A method for modifying low temperature low gluten wheat flour to enhance resistant starch production

Abstract

The application discloses a low-temperature low-gluten wheat flour modification method for strengthening resistant starch production and belongs to the technical field of grain deep processing. In the application, the low-gluten wheat flour is conditioned to 20%-25% of moisture, annealed in a temperature window of 55-62 DEG C for 8-12 minutes, and the gluten network is not reserved, so that the starch is fully swelled, a large amount of amylose is dissolved and orderly attached along the surface of the residual microcrystal and the crystal lattice is rearranged, high-melting-point RS3 type resistant starch with a melting temperature of greater than or equal to 120 DEG C is formed, then the fluidized bed is used to rapidly cool to below 25 DEG C within 90 seconds to lock the crystal lattice, and low-temperature drying is carried out. The application is a pure physical zero-addition process, the obtained product has a GI value of less than or equal to 59, a resistant starch content of greater than or equal to 8.5%, and a RS3 melting temperature of greater than or equal to 120 DEG C, and is suitable for high-end baked foods, such as cakes, cookies and crisp biscuits, which need a crisp and brittle taste.

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 low-gluten wheat flour, which enhances the formation of resistant starch while retaining the crisp texture of low-gluten wheat flour. Background Technology Low-gluten wheat flour is a basic ingredient in baked goods such as cakes, cookies, and shortbread. Traditional low-gluten wheat flour typically has a GI value between 70 and 85, classifying it as a high-GI food. Unlike high-gluten flour, which requires gluten protection, low-gluten flour does not need to retain the gluten protein network for processing, thus allowing for a more flexible temperature window to enhance RS3 formation. The applicant's prior art discloses a method for short-time high-temperature annealing of low-gluten wheat flour at 60-67°C, utilizing a two-stage high-temperature process to promote rapid and orderly rearrangement of amylose along the microcrystalline surface and rapid cooling to lock the crystals, reducing the GI value to below 59. However, in some production scenarios, if the equipment cannot stably reach the 65-67°C high-temperature range, or if the thermal stability of the raw material microcrystals is slightly low, a relatively mild low-temperature enhancement scheme is needed as an alternative. Existing technologies have never proposed a specific low-temperature RS3 enhancement annealing scheme for low-gluten flour. This invention provides a mild temperature window of 55-62°C, offering a more flexible temperature selection scheme for the industrial production of low-gluten flour. Summary of the Invention Purpose of the invention The purpose of this invention is to provide a low-temperature annealing method for low-gluten wheat flour, which achieves efficient generation of RS3 within a relatively mild temperature window, providing a more flexible temperature selection scheme for the industrial production of low-gluten flour. Technical solution The present invention includes the following steps: (1) conditioning to a moisture content of 20%-25%; (2) annealing for 8-12 minutes in a constant humidity environment of 55-62℃ and 80%-95%; (3) rapidly cooling to below 25℃ in 90 seconds using a fluidized bed to lock the crystal lattice; and (4) drying at a low temperature not exceeding 45℃. Core Mechanism Low-gluten wheat flour does not require the retention of the gluten protein network, therefore the annealing temperature can be higher than the critical gluten denaturation temperature of 55°C. The 55-62°C window is higher than the 50-55°C window for high-gluten flour, but lower than the 60-67°C high-temperature window of Patent No. 13, providing a separate, mild temperature range for low-gluten flour. Within this window, starch granules fully swell, and a large amount of amylose dissolves, undergoing heterogeneous nucleation and ordered rearrangement along the surface of the remaining natural microcrystals to form high-melting-point RS3. After annealing, the fluidized bed is rapidly cooled to below 25°C within 90 seconds, instantly locking the RS3 lattice and preventing lattice regression caused by natural cooling. Beneficial effects (1) Provides a low-temperature strengthening solution for low-gluten flour, forming a temperature gradient complementary with the high-temperature solution of Patent No. 13. (2) The annealing temperature window is milder, the requirements for equipment precision are relatively reduced, and it is suitable for production lines under different conditions. (3) The product GI value is ≤59, the resistant starch content is ≥8.5%, and the RS3 melting temperature is ≥120℃. (4) Purely physical with zero additives, the ingredient list contains only wheat flour. Detailed Implementation Example 1 (Low-gluten wheat flour low-temperature annealing) Take 1000g of low-gluten wheat flour (9% protein, 20% wet gluten), add water to adjust to 22%, and heat at 48℃. Anneal at 58℃ and 85% humidity for 10 minutes. Immediately after annealing, transfer to a fluidized bed and rapidly cool the flour temperature from 58℃ to 23℃ within 90 seconds using -3℃ cold air. Dry at 45℃ until the moisture content is 12.0%, and sieve to obtain the product. The resulting product showed a significantly lower GI value, an RS3 melting temperature above 120℃, and a significantly higher resistant starch content. The resulting cookies were crisp and crumbly, showing no significant difference from those made with untreated low-gluten flour. Comparative Example 1 (annealing temperature exceeding 62℃) The annealing temperature in Example 1 was changed to 65°C, while the other conditions remained unchanged. The resulting product exhibited excessive starch gelatinization, a significantly reduced microcrystal retention rate, low resistant starch content, and a sticky texture. This demonstrates that temperatures exceeding 62°C cause the microcrystalline framework to collapse and heterogeneous nucleation to be lost. Comparative Example 2 (annealing temperature below 55℃) The annealing temperature in Example 1 was changed to 50°C, while the other conditions remained unchanged. The resulting product had a low resistant starch content and no significant decrease in the GI value. This indicates that starch swelling is insufficient below 55℃, resulting in inadequate RS3 formation efficiency. Comparative Example 3 (Natural cooling instead of rapid cooling for crystal locking) The rapid cooling method in Example 1 was changed to natural cooling (the average cooling rate was about 0.3℃ / min, and it took about two hours to drop from 58℃ to below 25℃), while the other conditions remained unchanged. The resulting product showed no significant decrease in GI value, and the RS3 melting temperature was below 120°C. This demonstrates that natural cooling caused lattice regeneration in RS3, negating the effect of annealing. Detection methods The wet gluten content was determined according to GB / T 14608, the GI value was determined according to the ISO 26642:2010 standard method, the RS3 melting temperature was determined by differential scanning calorimetry, and the resistant starch content was determined according to the AOAC 2002.02 standard method. Industrial applications This invention can be implemented on existing continuous grain conditioning-annealing-cooling-drying production lines. The core equipment includes a biaxial differential atomizing continuous conditioning tank, a closed mesh belt 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 modifying low-temperature, low-gluten wheat flour to enhance resistant starch production, characterized in that, Includes the following steps: a. Conditioning: Add water to the low-gluten wheat flour and condition it to a moisture content of 20%-25%, and control the temperature at 45-50℃ to allow the starch to absorb water and swell; b. Isothermal annealing: The conditioned material is kept in a constant humidity environment with a relative humidity of 80%-95% for 8-12 minutes within a temperature window of 55-62℃, so that the starch swells fully, the amylose dissolves in large quantities and adheres and rearranges in an orderly manner along the surface of the residual microcrystals, forming high melting point 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 using a fluidized bed to lock the high melting point RS3 crystal structure; d. Low-temperature drying: Dry the cooled material at a temperature not exceeding 45°C until the moisture content is below 13%.

2. The method according to claim 1, characterized in that, The low-gluten wheat flour mentioned in step a has a protein content of ≤10% and a wet gluten content of ≤22%.

3. The method according to claim 1, characterized in that, The annealing temperature in step b is 58-60℃, and the annealing time is 10 minutes.

4. The method according to claim 1, characterized in that, The fluidized bed quenching in step c uses cold air from -5°C to 0°C to cool the material from the annealing temperature to below 25°C within 90 seconds.

5. The method according to claim 1, characterized in that, The annealing process in step b is carried out in an environment with a relative humidity of 82%-88%.

6. A low-gluten, low-glycemic index wheat flour, characterized in that, The wheat flour is prepared by the method described in any one of claims 1-5, and the wheat flour simultaneously meets the following requirements: wet gluten content ≤22%, GI value ≤59, RS3 resistant starch content ≥8.5%, RS3 melting temperature ≥120℃, and the ingredient list contains only wheat flour.

7. The application of the wheat flour according to claim 6 in the preparation of low-gluten, low-glycemic index baked goods, wherein the baked goods include, but are not limited to, cakes, cookies, shortbread, muffins, and waffles.