Starch annealing efficiency improvement method based on moisture activity regulation

Abstract

The application discloses a starch annealing efficiency improving method based on moisture activity regulation, and belongs to the technical field of grain deep processing. The starch-containing raw material is conditioned to a moisture activity of 0.75-0.95, annealing is carried out in a constant humidity environment with relative humidity matching the moisture activity at a temperature window of 50-65 DEG C for 8-20 minutes, the moisture activity is accurately controlled and kept constant during the annealing process, the straight-chain starch of the gelatinized part is orderly rearranged along the retained endogenous skeleton, and high-melting-point RS3 type resistant starch with a melting temperature of greater than or equal to 120 DEG C is formed; then, cooling, setting and low-temperature drying are carried out. The application is a pure physical zero-addition process, moisture activity is used as a key control variable for starch annealing for the first time, the stability of the annealing efficiency and the consistency between product batches are realized, the application is suitable for all starch-containing raw materials, the obtained product has a GI value of less than or equal to 65 and a resistant starch content of greater than or equal to 7%.

Description

Technical Field

[0001] This invention belongs to the field of deep grain processing technology, specifically relating to a purely physical modification method that improves starch annealing efficiency by precisely controlling water activity. Background Technology The applicant's prior art discloses a method for controlling starch crystallinity based on a ternary window of temperature, moisture, and time, in which moisture content is one of the core parameters. However, controlling only the moisture content while ignoring water activity will lead to continuous moisture exchange between the material and the surrounding environment during annealing, causing fluctuations in the actual water activity, which in turn affects the stability of annealing efficiency and the consistency between product batches. While water activity is a common concept in food preservation, it has never been used as a key control variable in starch annealing processes, nor has the method of precisely matching ambient relative humidity with material water activity to lock in water activity during annealing been proposed. Those skilled in the art have long believed that controlling moisture content is sufficient in starch annealing, failing to recognize the decisive impact of matching ambient humidity and water activity on annealing stability and batch-to-batch consistency. This technical bias has led to significant fluctuations in GI values ​​and resistant starch content between batches in industrial-scale annealing production, severely impacting quality stability, a problem that has remained unresolved for a long time. This invention, for the first time, links ambient humidity with material water activity for control, solving this technical problem. Summary of the Invention Purpose of the invention The purpose of this invention is to provide a starch annealing method based on precise control of water activity, which improves the stability of annealing efficiency and the consistency between product batches by controlling the water activity and keeping it constant during the annealing process. Technical solution The present invention includes the following steps: (1) conditioning to a water activity of 0.75-0.95; (2) annealing at 50-65°C for 8-20 minutes in a constant humidity environment where the relative humidity matches the water activity, wherein the matching means that the relative humidity of the environment is 100 times ±5% of the water activity; (3) cooling and setting; (4) low temperature drying. Core Mechanism Water activity is a thermodynamic parameter that measures the degree of freedom of water in a material, directly affecting the mobility of starch molecular chains and the stability of microcrystals. If the water activity is too low (<0.75), the starch molecular chains lack mobility, resulting in a significant decrease in annealing efficiency; if the water activity is too high (>0.95), there is excessive free water, leading to decreased microcrystal stability and premature melting during annealing. This invention precisely controls the water activity within a window of 0.75-0.95, and by matching the relative humidity of the annealing environment with the water activity of the material, the material neither absorbs nor loses water during the annealing process, maintaining a constant water activity. This ensures the stability of annealing efficiency and batch-to-batch consistency. According to the principle of thermodynamic equilibrium, when the relative humidity of the environment (RH%) equals the material's water activity (Aw) multiplied by 100, the material reaches a dynamic equilibrium in water exchange with the surrounding environment. Beneficial effects (1) For the first time, water activity was used as a key control variable for starch annealing, and dynamic locking of water activity was achieved through environmental humidity linkage control, which solved the problem of batch-to-batch quality fluctuations. (2) Purely physical with zero additives. (3) Annealing time of 8-20 minutes, suitable for industrial continuous production. (4) Good consistency between product batches. Detailed Implementation Example 1 (Wheat flour, water activity regulation) Take 1000g of medium-gluten wheat flour, add water to adjust to a water activity of 0.85, and heat at 48℃. Anneal for 14 minutes in a constant humidity environment of 85% relative humidity and 51℃. Gradually cool to 33℃, and dry at 42℃ to a moisture content of 12.0%. The resulting product exhibited a significantly lower GI value, an RS3 melting temperature exceeding 120℃, and a significantly higher resistant starch content. Continuous production across multiple batches showed minimal fluctuations in the product's GI value and good batch-to-batch consistency. Example 2 (Rice, Water Activity Regulation) Take 1000g of japonica rice, pre-cook it with normal pressure steam until the gelatinization degree is about 38%, and condition it to a water activity of 0.82. Anneal it for 10 minutes in a constant humidity environment of 82% relative humidity and 65℃. Quickly cool it to 23℃ by spraying it with cold water, and dry it at 45℃ until the moisture content is 11.9%. The resulting product has a significantly lower GI value, an RS3 melting temperature above 120℃, and good batch-to-batch consistency. Comparative Example 1 (low water activity) The water activity of Example 1 was adjusted to 0.65, which is lower than the effective window limit of 0.75, while the other conditions remained unchanged. The resulting product had a low resistant starch content and no significant decrease in the GI value. This demonstrates that when the water activity is below 0.75, the starch molecular chain mobility is insufficient, leading to a significant decrease in annealing efficiency. Comparative Example 2 (excessively high water activity) The water activity of Example 1 was adjusted to 0.97, which is higher than the upper limit of the effective window of 0.95, while the other conditions remained unchanged. The resulting product exhibited excessive starch gelatinization, a significantly reduced microcrystal retention rate, and low resistant starch content. This demonstrates that when the water activity exceeds 0.95, excessive free water leads to decreased microcrystal stability. Comparative Example 3 (Mismatch between humidity and water activity in the annealing environment) The relative humidity of the annealing environment in Example 1 was changed to 60%, which did not match the material's water activity of 0.85, while the other conditions remained unchanged. The resulting product continuously lost water during annealing, resulting in a constant decrease in water activity, unstable annealing efficiency, and large fluctuations in GI values ​​between batches. This demonstrates that matching relative humidity with water activity is a necessary condition for ensuring stable annealing efficiency. Detection methods Water activity was measured using a mirror-condenser water activity meter, and calibration was performed according to the instrument's instruction manual. Resistant starch content was determined using the AOAC 2002.02 standard method. GI values ​​were determined using the ISO 26642:2010 standard method. RS3 melting temperature was determined using differential scanning calorimetry. Industrial applications This invention can be implemented on existing continuous grain processing production lines. The core equipment includes a conditioning tank equipped with online water activity monitoring, a closed annealing tower with precise humidity control, and a multi-stage air-cooling or fluidized bed quenching system.

Claims

1. A method for improving starch annealing efficiency based on water activity regulation, characterized in that, Includes the following steps: a. Conditioning: Add water to the starch-containing raw materials to condition them so that their water activity reaches 0.75-0.95, and control the temperature at 45-50℃, so that the starch absorbs water and swells. b. Isothermal annealing: The conditioned material is kept in a constant humidity environment with relative humidity matching the water activity for 8-20 minutes within a temperature window of 50-65℃, so that the degree of starch gelatinization is controlled at 20%-65%, the residual natural microcrystal retention rate is ≥50%, and the amylose in the gelatinized part is orderly rearranged along the retained endogenous skeleton to form high melting point RS3 type resistant starch with a melting temperature ≥120℃; c. Cooling and shaping: Cool the annealed material to below 35°C; d. Low-temperature drying: Dry the cooled material at a temperature not exceeding 60°C until the moisture content is below 13%.

2. The method according to claim 1, characterized in that, The starch-containing raw material is any one or more of rice, wheat, corn, potato, sweet potato, cassava, oats, buckwheat, millet, and sorghum, or starch processed from them.

3. The method according to claim 1, characterized in that, The relative humidity mentioned in step b matching the water activity means that the ambient relative humidity is 100 times ± 5% of the water activity.

4. The method according to claim 1, characterized in that, When the raw material is wheat flour, the water activity is 0.82-0.88, the annealing temperature is 50-55℃, and the annealing time is 13-15 minutes; when the raw material is rice, the water activity is 0.78-0.85, the annealing temperature is 60-65℃, and the annealing time is 9-12 minutes.

5. The method according to claim 1, characterized in that, The cooling and shaping process in step c is selected from any one of gradient slow cooling, cold water spray cooling, or fluidized bed quenching; the gradient slow cooling is a first stage cooling from the annealing temperature to 40-42℃ at a rate of 3-5℃ / min, and a second stage cooling from 40-42℃ to below 35℃ at a rate of 1-2℃ / min; the fluidized bed quenching uses cold air from -5℃ to 0℃ to cool the material from the annealing temperature to below 25℃ within 90 seconds.

6. A low glycemic index cereal powder or starch, characterized in that, Prepared by the method described in any one of claims 1-5, and simultaneously satisfying the following conditions: GI value ≤ 65, resistant starch content ≥ 7%, and RS3 type resistant starch melting temperature ≥ 120℃.

7. The use of the cereal flour or starch according to claim 6 in the preparation of food, pet food, and biodegradable packaging materials.