Thermal inhibition porous starch as well as preparation method and application thereof

Abstract

The invention discloses thermal inhibition porous starch as well as a preparation method and application thereof, and belongs to the technical field of food and medicine processing. The preparation method comprises the following steps: adding water into waxy starch to prepare starch milk, heating to 36-55 DEG C, adding 0.5-5% of an alkalizer, adjusting the pH value to 7.5-9.5, and stirring for 1-4 hours to obtain alkalized starch milk; the preparation method comprises the following steps: adding the starch into a reaction kettle, carrying out centrifugal dewatering, drying for 6-12 hours at 105-125 DEG C to obtain ultra-dry alkalized starch, and carrying out dry heat reaction for 2-16 hours at 145-175 DEG C under the vacuum degree of-0.045--0.065 Mpa to obtain heat-inhibited starch; adding a buffer solution into the thermal inhibition starch, heating to 45-55 DEG C, adding 10-20 ml / Kg of compound amylase, reacting for 12-20 hours, cooling to 35-45 DEG C, adding sodium bicarbonate to adjust the pH to terminate the reaction, washing, concentrating and drying to obtain the thermal inhibition porous starch. The thermal inhibition porous starch not only has common characteristics of thermal inhibition starch and porous starch, but also has larger aperture and porosity, can meet adsorption and embedding of large-scale active microorganisms, meets complex processing working conditions, provides longer shelf stability, and has wide application prospects in food and pharmaceutical industries.

Description

Technical Field

[0001] The invention belongs to the technical field of food and medicine processing, and particularly relates to a thermally inhibited porous starch and a preparation method and application thereof. Background Art

[0002] Thermally inhibited starch is natural starch that is dehydrated to a low water activity state of ≤2%, and then heated to a glass transition temperature of above 145°C, causing the starch molecules to break and rearrange, thereby reshaping the crystal structure of the starch granules and inhibiting the aging and regeneration of natural starch. It has the characteristics of cross-linked starch, and has a lower disintegration value than natural starch, and improved freeze-thaw stability.

[0003] Porous starch is a new type of enzyme-modified starch. It uses a composite enzyme preparation to achieve directional enzymatic hydrolysis of starch particles to form a porous honeycomb structure. Compared with natural starch, porous starch has larger specific pore volume and specific surface area, and can achieve adsorption and embedding of microorganisms and macromolecular substances.

[0004] Therefore, how to combine the properties of thermally inhibited starch and porous starch to prepare a product that has the common properties of thermally inhibited starch and porous starch, has a larger pore size and porosity, and can meet the adsorption and embedding of larger-scale active microorganisms, meet complex processing conditions, and provide longer shelf stability, which is of great value for its application in the food, pharmaceutical industry and other fields. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a thermally inhibited porous starch and a preparation method and application thereof, which organically combines the two methods of thermal inhibition and enzymatic hydrolysis, and the prepared thermally inhibited porous starch has the common characteristics of thermally inhibited starch and porous starch, and has a larger pore size and porosity than single porous starch. Thermally inhibited porous starch can meet the requirements of adsorption and embedding of larger-scale active microorganisms, meet complex processing conditions, provide longer shelf stability, and has broad application prospects in the food and pharmaceutical industries.

[0006] The present invention is achieved through the following technical solutions: A method for preparing thermally inhibited porous starch comprises the following steps: (1) Waxy starch is added with water to prepare starch milk, the temperature is raised to 36-55°C, 0.5-5% of alkalizing agent based on the dry weight of waxy starch is added, the pH is adjusted to 7.5-9.5, and the mixture is stirred for 1-4 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 105-125° C. for 6-12 hours to obtain ultra-dried alkalized starch; (3) The ultra-dry alkalized starch in step (2) is subjected to dry heat reaction at a vacuum degree of -0.045 to -0.065 MPa and 145 to 175° C. for 2 to 16 hours to obtain heat-inhibited starch; (4) Adding the heat-inhibited starch in step (3) into a buffer solution to prepare a starch milk, heating the temperature to 45-55°C, adding the composite amylase in an amount of 10-20 ml / kg of absolute dry starch into the starch milk, reacting for 12-20 hours, cooling the temperature to 35-45°C after the reaction, adding sodium bicarbonate to adjust the pH to terminate the reaction, washing and concentrating to obtain a heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch.

[0007] Furthermore, in step (1), the mass ratio of waxy starch to water is 1:1.5-3.0; the waxy starch is one or more of waxy corn starch, waxy cassava starch, and waxy potato starch.

[0008] Furthermore, the alkalizing agent in step (1) is one or more of potassium citrate, sodium citrate and sodium carbonate.

[0009] Furthermore, in step (4), the composite amylase is an α-amylase and a saccharifying enzyme in a mass ratio of 2 to 5:1.

[0010] Furthermore, in step (4), the mass ratio of the heat-inhibited starch to the buffer solution is 1:1.8-2.5.

[0011] Furthermore, the pH of the buffer solution in step (4) is 3.0-4.5.

[0012] Furthermore, the water content of the ultra-dried alkalized starch in step (2) is ≤3.0wt%; and the water content of the heat-inhibited porous starch in step (5) is ≤13.5wt%. Furthermore, the water content of the ultra-dried alkalized starch in step (2) is ≤1.5wt%.

[0013] In the present invention, the heat-inhibited porous starch is prepared by the preparation method.

[0014] In the present invention, the application of heat-inhibited porous starch in the field of food or medicine is characterized in that it is used as an adsorbent, embedding agent, thickener or stabilizer.

[0015] In the present invention, the heat-inhibited porous starch is prepared by organically combining the heat inhibition and enzymatic hydrolysis methods using a non-chemical method. The heat-inhibited porous starch not only has the common characteristics of heat-inhibited starch and porous starch, but also has a larger pore size and porosity than single porous starch. The heat-inhibited porous starch can meet the adsorption and embedding of larger-scale active microorganisms, meet complex processing conditions, provide longer shelf stability, and has broad application prospects in the food and pharmaceutical industries.

[0016] Beneficial Effects The thermally inhibited porous starch prepared by the present invention has a complete particle structure, a breakage rate of ≤25%, a disintegration value of ≤5 BU, and a freeze-thaw stability of ≤35%. The product disintegration value and breakage rate are significantly reduced, and the freeze-thaw stability is greatly improved, which can meet the strict processing technology and shelf life stability. The porosity is ≥80%, the pore size is ≥1.5µm, the porosity and pore size are significantly improved, and the adsorption capacity is greatly improved. It can adapt to the adsorption and embedding of active microorganisms and various macromolecular substances under complex working conditions. It has broad application prospects in the fields of food and medicine. DETAILED DESCRIPTION

[0017] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0018] Example 1 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 3.0% potassium citrate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.4, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 120° C. for 6 hours to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤1.5wt%; (3) The ultra-dry alkalized starch in step (2) is added to a vacuum dry heat reactor, the vacuum degree is maintained at -0.045 MPa, and the dry heat reaction is carried out at 150° C. for 13 hours to obtain heat-inhibited starch; (4) The heat-inhibited starch in step (3) is added to a pH 4.0 buffer solution at a mass ratio of 1:1.8 to prepare starch milk, the temperature is raised to 50°C, and a composite amylase (a mass ratio of α-amylase and saccharifying enzyme of 3.0:1) is added to the starch milk at a mass ratio of 15 ml / kg of absolute dry heat-inhibited starch, and the reaction is carried out for 18 hours. After the reaction is completed, the temperature is lowered to 35°C, and sodium bicarbonate is added to adjust the pH to 6.0 to terminate the reaction. The reaction is cyclone-washed and concentrated for 5 times to obtain heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch, wherein the water content of the heat-inhibited porous starch is ≤13.5 wt %.

[0019] Example 2 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 2.5% sodium citrate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.8, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 120° C. for 6 h to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤2.0 wt%; (3) The ultra-dry alkalized starch in step (2) is added into a vacuum dry heat reactor, the vacuum degree is maintained at -0.045 MPa, and the dry heat reaction is carried out at 150° C. for 13 h to obtain heat-inhibited starch; (4) The heat-inhibited starch in step (3) is added to a pH 4.0 buffer solution at a mass ratio of 1:1.8 to prepare starch milk, the temperature is raised to 50°C, and a composite amylase (a mass ratio of α-amylase and saccharifying enzyme of 3.0:1) is added to the starch milk at a mass ratio of 15 ml / kg of absolute dry heat-inhibited starch, and the reaction is carried out for 18 hours. After the reaction is completed, the temperature is lowered to 35°C, and sodium bicarbonate is added to adjust the pH to 6.0 to terminate the reaction. The reaction is cyclone-washed and concentrated for 5 times to obtain heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch, wherein the water content of the heat-inhibited porous starch is ≤13.5 wt %.

[0020] Example 3 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 0.5% sodium carbonate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.6, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 120° C. for 6 hours to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤1.5wt%; (3) The ultra-dry alkalized starch in step (2) is added into a vacuum dry heat reactor, the vacuum degree is maintained at -0.045 MPa, and the dry heat reaction is carried out at 150° C. for 13 h to obtain heat-inhibited starch; (4) The heat-inhibited starch in step (3) is added to a pH 4.0 buffer solution at a mass ratio of 1:1.8 to prepare starch milk, the temperature is raised to 50°C, and a composite amylase (a mass ratio of α-amylase and saccharifying enzyme of 3.0:1) is added to the starch milk at a mass ratio of 15 ml / kg of absolute dry heat-inhibited starch, and the reaction is carried out for 18 hours. After the reaction is completed, the temperature is lowered to 35°C, and sodium bicarbonate is added to adjust the pH to 6.0 to terminate the reaction. The reaction is cyclone-washed and concentrated for 5 times to obtain heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch, wherein the water content of the heat-inhibited porous starch is ≤13.5 wt %.

[0021] Example 4 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 2.5% potassium citrate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.4, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 120° C. for 6 hours to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤1.5wt%; (3) The ultra-dry alkalized starch in step (2) is added into a vacuum dry heat reactor, the vacuum degree is maintained at -0.045 MPa, and the dry heat reaction is carried out at 160° C. for 8 hours to obtain heat-inhibited starch; (4) The heat-inhibited starch in step (3) is added to a pH 4.0 buffer solution at a mass ratio of 1:1.8 to prepare starch milk, the temperature is raised to 50°C, and a composite amylase (a mass ratio of α-amylase and saccharifying enzyme of 3.5:1) is added to the starch milk at a mass ratio of 15 ml / kg of absolute dry heat-inhibited starch, and the reaction is carried out for 18 hours. After the reaction is completed, the temperature is lowered to 35°C, and sodium bicarbonate is added to adjust the pH to 6.0 to terminate the reaction. The reaction is cyclone-washed and concentrated for 5 times to obtain heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch, wherein the water content of the heat-inhibited porous starch is ≤13.5 wt %.

[0022] Example 5 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 3.0% potassium citrate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.4, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 120° C. for 4 h to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤1.5wt%; (3) The ultra-dry alkalized starch in step (2) is added into a vacuum dry heat reactor, the vacuum degree is maintained at -0.045 MPa, and the dry heat reaction is carried out at 160° C. for 8 hours to obtain heat-inhibited starch; (4) The heat-inhibited starch in step (3) is added to a pH 4.0 buffer solution at a mass ratio of 1:1.8 to prepare starch milk, the temperature is raised to 50°C, and a composite amylase (a mass ratio of α-amylase and saccharifying enzyme of 3.0:1) is added to the starch milk at a mass ratio of 15 ml / kg of absolute dry heat-inhibited starch, and the reaction is carried out for 18 hours. After the reaction is completed, the temperature is lowered to 35°C, and sodium bicarbonate is added to adjust the pH to 6.0 to terminate the reaction. The reaction is cyclone-washed and concentrated for 5 times to obtain heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch, wherein the water content of the heat-inhibited porous starch is ≤13.5 wt %.

[0023] Example 6 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 3.0% potassium citrate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.4, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 110° C. for 5 h to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤2.0 wt%; (3) The ultra-dry alkalized starch in step (2) is added into a vacuum dry heat reactor, the vacuum degree is maintained at -0.045 MPa, and the dry heat reaction is carried out at 160° C. for 8 hours to obtain heat-inhibited starch; (4) The heat-inhibited starch in step (3) is added to a pH 4.0 buffer solution at a mass ratio of 1:1.8 to prepare starch milk, the temperature is raised to 50°C, and a composite amylase (a mass ratio of α-amylase and saccharifying enzyme of 3.5:1) is added to the starch milk at a mass ratio of 15 ml / kg of absolute dry heat-inhibited starch, and the reaction is carried out for 18 hours. After the reaction is completed, the temperature is lowered to 35°C, and sodium bicarbonate is added to adjust the pH to 6.0 to terminate the reaction. The reaction is cyclone-washed and concentrated for 5 times to obtain heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch, wherein the water content of the heat-inhibited porous starch is ≤13.5 wt %.

[0024] Example 7 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 3.0% potassium citrate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.4, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 120° C. for 4 h to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤1.5wt%; (3) The ultra-dry alkalized starch in step (2) is added into a vacuum dry heat reactor, the vacuum degree is maintained at -0.045 MPa, and the dry heat reaction is carried out at 150° C. for 12 hours to obtain heat-inhibited starch; (4) The heat-inhibited starch in step (3) is added to a pH 4.0 buffer solution at a mass ratio of 1:1.8 to prepare starch milk, the temperature is raised to 50°C, and a composite amylase (a mass ratio of α-amylase and saccharifying enzyme of 3.5:1) is added to the starch milk at a mass ratio of 15 ml / kg of absolute dry heat-inhibited starch, and the reaction is carried out for 18 hours. After the reaction is completed, the temperature is lowered to 35°C, and sodium bicarbonate is added to adjust the pH to 6.0 to terminate the reaction. The reaction is cyclone-washed and concentrated for 5 times to obtain heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch, wherein the water content of the heat-inhibited porous starch is ≤13.5 wt %.

[0025] Example 8 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 3.0% potassium citrate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.4, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 120° C. for 4 h to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤1.5wt%; (3) The ultra-dry alkalized starch in step (2) is added into a vacuum dry heat reactor, and the vacuum degree is maintained at -0.045 MPa and the temperature is 160° C. for dry heat reaction for 9 hours to obtain heat-inhibited starch; (4) The heat-inhibited starch in step (3) is added to a pH 4.0 buffer solution at a mass ratio of 1:1.8 to prepare starch milk, the temperature is raised to 50°C, and a composite amylase (a mass ratio of α-amylase and saccharifying enzyme of 3.5:1) is added to the starch milk at a mass ratio of 15 ml / kg of absolute dry heat-inhibited starch, and the reaction is carried out for 18 hours. After the reaction is completed, the temperature is lowered to 35°C, and sodium bicarbonate is added to adjust the pH to 6.0 to terminate the reaction. The reaction is cyclone-washed and concentrated for 5 times to obtain heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch, wherein the water content of the heat-inhibited porous starch is ≤13.5 wt %.

[0026] Example 9 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 3.0% potassium citrate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.4, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 120° C. for 4 h to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤1.5wt%; (3) The ultra-dry alkalized starch in step (2) is added into a vacuum dry heat reactor, the vacuum degree is maintained at -0.045 MPa, and the dry heat reaction is carried out at 170° C. for 5 hours to obtain heat-inhibited starch; (4) The heat-inhibited starch in step (3) is added to a pH 4.0 buffer solution at a mass ratio of 1:1.8 to prepare starch milk, the temperature is raised to 50°C, and a composite amylase (a mass ratio of α-amylase and saccharifying enzyme of 3.5:1) is added to the starch milk at a mass ratio of 15 ml / kg of absolute dry heat-inhibited starch, and the reaction is carried out for 18 hours. After the reaction is completed, the temperature is lowered to 35°C, and sodium bicarbonate is added to adjust the pH to 6.0 to terminate the reaction. The reaction is cyclone-washed and concentrated for 5 times to obtain heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch, wherein the water content of the heat-inhibited porous starch is ≤13.5 wt %.

[0027] Example 10 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 3.0% potassium citrate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.4, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 120° C. for 4 h to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤1.5wt%; (3) The ultra-dry alkalized starch in step (2) is added into a vacuum dry heat reactor, the vacuum degree is maintained at -0.045 MPa, and the dry heat reaction is carried out at 150° C. for 12 hours to obtain heat-inhibited starch; (4) The heat-inhibited starch in step (3) is added to a pH 4.0 buffer solution at a mass ratio of 1:1.8 to prepare starch milk, the temperature is raised to 50°C, and a composite amylase (α-amylase and saccharifying enzyme at a mass ratio of 3.0:1) is added to the starch milk at a mass ratio of 10 ml / kg of absolute dry heat-inhibited starch, and the reaction is carried out for 18 hours. After the reaction is completed, the temperature is lowered to 35°C, and sodium bicarbonate is added to adjust the pH to 6.0 to terminate the reaction. The reaction is cyclone-washed and concentrated for 5 times to obtain heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch, wherein the water content of the heat-inhibited porous starch is ≤13.5 wt %.

[0028] Embodiment 11 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 3.0% potassium citrate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.4, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 120° C. for 4 h to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤1.5wt%; (3) The ultra-dry alkalized starch in step (2) is added into a vacuum dry heat reactor, the vacuum degree is maintained at -0.045 MPa, and the dry heat reaction is carried out at 150° C. for 12 hours to obtain heat-inhibited starch; (4) The heat-inhibited starch in step (3) is added to a pH 4.0 buffer solution at a mass ratio of 1:1.8 to prepare starch milk, the temperature is raised to 50°C, and a composite amylase (α-amylase and saccharifying enzyme at a mass ratio of 2.5:1) is added to the starch milk at a mass ratio of 15 ml / kg of absolute dry heat-inhibited starch, and the reaction is carried out for 18 hours. After the reaction is completed, the temperature is lowered to 35°C, and sodium bicarbonate is added to adjust the pH to 6.0 to terminate the reaction. The reaction is cyclone-washed and concentrated for 5 times to obtain heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch, wherein the water content of the heat-inhibited porous starch is ≤13.5 wt %.

[0029] Example 12 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 3.0% potassium citrate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.4, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 120° C. for 4 h to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤1.5wt%; (3) The ultra-dry alkalized starch in step (2) is added into a vacuum dry heat reactor, the vacuum degree is maintained at -0.045 MPa, and the dry heat reaction is carried out at 150° C. for 12 hours to obtain heat-inhibited starch; (4) The heat-inhibited starch in step (3) is added to a pH 4.0 buffer solution at a mass ratio of 1:1.8 to prepare starch milk, the temperature is raised to 50°C, and a composite amylase (α-amylase and saccharifying enzyme at a mass ratio of 3.5:1) is added to the starch milk at a mass ratio of 18 ml / kg of absolute dry heat-inhibited starch, and the reaction is carried out for 18 hours. After the reaction is completed, the temperature is lowered to 35°C, and sodium bicarbonate is added to adjust the pH to 6.0 to terminate the reaction. The reaction is cyclone-washed and concentrated for 5 times to obtain heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch, wherein the water content of the heat-inhibited porous starch is ≤13.5 wt %.

[0030] Comparative Example 1 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 3.0% potassium citrate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.6, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 120° C. for 4 h to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤1.5wt%; (3) The ultra-dry alkalized starch in step (2) is added into a vacuum dry heat reactor, the vacuum degree is maintained at -0.045 MPa, and the dry heat reaction is carried out at 150° C. for 12 hours to obtain heat-inhibited starch; Comparative Example 2 (1) Prepare a buffer solution of pH 3.6 (1.52 g of anhydrous sodium acetate and 13.89 g of glacial acetic acid dissolved in 1 L of pure water to prepare a buffer solution), prepare starch milk according to the ratio of absolute dry waxy corn starch: buffer solution = 1:1.25, stir evenly, and heat to 50°C for use; mix α-amylase: saccharifying enzyme = 3.5:1 to prepare a composite enzyme solution, add the composite enzyme solution to the starch milk at a ratio of 18 ml / Kg (absolute dry starch), maintain the starch milk temperature at 50-54°C for reaction for 16 hours, cool to 40°C after the reaction, add sodium bicarbonate to adjust the pH to 6.0, and then wash and concentrate the mixture 5 times by cyclone to obtain a porous starch concentrate.

[0031] (2) The porous starch concentrate obtained in step (1) is centrifuged and dehydrated to a moisture content of ≤36%, and then dried to a moisture content of ≤8%, thereby obtaining a waxy porous starch.

[0032] Comparative Example 3 (1) Waxy corn starch and water are prepared into starch milk in a ratio of 1:1.5, the temperature is raised to 40°C, 3.0% potassium citrate based on the dry weight of the waxy starch is added, alkali is added to adjust the pH to 8.6, and the mixture is stirred for 1.5 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 120° C. for 4 h to obtain ultra-dried alkalized starch, wherein the moisture content of the ultra-dried alkalized starch is ≤1.5wt%; Performance Testing Disintegration value determination: The moisture content of Examples 1 to 12 and Comparative Examples 1 to 3 was determined according to an absolute dry concentration of 6%. A Brabender Viscograph-E viscometer was selected with a measuring range of 700 cmg, a heating and cooling rate of 1.5°C / min, a starting temperature of 50°C, a minimum temperature of 30°C, a viscosity curve was tested, and the high-temperature disintegration value (BU) was observed.

[0033] Determination of water holding rate: accurately weigh 3.0 g (absolutely dry) of the final product prepared in Examples 1 to 12 and Comparative Examples 1 to 3 into a 250 ml conical flask, add 147 ml of distilled water, mix and stir in a boiling water bath for 20 min, pour 100 ml of the paste into a 100 ml stoppered measuring cylinder after the starch is completely gelatinized, place it at 4°C and let it stand for 48 h, then observe and record the supernatant volume reading V1, water holding rate (%) = 100-V1 / 100.

[0034] High-speed shear crushing rate determination: accurately weigh 12.0 g (water content 12%) of the final product prepared in Examples 1 to 12 and Comparative Examples 1 to 3 into a 250 ml conical flask, add 188 ml of distilled water, mix and stir in a boiling water bath for 20 min, then pour into a high-speed shear disperser, treat at 10,000 r / min for 1-5 min, and count the proportion of broken starch particles under a microscope.

[0035] Freeze-thaw stability determination: accurately weigh 6.0 g (absolutely dry) of the final product prepared in Examples 1 to 12 and Comparative Examples 1 to 3 into a 250 ml conical flask, add 94 ml of distilled water, mix and stir in a boiling water bath for 20 min, pour an appropriate amount of paste M1 into a 10 ml stoppered measuring cylinder after the starch is completely gelatinized, the total mass of the paste and the stoppered measuring cylinder is M2, put it in -20°C and let it stand for 24 h, then thaw it to room temperature, repeat three times, centrifuge at 4000 r / min for 25 min, discard the centrifugal supernatant, weigh M3, and calculate: freeze-thaw stability (%) = (M2-M3) / M1.

[0036] Porosity and pore size determination: The ASAP2020 specific surface area and pore size analyzer produced by Micromeritics was used to determine the adsorption / desorption isotherms of microporous starch by nitrogen adsorption method, and its porosity and pore size distribution were calculated.

[0037] Table 1 Performance test results of final products of Examples 1 to 12 and Comparative Examples 1 to 3 .

Claims

1. A method for preparing thermally inhibited porous starch, characterized in that: Follow these steps: (1) Waxy starch is added with water to prepare starch milk, the temperature is raised to 36-55°C, 0.5-5% of alkalizing agent based on the dry weight of waxy starch is added, the pH is adjusted to 7.5-9.5, and the mixture is stirred for 1-4 hours to obtain alkalized starch milk; (2) The alkalized starch milk in step (1) is centrifuged and dehydrated, and dried at 105-125° C. for 6-12 hours to obtain ultra-dried alkalized starch; (3) The ultra-dry alkalized starch in step (2) is subjected to dry heat reaction at a vacuum degree of -0.045 to -0.065 MPa and 145 to 175°C for 2 to 16 hours to obtain heat-inhibited starch; (4) Adding the heat-inhibited starch in step (3) into a buffer solution to prepare a starch milk, heating the temperature to 45-55° C., adding a composite amylase in an amount of 10-20 ml / kg of absolute dry starch into the starch milk, reacting for 12-20 hours, cooling the temperature to 35-45° C. after the reaction, adding sodium bicarbonate to adjust the pH to terminate the reaction, washing and concentrating to obtain a heat-inhibited porous starch concentrate; (5) The porous starch emulsion in step (4) is dried to obtain heat-inhibited porous starch.

2. The method for preparing thermally inhibited porous starch according to claim 1, characterized in that: In step (1), the mass ratio of waxy starch to water is 1:1.5-3.0; the waxy starch is one or more of waxy corn starch, waxy cassava starch and waxy potato starch.

3. The method for preparing thermally inhibited porous starch according to claim 1, characterized in that: The alkalizing agent in step (1) is one or more of potassium citrate, sodium citrate and sodium carbonate.

4. The method for preparing thermally inhibited porous starch according to claim 1, characterized in that: In step (4), the composite amylase comprises α-amylase and saccharifying enzyme in a mass ratio of 2 to 5:

1.

5. The method for preparing thermally inhibited porous starch according to claim 1, characterized in that: In step (4), the mass ratio of heat-inhibited starch to buffer is 1:1.8-2.

5.

6. The method for preparing thermally inhibited porous starch according to claim 1, characterized in that: The pH of the buffer solution in step (4) is 3.0-4.

5.

7. The method for preparing thermally inhibited porous starch according to claim 1, characterized in that: The water content of the ultra-dried alkalized starch in step (2) is ≤3.0wt%; the water content of the heat-inhibited porous starch in step (5) is ≤13.5wt%.

8. The method for preparing thermally inhibited porous starch according to claim 1, characterized in that: The water content of the ultra-dried alkalized starch in step (2) is ≤1.5wt%.

9. A thermally inhibited porous starch prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the heat-inhibited porous starch according to claim 9 in the field of food or medicine, characterized in that: As adsorbent, embedding agent, thickener or stabilizer.