsequent high-temperature and high-pressure puffing is significantly reduced, and the formation of uniform porous structure of the puffed particles is ensured. At the same time, the constant temperature condition of 35℃~45℃ can ensure the endogenous enzyme activity of tartary buckwheat, promote the moderate degradation of pectin and cellulose in the cell wall to promote water absorption and expansion. When the temperature is lower, there is a risk of microbial growth during soaking; when the temperature is higher, heat-sensitive ingredients such as rutin will degrade in advance during soaking. In addition, setting the soaking time to 120min~180min can make the tartary buckwheat material bear uniform force without local accumulation, and it is easier to obtain uniform fine powder with D90≤50μm during subsequent ultra-micro grinding, which is beneficial to the efficient dissolution of active ingredients and flavor substances during subsequent high-pressure cooking, while reducing the insoluble precipitates of the prepared instant powder, and improving the product dissolution stability.

[0020] Understandably, in the application, the temperature of the rotating cage soaking includes but is not limited to 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, 41℃, 42℃, 43℃, 44℃, 45℃; the time of the rotating cage soaking includes but is not limited to 120min, 125min, 130min, 135min, 140min, 145min, 146min, 147min, 148min, 149min, 150min, 151min, 152min, 153min, 154min, 155min, 160min, 165min, 170min, 175min, 180min; the rotation speed of the rotating cage soaking includes but is not limited to 3r / min, 4r / min, 5r / min, 6r / min, 7r / min.

[0021] In one of the embodiments, the conditions of the rotating cage soaking include: the temperature is 35℃~45℃, the time is 150min, and the rotation speed is 5r / min.

[0022] Under the above preferred tumbling cage soaking conditions, the synergistic advantages of each process step are more pronounced. The rotation speed of 5 r / min neither causes material collision and breakage due to being too fast, nor leads to local accumulation due to being too slow. Combined with the soaking time of 150 min, the water absorption rate of each material can be stabilized at more than 140% and the water absorption is uniform, completely avoiding the problems of under-soaking or over-soaking of some particles. This uniform water absorption state can make the internal moisture of all particles vaporize synchronously during subsequent high-temperature and high-pressure puffing, forming a regular porous structure, reducing the generation of un-puffed particles, and further making the particle size of the micro-powder obtained after ultra-micro grinding more uniform, avoiding the occurrence of bimodal particle size distribution. At the same time, the uniform micro-powder state can improve the extraction efficiency during subsequent high-pressure cooking, making the dissolution of active ingredients and flavor substances more sufficient, ultimately making the instant powder have faster dissolution speed, more uniform taste, and the risk of microbial growth is effectively controlled, ensuring the stability of product quality.

[0023] In a more preferred embodiment, the conditions of tumbling cage soaking include a temperature of 40℃, a time of 150 min, and a rotation speed of 5 r / min.

[0024] In one embodiment, the conditions of high-temperature and high-pressure puffing include a temperature of 110℃ to 130℃, a pressure of 2 MPa to 4 MPa, and a time of 20 s to 40 s.

[0025] The present inventors found that even if high-temperature and high-pressure puffing is also adopted, if the temperature is lower than 110℃, the degree of tartary buckwheat starch gelatinization is insufficient, and it is relatively difficult to form a uniform porous structure during the puffing process, and hard cores are easily left in the particles during subsequent ultra-micro grinding, resulting in a slight decrease in the dissolution efficiency of active ingredients and flavor substances during the high-pressure cooking stage, and the cooking time needs to be extended to achieve similar dissolution effect; if the temperature is higher than 130℃, although the starch can be fully gelatinized, a small amount of protein in the tartary buckwheat will be slightly denatured, which will slightly reduce the clarity of the filtrate during the subsequent filtration step, and the number of filtration needs to be increased to ensure the purity of the filtrate. At the same time, if the puffing pressure is lower than 2 MPa, the pressure difference formed inside the material is not enough to support the pores to fully expand, the pore size of the puffed particles is small and unevenly distributed, and the infiltration speed is slightly slow when the micro-powder is mixed with water; if the puffing pressure is higher than 4 MPa, the pores are easily over-expanded, which can cause some puffed particles to have fine cracks, and a small amount of fine powder aggregation will occur during the grinding process, and an additional dispersion step is needed to ensure the uniformity of the micro-powder.

[0026] It can be understood that, in the present application, the temperature of high-temperature high-pressure puffing includes but is not limited to 110℃, 112℃, 114℃, 116℃, 118℃, 119℃, 120℃, 121℃, 122℃, 124℃, 126℃, 128℃, 130℃; the pressure of high-temperature high-pressure puffing includes but is not limited to 2MPa, 2.2MPa, 2.4MPa, 2.6MPa, 2.8MPa, 3MPa, 3.2MPa, 3.4MPa, 3.6MPa, 3.8MPa, 4MPa; the time of high-temperature high-pressure puffing includes but is not limited to 20s, 22s, 24s, 26s, 28s, 30s, 32s, 34s, 36s, 38s, 40s.

[0027] In a preferred embodiment, the conditions of high-temperature high-pressure puffing include: the temperature is 115℃~125℃, the pressure is 3MPa, and the time is 30s.

[0028] In one embodiment, the high-pressure cooking satisfies one or more of the following conditions:

[0029] (1) The ratio of material to water is 1:(0.5~1.5);

[0030] (2) The pressure is 0.1MPa~0.3MPa;

[0031] (3) The temperature is 100℃~140℃;

[0032] (4) The time is 15min~30min.

[0033] It can be understood that, in the present application, the ratio of material to water of high-pressure cooking includes but is not limited to 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5; the pressure of high-pressure cooking includes but is not limited to 0.1MPa, 0.2MPa, 0.3MPa; the temperature of high-pressure cooking includes but is not limited to 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃; the time of high-pressure cooking includes but is not limited to 15min, 20min, 25min, 30min.

[0034] The present inventors found that the above high-pressure cooking conditions can achieve multiple advantages. First, the moderate material-to-water ratio avoids excessive water consumption to increase subsequent concentration energy consumption, and prevents insufficient water from leading to insufficient extraction; the reasonable combination of pressure 0.1 MPa~0.3 MPa and temperature 100℃~140℃ can promote the efficient dissolution of active ingredients and flavor substances in tartary buckwheat while reducing the loss of heat-sensitive components caused by excessive high temperature; the cooking time controlled in 15min~30min can ensure the sufficient release of active ingredients, and avoid excessive cooking time to cause too much impurities to be dissolved, which affects the purity of the product.

[0035] In one embodiment, the concentration endpoint of vacuum freeze concentration is determined by the solid concentration reaching 55%~65%.

[0036] The 55%~65% solid concentration formed by vacuum freeze concentration can keep the concentrated liquid with appropriate fluidity, so that uniform atomization can be achieved in the subsequent freeze spray drying process. Meanwhile, the active ingredients in the material are not prone to aggregation and degradation due to excessive concentration at this solid concentration, and the low-temperature characteristics of freeze drying can further reduce the loss of heat-sensitive components.

[0037] In one embodiment, the atomization pressure of freeze spray drying is 0.1 MPa~0.2 MPa.

[0038] Understandably, in the present application, the atomization pressure of freeze spray drying includes but is not limited to 0.1 MPa, 0.12 MPa, 0.14 MPa, 0.16 MPa, 0.18 MPa, and 0.2 MPa.

[0039] The present inventors use the freeze spray drying process, which has higher efficiency and lower energy consumption than freeze drying, and can greatly reduce the loss of heat-sensitive active ingredients and volatile flavor substances in tartary buckwheat compared to traditional spray drying; further limiting the atomization pressure to 0.1 MPa~0.2 MPa can form uniform droplets of the concentrated liquid, ensuring sufficient low-temperature drying, avoiding the problem of too large droplets and low drying efficiency caused by too low pressure, and preventing too fine droplets and wall sticking loss caused by too high pressure.

[0040] In one embodiment, the D90 of the micro powder is ≤50μm.

[0041] The fine particle size characteristics of the micro powder with D90≤50μm can greatly increase its contact area with water during subsequent high-pressure cooking, allowing the active ingredients and flavor substances in tartary buckwheat to be more fully extracted without the need to extend the cooking time. Moreover, the micro powder with this particle size after extraction and drying forms a finer instant powder particle, which can quickly disperse in water during dissolution, reducing insoluble precipitates, and improving the dissolution stability and drinking taste of the instant powder.

[0042] In one embodiment, the conditions of the rotating cage soaking further include: adding stainless steel balls with a diameter of 8cm-12cm, and the weight of the stainless steel balls is 4.06kg-4.24kg.

[0043] More specifically, 1 stainless steel ball is added per 5kg of material.

[0044] The stainless steel balls with specific specifications and weights rotate with the rotating cage, which can promote the full tumbling of the tartary buckwheat coarse product, avoid local accumulation, and allow each tartary buckwheat to uniformly contact water, further improve the water absorption consistency, and reduce the situation of insufficient water absorption of some particles.

[0045] In one embodiment, the filter pressing uses plate and frame filter pressing, and the pressure is 0.5MPa.

[0046] The application also provides a tartary buckwheat instant powder prepared by the preparation method.

[0047] The beneficial effects of the application are embodied in,

[0048] Through the synergistic adaptation of multiple processes, significant advantages are formed in the nutrient retention and dissolution performance of the tartary buckwheat instant powder: the rotating cage soaking at a constant temperature of 35℃-45℃ for a time length of 120min-180min and at a low speed of 3r / min-7r / min can avoid insufficient water absorption caused by low-temperature soaking and premature loss of heat-sensitive components caused by high-temperature soaking, and can achieve uniform water absorption of tartary buckwheat through low-speed tumbling, and form uniform and porous structures of particles through high-temperature and high-pressure puffing; then the material contact area is expanded through ultra-micro grinding, combined with the high-efficiency dissolution of high-pressure cooking, and finally the loss of active ingredients such as rutin is greatly reduced through low-temperature treatment of vacuum freeze-drying concentration and frozen spray drying, and the instant powder particles are fine and easy to disperse, effectively solving the problems of more nutrient loss, slow dissolution and easy caking in traditional processes.

[0049] In addition, the technical scheme of the application also has advantages in flavor improvement: the rotating cage soaking and its specific parameter control can fully stimulate the terpene and phenolic flavor substances in tartary buckwheat, and the low-temperature drying process further retains these volatile components, avoids the burnt taste caused by traditional high-temperature baking, and makes the instant powder flavor more full; at the same time, the reasonable setting of the parameters of each process step can reduce the water redundancy and material loss in the production process, without the need for additional complex adjustment steps, which reduces the energy consumption while ensuring the product quality, and takes into account the product taste and production efficiency.

[0050] From the perspective of food safety, the present application realizes obvious improvement in the nutrition retention and dissolution performance of tartary buckwheat instant powder through the synergistic adaptation of multiple processes, without the need for additional addition of any organic solvent extractant in the whole process, completely relying on pure physical extraction method, avoiding the potential risk of chemical reagent residue on product safety from the root, and maximizing the retention of the true nutrition of food materials. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0052] The raw materials used in the embodiments of the present application are all commercially available products unless otherwise specified.

[0053] Embodiment 1

[0054] Tartary buckwheat with a particle size of ≥2 mm was sieved and rinsed with clean water until no visible stains were left after removing impurities; then the tartary buckwheat was placed in a constant temperature rotating cage at 40℃ and soaked at a rotating speed of 5 r / min for 150 minutes. During the soaking process, the tartary buckwheat gradually absorbed water and swelled, with a final water absorption rate of 140% and a volume expansion to 1.5 times the initial state, and the cell wall was uniformly softened. After the soaking was completed, the tartary buckwheat was transferred to a high-temperature and high-pressure puffing equipment, and puffed at a pressure of 3 MPa and a temperature of 120℃ for 30 seconds, so that the particles formed a uniform porous structure, and the proportion of particles that did not swell sufficiently was ≤3%. Then the puffed particles were subjected to ultrafine grinding treatment, and the particle size D90 of the ground particles was ≤50 μm. After the grinding was completed, pure water was added to the particles at a material to water ratio of 1:1, and high-pressure cooking extraction was carried out at a pressure of 0.2 MPa and a temperature of 120℃ for 20 minutes. Then, 0.5 MPa pressure was used for plate and frame pressure filtration, and the clear filtrate was collected. The filtrate was first pre-frozen at -40℃, and then concentrated by vacuum freeze-drying to increase the solid content of the filtrate to 60%. Finally, cold spray drying was carried out at a spray pressure of 0.15 MPa to obtain tartary buckwheat instant powder with a water content of ≤5%. The rutin retention rate was 92%, the instant powder yield was 85%, the instant powder dissolution time was only 3 seconds, the solution after dissolution was clear and transparent, without any insoluble precipitate, the aroma was rich, without any off-flavor such as astringency, burnt taste, etc., the natural roasting aroma of tartary buckwheat was pure and long-lasting, and the flavor purity and richness were optimal.

[0055] Embodiment 2

[0056] The process steps are basically consistent with those of Example 1, only the rotation speed of the rotating cage is adjusted to 7 r / min, the soaking time is 120 minutes, and the temperature is kept constant at 40°C. Due to the increased local tumbling intensity of the buckwheat particles in the rotating cage but the slightly shorter soaking time, some particles are slightly damaged due to collision, and the water absorption and penetration are slightly insufficient compared with Example 1. The final water absorption rate is 120%, and a small amount of rutin is lost due to the slight damage of the particles, and the rutin retention rate is 88%~90%.

[0057] Example 3

[0058] The process steps are basically consistent with those of Example 1, only the rotation speed of the rotating cage is adjusted to 3 r / min, the soaking time is 180 minutes, and the temperature is kept constant at 40°C. The tumbling frequency of the buckwheat particles in the rotating cage is insufficient, and there is slight accumulation in some local areas, but the prolonged soaking time makes up for the insufficient water absorption. The final water absorption rate is 135%~145%, the rutin retention rate is 87%~89%, and a small amount of particles are not uniformly hydrolyzed due to local accumulation. After ultrafine grinding, D90≤60μm, and the instant powder has a dissolution time of 4~4.5 seconds.

[0059] Example 4

[0060] Example 4 adjusts the high-pressure puffing parameters to 160°C temperature and 0.8MPa pressure, keeps the puffing time constant at 30 seconds, and the rest of the process is consistent with Example 1. The reduced puffing pressure results in insufficient steam pressure inside the particles, and the porous structure is not fully formed. The proportion of particles that are not fully expanded is 5%~8%, but the ultrafine grinding and subsequent extraction process are not affected. The instant powder has a dissolution time of 4~5 seconds, which is slightly high. The slight degradation of some rutin is caused by the high temperature, and the final rutin retention rate is 85%~88%. At this temperature, no obvious burnt smell is produced, and the natural fragrance of buckwheat is fully retained.

[0061] Example 5

[0062] Example 5 adjusts the material-to-water ratio of high-pressure cooking to 1:2, keeps the cooking pressure at 0.2MPa, the temperature at 120°C, and the time constant at 20 minutes, and the rest of the process is consistent with Example 1. After adjusting the material-to-water ratio, the concentration of the filtrate solids decreases, the energy consumption increases during the subsequent freeze-drying concentration stage, and the unit volume of active ingredients is reduced. The final yield of instant powder is 70%, although the dissolution time can still be maintained at 3 seconds, the production efficiency is significantly reduced, and the unit cost is increased.

[0063] Comparative Example 1

[0064] The process steps of Comparative Example 1 are basically the same as those of Example 1, only the dynamic soaking in a rotating cage is replaced by static soaking, and the soaking temperature of 40°C and the soaking time of 150 minutes remain unchanged. During the static soaking process, the tartary buckwheat presents a clear water gradient penetration phenomenon, and the final water absorption rate is only 82% to 88%. At the same time, the tartary buckwheat cell wall softens unevenly, the endogenous enzyme distribution is unbalanced, and the enzymolysis efficiency is significantly reduced, which directly affects the subsequent puffing process, resulting in 20% to 25% of the tartary buckwheat particles not being fully expanded, the porous structure being incomplete, the final instant powder having a dissolution time of 10 seconds, and the insoluble precipitate accounting for 8%.

[0065] Comparative Example 2

[0066] This comparative example omits the rotating cage soaking step in the example and directly puffs the tartary buckwheat after screening and cleaning at high temperature and high pressure, and the other steps and parameters are consistent with those of Example 1. Due to the lack of soaking pretreatment, the tartary buckwheat particle breakage rate is as high as 40% during the puffing process, and the material loss increases significantly. During subsequent ultrafine grinding, the particle size distribution appears a bimodal phenomenon, and part of the particles have a D90 greater than 80 μm. In addition, the active ingredient dissolution efficiency decreases during the high-pressure cooking stage, and the rutin retention rate is only 68%. The final instant powder has a clear layering after dissolution, and the drinking taste is poor.

[0067] Comparative Example 3

[0068] Comparative Example 3 adjusts the parameters of rotating cage soaking, reduces the soaking temperature to 25°C, the rotating speed to 2 r / min, and extends the soaking time to 300 minutes, and the remaining process steps and parameters remain unchanged. Under the low-temperature and low-speed soaking conditions, the risk of microbial contamination increases significantly, and the total number of molds detected is 420 CFU / g, while the total number of molds in Example 1 is less than 50 CFU / g. At the same time, the material bulk density increases, resulting in a temperature difference in the rotating cage, and the water absorption uniformity of tartary buckwheat decreases. The final instant powder has a wetting time of 12 seconds, and the insoluble precipitate accounts for 10% to 15%.

[0069] Comparative Example 4

[0070] Comparative Example 4 only adjusts the rotating cage soaking temperature to 60°C, keeps the rotating speed at 5 r / min and the soaking time at 150 minutes unchanged, and the remaining process is consistent with Example 1. The high-temperature soaking environment of 60°C causes the rutin in tartary buckwheat to degrade prematurely during the soaking stage, and the rutin retention rate in the final product is only 65%. At the same time, the surface of tartary buckwheat appears a slight gelatinization phenomenon, the particles are prone to clumping during the subsequent puffing process, and the loss of flavor substances causes the aroma intensity of the instant powder to decrease significantly.

[0071] Comparative Example 5

[0072] Comparative Example 5 replaced the freeze spray drying with traditional spray drying, with the drying parameters set to an inlet temperature of 180°C and an outlet temperature of 80°C, and the remaining process steps and parameters unchanged relative to Example 1. The high-temperature environment of traditional hot-air drying caused the rutin retention rate to drop to 75%, and the loss of heat-sensitive components was significant. At the same time, the instant powder had a slight burnt taste, which masked the natural fragrance of tartary buckwheat. The water content of the product also increased to 6-7%, which shortened the storage period.

[0073] Comparative Example 6

[0074] Comparative Example 6 replaced the high-temperature and high-pressure puffing step with atmospheric baking, with the process parameters set to 160°C for 40 minutes, and the remaining process steps and parameters unchanged relative to Example 1. Under atmospheric conditions, heat is mainly transferred by thermal conduction, and the temperature difference between the inside and outside of the tartary buckwheat particles is large. The outer layer is heated first and at a higher temperature, and the degradation of rutin is more severe. At the same time, the internal heating is insufficient and cannot achieve effective softening, further exacerbating the overall decrease in rutin retention rate. The rutin retention rate of the product was only 75%. At the same time, atmospheric baking only causes the surface of the particles to be slightly carbonized or dried, and cannot destroy the dense structure of the cell wall. Even after subsequent ultrafine grinding, the effective components such as starch and flavonoids in the cells are still difficult to fully release. In the high-pressure cooking and extraction link, the particles that are not fully broken will lead to a decrease in the dissolution rate of effective components, and a large amount of effective components will be removed with the filter residue during plate and frame filtration, ultimately resulting in a decrease in the yield of instant powder to 72%, an increase in the dissolution time to 15 seconds, and a slight separation of the solution. In terms of taste, the outer layer may generate a small amount of burnt substances due to the high temperature (but not to the extent of a burnt taste), while the internal flavor substances are insufficient, and the overall flavor coordination is poor.

[0075] Comparative Example 7

[0076] Comparative Example 7 replaced the high-pressure cooking and extraction step with hot water extraction, with the process parameters set to 80°C, a material-to-water ratio of 1:10, and a time of 60 minutes, and the remaining process steps and parameters unchanged relative to Example 1. Although the temperature of 80°C set for hot water extraction can promote the dissolution of some components, it will cause a large amount of starch in the form of small molecular fragments to enter the filtrate, and proteins are prone to denaturation to form colloidal particles that are not easy to filter, resulting in a significant increase in the turbidity of the filtrate after hot water extraction. Even after filtration, these small impurities are difficult to completely be trapped, and after subsequent vacuum freeze drying and concentration and freeze spray drying, the impurities will enter the instant powder along with the target components. When the instant powder is dissolved, these impurities that have not been removed will gradually aggregate and settle, causing the solution to be severely turbid, with a precipitate at the bottom and a weak flavor. On the other hand, the rutin dissolution rate is slow at 80°C, and a long extraction time of 60 minutes can compensate for the deficiency in dissolution rate to some extent. However, the rutin is prone to oxidative degradation reactions in an environment of 80°C for a long time, and the amount of degradation increases with the extension of the extraction time. The rutin retention rate of the final product was only 65%, the yield of instant powder was 68%, and the dissolution time was 20 seconds.

[0077] Comparative Example 8

[0078] Comparative Example 8 replaces the ultrafine pulverization step with ordinary pulverization, and the particle size D90 of the pulverized particles is ≥100 μm. The other process steps and parameters are the same as in Example 1. After ordinary pulverization, high-pressure cooking is performed, and the clarity of the filtrate after subsequent plate-and-frame pressure filtration decreases significantly. Coarse particles easily block the filter cloth pores during plate-and-frame pressure filtration, and the filtration time is significantly prolonged. The clarity of the filtrate decreases, and slight turbidity occurs. The rutin retention rate of the final product is only 70%, and the yield of the instant powder is only 69% due to insufficient dissolution and retention of coarse particles during filtration. After drying, the instant powder particles contain coarse particle fragments that have not been fully dissolved, the dissolution time is prolonged to 16 s, and slight turbidity occurs after dissolution, with fine insoluble precipitates appearing at the bottom.

[0079] In the description of the embodiments of the present application, the terms "first", "second", "third", "fourth" are only used for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", "third", "fourth" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0080] In the description of the embodiments of the present application, it should be understood that "-" and "~" represent the range of the same of two numerical values, and the range includes the endpoints. For example: "A-B" represents a range greater than or equal to A and less than or equal to B. "A~B" represents a range greater than or equal to A and less than or equal to B.

[0081] In the description of the embodiments of the present application, the term "and / or" herein is only a description of the association relationship between the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after it.

[0082] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a tartary buckwheat instant powder, characterized by, The method comprises the following steps: Sift, remove impurities, and wash tartary buckwheat to obtain a crude product; Mix the crude product with water and perform drum soaking to obtain high water absorption and expansion tartary buckwheat; Perform high-temperature and high-pressure puffing on the high water absorption and expansion tartary buckwheat to obtain puffed particles; Perform ultra-micro grinding on the puffed particles to obtain micro powder; Mix the micro powder with water and perform high-pressure cooking to obtain cooked material; Perform pressure filtration on the cooked material and take the filtrate; Pre-freeze the filtrate at-35℃ to-45℃ and then perform vacuum freeze-drying concentration to obtain a concentrated liquid; Perform freeze spray drying on the concentrated liquid; The conditions of drum soaking include a temperature of 35℃ to 45℃, a time of 120 min to 180 min, and a rotation speed of 3 r / min to 7 r / min. The conditions of high-temperature and high-pressure puffing include a temperature of 110℃ to 130℃, a pressure of 2 MPa to 4 MPa, and a time of 20 s to 40 s. The high-pressure cooking satisfies one or more of the following conditions: (1) The material-to-water ratio is 1:(0.5-1.5); (2) The pressure is 0.1 MPa to 0.3 MPa; (3) The temperature is 100℃ to 140℃; (4) The time is 15 min to 30 min.

2. The method of claim 1, wherein the buckwheat instant powder is prepared by the steps of: The conditions of drum soaking include a temperature of 35℃ to 45℃, a time of 150 min, and a rotation speed of 5 r / min.

3. The method of claim 1, wherein the buckwheat instant powder is prepared by the steps of: The conditions of high-temperature and high-pressure puffing include a temperature of 115℃ to 125℃, a pressure of 3 MPa, and a time of 30 s. ​ 4. The method of claim 1, wherein the buckwheat instant powder is prepared by the steps of: The concentration endpoint of vacuum freeze-drying concentration is that the solid content concentration reaches 55% to 65%. ​ 5. The method of claim 1, wherein the buckwheat instant powder is prepared by the steps of: The atomization pressure of freeze spray drying is 0.1 MPa to 0.2 MPa. ​ 6. The method of claim 1, wherein the buckwheat instant powder is prepared by the steps of: The D90 of the micro powder is ≤50 μm. ​ 7. The method of claim 1 to 6, wherein the preparation method of the tartary buckwheat instant powder is characterized by, The conditions of drum soaking further include adding stainless steel balls with a diameter of 8 cm to 12 cm, and the weight of the stainless steel balls is 4.06 kg to 4.24 kg.

8. Tartary buckwheat instant powder prepared by the preparation method in any one of claims 1-7.