Preparation method of freeze-thaw resistant stable modified starch

Abstract

The invention discloses a preparation method of freeze-thaw resistant stable modified starch, and relates to the field of material science and engineering. The raw material starch is subjected to a series of pretreatment and chemical modification, so that the finally obtained modified starch has excellent freeze-thaw resistance stability; in the pretreatment process, impurities are removed through screening, and the materials are crushed to specific granularity, so that a good basis is provided for subsequent reaction; the structure of the starch is further changed through microwave pretreatment, so that the starch is easier to accept chemical modification; in chemical modification, a specific modifier epoxypropane reacts with starch under specific conditions to form a more stable structure; in the frozen food industry, the modified starch can be used for effectively preventing the problems of poor taste, texture change, bleeding and the like of food in the freezing and thawing cycle process; even through multiple freezing and thawing cycles, the food can still keep good quality, the shelf life of the product is prolonged, and the satisfaction degree of consumers is improved.

Description

Technical Field

[0001] The invention relates to the field of material science and engineering, and in particular to a method for preparing freeze-thaw resistant stable modified starch. Background Art

[0002] In the field of materials science and engineering, the research and development of materials with specific properties has always been an important topic. As a widely used natural material, the optimization and modification of starch properties are of great significance. In the food industry, with the continuous expansion of the frozen food market, the demand for materials to maintain stability under freeze-thaw cycles has become more urgent.

[0003] Ordinary starch in frozen foods is prone to structural damage after repeated freezing and thawing. For example, products such as frozen dumplings will have problems such as broken skin and water leakage of fillings, which seriously affects the taste and quality of the food and greatly restricts the development of the frozen food industry. By modifying starch to be freeze-thaw stable, the quality and shelf life of frozen foods can be effectively improved.

[0004] In summary, the development of a preparation method for freeze-thaw stable modified starch has important practical significance and broad application prospects for materials science and engineering as well as food, cosmetics, papermaking and other fields. Summary of the invention

[0005] Based on this, the object of the present invention is to provide a method for preparing freeze-thaw stable modified starch to solve the technical problems mentioned in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing freeze-thaw resistant stable modified starch, comprising the following steps: S1: selecting raw starch for pretreatment; wherein the raw starch is one or more combinations of corn starch, potato starch, and cassava starch, and the pretreatment includes screening to remove impurities and crushing the starch to a particle size of less than 100 mesh; then pretreating the crushed starch with microwaves, with a microwave power of 300W to 500W and a treatment time of 5 minutes to 10 minutes; S2: placing the pretreated starch in a reaction vessel, adding a solvent according to a mass ratio of starch to a specific solvent of 1:2 to 1:3, at a temperature of 40°C to 60°C, the reaction time is 2 hours to 4 hours, adding a specific modifier to react, the specific solvent is a sodium hydroxide solution with a mass concentration of 10% to 15%, and the modifier is propylene oxide, and the addition amount thereof is 3% to 5% of the mass of the starch; S3: washing and drying the chemically modified starch to obtain freeze-thaw stable modified starch.

[0007] Furthermore, the washing is performed with deionized water for no less than 3 times.

[0008] Furthermore, the drying process is carried out at a temperature of 30° C. to 45° C., and the drying time is 4 hours to 6 hours.

[0009] Furthermore, during the pretreatment process, the impurity removal rate is not less than 95%.

[0010] Furthermore, the stirring speed during the chemical modification process is 100 to 150 revolutions per minute.

[0011] Furthermore, the water content of the modified starch after washing is not higher than 45%.

[0012] Furthermore, the moisture content of the modified starch after drying is not higher than 15%.

[0013] Furthermore, during the chemical modification process, the pH value of the reaction system is controlled at 10.5-11.5.

[0014] Furthermore, the washed starch is centrifuged before being dried, with the centrifugal speed being 2000 rpm to 3000 rpm.

[0015] Furthermore, during the chemical modification reaction, nitrogen is introduced intermittently to maintain the stability of the reaction system.

[0016] In summary, the present invention mainly has the following beneficial effects: 1. The present invention performs a series of pretreatments and chemical modifications on raw starch, so that the modified starch finally obtained has excellent freeze-thaw stability; in the pretreatment process, impurities are screened and removed and the starch is crushed to a specific particle size, which provides a good basis for subsequent reactions; microwave pretreatment further changes the structure of the starch, making it more receptive to chemical modification; in the chemical modification, a specific modifier propylene oxide reacts with the starch under specific conditions to form a more stable structure; in the frozen food industry, the use of this modified starch can effectively prevent the problems of poor taste, texture change and water precipitation in the freeze-thaw cycle of food; even after multiple freeze-thaw cycles, the food can still maintain good quality, extend the shelf life of the product, and improve consumer satisfaction.

[0017] 2. The modified starch in the present invention has the characteristics of freeze-thaw resistance and stability, so that it can be widely used in multiple fields; in the food field, it is not only suitable for frozen foods, but also can be applied to foods that need to maintain stability under different temperature conditions, such as refrigerated cakes, etc.; in the cosmetics field, it can provide stability for products and ensure the performance of cosmetics under different temperature environments; in the papermaking industry, it can improve the strength and durability of paper and adapt to various production and storage environments with temperature changes; this wide range of application fields provides enterprises with more development opportunities, reduces the risk of dependence on a single field, and also promotes technological progress and product upgrades in different industries.

[0018] 3. The present invention embodies the advantages of environmental protection and sustainability in multiple links. In the selection of solvent, the present invention adopts a sodium hydroxide solution with a mass concentration of 10% to 15%, which is relatively environmentally friendly and can be recycled and reused through appropriate treatment methods. Secondly, in the preparation process, the removal rate of impurities is required to be not less than 95%, which improves the utilization rate of raw materials and reduces the generation of waste. In addition, by strictly controlling the parameters of each link, such as drying temperature and time, washing times, etc., energy consumption is effectively controlled. This environmental protection and sustainability feature meets the requirements of modern society for green production, helps enterprises establish a good social image, and also contributes to sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a preparation flow chart of the present invention; Figure 2 This is a freeze-thaw stability comparison test effect diagram of the present invention; Figure 3 It is a schematic structural diagram of the reaction container of the present invention.

[0020] In the figure: 1. Reactor. DETAILED DESCRIPTION

[0021] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0022] The following describes an embodiment of the present invention based on its overall structure.

[0023] Embodiment 1 The preparation method of freeze-thaw stable modified starch provided in this embodiment is as follows: Figure 1 As shown, the following steps are included: S1: Select corn starch as raw material starch; during pretreatment, carefully screen and remove impurities to ensure that the impurity removal rate reaches 96%. Grind the starch to a particle size of less than 100 mesh;

[0024] Then, microwave pretreatment was performed, with the microwave power set to 400 W and the treatment time being 8 minutes; S2: The pretreated starch and water are mixed in a reactor 1 at a weight ratio of 1:1.2 to prepare powder milk, a sodium hydroxide solution with a mass concentration of 12% is added dropwise to the powder milk until the pH of the powder milk is 10.5-11.5, propylene oxide with a mass concentration of 4% of the starch is added as a modifier, and the mixture is reacted at a temperature of 50°C for 22 hours. During the reaction, the stirring speed is controlled at 120 revolutions per minute, and nitrogen is intermittently introduced during the chemical modification reaction to maintain the stability of the reaction system; S3: The chemically modified starch is washed with deionized water for 4 times, the washed starch is centrifuged at a speed of 2500 rpm, and then dried at 30°C for 6 hours to ensure that the moisture content of the modified starch after drying is not higher than 15%, and then crushed and passed through a 100-mesh sieve.

[0025] The freeze-thaw stable modified starch prepared in this embodiment is suitable for the frozen food industry. During the production and storage of frozen foods, the starch can effectively resist the adverse effects of freeze-thaw cycles and keep the taste and texture of the food stable. The advantage is that it extends the shelf life of frozen foods and improves the quality and market competitiveness of the products.

[0026] Embodiment 2 The preparation method of freeze-thaw stable modified starch provided in this embodiment is as follows: Figure 1 As shown, the following steps are included: S1: A combination of cassava starch and potato starch in a weight ratio of 3:1 is selected as raw material starch; during the pretreatment process, impurities are strictly screened and removed to achieve an impurity removal rate of 95%, and the starch is crushed to a particle size of less than 100 meshes. The microwave power of the microwave pretreatment is 450W and the treatment time is 6 minutes; S2: The pretreated starch and water are mixed in a reactor 1 at a weight ratio of 1:1.1 to prepare powder milk, a sodium hydroxide solution with a mass concentration of 12% is added dropwise to the powder milk until the pH of the powder milk is 10.5-11.5, propylene oxide with a mass concentration of 10% of the starch is added as a modifier, and the mixture is reacted at a temperature of 53° C. for 20 hours. During the reaction, the stirring speed is controlled at 120 revolutions per minute, and nitrogen is intermittently introduced during the chemical modification reaction to maintain the stability of the reaction system; S3: The modified starch was washed 4 times with deionized water, and the moisture content of the starch cake after washing was 45%. The starch cake was centrifuged at a speed of 2800 rpm, and then dried at 35°C for 5.5 hours, so that the moisture content of the dried modified starch was 13%. The starch cake was crushed and passed through a 100-mesh sieve.

[0027] The modified starch of this embodiment can be applied to the field of cosmetics. In cosmetics, the starch can maintain the stability of the product under different temperature conditions and prevent problems such as stratification and deterioration due to temperature changes. The benefit is that the quality and usage experience of cosmetics are improved, and consumers' demand for high-quality cosmetics is met.

[0028] The freeze-thaw stable modified starch prepared in this embodiment is also widely applicable in the frozen food industry. It can effectively resist the aging phenomenon caused by freeze-thaw cycles during the freeze-thaw storage stage of frozen food such as balls and slippers, and improve the stability of food taste and texture. Its advantage is that its surface remains moist after several freeze-thaw cycles, thereby extending the shelf life of the product.

[0029] Embodiment 3 The preparation method of freeze-thaw stable modified starch provided in this embodiment is as follows: Figure 1 As shown, the following steps are included: S1: corn starch is used as raw material starch; in the pretreatment stage, impurities are carefully screened, and the impurity removal rate reaches 97%; the starch is crushed to a particle size of less than 100 mesh, and the microwave power of microwave pretreatment is 350W, and the treatment time is 7 minutes; S2: The pretreated starch was placed in reactor 1, and a solvent was added at a mass ratio of 1:2.8 between starch and 13% sodium hydroxide solution; the reaction was carried out at 45°C for 3.5 hours, and propylene oxide was added at a mass ratio of 4.5% of the starch for modification; the stirring speed was set at 130 revolutions per minute, and the pH value of the reaction system was 9.5; S3: The chemically modified starch was washed with deionized water for 5 times; the washed starch was centrifuged at a speed of 2200 rpm; then dried at 40°C for 5 hours to ensure that the moisture content of the modified starch after drying was not higher than 14.5%; nitrogen was intermittently introduced during the chemical modification reaction. The modified starch of this embodiment has good application prospects in the papermaking industry; in the paper production process, adding the starch can improve the strength and durability of the paper, especially when experiencing temperature changes, the performance of the paper can still be kept stable; the benefit is that the quality of the paper is improved, the production cost is reduced, and the economic benefits of the enterprise are improved.

[0030] Embodiment 4 The preparation method of freeze-thaw stable modified starch provided in this embodiment is as follows: Figure 1As shown, the following steps are included: S1: potato starch is selected as raw material starch; during pretreatment, the impurity removal rate is ensured to be 95.5%; the starch is crushed to a particle size of less than 100 mesh, the microwave power of the microwave pretreatment is 480W, and the treatment time is 9 minutes; S2: Put the pretreated starch into reactor 1, add solvent according to the mass ratio of starch to 14% sodium hydroxide solution of 1:2.6; react at 58°C for 2.8 hours, add propylene oxide of 4.2% by mass of starch for modification; control the stirring speed at 140 revolutions per minute, and the pH value of the reaction system is 8.8; S3: The modified starch was washed 4 times with deionized water, and the water content of the starch after washing was 8%; centrifuged at a speed of 2600 rpm; then dried at 45°C for 4 hours, so that the water content of the modified starch after drying was 14.2%; during the chemical modification reaction, nitrogen was intermittently introduced.

[0031] The modified starch of this embodiment can be applied to the field of quick-frozen food packaging materials; using this starch in packaging materials can enhance the anti-freeze-thaw performance of the packaging and protect the quick-frozen food from the influence of temperature changes during transportation and storage; the benefit is that the quality and safety of the packaging are improved, and a better packaging solution is provided for the quick-frozen food industry.

[0032] Comparative Example 1 On the basis of Example 2, microwave pretreatment is not performed and the remaining steps remain unchanged.

[0033] Freeze-thaw stability comparison test: In order to verify the freeze-thaw stability effect of the freeze-thaw stable modified starch, a freeze-thaw stability comparison test was conducted on Example 1, Example 2 and Comparative Example 1. 40 g of dry weight of modified starch and 60 g of purified water were weighed and placed in a beaker, stirred in a 100°C water bath for 3 min, and after cooling, they were uniformly rolled into two balls of the same size. The balls were boiled in boiling water for 7 min, and the state was recorded after cooling. Then, they were frozen at -20°C, taken out to 25°C and left to stand for 2 h every 60 h, and the state characteristics were observed (see Figure 2 , from left to right in the figure are Example 1, Example 2, Comparative Example 1), and the results are shown in Table 1.

[0034] Table 1 Example 1 Example 2 Comparative Example 1 Before freezing Bright white color, moist surface, soft and elastic texture, slightly sticky Slightly yellow in color, moist surface, soft and elastic texture, slightly sticky The color is yellowish, the surface is moist, the texture is soft and elastic, and slightly sticky First freeze-thaw Bright white color, moist surface, soft and elastic texture, slightly sticky The color turns white, the surface becomes moist, the texture becomes soft and elastic, and the viscosity decreases The color turns white, the surface becomes moist, the texture becomes slightly harder and non-sticky Second freeze-thaw The surface wetness decreased slightly, and other indicators did not change significantly. No obvious change in appearance, the surface wetness is optimal, and it still maintains soft elasticity No obvious change in appearance, the texture becomes harder and non-sticky The third freeze-thaw The surface is dry and the elasticity is slightly reduced The surface is dry and the elasticity decreases significantly Obvious aging, cracking on the surface, and hardening of the texture The fourth freeze-thaw The surface is slightly peeling, but still maintains a little elasticity The surface is slightly peeling and the texture becomes hard The aging phenomenon is serious and the soft and elastic texture disappears Although an embodiment of the present invention has been shown and described, this specific embodiment is only an explanation of the present invention and is not a limitation of the invention. The specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. After reading this specification, those skilled in the art may make modifications, substitutions and variations to the embodiments without creative contribution as needed without departing from the principles and purpose of the present invention. However, as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A method for preparing freeze-thaw stable modified starch, characterized in that: The following steps are involved: S1: selecting raw starch for pretreatment; wherein the raw starch is one or more combinations of corn starch, potato starch, and cassava starch, and the pretreatment includes screening to remove impurities and crushing the starch to a particle size of less than 100 mesh; then pretreating the crushed starch with microwaves, with a microwave power of 300W to 500W and a treatment time of 5 minutes to 10 minutes; S2: placing the pretreated starch in a reactor (1), adding a solvent in a starch to specific solvent mass ratio of 1:2 to 1:3, adding a specific modifier to react at a temperature of 40° C. to 60° C. for a reaction time of 2 hours to 4 hours, wherein the specific solvent is a sodium hydroxide solution with a mass concentration of 10% to 15%, and the modifier is propylene oxide, and the amount of propylene oxide added is 3% to 5% of the mass of the starch; S3: washing and drying the chemically modified starch to obtain freeze-thaw stable modified starch.

2. The method for preparing freeze-thaw stable modified starch according to claim 1, characterized in that: The washing is performed with deionized water for no less than 3 times.

3. The method for preparing freeze-thaw stable modified starch according to claim 1, characterized in that: The drying process is performed at a temperature of 30° C. to 45° C., and the drying time is 4 to 6 hours.

4. The method for preparing freeze-thaw stable modified starch according to claim 1, characterized in that: During the pretreatment process, the impurity removal rate is not less than 95%.

5. The method for preparing freeze-thaw stable modified starch according to claim 1, characterized in that: The stirring speed during the chemical modification process is 100 to 150 revolutions per minute.

6. The method for preparing freeze-thaw stable modified starch according to claim 1, characterized in that: The water content of the modified starch after washing is not higher than 45%.

7. The method for preparing freeze-thaw stable modified starch according to claim 1, characterized in that: The moisture content of the dried modified starch is not higher than 15%.

8. The method for preparing freeze-thaw stable modified starch according to claim 1, characterized in that: During the chemical modification process, the pH value of the reaction system is controlled at 10.5 to 11.

5.

9. The method for preparing freeze-thaw stable modified starch according to claim 1, characterized in that: The washed starch is centrifuged before being dried, with the centrifugal speed being 2000 rpm to 3000 rpm.

10. The method for preparing freeze-thaw stable modified starch according to claim 1, characterized in that: During the chemical modification reaction, nitrogen is introduced intermittently to maintain the stability of the reaction system.

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