Preparation method of high-substitution degree V type pregelatinized hydroxypropyl starch

Abstract

The application discloses a preparation method of high-substitution V-type pregelatinized hydroxypropyl starch, and belongs to the technical field of starch modification. The preparation method comprises the following steps: (1) first, starch and an ethanol aqueous solution are extruded, dried and crushed to obtain extrusion modified starch A; (2) the extrusion modified starch A is added into an ethanol solution, the pH is adjusted to alkaline, then propylene oxide is added for reaction, the pH is adjusted to acid to terminate the reaction, and finally, the V-type pregelatinized hydroxypropyl starch is obtained through filtration, washing and drying. In the preparation method, the V-type pregelatinized starch with high reactivity, V-type single helix structure and a large number of exposed hydroxyl groups is obtained through alcohol-water extrusion treatment; subsequently, the hydroxypropylation reaction is carried out by using an organic solvent method, the reaction efficiency is improved, the product efficiency is improved, and the cost is reduced.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of high-substitution-degree V-type pregelatinized hydroxypropyl starch, and belongs to the technical field of starch modification. BACKGROUND

[0002] Hydroxypropyl starch is a starch substituent ether obtained by introducing a hydroxypropyl group into a starch molecule through the reaction of propylene oxide and the hydroxyl group in the starch molecule in an alkaline environment. Since the hydroxypropyl group has strong hydrophilicity, it can weaken the hydrogen bond strength in the starch molecule and increase the hydrogen bond strength between the starch molecule and the water molecule, so that the modification process can significantly improve the transparency, stability and anti-regeneration of the starch paste, and the starch paste has excellent performance in different application fields.

[0003] Hydroxypropyl pregelatinized starch is a functional starch obtained through double modification treatment of pregelatinization and hydroxypropylation. The hydroxypropyl pregelatinized starch has excellent solubility in water, especially the solubility in cold water is much higher than that of ordinary starch, and it is easy to process and use. Since the pregelatinization process makes the starch retain part of the gelatinization structure after drying, and the hydroxypropylation further improves the thermal stability and anti-regeneration of the starch, the starch shows strong stability and reduces the aging phenomenon. Therefore, the hydroxypropyl pregelatinized starch is widely used in instant food, beverages, medicines and other fields, and has important application value in products that require rapid dissolution, thickening and gelation.

[0004] The preparation of hydroxypropyl pregelatinized starch is usually carried out by first hydroxypropylation and then pregelatinization. However, since the structure of the ungelatinized starch particles is relatively dense, the hydroxypropylation reaction efficiency is low, and incomplete reaction or side reactions are prone to occur, which affects the quality of the final product. In addition, after hydroxypropylation, the molecular structure of the starch has changed, and if pregelatinization is performed again, the gelation characteristics and thickening performance of the starch may be reduced. Therefore, the above-mentioned traditional preparation method of hydroxypropyl pregelatinized starch has certain disadvantages. The process of pregelatinization first and then hydroxypropylation can effectively avoid the problems in the traditional preparation method and improve the overall performance of the starch, but the final prepared hydroxypropyl pregelatinized starch still has the problems of low substitution degree and high caking rate.

[0005] The problem of low substitution degree is usually optimized by adjusting the amount of propylene oxide, increasing the pH value of the reaction and increasing the reaction temperature. Among them, increasing the amount of propylene oxide is the most effective, which increases the reaction probability with the swollen starch free radicals by increasing the concentration of epoxy groups in the starch, thereby increasing the etherification degree. However, according to the requirements in GB 29930-2013, the mass fraction of hydroxypropyl in food additive hydroxypropyl starch should not be higher than 7%. Therefore, in the field of food additives, the addition amount of propylene oxide should not be higher than 7%, which limits the improvement of the substitution degree of the prepared hydroxypropyl pregelatinized starch.

[0006] Recent studies have found that alcohol-water extrusion modified V-type starch has stronger reactivity than raw starch, because the hydrophobic hydroxyl groups of V-type single helix are exposed, which can provide more attack sites for propylene oxide during the reaction. Therefore, using alcohol-water extrusion modified V-type starch to prepare hydroxypropyl pregelatinized starch is expected to achieve higher reaction efficiency, thereby increasing the degree of substitution of hydroxypropyl pregelatinized starch.

[0007] Currently, there is no technical report on using alcohol-water extrusion modified V-type starch for hydroxypropylation in the prior art. At the same time, the present application also found that not all alcohol-water extrusion modified V-type starch can successfully increase the degree of substitution of the prepared hydroxypropyl pregelatinized starch. In addition, the patents CN 118206669 A, CN 116284462 A, CN 112831081 A and CN 115975059 A all disclose methods for preparing V-type starch by alcohol-water extrusion, but none of them disclose that the prepared V-type starch can successfully prepare a high-substitution hydroxypropyl pregelatinized starch. Therefore, it is necessary to explore under what conditions alcohol-water extrusion modified V-type starch can successfully increase the degree of substitution of hydroxypropyl pregelatinized starch. SUMMARY

[0008] TECHNICAL PROBLEM

[0009] The existing preparation of pregelatinized hydroxypropyl starch generally has the problems of low substitution efficiency and complicated preparation process. Therefore, it is necessary to provide a simple and efficient method for preparing pregelatinized hydroxypropyl starch, so that the obtained product has a high degree of substitution while reducing production cost. Using alcohol-water extrusion modified V-type starch to prepare hydroxypropyl pregelatinized starch is a promising approach, but it is necessary to explore under what conditions V-type starch can successfully increase the degree of substitution of hydroxypropyl pregelatinized starch.

[0010] TECHNICAL SCHEME

[0011] The present application proposes an innovative process, that is, first preparing V-type pregelatinized starch by alcohol-water extrusion, and then performing hydroxypropylation. Unlike the traditional process of first hydroxypropylation and then gelatinization, the process of the present application effectively overcomes some limitations in the conventional method, and additionally finds that the V-type pregelatinized hydroxypropyl starch prepared by the process of the present application has better dispersibility and lower caking rate in cold water compared to traditional pregelatinized hydroxypropyl starch, which has certain reference significance for the research and development of instant instant powder. At the same time, the quality of the pregelatinized starch product is better and the yield of the extrusion method is larger, the cost is lower, and it has great market prospect.

[0012] The purpose of the present application is to provide a method for preparing V-type pregelatinized hydroxypropyl starch, comprising the following steps:

[0013] (1) first extruding and drying starch and ethanol aqueous solution, and then crushing to obtain extrusion modified starch A;

[0014] (2) adding extrusion modified starch A into ethanol solution, adjusting pH to alkaline, then adding propylene oxide to react, adjusting pH to acid to terminate the reaction, and finally obtaining V type pregelatinized hydroxypropyl starch by filtering, washing and drying.

[0015] In one embodiment of the present application, the starch includes one or more of common corn starch, rice starch, potato starch, wheat starch, barley starch and cassava starch.

[0016] In one embodiment of the present application, the concentration of ethanol in the ethanol aqueous solution in step (1) is 30-50%, v / v.

[0017] In one embodiment of the present application, the mass ratio of starch to ethanol aqueous solution in step (1) is 1:0.4-1:1.

[0018] In one embodiment of the present application, the extrusion in step (1) is performed by using an extruder.

[0019] In one embodiment of the present application, the parameters of the extruder are set as follows: the heating temperature of the premixing zone is 50-60℃, the temperature of the gelatinization zone is 70-100℃, the temperature of the forming zone is 40-50℃, and the rotation speed of the extruder is 80-200 r / min.

[0020] In one embodiment of the present application, the crushing in step (1) is performed by using a continuous cyclone crusher, and the screen size is 0.8-1.5 mm.

[0021] In one embodiment of the present application, the concentration of ethanol in the ethanol solution in step (2) is 80-100%, v / v.

[0022] In one embodiment of the present application, the mass ratio of extrusion modified starch A to ethanol solution in step (2) is 1:3-1:4.

[0023] In one embodiment of the present application, the adjustment of pH to alkaline in step (2) is adjusting the pH value to 10.5-12.0.

[0024] Preferably, the adjustment of pH to alkaline is adjusting the pH value to 11.0-11.5.

[0025] In one embodiment of the present application, the addition amount of propylene oxide in step (2) is 5-7% of the mass of the starch.

[0026] Specifically, the propylene oxide is added in an amount of 7% of the mass of the starch.

[0027] In one embodiment of the present application, the reaction in step (2) is carried out at a temperature of 60-80℃ for 4-10h after the addition of propylene oxide.

[0028] In one embodiment of the present application, the pH in step (2) is adjusted to be acidic by adjusting the pH of the system to 4.0-6.0.

[0029] In one embodiment of the present application, the washing is carried out using anhydrous ethanol or an ethanol aqueous solution.

[0030] In one embodiment of the present application, the drying temperature in step (2) is 40-60℃.

[0031] The present application provides a V-type pregelatinized hydroxypropyl starch prepared according to the above method.

[0032] The present application provides the use of the V-type pregelatinized hydroxypropyl starch prepared according to the above method in the food field.

[0033] Further, the use includes the preparation of instant soluble powder, seasoning sauce, soluble capsule or edible film.

[0034] Advantages

[0035] (1) The product has excellent performance: the present application uses the alcohol water extrusion method to obtain a V-type pregelatinized starch with high reactivity and a V-type single helix crystal structure, which can improve the degree of substitution in the subsequent hydroxypropylation, and the degree of substitution of the obtained hydroxypropyl starch is improved to more than 0.9, and the starch also has good water separation rate and low caking rate.

[0036] (2) The preparation is efficient and simple: the preparation process of the present application is simple, has few steps, and has large production, which is suitable for industrial application. In addition, a high-substitution hydroxypropyl starch is prepared when the amount of propylene oxide added is not more than 7%, which meets the national standard. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 X-ray diffraction patterns of the V-type pregelatinized starch, V-type pregelatinized hydroxypropyl starch and raw starch prepared in Example 1 of the present application and the corresponding relative crystallinity diagram DETAILED DESCRIPTION

[0038] The preferred embodiments of the present application are described below, and it should be understood that the embodiments are used to better explain the present application and are not used to limit the present application.

[0039] 1. Test method of freeze-thaw stability:

[0040] Weigh a certain amount of sample, put it in a pre-weighed centrifuge tube M0, make a 3% (calculated on dry basis) starch paste, record the total weight M1, cool to room temperature. Put it in the refrigerator at -18℃ for 24h, take it out, naturally thaw at room temperature for 2h, then centrifuge at 3000r / min for 20min, remove the supernatant and weigh M2, calculate the water separation rate, the formula is as follows:

[0041] Water separation rate% = [(M1-M2) / (M1-M0)]x100%

[0042] Repeat the cycle five times, and take the fifth water separation rate as the final data.

[0043] 2. Test method of crystallinity:

[0044] The crystalline structure of the sample was analyzed by X-ray diffractometer, the scanning angle was 3-36° (2θ), and the scanning speed was 0.05° / s. The relative crystallinity was calculated by MDI JADE software: the ratio of the area of V-type crystalline characteristic peaks (7.8°, 13.5° and 20.8°) or the area of A-type crystalline characteristic peaks (15°, 17°, 18° and 23°) to the total dispersion area, the calculation formula is as follows:

[0045] Relative crystallinity (%) = CDA / TDAx100

[0046] Where CDA represents the peak area of the characteristic crystalline peak, and TDA represents the total area of all diffraction peaks in the scanning interval.

[0047] 3. Test method of degree of substitution:

[0048] Accurately weigh 0.04-0.06 g of oxidized hydroxypropyl starch sample into a 100 mL volumetric flask, and add 25 mL of 0.5 mol / L sulfuric acid solution to the flask, and heat in a boiling water bath to gelatinize the starch. After 30 minutes of heating, cool the starch gel solution to room temperature. Prepare 25 mL glass test tubes with stoppers in advance, and immerse them in an ice water bath. Add 1 mL of the above starch gel solution to the glass test tubes, and then carefully and slowly add 8 mL of concentrated sulfuric acid. Mix the contents of the glass test tubes by inverting them. Heat the glass test tubes in a boiling water bath for 30 minutes, and immediately after the reaction is complete, place the glass test tubes in an ice water bath. After the sample has cooled to room temperature, slowly add 0.6 mL of 3% indantrione indicator solution, and mix by inverting the test tubes. Place the test tubes in a 25°C water bath for 100 minutes, and then add concentrated sulfuric acid to bring the volume of the liquid in the test tubes to 25 mL. Mix the contents of the test tubes by inverting them. Place the test tubes in a colorimetric cell for 5 minutes, and then measure the absorbance at 595 nm using a UV spectrophotometer. Calculate the molar substitution degree of the hydroxypropyl group in the sample based on the calculated propylene glycol content. The mass fraction of the hydroxypropyl group (H) % and the molar substitution degree of the hydroxypropyl starch (MS) are calculated according to the following formulas:

[0049] H (%) = F [M1 / W1 - M0 / W0] x 0.7763 x 100

[0050] MS = 2.79H / (100-H)

[0051] wherein:

[0052] H - the percentage content of the hydroxypropyl group, %;

[0053] F - the dilution factor of the sample or the blank;

[0054] M1 - the mass of propylene glycol in the sample, g, as determined from the standard working curve;

[0055] M0 - the mass of propylene glycol in the original starch blank sample, g, as determined from the standard working curve;

[0056] W1 - the mass of the sample, g;

[0057] W0 - the mass of the original starch, g;

[0058] 0.7763 - the conversion factor for converting the propylene glycol content to the hydroxypropyl content;

[0059] 2.79 - the conversion factor for converting the percentage content of the hydroxypropyl group to the degree of substitution.

[0060] 4. Test method for the caking rate:

[0061] Take 100 mL of deionized water and place it on an electromagnetic oven to heat to boiling. Weigh 5 g of the sample and place it in a beaker, take 30 mL of deionized water cooled to 80 ℃ and add it to the beaker, and stir it thoroughly with a glass rod for 5 min, then stand for 1 min to observe whether there is a stratification phenomenon; take a 20-mesh screen (record the weight), filter the sample solution, and slowly rinse the caked material with clean water, then place it in a 105 ℃ oven to dry to constant weight and weigh it. Subtract the weight of the screen to obtain the dry weight of the caked material. The caking rate is calculated according to formula (2-1).

[0062]

[0063] In the formula, m is the dry weight of the caked material (g), M is the mass of the sample (g), and a is the moisture content of the sample (%).

[0064] Example 1

[0065] Select cassava starch, set the solid feed rate of the extruder to 600 g / h; configure an ethanol aqueous solution with a volume concentration of 40% ethanol and set the liquid feed rate so that the mass ratio of starch to ethanol aqueous solution is 1:0.56. The operating parameters of the extruder are: the heating temperature of the premixing zone is 60 ℃, the temperature of the gelatinization zone is 95 ℃, the temperature of the shaping zone is 50 ℃, and the rotation speed of the extruder is 100 r / min. Cut the extrudate into 0.5 cm small pieces and place them in an oven at 40 ℃ for drying for 20 h. Then take them out and place them in a continuous cyclone crusher (with a screen size of 1.0 mm) for crushing, and V-type pregelatinized starch A is obtained.

[0066] Then take 10 g of V-type pregelatinized starch A and place it in a 50 mL centrifuge tube, add 30 mL of an ethanol aqueous solution with a volume concentration of 85%, adjust the pH to 11.0 with a 10% sodium hydroxide solution, then add 0.7 g of propylene oxide, and react in a 75 ℃ water bath for 6 h. Finally, adjust the pH to 5.0 with a 10% hydrochloric acid solution to terminate the reaction, wash by suction filtration, dry, and crush to obtain pregelatinized hydroxypropyl starch.

[0067] Example 2

[0068] Select potato starch, set the solid feed rate of the extruder to 600 g / h; configure an ethanol aqueous solution with a volume concentration of 35% ethanol and set the liquid feed rate so that the mass ratio of starch to ethanol aqueous solution is 1:0.48. The operating parameters of the extruder are: the heating temperature of the premixing zone is 60 ℃, the temperature of the gelatinization zone is 100 ℃, the temperature of the shaping zone is 50 ℃, and the rotation speed of the extruder is 100 r / min. Cut the extrudate into 0.5 cm small pieces and place them in an oven at 40 ℃ for drying for 24 h. Then take them out and place them in a continuous cyclone crusher (with a screen size of 1.0 mm) for crushing, and V-type pregelatinized starch A is obtained.

[0069] Subsequently, 10 g of the V-type pregelatinized starch A was weighed into a 50 mL centrifuge tube, 30 mL of an aqueous ethanol solution with a volume concentration of 90% was added, 0.7 g of propylene oxide was added after the pH was adjusted to 11.6 with a 10% sodium hydroxide solution, and the reaction was carried out in a water bath at 80°C for 8 h. Finally, the pH was adjusted to 5.0 with a 10% hydrochloric acid solution to terminate the reaction, and the hydroxypropyl starch was obtained by washing, drying, and crushing after suction filtration.

[0070] Example 3

[0071] Barley starch was selected, and the solid feeding speed of the extruder was set to 600 g / h. An aqueous ethanol solution with a volume concentration of 40% was configured, and the mass ratio of the starch to the aqueous ethanol solution was 1:0.56 by setting the liquid feeding speed. The operating parameters of the extruder were as follows: the heating temperature of the premixing zone was 60°C, the temperature of the gelatinization zone was 95°C, the temperature of the forming zone was 50°C, and the rotation speed of the extruder was 140 r / min. The extrudate was cut into small pieces with a length of 0.5 cm and then placed in an oven at 40°C for drying for 20 h. Subsequently, the extrudate was taken out and crushed in a continuous cyclone crusher (with a screen size of 1.0 mm) to obtain the V-type pregelatinized starch A.

[0072] Subsequently, 10 g of the V-type pregelatinized starch A was weighed into a 50 mL centrifuge tube, 30 mL of an aqueous ethanol solution with a volume concentration of 95% was added, 0.7 g of propylene oxide was added after the pH was adjusted to 11.7 with a 10% sodium hydroxide solution, and the reaction was carried out in a water bath at 65°C for 6 h. Finally, the pH was adjusted to 5.0 with a 10% hydrochloric acid solution to terminate the reaction, and the hydroxypropyl starch was obtained by washing, drying, and crushing after suction filtration.

[0073] Example 4

[0074] Ordinary corn starch was selected, and the solid feeding speed of the extruder was set to 600 g / h. An aqueous ethanol solution with a volume concentration of 40% was configured, and the mass ratio of the starch to the aqueous ethanol solution was 1:0.4 by setting the liquid feeding speed. The operating parameters of the extruder were as follows: the heating temperature of the premixing zone was 60°C, the temperature of the gelatinization zone was 90°C, the temperature of the forming zone was 50°C, and the rotation speed of the extruder was 120 r / min. The extrudate was cut into small pieces with a length of 0.5 cm and then placed in an oven at 40°C for drying for 20 h. Subsequently, the extrudate was taken out and crushed in a continuous cyclone crusher (with a screen size of 1.0 mm) to obtain the V-type pregelatinized starch A.

[0075] Subsequently, 10 g of the V-type pregelatinized starch A was weighed into a 50 mL centrifuge tube, 30 mL of an aqueous ethanol solution with a volume concentration of 95% was added, 0.7 g of propylene oxide was added after the pH was adjusted to 11.7 with a 10% sodium hydroxide solution, and the reaction was carried out in a water bath at 65°C for 6 h. Finally, the pH was adjusted to 5.0 with a 10% hydrochloric acid solution to terminate the reaction, and the hydroxypropyl starch was obtained by washing, drying, and crushing after suction filtration.

[0076] Example 5

[0077] Wheat starch was selected, and the solid feeding speed of the extruder was set to 600 g / h; 40% ethanol aqueous solution was configured, and the liquid feeding speed was set to make the mass ratio of starch to ethanol aqueous solution 1:0.7. The operating parameters of the extruder were as follows: the heating temperature of the premixing zone was 60°C, the temperature of the gelatinization zone was 80°C, the temperature of the forming zone was 50°C, and the rotating speed of the extruder was 160 r / min. The extrudates were cut into small pieces of 0.5 cm and then placed in an oven at 40°C for drying for 24 h. Subsequently, the extrudates were taken out and placed in a continuous cyclone crusher (the screen size was 1.0 mm) for crushing, thereby obtaining V-type pregelatinized starch A.

[0078] Subsequently, 10 g of V-type pregelatinized starch A was taken and placed in a 50 mL centrifuge tube, 40 mL of anhydrous ethanol was added, 10% sodium hydroxide solution was used to adjust the pH to 11.0, then 0.7 g of propylene oxide was added, and the reaction was carried out in a water bath at 65°C for 8 h. Finally, 10% hydrochloric acid solution was used to adjust the pH value to 5.0 to terminate the reaction, and the hydroxypropyl starch was obtained by filtration, washing, drying, and crushing.

[0079] Example 6

[0080] Rice starch was selected, and the solid feeding speed of the extruder was set to 600 g / h; 40% ethanol aqueous solution was configured, and the liquid feeding speed was set to make the mass ratio of starch to ethanol aqueous solution 1:0.9. The operating parameters of the extruder were as follows: the heating temperature of the premixing zone was 60°C, the temperature of the gelatinization zone was 75°C, the temperature of the forming zone was 50°C, and the rotating speed of the extruder was 160 r / min. The extrudates were cut into small pieces of 0.5 cm and then placed in an oven at 40°C for drying for 20 h. Subsequently, the extrudates were taken out and placed in a continuous cyclone crusher (the screen size was 1.0 mm) for crushing, thereby obtaining V-type pregelatinized starch A.

[0081] Subsequently, 10 g of V-type pregelatinized starch A was taken and placed in a 50 mL centrifuge tube, 40 mL of anhydrous ethanol was added, 10% sodium hydroxide solution was used to adjust the pH to 11.0, then 0.7 g of propylene oxide was added, and the reaction was carried out in a water bath at 65°C for 8 h. Finally, 10% hydrochloric acid solution was used to adjust the pH value to 5.0 to terminate the reaction, and the hydroxypropyl starch was obtained by filtration, washing, drying, and crushing.

[0082] Comparative Example 1

[0083] The difference between Comparative Example 1 and Example 1 was only that no ethanol was added in step (1), and deionized water was used for extrusion. The specific steps were as follows:

[0084] Selecting cassava starch, set the extruder solid feed rate of 600 g / h; take deionized water and by setting the liquid feed rate, so that the mass ratio of starch and deionized water is 1:0.56. Extruder operating parameters: pre-mixing zone heating temperature is 60℃, gelatinization zone temperature is 95℃, forming zone temperature is 50℃, extruder speed 100 r / min. The extrudate is cut into 0.5 cm small section and placed in the oven 40℃ drying 20 h. Then take out and placed in the continuous cyclone grinder (screen size is 1.0 mm) for crushing, namely the non-alcohol extrusion pre-gelatinized starch is obtained.

[0085] Then take 10 g non-alcohol extrusion pre-gelatinized starch, placed in 50 mL centrifuge tube, add 30 mL 85% ethanol aqueous solution, adjust pH to 11.0 with 10% sodium hydroxide solution, then add 0.7 g propylene oxide, water bath reaction at 75℃ for 6 h, finally use 10% hydrochloric acid solution to adjust the pH value to 5.0 to terminate the reaction, after filtration, washing, drying, crushing, pre-gelatinized hydroxypropyl starch is prepared.

[0086] Comparative example 2

[0087] Comparative example 2 and example 1 are different in that step (1) is not carried out, and the original starch is directly subjected to hydroxypropyl substitution reaction; the specific steps are as follows:

[0088] Take 10 g cassava starch, placed in 50 mL centrifuge tube, add 30 mL 85% ethanol aqueous solution, adjust pH to 11.0 with 10% sodium hydroxide solution, then add 0.7 g propylene oxide, water bath reaction at 75℃ for 6 h, finally use 10% hydrochloric acid solution to adjust the pH value to 5.0 to terminate the reaction, after filtration, washing, drying, crushing, hydroxypropyl starch is prepared.

[0089] Comparative example 3

[0090] Selecting cassava starch, set the extruder solid feed rate of 600 g / h; configure the ethanol aqueous solution with 40% volume concentration and by setting the liquid feed rate, so that the mass ratio of starch and ethanol aqueous solution is 1:1.5. Extruder operating parameters: pre-mixing zone heating temperature is 60℃, gelatinization zone temperature is 95℃, forming zone temperature is 50℃, extruder speed 100 r / min. The extrudate is cut into 0.5 cm small section and placed in the oven 40℃ drying 20 h. Then take out and placed in the continuous cyclone grinder (screen size is 1.0 mm) for crushing, namely the V-type pre-gelatinized starch A is obtained.

[0091] Subsequently, 10 g of V-type pregelatinized starch A was taken and placed in a 50 mL centrifuge tube, 30 mL of 85% ethanol aqueous solution was added, 0.7 g of propylene oxide was added after the pH was adjusted to 11.0 with 10% sodium hydroxide solution, and the reaction was carried out in a water bath at 75°C for 6 h. Finally, the pH was adjusted to 5.0 with 10% hydrochloric acid solution to terminate the reaction, and the product was washed, dried, and crushed to obtain the pregelatinized hydroxypropyl starch.

[0092] The degree of substitution and the water separation rate of the hydroxypropyl starch prepared in Examples 1-6 and Comparative Examples 1-2 were detected, and the specific results are shown in Table 1 below:

[0093] Table 1 Examples 1-6 and Comparative Examples 1-2

[0094]

[0095] As can be seen from Table 1, the degree of substitution of the hydroxypropyl starch prepared in the examples is greater than 0.09 and as high as 0.157, which is significantly higher than that of the hydroxypropyl starch prepared in Comparative Examples 1-2, using only 7% propylene oxide addition. It can be seen that the V-type starch after alcohol-water extrusion has high reactivity and can be used to efficiently prepare hydroxypropyl pregelatinized starch. Since the hydroxypropyl group itself is relatively large, there is a certain steric hindrance between the sugar chains, and the hydroxypropyl group enhances the hydrogen bond between the starch molecules and the water molecules in the water system, so that the starch is more easily dispersed and dissolved.

[0096] The above examples are not intended to limit the scope of the present application, and the described steps are not intended to limit the execution order. Those skilled in the art can make obvious improvements to the present application based on the existing common knowledge, which also falls within the protection scope defined by the claims of the present application.

Claims

1. A process for the preparation of V-type pregelatinized hydroxypropyl starch, characterized in that, Comprising the following steps: (1) First, the starch and ethanol aqueous solution are extruded and then dried and crushed to obtain extrusion modified starch A; the concentration of ethanol in the ethanol aqueous solution is 30-50%, v / v; the mass ratio of starch to ethanol aqueous solution is 1:0.4-1; (2) The extrusion modified starch A is added to an ethanol solution, the pH is adjusted to alkaline, then propylene oxide is added for reaction, the pH is adjusted to acidic to terminate the reaction, then the product is filtered, washed and dried to obtain V-type pregelatinized hydroxypropyl starch.

2. The method of claim 1, wherein, The starch includes one or more of ordinary corn starch, rice starch, potato starch, wheat starch, barley starch and cassava starch.

3. The method as claimed in claim 1, characterized in that In step (1), the extrusion is performed by using an extruder; the parameter settings of the extruder are as follows: the heating temperature of the premixing zone is 50-60℃, the temperature of the gelatinization zone is 70-100℃, the temperature of the forming zone is 40-50℃, and the rotation speed of the extruder is 80-200 r / min.

4. The method as claimed in claim 1, characterized in that In step (2), the concentration of ethanol in the ethanol solution is 80-100%, v / v.

5. The method as claimed in claim 1, wherein, In step (2), the mass ratio of the extrusion modified starch A to the ethanol solution is 1:3-1:

4.

6. The method of claim 1, wherein, In step (2), the adjustment of the pH to alkaline is to adjust the pH value to 10.5-12.

0.

7. The method as claimed in claim 1, wherein, In step (2), the amount of propylene oxide added is 5-7% of the mass of the starch; in the reaction process of step (2), the temperature is maintained at 60-80℃ after the addition of propylene oxide, and the reaction is performed for 4-10 h.

8. The method of claim 1, wherein, In step (2), the adjustment of the pH to acidic is to adjust the pH value of the system to 4.0-6.

0.

9. A V-type pregelatinized hydroxypropyl starch, characterized in that, The V-type pregelatinized hydroxypropyl starch is prepared according to the method of any one of claims 1-8.

10. The V-type pregelatinized hydroxypropyl starch of claim 9 is used in the field of food.

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