A preparation method of sodium octenyl succinate starch based on alcohol-free esterification system

Abstract

The invention discloses a preparation method of sodium octenyl succinate starch based on an alcohol-free esterification system. The method comprises the following steps: adding an emulsifier to octenyl succinic anhydride, stirring and heating, emulsifying with water through shearing and high-pressure homogenization to obtain an octenyl succinic anhydride emulsion; adding the octenyl succinic anhydride emulsion to starch for esterification reaction to obtain esterified starch; dehydrating the esterified starch through a vacuum dehydrator, washing with water, and then airflow drying to obtain sodium octenyl succinate starch. The preparation method of sodium octenyl succinate starch based on the alcohol-free esterification system reduces the use of organic reagents in the SSOS production process, improves the uneven dripping of octenyl succinic anhydride, the low efficiency of esterification reaction, the long drying time and low efficiency of sodium octenyl succinate starch, and the uneven heating that easily produces gelatinization.

Description

Technical Field

[0001] The invention relates to a method for preparing sodium octenyl succinate starch based on an alcohol-free esterification system. Background Art

[0002] Starch is a natural organic matter synthesized by organisms through photosynthesis using carbon dioxide and water. It is a high molecular polymer formed by D-glucose bonded by α-1,4 and α-1,6 glycosidic bonds. It is abundant in source, safe and harmless to human body, and is an important raw material in industrial production process. However, as the application scope of natural starch gradually expands, its processing defects such as poor solubility, poor dispersibility, poor film-forming property and easy aging gradually emerge. Therefore, in the modern starch processing industry, starch is often processed by physical or chemical methods to change the structure of starch, thereby changing the properties of starch and expanding its industrial application.

[0003] Esterification modification is one of the commonly used methods for chemical modification of starch. By introducing chemical groups into starch molecules, specific esterified starch is formed to improve starch gelatinization properties, freeze-thaw stability and other processing properties, and expand the application range of starch. Starch sodium octenyl succinate (SSOS) is a food additive made by esterifying starch with octenyl succinic anhydride (OSA) and combining one or more of the following methods: enzyme treatment, dextrinization, acid treatment, bleaching treatment, and pregelatinization. SSOS is an amphiphilic polymer emulsifier with surface activity, thickening, stabilization and certain moisture retention properties, and it has received increasing attention due to its plant origin.

[0004] There are generally three methods for preparing SSOS: wet method, organic solvent method and dry production. The organic solvent method is to suspend starch in an inert organic solvent and then add OSA to react. When adding OSA in the wet and dry methods, organic solvents such as ethanol and isopropanol are required to dilute the anhydride before reacting with starch. After the reaction is completed, if the DE value of the starch is low and it is dissolved in the reaction system, the starch needs to be washed with an organic solvent. The use of organic reagents to dilute the anhydride is because OSA has low solubility in water. It is necessary to use ethanol or isopropanol to dilute OSA and disperse it on the surface of starch particles in the reaction system to improve the reaction efficiency. However, due to the structure of starch, the efficiency of esterification reactions is generally not high. In order to solve this problem, current research and patents are mostly focused on pre-treating starch through ultrasonic assistance, enzymatic hydrolysis, mechanical activation and other technologies to improve the product performance of SSOS. There is little research on the step that OSA needs to be dispersed with organic reagents during the esterification reaction.

[0005] In 2022, Wang Jinwei of Tianjin University of Science and Technology applied for a doctoral dissertation titled "Study on Modification of Starch Octenyl Succinic Anhydride Based on Ionic Liquid System and Its Application". The method for preparing the octenyl succinic acid starch ester sample is as follows: suspend the native starch in a water mixture to obtain a 15% (w / w) starch suspension. The pH value of the suspension was adjusted to 8.1-8.5 with a 3% NaOH solution. The OSA reagent (starch dry weight) with a concentration of 3% was accurately weighed and diluted 5 times with isopropanol (v / v), and then slowly added dropwise to the above starch suspension within 2 hours. The reaction was carried out at pH 8.1-8.5 and 35°C for another 2 hours, after which the pH was adjusted to 6.5 with a 3% HCl solution. The reaction mixture was centrifuged at 4500g for 10 minutes. The centrifuged precipitate was washed 3 times with deionized water and 75% ethanol (v / v) to remove the ionic liquid and residual OSA reagent. The starch samples were dried in an oven at 35 °C for 24 h and ground through a 100-mesh screen. OSA was diluted with isopropanol and the starch samples were washed with ethanol.

[0006] In 2023, Zhou Yang and others from Changzhou University published "Preparation of Octenyl Succinate Porous Corn Starch and Its Application in Curcumin Microcapsule Wall Materials" in the Journal of Chinese Institute of Food Science and Technology. The preparation process of octenyl succinate porous corn starch is as follows: weigh the prepared porous starch, mix it with distilled water, prepare a starch emulsion with a mass fraction of 30%, form a suspension, put it into a 50℃ constant temperature water bath, stir it magnetically for 20 minutes, add a 3% mass fraction of NaOH solution until the pH value of the starch emulsion is 8.5~9.0, slowly drop OSA, which accounts for 3% of the mass of the porous starch and is diluted 3 times with anhydrous ethanol, during the reaction, control the pH value of the solution to be around 8.5, and react for 4 hours in a 40℃ water bath. After the reaction, filter it, wash the precipitate with 3% HCl solution to neutrality, then wash it with anhydrous ethanol 3 times, detect the absence of Cl ions with AgNO3, put it in a 50℃ oven to dry for 24 hours, take it out and grind it, seal it and dry it for storage. The preparation method utilizes anhydrous ethanol to dilute OSA and wash the esterified sample.

[0007] In 2023, Zhang Biao of Central South University of Forestry and Technology applied for a master's degree thesis "Effects of Octenyl Succinic Anhydride (OSA) Treatment on the Structure, Digestibility and Emulsion Stability of Different Crystalline Starches". The preparation method of OSA starch is as follows: Weigh the starch sample and add distilled water to make a 30% suspension, gelatinize in a boiling water bath for 1 hour, and stir while gelatinizing to make it gelatinized evenly. Then use a high-speed shearing machine (14500r / min) to shear for 15 minutes, place it in a 35°C water bath, and adjust the system pH to 8.5 with 3% NaOH solution. Dilute OSA 3 times with anhydrous ethanol, gradually add it to the starch suspension within 2 hours, and continue stirring for 2 hours. The pH is always maintained at 8.5 during the reaction. After the reaction, adjust the pH to 6.5 with 3% HCl solution. Use anhydrous ethanol for alcohol precipitation at a ratio of 1:6. Then centrifuge, dry, grind into powder several times and put it into a ziplock bag for use. This preparation method also uses anhydrous ethanol to dilute OAS and precipitate the esterified sample.

[0008] In 2010, Zheng Maoqiang and others from Wuxi Scientific Research and Design Institute published "Study on Preparation of Octenyl Succinic Anhydride Waxy Corn Starch by Microemulsion Method" in "Grain and Food Industry". They used Tween and isopropanol to prepare OSA microemulsion and prepare octenyl succinic anhydride waxy corn starch, which is beneficial to improve the degree of substitution of the product. This method also treats OSA, but the organic reagent isopropanol is still used in the treatment process.

[0009] In 2009, Gansu Shengda Ark Potato Modified Starch Co., Ltd. applied for a Chinese invention patent "A method for preparing octenyl succinate starch ester", application announcement number CN106279450A, which specifically discloses a method for preparing porous octenyl succinate starch ester, which mainly includes the following steps: dissolving starch in water to obtain starch milk, adjusting pH, adding raw amylase, reacting at a certain temperature for a period of time, further adjusting pH and temperature, slowly adding octenyl succinic anhydride diluted with anhydrous ethanol to react for a period of time, washing the reaction liquid with anhydrous ethanol after the reaction, collecting solids for drying and crushing, and obtaining porous octenyl succinate starch ester. This patent also uses anhydrous ethanol to dilute OSA and wash the reaction liquid.

[0010] In summary, in the existing technical system, for the process of preparing SSOS by the aqueous phase method, organic reagents are generally used to disperse OSA. However, in the process of promoting large-scale industrial production, in view of the strict requirements of environmental protection standards, measures must be implemented to recycle the organic reagents used in the production process. This not only adds to the complexity of the production process, but also significantly increases the processing cost. In addition, as an oily droplet, octenyl succinic anhydride has limited penetration ability and is difficult to penetrate into the starch granules, resulting in the reaction being mainly limited to the surface of the starch granules, and the preparation process often adopts a slow drop-by-drop addition method. When the amount of starch is large, this addition method is prone to uneven distribution, thereby reducing the efficiency of the esterification reaction. Furthermore, the drying process of SSOS in the later stage of preparation generally relies on the oven drying method, which has the problems of long drying cycle and low efficiency. At the same time, due to uneven heating, it is easy to cause gelatinization, which has an adverse effect on the emulsification properties and product quality of SSOS. Summary of the invention

[0011] In view of the deficiencies in the prior art, the object of the present invention is to provide a method for preparing sodium starch octenyl succinate based on an alcohol-free esterification system, which reduces the use of organic reagents in the production process of SSOS, improves the uneven dripping of OSA, the low efficiency of the esterification reaction, the long drying time and low efficiency of SSOS, and the uneven heating that easily produces gelatinization.

[0012] The technical solution adopted by the present invention to solve its technical problem is:

[0013] A method for preparing sodium octenyl succinate starch based on an alcohol-free esterification system comprises the following steps:

[0014] An emulsifier is added to octenyl succinic anhydride, stirred and heated, and emulsified with water by shearing and high-pressure homogenization to obtain an octenyl succinic anhydride emulsion;

[0015] adding octenyl succinic anhydride emulsion to starch for esterification reaction to obtain esterified starch;

[0016] The esterified starch is dehydrated by a vacuum dehydrator, washed with water, and then air-dried to obtain sodium octenyl succinate starch.

[0017] Preferably, the emulsifier is soybean lecithin, and the added amount is 0.5% to 1.0% of the mass fraction of octenyl succinic anhydride.

[0018] Preferably, the temperature range for stirring and heating after adding the emulsifier to the octenyl succinic anhydride is 40° C. to 60° C., and the stirring time is 5 min to 10 min.

[0019] Preferably, when emulsifying with water by shearing and high-pressure homogenization, the shear rate is 2000r / min~3000r / min, and the shear time is 5min~10min; the high-pressure homogenization pressure is 30Mpa~50Mpa, and the number of cycles of homogenization is 2~3 times. The homogenized octenyl succinic anhydride emulsion is kept in a stirring state, and the water used is purified water, and its mass is 4~6 times that of octenyl succinic anhydride.

[0020] Preferably, the starch includes one or more of waxy corn starch, tapioca starch, corn starch, potato starch, and sweet potato starch.

[0021] Preferably, the method of adding octenyl succinic anhydride emulsion to starch for esterification reaction is:

[0022] The reaction was carried out in a sealed micro-pressure tank and an inert gas N was introduced. 2 Regulate the pressure in the tank;

[0023] Two PE thin tubes are arranged in the reaction tank, and the PE thin tubes are densely covered with micropores;

[0024] Put the starch suspension into a sealed micro-pressure tank;

[0025] The octenyl succinic anhydride emulsion is pressurized and infiltrated into the starch suspension under stirring through the micropores of one of the PE thin tubes, and a 6% to 8% sodium hydroxide solution is pressurized and added into the starch suspension through another PE thin tube;

[0026] The flow rates of the octenyl succinic anhydride emulsion and the sodium hydroxide solution were controlled by adjusting the osmotic pressure. The addition time of the octenyl succinic anhydride emulsion was 1.5 h to 2.0 h. The pH value was maintained within the range of 8.5±0.2. The esterification reaction time was 4 h to 6 h.

[0027] Preferably, after the pH value is completely stable, 0.8 mol / L to 1.2 mol / L dilute hydrochloric acid is added to the starch suspension through a sodium hydroxide PE capillary tube washed with pure water to adjust the pH value to 6.5 to 7.0;

[0028] Preferably, the vacuum degree in the storage tank of the vacuum dehydrator is maintained at 0.053Mpa~0.067Mpa, and when the vacuum pump is out of range, the filter cloth of the vacuum dehydrator is replaced or cleaned.

[0029] Preferably, the method of washing with water is as follows: the dehydrated semi-dry starch ester is transported to a temporary storage tank, pure water is added for dispersion and stirring, and then pumped into a vacuum dehydrator for dehydration again, and the washing is repeated 2 to 3 times.

[0030] Preferably, the airflow drying method is: drying is performed using an airflow dryer consisting of a heating device, a fan, a drying pipe and a cyclone separator, the hot air temperature in the airflow drying is 140° C. to 150° C., and the drying time is 2s to 5s.

[0031] The beneficial effects of the present invention are:

[0032] In the emulsification process of OSA, shearing and high-pressure homogenization technology are used to finely disperse octenyl succinic anhydride into small particles with a micron size. To ensure the stability of the emulsion, an appropriate amount of emulsifier is added. This emulsified octenyl succinic anhydride replaces the traditional isopropanol or anhydrous ethanol in the esterification reaction and is used as an esterifying agent. After the esterification is completed, the product undergoes multiple washings with pure water in a vacuum dehydrator. The use of organic reagents is strictly avoided in the entire SSOS production process.

[0033] The esterification reaction is carried out in a carefully designed sealed micro-pressure tank, which is made of high-quality 316L stainless steel to ensure the safety and durability of the process. Through the automatic adjustment system, inert gas N is introduced into the tank. 2 , in order to maintain a stable micro-pressure environment. Two layers of DN25 PE tubes are cleverly arranged in the reaction tank, and the surface of the tubes is densely covered with micropores to ensure uniform distribution of materials. These tubes are set on the starch slurry, and the octenyl succinic anhydride emulsion and the sodium hydroxide solution pass through different PE tubes respectively, and enter the stirring starch suspension in the form of microporous penetration under pressure. By precisely controlling the osmotic pressure, we can effectively control the flow rate of the two liquids, ensure sufficient contact between OSA and starch, and accelerate the esterification reaction under micro-pressure conditions, significantly improving the reaction efficiency.

[0034] For the esterified SSOS, we use advanced vacuum dehydration machine combined with airflow drying technology for processing. This method not only greatly shortens the drying time and improves the drying efficiency, but also significantly improves the final quality of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the effect of 0%-0.25% mass fraction of mono- and di-glycerol fatty acid esters (MDFA) on the centrifugal stability of OSA emulsion;

[0036] Figure 2 Schematic diagram of the effect of 0.5%-1% mass fraction of MDFA on the centrifugal stability of OSA emulsion;

[0037] Figure 3 Schematic diagram of the effect of 2%-4% mass fraction of MDFA on the centrifugal stability of OSA emulsion;

[0038] Figure 4Schematic diagram of the effect of 0%-0.25% mass fraction of soybean lecithin (SP) on the centrifugal stability of OSA emulsion;

[0039] Figure 5 Schematic diagram of the effect of 0.5%-1% mass fraction of SP on the centrifugal stability of OSA emulsion;

[0040] Figure 6 Schematic diagram of the effect of 2%-4% mass fraction of SP on the centrifugal stability of OSA emulsion;

[0041] Figure 7 Schematic diagram of the effect of 0.25%-1% mass fraction of QE on the centrifugal stability of OSA emulsion;

[0042] Figure 8 Schematic diagram of the effect of 2%-8% mass fraction of QE on the centrifugal stability of OSA emulsion;

[0043] Fig. 9 Schematic diagram of the effect of different SP addition amounts on the particle size distribution of OSA emulsion;

[0044] Fig.10 Schematic diagram of the effect of SP on the Zeta potential of OSA emulsion;

[0045] Fig.11 It is the SSOS Fourier infrared spectrum;

[0046] Fig.12 To use MB at the same excitation intensity + Confocal laser scanning (CLSM) images of unesterified starch (A), isopropanol-SSOS (B), and 1% SP-SSOS sample particles (C) obtained after staining. DETAILED DESCRIPTION

[0047] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. The present invention is described in more detail by way of example in the following paragraphs. According to the following description and claims, the advantages and features of the present invention will become clearer.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0049] Example 1: Construction of an alcohol-free esterification system and its application in the production of sodium octenyl succinate starch, comprising the following steps:

[0050] (1) Add 3% octenyl succinic anhydride by weight of starch and 0.5% soybean lecithin by weight of octenyl succinic anhydride to reaction tank No. 1, heat to 50°C, and stir for 5 minutes;

[0051] (2) Add pure water 5 times the mass of octenyl succinic anhydride into the No. 2 reaction tank, add the mixed solution in the No. 1 reaction tank under the shearing state of 2000r / min, shear for 10min, and cycle 30Mpa high pressure homogenization for 2 times. After homogenization, keep the octenyl succinic anhydride emulsion in a slightly stirred state;

[0052] (3) After acid hydrolysis of waxy corn starch, the peak viscosity of starch decreases from 400BU~500BU to 30BU~50BU. The acid-hydrolyzed waxy corn starch is added to a sealed micro-pressure tank, the starch slurry concentration is adjusted to 40%, and the pH value is adjusted to 8.5 using 8% sodium hydroxide solution. The sealed micro-pressure tank is closed and adjusted to a micro-pressure state by introducing inert gas N2;

[0053] (4) The octenyl succinic anhydride emulsion is pressurized and infiltrated into the starch suspension under stirring through the micropores of a PE capillary tube. An 8% sodium hydroxide solution is pressurized and added to the starch suspension through another PE capillary tube. The flow rates of the octenyl succinic anhydride emulsion and the sodium hydroxide solution are controlled by adjusting the osmotic pressure. The octenyl succinic anhydride emulsion is added for 2.0 h, the pH value is maintained within the range of 8.5±0.2, and the esterification reaction time is 5 h.

[0054] (5) After the pH value is completely stable, 1.0 mol / L dilute hydrochloric acid is added to the starch suspension through a sodium hydroxide PE capillary that has been washed with pure water to adjust the pH value to 6.5. The esterified starch slurry is pumped into a vacuum dehydrator, and the vacuum degree of the storage tank is adjusted to 0.060 MPa to dehydrate the starch. The semi-dry starch ester after dehydration is transported to a temporary storage tank, an appropriate amount of pure water is added, dispersed and stirred, and then pumped into the vacuum dehydrator again for dehydration. The washing is repeated 3 times;

[0055] (6) The washed starch ester is sucked into an air flow dryer through a fan for drying. The heating temperature is set to 145° C. The drying time of the esterified starch is controlled to be 3 seconds by adjusting the fan speed. The dried starch ester is crushed by a vibrating screen and then packaged to obtain sodium starch octenyl succinate.

[0056] Example 2: Construction of an alcohol-free esterification system and its application in the production of sodium octenyl succinate starch, comprising the following steps:

[0057] (1) Add 3% of the mass of starch in octenyl succinic anhydride and 1.0% of the mass of octenyl succinic anhydride in reaction tank No. 1, heat to 50°C, and stir for 10 minutes;

[0058] (2) Add pure water 5 times the mass of octenyl succinic anhydride into the No. 2 reaction tank, add the mixed solution in the No. 1 reaction tank under the shearing state of 2500r / min, shear for 8min, and cycle 2 times of 40Mpa high pressure homogenization. After homogenization, keep the octenyl succinic anhydride emulsion in a slightly stirred state;

[0059] (3) After the cassava starch is properly hydrolyzed by α-amylase, it is added to a sealed micro-pressure tank, the starch slurry concentration is adjusted to 35%, the pH value is adjusted to 8.5 using 6% sodium hydroxide solution, the sealed micro-pressure tank is closed, and the inert gas N2 is introduced to adjust the pressure to a micro-pressure state;

[0060] (4) The octenyl succinic anhydride emulsion is pressurized and infiltrated into the starch suspension under stirring through the micropores of a PE capillary tube. A 6% sodium hydroxide solution is pressurized and added to the starch suspension through another PE capillary tube. The flow rates of the octenyl succinic anhydride emulsion and the sodium hydroxide solution are controlled by adjusting the osmotic pressure. The octenyl succinic anhydride emulsion is added for 1.5 h, the pH value is maintained within the range of 8.5±0.2, and the esterification reaction time is 4 h.

[0061] (5) After the pH value is completely stable, 0.8 mol / L dilute hydrochloric acid is added to the starch suspension through a sodium hydroxide PE capillary tube washed with pure water to adjust the pH value to 7.0. The esterified starch slurry is pumped into a vacuum dehydrator, and the vacuum degree of the storage tank is adjusted to 0.062 MPa to dehydrate the starch. The semi-dry starch ester after dehydration is transported to a temporary storage tank, an appropriate amount of pure water is added, dispersed and stirred, and then pumped into the vacuum dehydrator again for dehydration. The washing is repeated twice;

[0062] The washed starch ester is sucked into an air flow dryer through a fan for drying. The heating temperature is set at 140° C. The drying time of the esterified starch is controlled to be 4 seconds by adjusting the fan speed. The dried starch ester is crushed by a vibrating screen and then packaged to obtain sodium starch octenyl succinate.

[0063] Example 3: Construction of an alcohol-free esterification system and its application in the production of sodium octenyl succinate starch, comprising the following steps:

[0064] (1) Add 4% octenyl succinic anhydride by weight of starch and 0.8% soybean lecithin by weight of octenyl succinic anhydride to reaction tank No. 1, heat to 55°C, and stir for 8 minutes.

[0065] (2) Add pure water 6 times the mass of octenyl succinic anhydride into reaction tank No. 2, add the mixed solution in reaction tank No. 1 under shearing state of 2300r / min, shear for 9 minutes, and cycle 35Mpa high pressure homogenization for 2 times. After homogenization, keep the octenyl succinic anhydride emulsion in a slightly stirred state.

[0066] (3) After enzymatic hydrolysis, the potato starch was added to a sealed micro-pressure tank, and the starch slurry concentration was adjusted to 38%. The pH value was adjusted to 8.2 using 7% sodium hydroxide solution. The sealed micro-pressure tank was closed and adjusted to a micro-pressure state by introducing inert gas N2.

[0067] (4) Octenyl succinic anhydride emulsion was pressurized and infiltrated into the starch suspension under stirring through the micropores of a PE capillary tube. A 7% sodium hydroxide solution was pressurized and added into the starch suspension through another PE capillary tube. The flow rates of the octenyl succinic anhydride emulsion and the sodium hydroxide solution were controlled by adjusting the osmotic pressure. The octenyl succinic anhydride emulsion was added for 1.8 h. The pH value was maintained within the range of 8.2±0.2. The esterification reaction time was 4.5 h.

[0068] (5) After the pH value is completely stable, 0.9 mol / L dilute hydrochloric acid is added to the starch suspension through a sodium hydroxide PE tube that has been washed with pure water to adjust the pH value to 7.2. The esterified starch slurry is pumped into a vacuum dehydrator and the vacuum degree of the storage tank is adjusted to 0.058 MPa to dehydrate the starch. The semi-dry starch ester after dehydration is transported to a temporary storage tank, an appropriate amount of pure water is added to disperse and stir, and then it is pumped into the vacuum dehydrator again for dehydration. The washing is repeated twice.

[0069] (6) The washed starch ester is sucked into an air flow dryer through a fan for drying. The heating temperature is set to 142° C. The drying time of the esterified starch is controlled to be 3.5 s by adjusting the fan speed. The dried starch ester is crushed by a vibrating screen and then packaged to obtain sodium starch octenyl succinate.

[0070] Example 4: Construction of an alcohol-free esterification system and its application in the production of sodium octenyl succinate starch, comprising the following steps:

[0071] (1) Add 2.5% of the mass of starch in octenyl succinic anhydride and 0.7% of the mass of octenyl succinic anhydride in soy lecithin to reaction tank No. 1, heat to 52°C, and stir for 7 minutes.

[0072] (2) Add pure water 4 times the mass of octenyl succinic anhydride into reaction tank No. 2, add the mixed solution in reaction tank No. 1 under shearing state of 2100r / min, shear for 8min, and perform 32Mpa high-pressure homogenization cycle twice. After homogenization, keep the octenyl succinic anhydride emulsion in a slightly stirred state.

[0073] (3) After enzymatic hydrolysis, the rice starch was added to a sealed micro-pressure tank, and the starch slurry concentration was adjusted to 42%. The pH value was adjusted to 8.3 using 6.5% sodium hydroxide solution. The sealed micro-pressure tank was closed and adjusted to a micro-pressure state by introducing inert gas N2.

[0074] (4) Octenyl succinic anhydride emulsion was pressurized and infiltrated into the starch suspension under stirring through the micropores of a PE capillary tube. A 6.5% sodium hydroxide solution was pressurized and added into the starch suspension through another PE capillary tube. The flow rates of the octenyl succinic anhydride emulsion and the sodium hydroxide solution were controlled by adjusting the osmotic pressure. The octenyl succinic anhydride emulsion was added for 1.7 h. The pH value was maintained within the range of 8.3±0.2. The esterification reaction time was 4.2 h.

[0075] (5) After the pH value is completely stable, 1.1 mol / L dilute hydrochloric acid is added to the starch suspension through a sodium hydroxide PE tube that has been washed with pure water to adjust the pH value to 7.0. The esterified starch slurry is pumped into a vacuum dehydrator and the vacuum degree of the storage tank is adjusted to 0.056 MPa to dehydrate the starch. The semi-dry starch ester after dehydration is transported to a temporary storage tank, an appropriate amount of pure water is added to disperse and stir, and then it is pumped into the vacuum dehydrator again for dehydration. The washing is repeated 4 times.

[0076] (6) The washed starch ester is sucked into an air flow dryer through a fan for drying. The heating temperature is set to 140° C. The drying time of the esterified starch is controlled to be 3.8 s by adjusting the fan speed. The dried starch ester is crushed by a vibrating screen and then packaged to obtain sodium octenyl succinate starch.

[0077] Example 5: Construction of an alcohol-free esterification system and its application in the production of sodium octenyl succinate starch, comprising the following steps:

[0078] (1) Add 3% octenyl succinic anhydride by weight of starch into reaction tank No. 1, then add 0.8% octenyl succinic anhydride by weight of soybean lecithin, heat to 50°C, and stir for 8 minutes.

[0079] (2) Add pure water 5 times the mass of octenyl succinic anhydride into reaction tank No. 2, add the mixed solution in reaction tank No. 1 under shearing state of 2300r / min, shear for 9 minutes, and cycle 35Mpa high pressure homogenization for 2 times. After homogenization, keep the octenyl succinic anhydride emulsion in a slightly stirred state.

[0080] (3) After appropriate enzymatic hydrolysis, the cassava starch is added to a sealed micro-pressure tank, the starch slurry concentration is adjusted to 38%, the pH value is adjusted to 8.5 using 7% sodium hydroxide solution, the sealed micro-pressure tank is closed, and the inert gas N2 is introduced to adjust to a micro-pressure state.

[0081] (4) Octenyl succinic anhydride emulsion was pressurized and infiltrated into the starch suspension under stirring through the micropores of a PE capillary tube. A 7% sodium hydroxide solution was pressurized and added into the starch suspension through another PE capillary tube. The flow rates of the octenyl succinic anhydride emulsion and the sodium hydroxide solution were controlled by adjusting the osmotic pressure. The octenyl succinic anhydride emulsion was added for 1.8 h. The pH value was maintained within the range of 8.5±0.2. The esterification reaction time was 4.5 h.

[0082] (5) After the pH value is completely stable, 0.9 mol / L dilute hydrochloric acid is added to the starch suspension through a sodium hydroxide PE tube washed with pure water to adjust the pH value to 7.2. The esterified starch slurry is pumped into a vacuum dehydrator and the vacuum degree of the storage tank is adjusted to 0.058 MPa to dehydrate the starch. The semi-dry starch ester after dehydration is transported to a temporary storage tank, an appropriate amount of pure water is added, dispersed and stirred, and then pumped into the vacuum dehydrator again for dehydration. The washing is repeated twice.

[0083] (6) The washed starch ester is sucked into an air flow dryer through a fan for drying. The heating temperature is set to 142° C. The drying time of the esterified starch is controlled to be 3.5 s by adjusting the fan speed. The dried starch ester is crushed by a vibrating screen and then packaged to obtain sodium starch octenyl succinate.

[0084] Experimental example;

[0085] In the experiment, we selected three commonly used emulsifiers - mono- and di-glycerol fatty acid esters (MDFA), soy lecithin (SP) and Quillaja saponaria extract (QE) - to emulsify octenyl succinic anhydride (OSA) with water. Specifically, the addition amount of MDFA and SP was added to OSA in increments of 0%, 0.25%, 0.5%, 1%, 2%, 3%, and 4% of the mass fraction of OSA, while QE was added to the aqueous phase in the same proportion (but with an upper limit of 8%). Subsequently, the stability of the prepared OSA emulsion was tested by centrifugal stability analysis to preliminarily screen out suitable emulsifiers and their optimal addition amounts.

[0086] The stability analyzer was used to evaluate the effects of three emulsifiers on the centrifugal stability of OSA emulsions. Figure 1-9 As shown. Centrifugal stability analysis is a technique that combines light projection and centrifugation to determine the aggregation stability of emulsions. The principle is similar to turbidity measurement, but the process is completed in a shorter time under centrifugal conditions. The curve change of the projected spectrum reflects the change in the concentration of oil droplets in the sample length over time. Specifically, the smaller the change in the transmittance of the sample during the centrifugation process, the higher its stability.

[0087] The experimental results show that the OSA emulsion prepared by QE performs the worst in terms of centrifugal stability, especially when the addition amount reaches or exceeds 2%, the emulsion shows obvious stratification. This may be due to the fact that QE, as a natural emulsifier, has a relatively complex structure and relatively weak emulsification ability. In contrast, the centrifugal stability of the OSA emulsion prepared by MDFA shows a trend of first increasing and then decreasing. When the addition amount of MDFA is low, the interfacial film formed is not tight enough, the emulsification effect is not sufficient, and fat precipitation occurs; when the addition amount is too much, the emulsifier itself may separate, which in turn causes emulsion stratification.

[0088] The OSA emulsion prepared by SP showed excellent centrifugal stability, and its stability gradually increased with the increase of SP addition. However, when the addition amount reached a certain threshold, although the OSA emulsion remained uniform as a whole, a small amount of coagulation was observed on the surface, which was consistent with the observation results of the spectrum. In order to further explore the specific effect of SP addition on the formation process of OSA emulsion, we further analyzed its particle size, Zeta potential and microstructure in detail.

[0089] Fig.10 The effect of different amounts of SP added on the particle size distribution of OSA emulsion is shown. The results show that with the gradual increase in the amount of SP added, the average particle size of OSA emulsion shows a trend of gradually decreasing. However, when the amount of SP added exceeds 1%, the distribution range of particle size begins to widen. This phenomenon may be attributed to the specific mechanism of action of SP in the process of stabilizing OSA emulsion: that is, the phospholipid hydrophobic groups of SP can tightly cover the surface of OSA oil droplets to form an effective wrapping layer; at the same time, the hydrophilic groups of phospholipids can extend into the aqueous phase to construct a stable amphiphilic structure, thereby significantly improving the overall stability of the emulsion. However, when the amount of SP added reaches a certain level, some SP may form new droplets with a different size from the emulsion droplets, resulting in uneven distribution of OSA emulsion droplets, increased particle size differences, and then triggering the aggregation and migration of droplets, making the particle size distribution range correspondingly wider. According to the graphical results, it can be judged that in the range of 0.25% to 1% of SP addition, OSA emulsion presents a relatively ideal particle size distribution.

[0090] Fig.11The effect of SP on the Zeta potential of OSA emulsion is shown. In general, an increase in the absolute value of Zeta potential indicates that the stability of OSA emulsion has been improved. This is because a higher absolute value of Zeta potential can form a strong electrostatic barrier, effectively preventing aggregation and flocculation between particles. When the amount of SP (stabilizer) added is gradually increased, the absolute value of Zeta potential will increase accordingly. However, when the amount of SP added exceeds 1%, the absolute value of Zeta potential begins to gradually decrease; especially when the amount added reaches more than 3%, this decreasing trend becomes particularly significant. In the range of 0.5% to 1.0% SP addition, strong electrostatic repulsion will be generated between OSA emulsion droplets, and this repulsion has a positive effect on the stability of the emulsion.

[0091] In addition, in order to further explore the effects of different preparation methods on the performance of sodium starch octenyl succinate (SSOS), we used two different routes for comparative experiments. One is to use cassava starch pretreated by enzymatic hydrolysis as the base material, and use OSA emulsion with SP added as an esterifying agent to prepare sodium starch octenyl succinate (denoted as SP-SSOS); the other is to follow the conventional method and use isopropanol to disperse acid anhydride to prepare sodium starch octenyl succinate (denoted as isopropanol-SSOS). Subsequently, we conducted a comparative analysis of the SSOS prepared by these two methods in terms of the content of octenyl succinic acid groups (OS groups), degree of substitution (DS), and substitution efficiency (SE). The specific results are shown in Table 1 below:

[0092] Table 1 Octenyl succinic acid group content, substitution degree and substitution efficiency

[0093]

[0094] Note: Different lowercase letters in the same column indicate significant differences (P<0.05).

[0095] In the comparative experiment, we conducted an in-depth analysis of the OSA emulsion prepared by adding SP and cassava starch ester (SP-SSOS) and the SSOS prepared by the conventional isopropanol OSA dispersion method (isopropanol-SSOS), focusing on key indicators such as OS group content, degree of substitution (DS) and substitution efficiency (SE), as shown in Table 1. The results show that with the gradual increase in the amount of SP added, the OS group content, DS and SE all show a trend of first increasing and then decreasing. Specifically, in the range of 0.5% to 1% SP addition, the above three indicators all reach peak values, which is consistent with the stability trend of the OSA emulsion prepared by SP.

[0096] On the other hand, the various indicators of isopropanol-SSOS are significantly lower than those of SP-SSOS. This phenomenon may be attributed to the fact that although OSA is dispersed in isopropanol, when it is added to the starch slurry, OSA exists in the form of a mixture of a large number of insoluble oil droplets and a small amount of dissolved OSA, resulting in extremely uneven reaction between starch granules and OSA, and uneven distribution of substituents between granules, thereby reducing the degree of substitution.

[0097] Further analysis showed that the reason why the alcohol-free esterification system showed advantages may be that OSA was effectively dispersed into micron-sized oil droplets through high-pressure homogenization and emulsifiers, which not only significantly increased the contact area between OSA and starch particles, but also made it easier for smaller OSA oil droplets to penetrate into the starch particles, thereby improving the reaction efficiency between starch and OSA. Therefore, we selected the sample with 1% SP addition for subsequent structural analysis.

[0098] In addition, we used infrared spectroscopy scanning technology to conduct qualitative analysis on unesterified starch, 1% SP-SSOS and isopropanol-SSOS to explore the grafting of OS groups on esterified starch and the degree of change in the short-range ordered structure. Fig.12 As shown in the figure, 1% SP-SSOS and isopropanol-SSOS are both at 1572 cm -1 and 1726cm -1 New characteristic peaks appeared at , which correspond to the asymmetric stretching vibration of the carboxyl group and the stretching vibration of C=O, respectively, indicating that the carbonyl group in starch has been successfully replaced by the ester carbonyl and carboxyl group of OSA, and OSA has been effectively connected to the starch molecule. It is worth noting that at the same OSA addition amount, the characteristic peak intensity of 1% SP-SSOS is significantly higher than that of isopropanol-SSOS, and this finding is consistent with the test results of indicators such as degree of substitution.

[0099] Fig.12 shows that MB + CLSM images of unesterified starch, isopropanol-SSOS, and 1% SP-SSOS sample particles obtained after dyeing. Unesterified starch ( Fig.12 A) was not excited to emit fluorescence. Different levels of fluorescence intensity were detected for isopropanol-SSOS and 1% SP-SSOS, indicating that MB+ can specifically label the -COO- of the OS group. Fig.12 Most of the fluorescence in B is reflected on the periphery of starch granules, which may be because organic reagents are used to disperse OSA, and the esterification reaction occurs on the surface of the granules and cannot penetrate into the amorphous region of starch. Fig.12 The fluorescence intensity of C in the image is slightly stronger, and the distribution of fluorescence spots is relatively Fig.12The B in the sample is relatively uniform, and a small number of starch granules also show OSA groups inside. This proves that without changing the starch granules, using high-pressure homogenization and emulsifiers to disperse OSA into micron-sized oil droplets and then esterify can increase the contact area between OSA and starch, thereby improving the efficiency of the esterification reaction, which is consistent with the previous results of substitution degree and Fourier infrared spectroscopy analysis.

[0100] The above results show that the sodium octenyl succinate starch prepared by the technical solution can replace the organic reagent to disperse octenyl succinic anhydride to esterify starch, and the prepared product has a higher degree of substitution and substitution efficiency than conventional products.

[0101] The above embodiments of the present invention are not intended to limit the protection scope of the present invention, and the implementation modes of the present invention are not limited thereto. All other modifications, replacements or changes made to the above structures of the present invention based on the above contents of the present invention, in accordance with common technical knowledge and customary means in the art, without departing from the above basic technical ideas of the present invention, should fall within the protection scope of the present invention.

Claims

1. A method for preparing sodium octenyl succinate starch based on an alcohol-free esterification system, comprising the following steps: (1) Add 3% octenyl succinic anhydride by weight of starch and 1.0% soybean lecithin by weight of octenyl succinic anhydride to reaction tank No. 1, heat to 50°C, and stir for 10 minutes; (2) Add pure water 5 times the mass of octenyl succinic anhydride into the No. 2 reaction tank, add the mixed solution in the No. 1 reaction tank under the shearing state of 2500r / min, shear for 8min, and cycle 2 times of 40Mpa high pressure homogenization. After homogenization, keep the octenyl succinic anhydride emulsion in a slightly stirred state; (3) After the cassava starch is properly hydrolyzed by α-amylase, it is added to a sealed micro-pressure tank, the starch slurry concentration is adjusted to 35%, the pH value is adjusted to 8.5 using 6% sodium hydroxide solution, the sealed micro-pressure tank is closed, and the inert gas N2 is introduced to adjust the pressure to a micro-pressure state; (4) The octenyl succinic anhydride emulsion is pressurized and infiltrated into the starch suspension under stirring through the micropores of a PE capillary tube. A 6% sodium hydroxide solution is pressurized and added to the starch suspension through another PE capillary tube. The flow rates of the octenyl succinic anhydride emulsion and the sodium hydroxide solution are controlled by adjusting the osmotic pressure. The octenyl succinic anhydride emulsion is added for 1.5 h, the pH value is maintained within the range of 8.5±0.2, and the esterification reaction time is 4 h. (5) After the pH value is completely stable, 0.8 mol / L dilute hydrochloric acid is added to the starch suspension through a sodium hydroxide PE tube washed with pure water to adjust the pH value to 7.0, and the esterified starch slurry is pumped into a vacuum dehydrator. The vacuum degree of the storage tank is adjusted to 0.062 MPa to dehydrate the starch. The semi-dry starch ester after dehydration is transported to a temporary storage tank, an appropriate amount of pure water is added, dispersed and stirred, and then pumped into the vacuum dehydrator again for dehydration. The washing is repeated twice; the washed starch ester is sucked into an air flow dryer through a fan for drying, the heating temperature is set to 140°C, and the drying time of the esterified starch is controlled to 4 s by adjusting the fan speed. The dried starch ester is crushed by a vibrating screen and packaged to obtain sodium starch octenyl succinate.

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