CN107573421B - Preparation method of high-performance modified starch - Google Patents
Preparation method of high-performance modified starch Download PDFInfo
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Abstract
The invention discloses a preparation method of high-performance modified starch, which comprises the steps of filling dry starch into a sealed bag, firstly carrying out forward surface irradiation treatment at low dosage rate on the sealed bag, then carrying out oxygenation on the sealed bag, then regulating the shape of the oxygenated sealed bag, and finally carrying out reverse surface irradiation treatment at high dosage rate on the sealed bag to obtain the high-performance modified starch. The method for preparing the high-performance modified starch adopts comprehensive irradiation technologies such as oxygenation, alternate irradiation at different dose rates, packaging and shaping, overturning and the like, so that the radiation dose nonuniformity is less than 1.1, the viscosity fluctuation rate of the starch after irradiation modification is less than 10%, the irradiation efficiency is high, and the cost is reduced.
Description
Technical Field
The invention relates to the technical field of starch modification and application thereof, in particular to a method for preparing modified starch with moderate viscosity and excellent usability by applying a high-energy ray radiation technology and auxiliary means.
Background
The chemical composition of starch is heterogeneous, and mainly comprises amylose, amylopectin and lightly branched amylose, and in addition, associated components such as protein, lipid, ash and moisture, and starch granules have a semi-crystalline structure. These complex structures of starch determine the complexity of the action of radiation on starch. The action of high-energy radiation on starch is mainly carried out in two ways: firstly, rays directly act on starch molecules; the second is indirectly acting on starch molecules through free radical reactions. The starch molecule is destroyed in structure and changed in physical and chemical properties as a result of the action. Research has shown that: after the starch is radiated, the starch chain is broken, the polymerization degree is reduced, and the starch is sensitive to the action of enzyme. Radiation-modified starch has been successfully used in textile applications. The modified starch slurry has good adhesion, and the tensile strength, toughness and solubility of the slurry film are improved, so that the modified starch slurry can be mixed with PVA slurry or can replace part of PVA. Not only greatly reduces the slashing cost, but also reduces the pollution of PVA to the environment. At present, the Co-60 gamma ray irradiation method is adopted more frequently. Due to the problems of starch type and irradiation process (dose rate and unevenness), the irradiation modified starch has high intrinsic viscosity dispersity, and the coupling force of the product is unstable.
Patent CN201510951867.X discloses a preparation method of irradiation chemical composite modified starch, and provides a method for firstly irradiating starch by 2-12kGy and then esterifying, so that gelatinization temperature can be reduced, and binding force can be improved. Patent CN200610019748.1 discloses a preparation method of radiation-initiated cationic starch, and provides a method for etherifying starch with water content of 12-15% by using a liquid etherifying agent and then irradiating, wherein the dose is 3-15kGy. Patent CN201110316350.5 discloses a radiation modified starch biodegradable material and a preparation method thereof, and provides a method for preparing the modified starch biodegradable material by stirring and mixing starch, succinic anhydride and glycerol, vacuum packaging and then irradiating for 20-40 kGy. The above starch irradiation modification method is carried out in a solution system or in a wet state, and the final product needs drying treatment.
Therefore, according to the application target requirement, a proper radiation modification condition is selected, and the process flow is simplified, so that the cost reduction is a key problem to be solved in the development of the starch radiation modification industry.
Disclosure of Invention
The invention aims to solve the problems of unstable product quality, high irradiation cost and the like caused by high radiation modified viscosity dispersity of starch, and provides a preparation method of high-performance modified starch.
The object of the invention can be achieved by the following measures:
a preparation method of high-performance modified starch comprises the following steps: and (2) filling the dry starch into a sealed package, performing forward surface irradiation treatment at a low dosage rate on the sealed package, then oxygenating the sealed package, regulating the shape of the oxygenated sealed package, and finally performing reverse surface irradiation treatment at a high dosage rate on the sealed package to obtain the high-performance modified starch.
The high-performance modified starch obtained by the method can accurately control the viscosity value of the obtained modified starch to a certain extent, the obtained modified starch has a stable viscosity value range, the viscosity fluctuation rate can be controlled within 10 percent, and the high-performance modified starch can be applied to the production of various high-quality products according to different requirements.
The irradiation treatment in the method, especially the reverse surface irradiation treatment, has a high requirement on the dose nonuniformity of irradiation, which can be made to be less than 1.2, and more preferably to be less than 1.1, by means of regulating the shape of the oxygenated sealed bag, or turning the orientation of the packaging bag to ensure the irradiation uniformity of each part, and the like. Experiments show that the absorbed dose nonuniformity of the product has a fluctuation relation with the viscosity of the starch product, the radiation dose nonuniformity directly influences the consistency of the starch viscosity (see figure 2), and when the dose nonuniformity is more than 1.2, the fluctuation rate of the product viscosity is more than 25%, and the performance of the modified starch is seriously influenced. Therefore, the difference between the maximum product absorbed dose and the minimum product absorbed dose is controlled within a certain range by various conditions in the invention.
The starch in the present invention may be various common starches such as corn starch, wheat starch, tapioca starch, potato starch or sweet potato starch, and the like. The method has certain requirements on the water content of the starch, the starch is required to be dry starch, and further, the water content of the dry starch is below 8%, preferably 7-8%. The dry starch in the method can be obtained by drying common starch with the water content of 10-20%, and the drying treatment can be any method such as microwave, infrared drying, sun drying, freeze drying and the like.
The radiation treatment in the method may consist of Co 60 And Cs 137 The gamma rays generated or the electron beams or the X rays generated by the electron accelerator. The dose rate is not as high as that described above in the case of electron beam processing using an electron accelerator.
The sealed bag in the method is a packaging bag or a packaging box which can seal the air and water inside and outside the bag and can bear certain pressure. In the method, the sealed package needs to be filled or packed to the degree that the sealed package is shaped, and oxygen needs to be filled into the sealed package in the irradiation treatment process, so that an air inlet device capable of supplementing oxygen and a sealing device for maintaining the pressure of the oxygen in the sealed package need to be reserved in the sealed package.
In a preferred scheme, the sealing bag is a shaped sealing bag, such as a paper bag, the inner surface of the sealing bag is provided with a waterproof film, and the shape of the sealing bag is a rectangular flat shape; the oxygenated bales are also shaped to a rectangular flat shape when shaped. In the embodiment of the invention, a rectangular flat paper bag with a waterproof film inside is adopted, the thickness of the bag is less than 10cm, and the length, the width and the thickness of each bag are respectively not more than 40cm, 30cm and 8cm.
The measurement of the absorbed dose or dose rate of the product in the present method may be performed by direct or indirect methods. The method provides a specific measuring method, namely at least 2 or more dosimeters for tracking and determining the absorbed dose of the product are arranged on the shaped sealing bag, and the absorbed dose or the dose unevenness and the like of the product are accurately measured in time.
The molecular structure of the starch contains more hydroxyl groups, and the starch has stronger water absorption. Under normal atmospheric conditions, corn starch has a water content of about l2%, and potato starch is still higher. The complex structure and properties of starch and the presence of moisture and oxygen determine the radiation degradation process of the starchComplexity. The radiation treatment of the starch at room temperature leads the molecules in the amorphous area to be loosely arranged, oxygen can permeate into the amorphous area to be combined with free radicals to generate peroxide, and the macromolecular chains of the starch are cut off. The radiation not only oxidizes partial hydroxyl and reducing aldehyde end groups of the starch into carboxyl groups, but also can cut off C 2 -C 3 And finally oxidized to carboxyl groups.
The total product absorbed dose of the irradiation treatment of the forward surface and the irradiation treatment of the reverse surface is 1-10 kGy, and the method can be adaptively adjusted according to the amount of starch raw materials and the properties of required products. We have found that the radiation dose rate in the irradiation treatment has a significant effect on the relative viscosity of the destructured starch, for example, the viscosity of the starch decreases more rapidly with the same dose rate irradiation (see figure 3). Tests have found that beyond the total product absorption dose range claimed in the present invention, the starch viscosity values are higher or lower at too high or too low irradiation doses, so that the resulting products do not meet the product performance requirements. Under the coordination of other conditions, the invention maintains the relative viscosity of the final product at a reasonable degree through the alternate irradiation of different dose rates, not only ensures that the viscosity fluctuation rate of the starch after irradiation modification is small, but also can improve the irradiation efficiency and reduce the cost.
In a preferable embodiment, the dose rate of the forward surface irradiation treatment is 0.2 to 1.0 kGy/hour, the dose rate of the reverse surface irradiation treatment is 0.8 to 4.0 kGy/hour, and the dose rate of the forward surface irradiation treatment is lower than the dose rate of the reverse surface irradiation treatment.
The irradiation time in the invention can be adjusted according to the total product absorbed dose and the dose rate in different steps, but the requirement in the invention is that the irradiation treatment time of the forward surface is far longer than that of the reverse surface, and the method ensures that the performance and the irradiation efficiency of the final product are maintained at high level by adjusting the irradiation time and adjusting other conditions such as dose rate. And taking the total irradiation time of the forward surface irradiation treatment and the reverse surface irradiation treatment as t, wherein the irradiation time of the forward surface irradiation treatment is 0.7-0.9 t, and the irradiation time of the reverse surface irradiation treatment is 0.3-0.1 t (the sum of the irradiation treatment time of the forward surface and the reverse surface is 1 t). In a preferred embodiment, the irradiation time of the forward surface irradiation treatment is 0.8t, and the irradiation time of the reverse surface irradiation treatment is 0.2t.
It was found in the present invention that starch viscosity decreases sharply with increasing radiation dose, and that oxygenation irradiation may be able to accelerate starch viscosity decrease relative to air irradiation (see fig. 1). However, we have found in experiments that oxygenation before irradiation begins not only wastes a large amount of oxygen, but also increases the viscosity fluctuation rate, so that the control conditions for the viscosity of starch in the preparation process become harsh and difficult. In the method, oxygen is supplemented after the irradiation treatment of the forward surface and before the irradiation treatment of the reverse surface, so that the packaging and sizing are facilitated, residual oxygen (the oxygen content in the air is 21%) of the original starch is fully utilized, the oxygen charging amount is reduced, and the accurate control of the product performance is possible. In the method, the inside of the sealed bag is charged with oxygen until the oxygen partial pressure in the bag becomes 0.08MPa or more, preferably 0.09MPa or more, and more preferably 0.1MPa or more.
The invention provides a specific preparation method of high-performance modified starch, which comprises the following steps: filling starch with the water content of below 8% into a sealed bag for shaping, and respectively carrying out irradiation treatment on a forward surface and a reverse surface on the sealed bag, wherein the total product absorbed dose is 1-10 kGy, and the total irradiation time is t; wherein the irradiation treatment process comprises the steps of firstly carrying out forward surface irradiation treatment on the sealed package at the dose rate of 0.2-1.0 kGy/hour for 0.7-0.9 t; then, the sealed bag is oxygenated, so that the partial pressure of oxygen in the bag is over 0.08 MPa; regulating the shape of the oxygenated sealed bag; finally, the oxygenated sealed package is irradiated on the reverse surface at a dose rate of 0.8-4.0 kGy/hour for 0.3-0.1 t.
The invention further provides a preparation method of the more specific high-performance modified starch, which comprises the following steps: it comprises the following steps:
1) Drying common starch with water content of 10-20%, and stirring to water content below 8%;
2) Filling the dried starch into a shapeable sealed packaging bag, and arranging at least 2 dosimeters on the packaging bag to track and measure the absorbed dosage of the product;
3) Performing double-sided irradiation treatment on the forward surface and the reverse surface of the starch packaged in a sealing way, wherein the absorbed dose of a product is 1-10 kGy, and the total irradiation time is t;
4) Firstly, carrying out forward surface irradiation treatment on starch packaged in a sealing way, wherein the dosage rate is 0.2-1.0 kGy/hour, and the time is 0.8t;
5) Supplementing oxygen to the sealed package starch subjected to the positive surface irradiation treatment to enable the oxygen partial pressure in the sealed package human bag to be more than 0.1MPa;
6) Packaging and shaping the oxygenated starch in sealed bags to keep regular rectangular flat shapes, and turning the orientation of the packaging bags to ensure that all parts are irradiated uniformly, wherein the dose unevenness is not more than 1.1;
7) Then carrying out reverse surface irradiation treatment on the oxygenated and regulated packaged starch, wherein the dose rate is 0.8-4.0 kGy/hour, and the irradiation time is 0.2t of the total time;
8) And storing the irradiated modified starch under the moisture-proof and damp-proof conditions.
After the product is prepared, the absorbed dose and the starch viscosity of the product can be further measured, the dose nonuniformity can be calculated, and the fluctuation rate of the product viscosity can be analyzed.
The invention has the beneficial effects that:
1. the obtained modified starch has uniform viscosity and good consistency. Good quality slurry is required to have good viscosity stability, and the viscosity fluctuation rate of the slurry is generally ensured to be less than 15%. Because the irradiation absorbed dose is uniform, the ratio of the maximum absorbed dose to the minimum absorbed dose is less than 1.1, and the low moisture content is favorable for controlling the indirect radiation effect, the viscosity fluctuation rate of the modified starch prepared by the invention is within 10 percent, the viscosity stability is more than 90 percent, and other conventional indexes meet the requirements of B12309-90 first-grade products.
2. The oxygenation treatment reduces the absorbed dose of products required by starch modification, and correspondingly reduces the production cost. Compared with the irradiation in the air, the irradiation of the starch is easy to cause the radiolysis reaction due to the existence of high-concentration oxygen, so that the absorbed dose of a product required by degrading starch macromolecules is reduced.
3. The total irradiation time t is reduced. Lower irradiation dose rates favor a reduction in starch viscosity. The product adopts irradiation on the front side and the back side, the first time adopts low dose rate (0.2-1.0 kGy/hour) irradiation, and the second time adopts high dose rate (0.8-4.0 kGy/hour) irradiation. Under the condition that the absorbed dose and the irradiation degradation effect of the product are kept unchanged, compared with the irradiation with single low dose rate, the total irradiation time t is reduced.
4. The oxygen consumption is saved. And oxygen is supplemented after irradiation, so that the packaging and shaping are facilitated, the residual oxygen (the oxygen in the air accounts for 21%) of the original starch is fully utilized, and the oxygen filling amount is reduced.
5. And energy is saved. Because the method adopts dry irradiation, the final product can be obtained after irradiation, and drying and sieving are not needed.
6. No chemical additive. Compared with a chemical method, solution reaction is carried out without adding any oxidant, residue treatment is not needed, and pollution discharge is avoided.
The method for preparing the high-performance modified starch adopts comprehensive irradiation technologies such as oxygenation, alternate irradiation at different dose rates, packaging and shaping, overturning and the like, so that the radiation dose nonuniformity is less than 1.1, the viscosity fluctuation rate of the starch after irradiation modification is less than 10%, the irradiation efficiency is high, and the cost is reduced.
Drawings
FIG. 1 graph of the effect of oxygen-containing irradiation on starch viscosity;
FIG. 2 is a graph of the variation in absorbed dose of the product as a function of the variation in viscosity of the starch;
FIG. 3 graph of the effect of dose rate on starch viscosity (6 kGy).
Detailed Description
The invention is further described below with reference to the figures and examples. However, the scope of the present invention is not limited to the following examples.
Example 1:
taking corn starch with the water content of 12.3 percent to carry out microwave drying treatment, and stirring for not less than 20 times, wherein the water content of each part is 8 percent; packaging the dried starch in a shaped sealing bag, wherein the length multiplied by the width multiplied by the thickness =40cm multiplied by 30cm multiplied by 8cm, and placing 2 dosimeters on the outer side of the packaging bag in advance; the absorption dose of the preset product is 1kGy, and the total irradiation time is 3.125 hours; placing the starch bag into a special irradiation box, and performing positive surface irradiation treatment by adopting gamma rays, wherein the dose rate is 0.2 kGy/hour, and the irradiation time is 2.5 hours; then, oxygenating the irradiated starch in the sealed bag, and supplementing oxygen to 0.1MPa; shaping to keep the surface of the cuboid flat; and (3) reversing the direction and the direction of the oxygenated and shaped sealed packaging bag, and performing reverse surface irradiation treatment at the dose rate of 0.8 kGy/hour for 0.625 hours. The total irradiation time was 3.125 hours. The modified starch after the irradiation treatment is taken out and stored in a warehouse, and is moisture-proof and damp-proof.
The minimum product absorbed dose of the radiation modified starch is 1.0kGy, the maximum product absorbed dose is 1.07kGy, and the unevenness of the product absorbed dose is 1.07; the maximum value and the minimum value of the viscosity of the corn starch are 767.06mPa.s and 716.88mPa.s, and the fluctuation rate of the viscosity of the corn starch is 6.5%.
Comparative example 1
The procedure of example 1 was followed, wherein the microwave drying treatment was not carried out, and the modified starch after the irradiation treatment was taken out and stored in a warehouse for moisture prevention and prevention.
The irradiation modified starch is not subjected to microwave drying treatment, the minimum product absorbed dose is 0.95kGy, the maximum product absorbed dose is 1.07kGy, and the product absorbed dose unevenness is 1.13; the maximum value of the viscosity of the corn starch is 907.84mPa.s, the minimum value of the viscosity of the corn starch is 803.34mPa.s, and the fluctuation rate of the viscosity of the corn starch is 11.5%.
Comparative example 2
Taking corn starch with the water content of 12.3 percent to carry out microwave drying treatment, and stirring for not less than 20 times, wherein the water content of each part is 8 percent; packaging the dried starch in a shaping sealing bag, wherein the length multiplied by the width multiplied by the thickness =40cm multiplied by 30cm multiplied by 8cm, and placing 2 dosimeters on the outer side of the packaging bag in advance; the absorption dose of the predetermined product is 1kGy, and the total irradiation time is 3.125 hours; the starch bag is supplemented with oxygen at a time until the partial pressure reaches 0.12MPa, and then is placed into a special irradiation box, and the forward surface irradiation treatment is carried out by adopting gamma rays, wherein the dose rate is 0.32 kGy/hour, and the irradiation time is 1.5625 hours; then shaping the irradiated sealing bag to maintain the cuboid shape as much as possible; the sealed packaging bag is subjected to reverse surface irradiation treatment by reversing the orientation and the direction, the dose rate is 0.32 kGy/hour, and the irradiation time is 1.5625 hours. The total irradiation time was 3.125 hours. The modified starch after the irradiation treatment is taken out and stored in a warehouse, and is moisture-proof and damp-proof.
In the example, the irradiation is firstly oxygenated, and then the forward and reverse irradiation is carried out, wherein the minimum product absorbed dose of the irradiated and modified starch is 1.0kGy, the maximum product absorbed dose is 1.2kGy, and the product absorbed dose unevenness is 1.2; the maximum value and the minimum value of the viscosity of the corn starch are 875.09mPa.s and 729.24mPa.s respectively, and the fluctuation rate of the viscosity of the corn starch is 16.7%.
Comparative example 3
Taking corn starch with the water content of 12.3 percent to carry out microwave drying treatment, and stirring for not less than 20 times, wherein the water content of each part is 8 percent; packaging the dried starch in a shaped sealing bag, wherein the length multiplied by the width multiplied by the thickness =40cm multiplied by 30cm multiplied by 8cm, and placing 2 dosimeters on the outer side of the packaging bag in advance; the absorption dose of the preset product is 1kGy, and the total irradiation time is 3.225 hours; placing the starch bag into a special irradiation box, and performing positive surface irradiation treatment by adopting gamma rays, wherein the dose rate is 0.16 kGy/hour, and the irradiation time is 3.125 hours; then, oxygenating the irradiated starch in the sealed bag, and supplementing oxygen to 0.1MPa; shaping to keep the cuboid surface flat; and (3) reversing the direction and the direction of the oxygenated and shaped sealed packaging bag, and performing reverse surface irradiation treatment at the dose rate of 5 kGy/hour for 0.1 hour. The total irradiation time was 3.225 hours. The modified starch after the irradiation treatment is taken out and stored in a warehouse, and is moisture-proof and damp-proof.
In the example, the forward and reverse irradiation dose rate and the irradiation time are beyond the range required by the invention, the minimum product absorbed dose of the obtained modified starch product is 0.98kGy, the maximum product absorbed dose is 1.21kGy, and the unevenness of the product absorbed dose is 1.23; the maximum value and the minimum value of the viscosity of the corn starch are 881.76mPa.s and the fluctuation rate of the viscosity of the corn starch is 18.7 percent.
Compared to example 1, the products of comparative examples 1, 2, 3 have an absorbed dose non-uniformity of greater than 1.1; the viscosity fluctuation rate of the corn starch is more than 10 percent.
Example 2:
taking corn starch with the water content of 12.3 percent to carry out infrared drying treatment, and stirring for not less than 20 times, wherein the water content of each part is 6.7 percent; packaging the dried starch in a shaping sealing bag, wherein the length multiplied by the width multiplied by the thickness =38cm multiplied by 28cm multiplied by 7.5cm is preset for placing 2 dosimeters outside the packaging bag; the predetermined product absorbed dose is 3kGy; placing the starch bag into a special irradiation box, and performing forward surface irradiation treatment by adopting X rays, wherein the dose rate is 0.75 kGy/hour, and the irradiation time is 2 hours; then, oxygenating the irradiated starch in the sealed bag, and supplementing oxygen to the partial pressure of 0.1MPa; shaping to keep the surface of the cuboid flat; and (3) reversing the direction and the direction of the oxygenated and shaped sealed packaging bag, and performing reverse surface irradiation treatment at the dose rate of 3 kGy/hour for 0.5 hour. The total irradiation time was 2.5 hours. The modified starch after the irradiation treatment is taken out and stored in a warehouse, and is moisture-proof and damp-proof.
And (3) measuring results: the minimum product absorbed dose of the modified starch is 3.0kGy, the maximum product absorbed dose is 3.27kGy, and the dose unevenness is 1.09; the viscosity of the corn starch has a maximum value of 309.87mPa.s, a minimum value of 284.28mPa.s and a fluctuation rate of 8.3 percent.
Example 3:
drying corn starch with water content of 12.3% in the sun, and stirring for at least 20 times to obtain water content of 8.0%; packaging the dried starch in a shaped sealed bag, wherein each bag has a length multiplied by a width multiplied by a thickness =40cm multiplied by 30cm multiplied by 5cm, and at least 3 dosimeters are pre-arranged on the outer side of the packaging bag; the predetermined product absorbed dose is 6kGy; placing the starch bag into a special irradiation box, and performing positive surface irradiation treatment by adopting an electron beam for 10 minutes; then, oxygenating the irradiated starch in the sealed bag, and supplementing oxygen to 0.1MPa; shaping to keep the surface of the cuboid flat; the oxygenated and shaped sealed packaging bag is turned upside down and subjected to reverse surface irradiation treatment for 2.5 minutes in conveying time. The modified starch after the irradiation treatment is taken out and stored in a warehouse, and is moisture-proof and damp-proof.
And (3) measuring results: the minimum product absorbed dose of the modified starch is 6.0kGy, the maximum product absorbed dose is 6.6kGy, and the dose unevenness is 1.1; the viscosity of the corn starch has a maximum value of 244.73mPa.s and a minimum value of 222.48mPa.s, and the fluctuation rate of the viscosity of the starch is 9.1%.
Comparative example 4
Packaging 3 bags of corn starch with a water content of 12.3% by using a common plastic bag, wherein the length multiplied by the width multiplied by the thickness =60cm multiplied by 40cm multiplied by 20cm, and 2 dosimeters are placed in advance on the outer side of each packaging bag; the preset irradiation doses are 1, 3 and 6kGy respectively; placing the starch bag into a special irradiation box, and respectively adopting gamma rays, X rays and electron beams to carry out forward surface irradiation treatment; the dose rate is 0.5 kGy/h when gamma rays and X rays are treated, the irradiation time is 1 hour and 3 hours respectively, and the corresponding delivery time of electron beam irradiation is 10 minutes; and then reversing the direction and the direction, and carrying out reverse surface irradiation treatment, wherein the dose rate is 0.5 kGy/h, the irradiation time is 1 hour and 3 hours, and the corresponding conveying time of electron beam irradiation is 10 minutes. After irradiation treatment, the starch is taken out and stored in a warehouse, and is moisture-proof and damp-proof.
The results are shown in Table 1. Comparative example 4 has a starch viscosity dispersion of more than 25% in both conventional packaging and irradiation processes, while the starch viscosity dispersions of examples 1, 2 and 3 have less than 10% at the same predetermined irradiation dose.
TABLE 1 results of sample determination of common corn starch after different ray treatments
Example 4:
carrying out infrared drying treatment on wheat starch with the water content of 13.3%, and stirring for at least 20 times, wherein the water content of each part is 6.7%; packaging the dried starch in a shaping sealing bag, wherein the length multiplied by the width multiplied by the thickness =38cm multiplied by 28cm multiplied by 7.8cm of each bag is preset with 2 dosimeters outside the packaging bag; the predetermined product absorbed dose is 3.2kGy; placing the starch bag into a special irradiation box, and performing positive surface irradiation treatment by adopting gamma rays, wherein the dose rate is 0.8 kGy/hour, and the irradiation time is 2 hours; then, oxygenating the irradiated starch in the sealed bag, and supplementing oxygen to 0.1MPa; shaping to keep the surface of the cuboid flat; and (3) inverting the orientation and the direction of the oxygenated and shaped sealed packaging bag, and performing reverse surface irradiation treatment, wherein the dose rate is 3.2 kGy/hour, and the irradiation time is 0.5 hour. The total irradiation time was 2.5 hours. The modified starch after the irradiation treatment is taken out and stored in a warehouse, and is moisture-proof and damp-proof.
And (3) measuring results: the minimum product absorbed dose of the modified starch is 3.2kGy, the maximum product absorbed dose is 3.46kGy, and the dose unevenness is 1.08; the maximum value of the viscosity of the wheat starch is 1313.11mPa.s, the minimum value is 1215.84mPa.s, and the fluctuation rate of the viscosity of the wheat starch is 7.4%.
Example 5:
carrying out infrared drying treatment on potato starch with the water content of 18.1%, and stirring for at least 20 times, wherein the water content of each part is 8.0%; packaging the dried starch in a shaping sealing bag, wherein the length, the width and the thickness of each bag are =39.5cm, 27cm and 7.2cm, and 2 dosimeters are arranged on the outer side of the packaging bag in advance; the absorption dose of the predetermined product is 7.0kGy, and the total irradiation time is 4.375 hours; placing the starch bag into a special irradiation box, and performing positive surface irradiation treatment by adopting gamma rays, wherein the dose rate is 1.0 kGy/hour, and the irradiation time is 3.5 hours; then, oxygenating the irradiated starch in the sealed bag, and supplementing oxygen to 0.1MPa; shaping to keep the surface of the cuboid flat; and (3) reversing the direction and the direction of the oxygenated and shaped sealed packaging bag, and performing reverse surface irradiation treatment at the dose rate of 4.0 kGy/hour for 0.875 hour. The total irradiation time was 4.375 hours. The modified starch after the irradiation treatment is taken out and stored in a warehouse, and is moisture-proof and damp-proof.
And (3) measuring results: the minimum product absorbed dose of the modified starch is 7.0kGy, the maximum product absorbed dose is 7.7kGy, and the dose unevenness is 1.1; the maximum value of the viscosity of the potato starch is 528.0mPa.s, the minimum value of the viscosity of the potato starch is 480.0mPa.s, and the fluctuation rate of the viscosity of the potato starch is 9.1%.
Comparative example 5:
respectively packaging wheat and potato starch with water content of 13.3% and 18.1% in 3 bags with common plastic bags, wherein the length multiplied by the width multiplied by the thickness =60cm multiplied by 38.5cm multiplied by 25cm, and 2 doses are respectively pre-placed on the outer side of each packaging bag; the preset irradiation doses are 3.2 and 7kGy respectively; placing the starch bag into a special irradiation box, and performing positive surface irradiation treatment by adopting gamma rays; the dose rate is 1.28 and 1.6 kGy/h respectively during gamma ray treatment, and the irradiation time is 1.25 and 2.1875 hours respectively; and reversing the direction and the direction, and performing reverse surface irradiation treatment, wherein the dose rate and the irradiation time are the same as those of the forward surface irradiation. The total irradiation time was 2.5 and 4.375 hours, respectively. After irradiation treatment, the starch is taken out and stored in a warehouse, and is moisture-proof and damp-proof.
The measurement results are shown in Table 2. Comparative example 5 the viscosity dispersivity of wheat starch and potato starch was greater than 30% under conventional packaging and irradiation process, while the viscosity dispersivity of starch of examples 4 and 5 under the same irradiation dose was less than 10%.
TABLE 2 results of samples of common wheat/potato starch treated with gamma rays
The parts not involved in influencing the present invention are the same as or can be implemented using the prior art.
Claims (7)
1. A preparation method of high-performance modified starch is characterized in that dry starch is filled into a paper sizing sealing bag, forward surface irradiation treatment with low dose rate is firstly carried out on the sealing bag, then oxygen is added into the sealing bag until the oxygen partial pressure in the sealing bag reaches more than 0.1MPa, then the oxygenated sealing bag is regular in shape and is rectangular flat in shape, and finally reverse surface irradiation treatment with high dose rate is carried out on the sealing bag, so that the high-performance modified starch is obtained; the irradiation of each part of the sealing bag is kept uniform in the process of the reverse surface irradiation treatment, and the dose unevenness is below 1.1; the water content of the dry starch is below 8%, the dose rate of the forward surface irradiation treatment is 0.2-1.0 kGy/h, the dose rate of the reverse surface irradiation treatment is 0.8-4.0 kGy/h, the dose rate of the forward surface irradiation treatment is lower than that of the reverse surface irradiation treatment, the total irradiation time of the forward surface irradiation treatment and the reverse surface irradiation treatment is t, the irradiation time of the forward surface irradiation treatment is 0.7-0.9 t, and the irradiation time of the reverse surface irradiation treatment is 0.3-0.1 t; the length, the width and the thickness of each bag of the sealed bag are respectively not more than 40cm, 30cm and 8cm.
2. The method according to claim 1, characterized in that the starch is any one of corn starch, wheat starch, tapioca starch, potato starch or sweet potato starch; the water content of the dry starch is 7-8%; the dry starch is obtained by drying starch with the water content of 10-20%.
3. The method of claim 1 wherein a plurality of dosimeters are provided on said paper-based shaped sealed pouch for tracking absorbed doses of a product.
4. The method of claim 1, wherein the sealed bag is a paper bag having a waterproof film on an inner surface thereof and having a rectangular flat shape; the oxygenated sealed bag is also shaped to a rectangular flat shape when shaped.
5. The method according to claim 1, wherein the absorbed dose of the forward side irradiation treated product and the reverse side irradiation treated product is 1 to 10kGy; the dose rate of the forward surface irradiation treatment is 0.2-1.0 kGy/h, the dose rate of the reverse surface irradiation treatment is 0.8-4.0 kGy/h, and the dose rate of the forward surface irradiation treatment is lower than that of the reverse surface irradiation treatment.
6. The method according to claim 1, wherein starch with a water content of less than 8% is filled into a sealed bag for shaping, the sealed bag is subjected to irradiation treatment on the front surface and the reverse surface respectively, the absorbed dose of the product is 1-10 kGy, and the total irradiation time is t; wherein the irradiation treatment process comprises the steps of firstly carrying out irradiation treatment on the positive surface of the sealed bag at the dose rate of 0.2-1.0 kGy/hour for 0.7-0.9 t; then, the sealed bag is oxygenated, so that the oxygen partial pressure in the bag is over 0.1MPa; regulating the shape of the oxygenated sealed bag; finally, the oxygenated sealed bag is subjected to reverse surface irradiation treatment with the dosage rate of 0.8-4.0 kGy/hour, and the irradiation time is 0.3-0.1 t.
7. Method according to claim 1, characterized in that it comprises the following steps:
1) Drying common starch with the water content of 10-20%, and stirring uniformly to ensure that the water content of each part is below 8%;
2) Filling the dried starch into a settable sealed bag, and laying at least 2 dosimeters on the bag to track and determine the absorbed dosage of the product;
3) Performing double-sided irradiation treatment on the forward surface and the reverse surface of the sealed bagged starch, wherein the absorbed dose of the product is 1-10 kGy, and the total irradiation time is t;
4) Firstly, carrying out forward surface irradiation treatment on starch in a sealed bag at a dose rate of 0.2-1.0 kGy/hour for 0.8t;
5) Supplementing oxygen to the starch in the sealed bag after the positive surface irradiation treatment, so that the oxygen partial pressure in the sealed bag is over 0.1MPa;
6) Packaging and shaping the oxygenated starch in sealed bags to keep regular rectangular flat shapes, and turning the orientation of the packaging bags to ensure that all parts are irradiated uniformly, wherein the dose unevenness is not more than 1.1;
7) Then carrying out reverse surface irradiation treatment on the oxygenated and regulated packaged starch, wherein the dose rate is 0.8-4.0 kGy/hour, and the irradiation time is 0.2t of the total time;
8) And storing the irradiated modified starch under the moisture-proof and damp-proof conditions.
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