Preparation method of low-moisture and low-water-activity xylooligosaccharide powder

Abstract

The invention discloses a preparation method of low-moisture and low-water-activity xylooligosaccharide powder, and belongs to the field of functional sugar alcohol. The method comprises the following steps: taking a xylooligosaccharide solution with the refractive index of 35-50%, adding activated carbon for decoloration, filtering, adding deionized water to adjust the refractive index to 40-48%, and purifying through cation exchange resin, anion exchange resin, anion exchange resin and cation exchange resin in sequence; evaporating the purified solution until the refractive index is 50-55%; homogenizing the concentrated solution, spraying the homogenized concentrated solution into a spray drying tower through a spray head, and drying the homogenized concentrated solution in a heating evaporation area and a cooling collection area under the pressure of 100-150Pa in the tower; and drying, screening with a 60-mesh screen, feeding into a clean room, cooling, and packaging. The water content of the prepared xylooligosaccharide powder is 0.1%-1%, the water activity is 0.1% or below, the product fluidity is good, crushing treatment is not needed, the process is simple and efficient, and the xylooligosaccharide powder is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of functional sugar alcohol technology, and more particularly to a method for preparing low-moisture, low-water-activity xylooligosaccharide powder. Background Technology

[0002] Xylooligosaccharides, also known as xylooligosaccharides, are functional polymeric sugars composed of 2-7 xylose molecules linked by β-1,4 glycosidic bonds. They are an important product in the field of functional sugar alcohols. The production process of xylooligosaccharides typically involves enzymatic hydrolysis of corn cobs, followed by purification and concentration to obtain a powdered functional sugar product. Xylooligosaccharides possess excellent prebiotic properties and have broad application prospects in the food, health product, and pharmaceutical industries.

[0003] Currently, most manufacturers of xylooligosaccharide powder use a vacuum belt drying process, which requires drying the syrup in a vacuum belt to obtain the powder. However, this process produces xylooligosaccharide powder with several problems: First, the dried product is in block or flake form, requiring additional pulverization, increasing production costs and process complexity; second, the product has a high moisture content, making it prone to absorbing moisture and clumping, severely affecting its flowability and storage stability; third, the product has a high water activity, which is detrimental to long-term storage and transportation. These are common technical challenges faced by xylooligosaccharide producers, necessitating the development of a new preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing low-moisture, low-water-activity xylooligosaccharide powder, so as to solve the problems existing in the prior art.

[0005] This invention provides a method for preparing low-moisture, low-water-activity xylooligosaccharide powder, comprising the following steps: Step 1: Decolorization and purification: Take a xylooligosaccharide solution with a refractive index of 35%-50%, add activated carbon at 5% of the dry matter weight, and stir at 70-80℃ for 25-30 minutes at a stirring speed of 400 rpm. After decolorization, filter to obtain a decolorized solution. Add deionized water to the decolorized solution to adjust the refractive index to 40-48%, and then pass it sequentially through a cation exchange resin, anion exchange resin, anion exchange resin, and cation exchange resin to obtain a purified xylooligosaccharide solution. Step 2, Evaporation and Concentration: The purified xylooligosaccharide solution is sent to an evaporator and evaporated until the refractive index is 50-55% to obtain a concentrated xylooligosaccharide solution; Step 3, Spray Drying: The concentrated xylooligosaccharide solution is homogenized in a homogenizer and then sprayed into a spray drying tower through a nozzle. The spray drying tower is divided into a heating evaporation zone and a cooling collection zone. The heating evaporation zone is heated using hot air generated by steam heat exchange and electric heating exchange, while the cooling collection zone is cooled using cold air. The pressure inside the tower is 100-150 Pa. After drying, xylooligosaccharide powder is obtained. After being sieved through a 60-mesh sieve, it is sent to a clean room for static cooling. The temperature in the clean room is controlled at 25℃ or below, and the relative humidity is controlled at 40% or below. After cooling, it is packaged.

[0006] The above technical solution—combining activated carbon decolorization with ion exchange resin purification, evaporation and concentration to a specific refractive index, and spray drying—achieves one-step drying of xylooligosaccharide powder. The resulting xylooligosaccharide powder has a moisture content of 0.1%-1% and a water activity below 0.1%, representing a reduction of over 60% in moisture content and over 70% in water activity compared to conventional vacuum belt drying methods. The product requires no pulverization; sieving is sufficient to obtain a uniformly distributed, free-flowing powder, significantly improving production efficiency, reducing production costs, and ensuring high product stability and excellent storage and transportation performance.

[0007] Furthermore, in step three, the working pressure of the homogenizer is 8.0 MPa, and the nozzle orifice diameter is 1.4 mm.

[0008] Furthermore, in step three, the temperature of the heating evaporation zone is 200℃±10℃, and the temperature of the cooling collection zone is 25℃±2℃.

[0009] Furthermore, in step three, the feed rate of the spray drying tower is 200-300 kg / h, and the evaporation water volume is 100-150 kg / h.

[0010] Furthermore, in step three, the temperature of the dried xylooligosaccharide powder is 30-45℃.

[0011] Furthermore, in step one, the conductivity of the purified xylooligosaccharide solution is less than or equal to 10 μS / cm.

[0012] Furthermore, in step three, the main structure of the spray drying tower consists of a cylinder on the upper layer and a cone on the lower layer, with the tower body using a sandwich design and the inner wall made of food-grade stainless steel.

[0013] Furthermore, the prepared xylooligosaccharide powder has a water content of 0.1%-1% and a water activity of less than 0.1%.

[0014] The beneficial effects of this invention are: 1. The prepared xylooligosaccharide powder has the characteristics of low moisture and low water activity, with a moisture content of 0.1%-1% and a water activity of less than 0.1%. Compared with the conventional vacuum belt drying method, the moisture content is reduced by more than 60% and the water activity is reduced by more than 70%. The product is not prone to moisture absorption and clumping, has good flowability, and is easy to store and transport.

[0015] 2. The process is simple and efficient. The spray drying technology enables one-step molding of xylooligosaccharide powder. The product does not require crushing and only needs to be sieved to obtain the final product. This simplifies the production process, reduces production costs, and improves production efficiency, making it suitable for large-scale continuous industrial production.

[0016] 3. The drying process is automatically controlled by a computer system, which controls the temperature, pressure, and feeding speed. The high degree of automation and intelligence reduces manual operation and labor intensity, while ensuring the stability and consistency of product quality. The short drying time effectively avoids Maillard reaction, resulting in high product purity and stable content of various xylooligosaccharide components. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should also be noted that, to make the embodiments more comprehensive, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some well-known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0020] It should be noted that the use of terms such as "an embodiment," "an embodiment," "an exemplary embodiment," and "some embodiments" in the specification indicates that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the art.

[0021] Generally, terms can be understood at least partly from their use in context. For example, depending at least partly on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or a combination of features, structures, or characteristics in a plural sense. Additionally, the term "based on" can be understood not necessarily to convey an exclusive set of factors, but rather, alternatively, depending at least partly on the context, to allow for the presence of other factors that are not necessarily explicitly described.

[0022] See Figure 1 As shown This invention provides a method for preparing low-moisture, low-water-activity xylooligosaccharide powder, comprising three main steps: decolorization and purification, evaporation and concentration, and spray drying. The xylooligosaccharide solution described in this invention is a functional polymeric sugar solution containing 2-7 xylose molecules linked by β-1,4 glycosidic bonds, obtained by enzymatic hydrolysis of corn cobs followed by purification and concentration processes.

[0023] In the decolorization and purification step, firstly, a xylooligosaccharide solution with a refractive index of 35%-50% is taken, and activated carbon is added at 5% of the dry matter weight of the solution. The solution is then subjected to decolorization by stirring at a temperature of 70-80℃. The stirring speed is controlled at 400 rpm, and stirring is continued for 25-30 minutes. The activated carbon adsorbs and removes residual catalysts and other solid impurities from the solution. After decolorization, the mixture is filtered to remove the activated carbon, yielding a decolorized solution. Deionized water is then added to the decolorized solution to adjust its refractive index to the range of 40-48%. The decolorized solution is then passed sequentially through cation exchange resin, anion exchange resin, and cation exchange resin. Ion exchange removes anions, cations, gums, and pigments from the xylooligosaccharide decolorization solution, achieving deep purification of the solution and ultimately obtaining a purified xylooligosaccharide solution.

[0024] In the evaporation and concentration step, the purified xylooligosaccharide solution is fed into an evaporator for concentration. Evaporation removes some of the water from the solution, bringing its refractive index to 50-55%. A refractive index below 50% leads to a relatively higher evaporation rate during subsequent spray drying, reducing production efficiency and potentially causing incomplete drying. A refractive index above 55% results in excessively high solution viscosity, placing excessive demands on the spray drying tower nozzles and easily causing nozzle clogging, thus affecting normal production. Therefore, controlling the refractive index within the range of 50-55% achieves the optimal drying effect.

[0025] In the spray drying step, the above-mentioned xylooligosaccharide concentrate is first homogenized in a homogenizer at a working pressure of 8.0 MPa. The homogenized solution is then sprayed into the spray drying tower through nozzles with an orifice size of 1.4 mm, atomizing the concentrate into fine droplets. The main structure of the spray drying tower is a sealed space, with a cylindrical upper layer and a conical lower layer. The tower body employs a sandwich design, and the inner wall is made of food-grade stainless steel. Functionally, the spray drying tower is divided into a heating and evaporation zone and a cooling and collection zone. Hot air ducts are installed at the top, and the temperature and power parameters of each zone are controlled by a computer system.

[0026] The heating and evaporation zone uses a combination of steam heat exchange and electric heating to generate hot, dry air, with the temperature controlled at 200℃±10℃. Xylooligosaccharide droplets come into contact with the high-temperature hot, dry air in the heating and evaporation zone, causing the water in the solution to evaporate instantly, forming powdery solid particles. Due to the high air velocity set within the tower, the powder particles quickly fall to the bottom of the tower, resulting in a very short drying process that effectively avoids the Maillard reaction and prevents browning of the product. The cooling and collection zone uses cold air or cold water for cooling, with the temperature controlled at 25℃±2℃, allowing the dried powder to cool down rapidly. The entire spray drying tower maintains a negative pressure environment of 100-150 Pa, which is monitored and regulated in real time by a computer system.

[0027] The feed rate of the spray drying tower is 200-300 kg / h, and the evaporation rate is 100-150 kg / h, correspondingly producing low-moisture, low-water-activity xylooligosaccharide powder at a rate of 100-150 kg / h. The dried xylooligosaccharide powder is produced at a temperature between 30-45℃, with a moisture content controlled at 0.1%-1% and a water activity controlled below 0.1%. The dried xylooligosaccharide powder is collected through a receiving pipe. The entire process is continuous and efficient, suitable for large-scale industrial production.

[0028] The collected xylooligosaccharide powder needs to be sieved through a 60-mesh sieve. The sieved powder particles are uniformly distributed and have good flowability. The xylooligosaccharide powder prepared by this invention does not require pulverization; the final product can be obtained simply by sieving, simplifying the production process. The sieved xylooligosaccharide powder is immediately sent to a clean room for static cooling. The temperature of the clean room is strictly controlled at 25°C or below, and the relative humidity is controlled at 40% or below. Allowing the powder to stand in the clean room for a period of time further reduces its temperature to room temperature, effectively preventing agglomeration and maintaining good flowability and dispersibility. After cooling, it can be packaged and then stored or transported.

[0029] All percentages mentioned in this invention are weight percentages.

[0030] Example 1 1500 kg of xylooligosaccharide syrup with a refractive index of 35% was taken, and the xylooligosaccharide content in the dry matter of the syrup was 97%. Activated carbon was added at 5% of the dry matter weight, and the solution was stirred and decolorized at 75°C to remove residual catalyst and other solid impurities. The stirring speed was set to 400 rpm and stirred continuously for 30 minutes. After decolorization, the solution was filtered to remove the activated carbon, yielding a decolorized solution. Deionized water was added to the decolorized solution to adjust the refractive index to the range of 30-48%. The decolorized solution was then passed sequentially through cation exchange resin, anion exchange resin, and cation exchange resin to remove anions, cations, gums, and pigments from the xylooligosaccharide decolorized solution, achieving deep purification of the solution. The purified solution was then sent to an evaporator for evaporation and concentration to obtain 1000 kg of xylooligosaccharide solution with a conductivity less than or equal to 10 μS / cm and a refractive index of 50%.

[0031] The above xylooligosaccharide solution was homogenized in a homogenizer at a working pressure of 8.0 MPa. The homogenized solution was then sprayed into a spray drying tower through nozzles with an orifice diameter of 1.4 mm. The spray drying tower is divided into a heating and evaporation zone and a cooling and collection zone. The heating and evaporation zone uses hot air obtained from steam heat exchange and electric heating exchange, with the temperature controlled at 210℃±2℃. The cooling and collection zone uses cold air for cooling and collection, with the temperature controlled at 25℃±2℃. The temperatures in both zones are controlled by a computer system to maintain a constant temperature. The pressure inside the tower is maintained at 100-150 Pa. The feed rate of the spray drying tower is 200 kg / h, the evaporation rate is 100 kg / h, and the production rate of low-moisture, low-water-activity xylooligosaccharide powder is 100 kg / h.

[0032] After drying, xylooligosaccharide powder with a temperature of 30-45℃ is obtained. After sieving through a 60-mesh sieve, 500 kg of powdered solid is obtained, which is the finished xylooligosaccharide powder with a moisture content of 0.18%. The xylooligosaccharide powder is then placed in a clean room to cool down. The temperature of the clean room is controlled at 25℃ or below, and the relative humidity is controlled at 40% or below. After cooling, it is packaged.

[0033] The contents of various xylooligosaccharides in the dry matter before drying and in the low-moisture, low-water-activity xylooligosaccharide powder obtained after drying were determined, and the results are shown in Table 1. Table 1 shows that before drying, the xylobiose content was 27.76%, xylotriose content was 31.40%, xylotetraose content was 20.87%, and xylopentanose to xyloheptaose content was 18.08%, totaling 98.11%; after drying, the xylobiose content was 27.74%, xylotriose content was 31.30%, xylotetraose content was 20.95%, and xylopentanose to xyloheptaose content was 18.03%, totaling 98.02%. The changes in each component were xylobiose -0.02%, xylotriose -0.1%, xylotetraose +0.08%, xylopentaose to xyloheptaose -0.05%, and total -0.09%, respectively. This indicates that the content of each xylooligosaccharide component did not change at all before and after drying, proving that the preparation method of the present invention can well maintain the composition and purity of xylooligosaccharides.

[0034] Table 1 Comparison of the contents of each component of xylooligosaccharide before and after drying.

[0035] The moisture content and water activity of the low-moisture, low-water-activity xylooligosaccharide powder prepared in this embodiment were tested, and compared with xylooligosaccharide powder produced by conventional vacuum belt drying. The results are shown in Table 2. The conventional vacuum belt drying process for producing xylooligosaccharide powder involves concentrating the xylooligosaccharide solution to 75%, spreading the solution evenly on a conveyor belt, heating it in three heating zones to evaporate the water in the syrup, cooling it in a cooling zone, and then pulverizing and sieving it to obtain the final product. As can be seen from Table 2, under the same humidity and temperature conditions, the initial sample of 10g of spray-dried xylooligosaccharide powder had a moisture content of 0.85% and a water activity of 0.07%; the initial sample of 10g of vacuum belt-dried xylooligosaccharide powder had a moisture content of 2.43% and a water activity of 0.45%. The comparison results show that the low-moisture, low-water-activity xylooligosaccharide powder prepared by the method of the present invention has a significantly lower moisture content than xylooligosaccharide powder produced by conventional vacuum belt drying, and the water activity is also significantly reduced. This indicates that the xylooligosaccharide powder produced by the present invention has lower moisture and lower water activity, and the product quality is excellent.

[0036] Table 2 Comparison of moisture content and water activity of xylooligosaccharide powders dried using different methods

[0037] Example 2 1500 kg of xylooligosaccharide syrup with a refractive index of 35% was taken, and the xylooligosaccharide content in the dry matter of the syrup was 98%. Activated carbon was added at 5% of the dry matter weight, and the solution was stirred and decolorized at 75°C to remove residual catalyst and other solid impurities. The stirring speed was set to 400 rpm and stirred continuously for 30 minutes. After decolorization, the solution was filtered to remove the activated carbon, yielding a decolorized solution. Deionized water was added to the decolorized solution to adjust the refractive index to the range of 30-48%. The decolorized solution was then passed sequentially through cation exchange resin, anion exchange resin, and cation exchange resin to remove anions, cations, gums, and pigments from the xylooligosaccharide decolorized solution, achieving deep purification of the solution. The purified solution was then sent to an evaporator for evaporation and concentration to obtain 750 kg of xylooligosaccharide solution with a conductivity less than or equal to 10 μS / cm and a refractive index of 50%.

[0038] The above xylooligosaccharide solution was homogenized in a homogenizer at a working pressure of 8.0 MPa. The homogenized solution was then sprayed into a spray drying tower through nozzles with an orifice diameter of 1.4 mm. The spray drying tower is divided into a heating and evaporation zone and a cooling and collection zone. The heating and evaporation zone uses hot air obtained from steam heat exchange and electric heating exchange, with the temperature controlled at 200℃±2℃. The cooling and collection zone uses cold air for cooling and collection, with the temperature controlled at 25℃±2℃. The temperatures in both zones are controlled by a computer system to maintain a constant temperature. The pressure inside the tower is maintained at 100-150 Pa. The feed rate of the spray drying tower is 250 kg / h, the evaporation rate is 100 kg / h, and the production rate of low-moisture, low-water-activity xylooligosaccharide powder is 150 kg / h.

[0039] After drying, xylooligosaccharide powder with a temperature of 30-45℃ is obtained. After sieving through a 60-mesh sieve, 500 kg of powdered solid is obtained, which is the finished xylooligosaccharide powder with a moisture content of 0.18%. The xylooligosaccharide powder is then placed in a clean room to cool down. The temperature of the clean room is controlled at 25℃ or below, and the relative humidity is controlled at 40% or below. After cooling, it is packaged.

[0040] The moisture content and water activity of the low-moisture, low-water-activity xylooligosaccharide powder prepared in this embodiment were tested, and compared with xylooligosaccharide powder produced by conventional vacuum belt drying. The results are shown in Table 3. The conventional vacuum belt drying process for producing xylooligosaccharide powder involves concentrating the xylooligosaccharide solution to 75%, spreading the solution evenly on a conveyor belt, heating it in three heating zones to evaporate the water in the syrup, cooling it in a cooling zone, and then pulverizing and sieving it to obtain the final product. As can be seen from Table 3, under the same humidity and temperature conditions, the initial sample of 10g of spray-dried xylooligosaccharide powder had a moisture content of 0.63% and a water activity of 0.06%; the initial sample of 10g of vacuum belt-dried xylooligosaccharide powder had a moisture content of 1.93% and a water activity of 0.42%. The comparison results show that the low-moisture, low-water-activity xylooligosaccharide powder prepared by the method of the present invention has a significantly lower moisture content than xylooligosaccharide powder produced by conventional vacuum belt drying, and the water activity is also significantly reduced. This indicates that the xylooligosaccharide powder produced by the present invention has lower moisture and lower water activity, and the product quality is excellent.

[0041] Table 3 Comparison of moisture content and water activity of xylooligosaccharide powders dried using different methods

[0042] Example 3 1500 kg of xylooligosaccharide syrup with a refractive index of 35% was taken, and the xylooligosaccharide content in the dry matter of the syrup was 96%. Activated carbon was added at 5% of the dry matter weight, and the solution was stirred and decolorized at 75°C to remove residual catalyst and other solid impurities. The stirring speed was set to 400 rpm and stirred continuously for 30 minutes. After decolorization, the solution was filtered to remove the activated carbon, yielding a decolorized solution. Deionized water was added to the decolorized solution to adjust the refractive index to the range of 30-48%. The decolorized solution was then passed sequentially through cation exchange resin, anion exchange resin, and cation exchange resin to remove anions, cations, gums, and pigments from the xylooligosaccharide decolorized solution, achieving deep purification of the solution. The purified solution was then sent to an evaporator for evaporation and concentration to obtain 750 kg of xylooligosaccharide solution with a conductivity less than or equal to 10 μS / cm and a refractive index of 50%.

[0043] The above xylooligosaccharide solution was homogenized in a homogenizer at a working pressure of 8.0 MPa. The homogenized solution was then sprayed into a spray drying tower through nozzles with a 1.4 mm orifice. The spray drying tower consisted of a heating and evaporation zone and a cooling and collection zone. The heating and evaporation zone used hot air obtained through steam and electric heating exchanges, with the temperature controlled at 190℃±2℃. The cooling and collection zone used cold air for cooling and collection, with the temperature controlled at 25℃±2℃. The temperatures in both zones were controlled by a computer system to maintain a constant temperature. The pressure inside the tower was maintained at 100-150 Pa. The feed rate of the spray drying tower was 300 kg / h, the evaporation rate was 140 kg / h, and the production rate of low-moisture, low-water-activity xylooligosaccharide powder was 160 kg / h.

[0044] After drying, xylooligosaccharide powder with a temperature of 30-45℃ is obtained. After sieving through a 60-mesh sieve, 500 kg of powdered solid is obtained, which is the finished xylooligosaccharide powder with a moisture content of 0.18%. The xylooligosaccharide powder is then placed in a clean room to cool down. The temperature of the clean room is controlled at 25℃ or below, and the relative humidity is controlled at 40% or below. After cooling, it is packaged.

[0045] The moisture content and water activity of the low-moisture, low-water-activity xylooligosaccharide powder prepared in this embodiment were tested, and compared with xylooligosaccharide powder produced by conventional vacuum belt drying. The results are shown in Table 4. The conventional vacuum belt drying process for producing xylooligosaccharide powder involves concentrating the xylooligosaccharide solution to 75%, spreading the solution evenly on a conveyor belt, heating it in three heating zones to evaporate the water in the syrup, cooling it in a cooling zone, and then pulverizing and sieving it to obtain the final product. As can be seen from Table 4, under the same humidity and temperature conditions, the initial sample of 10g of spray-dried xylooligosaccharide powder had a moisture content of 0.15% and a water activity of 0.07%; the initial sample of 10g of vacuum belt-dried xylooligosaccharide powder had a moisture content of 1.93% and a water activity of 0.35%. The comparison results show that the low-moisture, low-water-activity xylooligosaccharide powder prepared by the method of the present invention has a significantly lower moisture content than xylooligosaccharide powder produced by conventional vacuum belt drying, and the water activity is also significantly reduced. This indicates that the xylooligosaccharide powder produced by the present invention has lower moisture and lower water activity, and the product quality is excellent.

[0046] Table 4 Comparison of moisture content and water activity of xylooligosaccharide powders dried using different methods

[0047] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0048] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing low-moisture, low-water-activity xylooligosaccharide powder, characterized in that, Includes the following steps: Step 1: Decolorization and purification: Take a xylooligosaccharide solution with a refractive index of 35%-50%, add activated carbon at 5% of the dry matter weight, and stir at 70-80℃ for 25-30 minutes at a stirring speed of 400 rpm. After decolorization, filter to obtain a decolorized solution. Add deionized water to the decolorized solution to adjust the refractive index to 40-48%, and then pass it sequentially through a cation exchange resin, anion exchange resin, anion exchange resin, and cation exchange resin to obtain a purified xylooligosaccharide solution. Step 2, Evaporation and Concentration: The purified xylooligosaccharide solution is sent to an evaporator and evaporated until the refractive index is 50-55% to obtain a concentrated xylooligosaccharide solution; Step 3, Spray Drying: The concentrated xylooligosaccharide solution is homogenized in a homogenizer and then sprayed into a spray drying tower through a nozzle. The spray drying tower is divided into a heating evaporation zone and a cooling collection zone. The heating evaporation zone is heated using hot air generated by steam heat exchange and electric heating exchange, while the cooling collection zone is cooled using cold air. The pressure inside the tower is 100-150 Pa. After drying, xylooligosaccharide powder is obtained. After being sieved through a 60-mesh sieve, it is sent to a clean room for static cooling. The temperature in the clean room is controlled at 25℃ or below, and the relative humidity is controlled at 40% or below. After cooling, it is packaged.

2. The method for preparing low-moisture, low-water-activity xylooligosaccharide powder according to claim 1, characterized in that: In step three, the working pressure of the homogenizer is 8.0 MPa, and the nozzle orifice diameter is 1.4 mm.

3. The method for preparing low-moisture, low-water-activity xylooligosaccharide powder according to claim 1, characterized in that: In step three, the temperature of the heating evaporation zone is 200℃±10℃, and the temperature of the cooling collection zone is 25℃±2℃.

4. The method for preparing low-moisture, low-water-activity xylooligosaccharide powder according to claim 1, characterized in that: In step three, the feed rate of the spray drying tower is 200-300 kg / h, and the evaporation water volume is 100-150 kg / h.

5. The method for preparing low-moisture, low-water-activity xylooligosaccharide powder according to claim 1, characterized in that: In step three, the temperature of the dried xylooligosaccharide powder is 30-45℃.

6. The method for preparing low-moisture, low-water-activity xylooligosaccharide powder according to claim 1, characterized in that: In step one, the conductivity of the purified xylooligosaccharide solution is less than or equal to 10 μS / cm.

7. The method for preparing low-moisture, low-water-activity xylooligosaccharide powder according to claim 1, characterized in that: In step three, the main structure of the spray drying tower consists of a cylinder on the upper layer and a cone on the lower layer. The tower body is sandwiched and the inner wall is made of food-grade stainless steel.

8. The method for preparing low-moisture, low-water-activity xylooligosaccharide powder according to claim 1, characterized in that: The prepared xylooligosaccharide powder has a water content of 0.1%-1% and a water activity of less than 0.1%.

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