A two-stage annealing coupling quenching drying modified method of low gluten wheat flour

Abstract

The application discloses a modified method of low-gluten wheat flour two-stage annealing coupling quenching and drying, and belongs to the technical field of grain deep processing. The low-gluten wheat flour is conditioned to moisture of 20%-25%, first annealed at a mild temperature of 50-55 DEG C for 3-5 minutes in the first stage, so that the starch is preliminarily swelled and the microcrystalline skeleton is reserved; then annealed at a higher temperature of 60-65 DEG C for 4-6 minutes in the second stage, so that the straight-chain starch is promoted to rapidly and orderly rearrange along the microcrystalline surface, and high-melting-point RS3 type resistant starch with a melting temperature of greater than or equal to 120 DEG C is formed; after the two-stage annealing is completed, the low-gluten wheat flour is directly sent into a fluidized bed, quenched to below 25 DEG C within 90 seconds and dried at the same time. The application is a pure physical zero-addition process, and the two-stage annealing is integrated with the quenching and drying, the obtained product has a GI value of less than or equal to 59 and a resistant starch content of greater than or equal to 8.5%, and is suitable for high-end baked foods such as cakes, cookies and crisp biscuits.

Description

Technical Field

[0001] This invention belongs to the field of deep grain processing technology, specifically relating to a purely physical modification method for low-gluten wheat flour that integrates two-stage annealing and rapid cooling drying. Background Technology Low-gluten wheat flour is a basic ingredient in baking cakes, cookies, shortbread, and other baked goods. Traditional low-gluten wheat flour typically has a glycemic index (GI) between 70 and 85, classifying it as a high-GI food. The applicant's prior art discloses a method for high-temperature single-stage or two-stage annealing of low-gluten wheat flour at 60-67℃. However, both single-stage and two-stage annealing are completed within the same high-temperature window, failing to fully utilize the differentiated effects of temperature gradients on the starch swelling and ordered rearrangement stages. While there have been studies on two-step starch annealing in academia, these studies have all used high-moisture excess water systems and focused on the theoretical limits of gelatinization temperature. They have never addressed industrial-scale GI reduction schemes for low-gluten wheat flour under low-moisture conditions, nor have they proposed an integrated design that couples two-stage annealing with rapid cooling. This invention is the first to propose a temperature gradient design under low-moisture conditions—a first-stage gentle temperature protects the microcrystalline framework, and a second-stage higher temperature promotes ordered rearrangement—followed by the integrated coupling of two-stage annealing and rapid cooling, simplifying the process and improving RS3 formation efficiency. Summary of the Invention Purpose of the invention The purpose of this invention is to provide a two-stage annealing coupled rapid cooling drying method for low-gluten wheat flour, which optimizes the two stages of starch swelling and ordered rearrangement through temperature gradient design to achieve efficient generation of RS3. Technical solution The present invention includes the following steps: (1) conditioning to a moisture content of 20%-25%; (2) first-stage annealing at 50-55°C for 3-5 minutes to allow the starch to initially swell while retaining the natural microcrystalline skeleton; (3) second-stage annealing at 60-65°C for 4-6 minutes to promote the rapid and orderly rearrangement of amylose along the microcrystalline surface; (4) directly feeding into a fluidized bed and rapidly cooling to below 25°C within 90 seconds while drying. Core Mechanism The two-stage annealing design is based on two key stages of starch modification: the first stage involves the swelling of starch granules and the dissolution of amylose, requiring mild temperature conditions (50-55℃) to avoid premature destruction of the microcrystalline framework; the second stage involves the ordered rearrangement of the dissolved amylose along the microcrystalline surface and lattice repair, requiring higher temperatures (60-65℃) to provide sufficient driving force for molecular chain motion. The two-stage annealing is continuous without interruption, forming a complete temperature gradient. After annealing, the material is directly fed into a fluidized bed for rapid cooling, crystal locking, and drying within 90 seconds, avoiding RS3 retrogradation and increased energy consumption caused by separating cooling and drying in traditional methods. Beneficial effects (1) The two-stage annealing coupled with rapid drying integrated design makes the process simpler and the energy consumption lower. (2) The temperature gradient design optimizes the two stages of starch swelling and ordered rearrangement, resulting in higher RS3 generation efficiency. (3) The product has a GI value ≤59, a resistant starch content ≥8.5%, and an RS3 melting temperature ≥120℃. (4) It is purely physical with zero additives, and the ingredient list contains only wheat flour. Detailed Implementation Example 1 (Two-stage annealing of low-gluten wheat flour) Take 1000g of low-gluten wheat flour (9% protein, 20% wet gluten), add water to adjust to 22%, and adjust the temperature to 48℃. Feed the material into a constant temperature and humidity annealing device. The first stage is annealing at 52℃ and 85% humidity for 4 minutes to allow the starch to initially swell. Then, directly raise the temperature to 62℃ and continue annealing at the same humidity for 5 minutes to promote the rapid and orderly rearrangement of amylose along the microcrystalline surface. After two stages of annealing, the material is directly fed into a fluidized bed and rapidly cooled from 62℃ to 23℃ within 90 seconds with -3℃ cold air, while simultaneously drying to a moisture content of 12.0%. Sieve to obtain the final 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 (using only the first stage of low-temperature annealing) The second-stage annealing in Example 1 was cancelled, and only the first-stage annealing at 52°C for 4 minutes was performed, while the other conditions remained unchanged. The resulting product had a low resistant starch content and a high GI value. This demonstrates that low-temperature annealing alone is insufficient to achieve sufficient RS3 formation, requiring a second stage of ordered rearrangement at a higher temperature. Comparative Example 2 (using only the second-stage high-temperature annealing) The first-stage annealing in Example 1 was cancelled, and the second-stage annealing at 62°C for 5 minutes was performed directly, while the other conditions remained unchanged. The resulting product had a lower resistant starch content than in Example 1, and its texture was slightly sticky. This indicates the absence of a first-stage mild swelling phase, resulting in insufficient swelling of the starch granules, partial destruction of the microcrystalline framework, and a decrease in RS3 formation efficiency. Comparative Example 3 (natural cooling after two-stage annealing) The rapid cooling and drying method in Example 1 was changed to natural cooling to room temperature followed by drying, while the other conditions remained unchanged. The resulting product had a high GI value, and the RS3 melting temperature was below 120℃. This indicates 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-quench drying production lines. The core equipment includes a biaxial differential atomizing continuous conditioning tank, a closed mesh belt continuous annealing tower with ±0.5℃ global temperature control accuracy and independent zone temperature control, and an integrated fluidized bed quench drying system. The zone-controlled annealing tower can be set to 50-55℃ and 60-65℃ in different temperature zones, with the material continuously conveyed by a mesh belt to achieve continuous heating between the two annealing stages.

Claims

1. A method for modifying low-gluten wheat flour by two-stage annealing coupled with rapid cooling and drying, 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%, while controlling the temperature at 45-50℃; b. First-stage annealing: The conditioned material is kept in a constant humidity environment with a relative humidity of 80%-95% for 3-5 minutes within a temperature window of 50-55℃ to allow the starch to initially swell while retaining the natural microcrystalline skeleton. c. Second-stage annealing: The material after the first-stage annealing is heated to 60-65℃ in the same constant humidity environment and annealed for 4-6 minutes to promote the rapid and orderly rearrangement of the amylose along the retained microcrystalline surface to form high-melting-point RS3 type resistant starch with a melting temperature ≥120℃. d. Rapid cooling and drying: The material after the second-stage annealing is directly fed into a fluidized bed and rapidly cooled to below 25°C within 90 seconds, while being dried to a moisture content of 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, In step b, the first-stage annealing temperature is 52-54℃ and the time is 4 minutes; in step c, the second-stage annealing temperature is 62-64℃ and the time is 5 minutes.

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

5. The method according to claim 1, characterized in that, The annealing process in steps b and c is carried out in an environment with a relative humidity of 82%-88%, and the two-stage annealing is carried out continuously without interruption.

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.