A method for inducing high resistant starch in potato starch

Abstract

The application discloses a high-resistant starch induction method of potato starch and belongs to the technical field of deep processing of grains. The potato starch is adjusted to a moisture content of 20%-35% by adding water, annealed in a constant humidity environment at 55-65 DEG C for 10-18 minutes, so that linear starch molecules are orderly rearranged along the surface of residual microcrystals to form RS3 type resistant starch with a melting temperature of greater than or equal to 120 DEG C, and then low-temperature drying is performed after quenching and crystal locking. The application is specially optimized according to the characteristics of the potato starch, such as large particle size, moderate linear content and low gelatinization temperature, the product has a GI value of less than or equal to 60, the RS3 type resistant starch content is greater than or equal to 8%, and the product is suitable for sugar-controlled food and functional food raw materials.

Description

Technical Field

[0001] This invention belongs to the field of deep grain processing technology, specifically relating to a purely physical annealing modification method for potato starch. Background Technology Potato starch is the world's second-largest commercial starch after corn starch, widely used in the food, chemical, and pharmaceutical industries. Its amylose content is typically 20%-25%, with large particle size (15-100μm) and low gelatinization temperature (58-65℃). These characteristics significantly differ from corn starch (25%-30% amylose, 5-20μm particle size, gelatinization temperature 62-72℃). The glycemic index (GI) of ordinary potato starch is usually between 65-75, classifying it as a medium-to-high GI food. In existing technologies, annealing modification research has largely focused on corn starch and high-amylose corn starch, with few reports on optimizing annealing parameters for potato starch. Potato starch is unique in that its large particle size results in a long heat and mass transfer path, and its low gelatinization temperature means a narrower annealing window—slightly higher temperatures cause particle breakage and microcrystal collapse, while slightly lower temperatures result in insufficient amylose dissolution. Directly applying the annealing parameters for corn starch (60-65℃) causes partial breakage of potato starch particles due to heat sensitivity, resulting in the product losing the high viscosity and transparent luster characteristic of potato starch. Therefore, potato starch requires a separately optimized annealing process. Summary of the Invention Purpose of the invention The purpose of this invention is to provide an annealing modification method specifically for potato starch, which, by adapting to its characteristics of large particle size and low gelatinization temperature, efficiently induces the formation of RS3-type resistant starch while protecting the integrity of starch particles. Technical solution The present invention includes the following steps: (1) conditioning potato starch to a moisture content of 20%-35%; (2) annealing in a constant humidity environment of 55-65℃ and 80%-95% for 10-18 minutes; (3) rapidly cooling to lock crystals; (4) drying at a low temperature not exceeding 50℃ to a moisture content of less than 13%. Core Mechanism Potato starch granules are large, and the migration path of amylose from the interior to the surface of the granules is long, requiring a longer annealing time (10-18 minutes) to ensure sufficient dissolution. Simultaneously, its gelatinization temperature is low (58-65℃), and the annealing temperature window must be controlled within 55-65℃—the upper limit should not exceed 65℃ to prevent granule breakage and microcrystal collapse, and the lower limit should not be lower than 55℃ to ensure sufficient dissolution of amylose. This differs from the 60-65℃ window of corn starch—the lower limit for potatoes is even lower because of its lower amylose content and lower gelatinization initiation temperature. Beneficial effects (1) A special annealing scheme for potato starch was proposed for the first time, with a GI value ≤60 and RS3 content ≥8%. (2) The starch granules are intact after annealing, retaining the high viscosity and transparent luster of potato starch. (3) Pure physical process with zero additives. Detailed Implementation Example 1 (Antenerage Modification of Potato Starch) Take 1000 kg of potato starch, add water to adjust to 28%, and adjust the temperature to 45℃. Feed the adjusted material into a constant temperature and humidity annealing equipment and anneal at 60℃ and 85% humidity for 14 minutes. Immediately after annealing, feed it into a fluidized bed and rapidly cool it to below 25℃ within 90 seconds using cold air from -5℃ to 0℃. Dry at 42℃ until the moisture content is 12.0%, thus obtaining the product. The resulting product has a GI value of 58, a melting temperature of 123℃ for RS3 resistant starch, an RS3 resistant starch content of ≥8%, and intact starch granules. Comparative Example 1 (annealing temperature too high, particle breakage) The annealing temperature in Example 1 was changed to 68°C (exceeding the upper limit of 65°C), while the other conditions remained unchanged. The resulting product showed extensive starch granule rupture and microcrystal collapse, low RS3 content, and an RS3-type resistant starch melting temperature <120℃. This demonstrates that temperatures exceeding 65℃ cause structural damage to potato starch granules. Comparative Example 2 (annealing temperature too low, RS3 insufficient) The annealing temperature in Example 1 was changed to 50°C (below the lower limit of 55°C), while the other conditions remained unchanged. The resulting product showed insufficient amylose dissolution, low RS3 formation, and an RS3-type resistant starch melting temperature <120℃, with a high GI value. This demonstrates that high-melting-point RS3 cannot be effectively generated below 55℃. Comparative Example 3 (using corn parameters, with damaged kernels) The annealing conditions in Example 1 were changed to 62°C and 12 minutes (the conventional annealing parameters for ordinary corn starch), while the other conditions remained unchanged. The resulting product showed cracks in some particles, decreased viscosity, and reduced transparency and gloss. This demonstrates that the annealing parameters for corn starch cannot be directly applied to potato starch. Detection methods The melting temperature of RS3 resistant starch was determined by differential scanning calorimetry (DSC): heating rate 10℃ / min, nitrogen atmosphere, sample amount 3-5 mg, temperature range 30-180℃. The content of RS3 resistant starch was determined according to the AOAC 2002.02 standard method. The GI value was determined according to the ISO 26642:2010 standard method. Industrial applications This invention can be implemented on existing continuous tempering-annealing-cooling-drying production lines. The core equipment includes a biaxial differential atomizing continuous tempering tank, a closed continuous annealing tower with a temperature control accuracy of ±0.5℃ across the entire range, a fluidized bed quenching system, and a low-temperature airflow drying device.

Claims

1. A method for inducing highly resistant starch in potato starch, characterized in that, Includes the following steps: a. Conditioning: Add water to potato starch and condition it to a moisture content of 20%-35%, while controlling the temperature at 40-50℃, so that the starch absorbs water and swells; b. Isothermal annealing: The conditioned material is kept in a constant humidity environment with a relative humidity of 80%-95% for 10-18 minutes within a temperature window of 55-65℃, so that the amylose molecules rearrange in an orderly manner along the residual microcrystal surface to form RS3 type resistant starch with a melting temperature ≥120℃. c. Rapid cooling and crystal locking: The annealed material is rapidly cooled to below 25°C within 90 seconds to lock the RS3 lattice structure; d. Low-temperature drying: Dry the rapidly cooled material at a temperature not exceeding 50°C until the moisture content is below 13%.

2. The method according to claim 1, characterized in that, The moisture content of the conditioning process in step a is preferably 25%-30%, and the conditioning temperature is preferably 42-48℃.

3. The method according to claim 1, characterized in that, The annealing temperature in step b is preferably 58-63℃, more preferably 60-62℃; the annealing time is preferably 12-16 minutes, more preferably 13-15 minutes.

4. The method according to claim 1, characterized in that, The rapid cooling described in step c uses fluidized bed rapid cooling, which uses cold air at -5°C to 0°C to cool the material to below 25°C within 90 seconds.

5. The method according to claim 1, characterized in that, The drying temperature described in step d is 40-45℃.

6. A low glycemic index potato starch, characterized in that, The starch is prepared by the method according to any one of claims 1-5, and the starch simultaneously meets the following requirements: GI value ≤ 60, RS3 resistant starch content ≥ 8%, RS3 resistant starch melting temperature ≥ 120℃, and the ingredient list contains only potato starch.

7. The application of the starch according to claim 6 in the preparation of sugar-controlled foods, meal replacement powders, and functional food ingredients.