Annealing crystallization strengthening method specific to high straight chain rice

Abstract

The application discloses a high-straight-chain rice-specific annealing crystallization strengthening method and belongs to the technical field of grain deep processing. High-straight-chain rice with a straight-chain starch content of more than or equal to 28% is wet-heat precooked to a gelatinization degree of 45%-65%, and then immediately annealed in a constant-humidity environment at 65-70 DEG C for 10-15 minutes, so that the gelatinized straight-chain starch molecules are fully and orderly rearranged along the residual microcrystal surface to form high-melting-point RS3 resistant starch with a melting temperature of more than or equal to 120 DEG C; then, forced rapid cooling is performed until the rice body center temperature is less than or equal to 25 DEG C, low-temperature drying is performed at a temperature of not more than 50 DEG C until the moisture content is 11%-13%, and sealing packaging is performed. The application performs crystallization strengthening according to the characteristics of high straight-chain rice, i.e., high straight-chain starch content, and the obtained product has a GI value of less than or equal to 55, a resistant starch content of more than or equal to 10%, and a RS3 melting temperature of more than or equal to 120 DEG C, and is suitable for sugar-controlled staple food and functional food raw materials.

Description

Technical Field

[0001] This invention belongs to the field of deep grain processing technology, specifically involving a purely physical annealing modification method for high amylose rice varieties, used to maximize the generation of RS3 type resistant starch. Background Technology High-amylose rice refers to a special variety with a significantly higher amylose content than ordinary rice, typically ≥28%, far exceeding the 20%-25% of ordinary indica rice and the 15%-20% of japonica rice. A high amylose content means more amylose molecules can participate in ordered rearrangement during annealing, resulting in a greater potential for RS3 formation. However, existing rice annealing processes are designed for rice with ordinary amylose content and have not been specifically optimized for high-amylose rice. If the annealing parameters for ordinary indica or japonica rice are directly applied, the amylose dissolution in high-amylose rice will be insufficient, failing to fully realize its RS3 formation potential. Therefore, high-amylose rice requires a specially optimized annealing process that fully utilizes its high amylose advantage while achieving enhanced RS3 crystallization through higher annealing temperatures and longer annealing times. Summary of the Invention Purpose of the invention The purpose of this invention is to provide an annealing modification method specifically for high amylose rice, which maximizes the generation efficiency of RS3 resistant starch by optimizing the matching of temperature and time, resulting in a product GI value ≤ 55 and a resistant starch content ≥ 10%. Technical solution The present invention includes the following steps: (1) pre-cooking high amylose rice with wet heat to a gelatinization degree of 45%-65%; (2) annealing in a constant humidity environment of 65-70℃ and 80%-95% for 10-15 minutes, the temperature window being higher than that of ordinary rice annealing temperature window; (3) forcibly and rapidly cooling to a core temperature of ≤25℃; (4) drying at a low temperature not exceeding 50℃; and (5) sealing and packaging. Core Mechanism High-amylose rice has an amylose content ≥28%, requiring higher temperatures and longer annealing times to ensure sufficient amylose dissolution and orderly rearrangement. The 65-70℃ annealing window, higher than the 62-65℃ window of ordinary indica rice and the 65-68℃ window of japonica rice, provides a stronger driving force for molecular chain motion. Excessively high temperatures (>70℃) can lead to microcrystalline melting and collapse, resulting in the loss of heterogeneous nucleation; excessively low temperatures (<65℃) result in insufficient amylose dissolution, preventing the full realization of RS3 formation potential. The annealing time of 10-15 minutes, longer than that of ordinary rice, is necessary to fully utilize the RS3 formation potential of high-amylose rice. Beneficial effects (1) A special annealing scheme for high amylose rice was proposed for the first time, which reduced the GI value to below 55 and increased the resistant starch content to above 10%. (2) The resistant starch retention rate after secondary cooking of the product is ≥75%. (3) The annealing time is 10-15 minutes, which is suitable for industrial continuous production. (4) Pure physical process with zero additives. Detailed Implementation Example 1 (High-amylose rice annealing and crystallization enhancement) Take 1000 kg of high amylose rice (amylose content 30%) and pre-cook it with normal pressure steam until the gelatinization degree reaches 55%. Transfer the pre-cooked rice to a constant temperature and humidity annealing equipment and anneal at 68℃ and 85% humidity for 13 minutes. After annealing, cool it with cold water spray combined with side blowing for 75 seconds until the core temperature of the rice reaches 23℃. Then, dry it at 45℃ for 3 hours until the moisture content reaches 12.0%, and vacuum seal it for packaging. The resulting product showed a significantly lower GI value, a significantly higher resistant starch content, and an RS3 melting temperature exceeding 120℃. The rice had a normal texture after secondary cooking. Comparative Example 1 (annealing temperature exceeding 70°C) The annealing temperature in Example 1 was changed to 72°C, 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 temperatures exceeding 70°C lead to the collapse of the microcrystalline framework and the loss of heterogeneous nucleation. Comparative Example 2 (annealing temperature below 65℃) The annealing temperature in Example 1 was changed to 62°C, while the other conditions remained unchanged. The resulting product had a low resistant starch content, insufficient RS3 formation efficiency, and a high GI value. This indicates that amylose dissolution is insufficient below 65℃, leading to a significant decrease in annealing efficiency. Comparative Example 3 (annealing time too short) The annealing time of Example 1 was shortened to 8 minutes, while the other conditions remained unchanged. The resulting product had a resistant starch retention rate of less than 75% after secondary cooking and a high GI value. This indicates that insufficient annealing time led to inadequate RS3 lattice repair. Comparative Example 4 (annealing time too long) The annealing time of Example 1 was extended to 18 minutes, while the other conditions remained unchanged. The resulting rice was harder after being steamed a second time. This indicates that excessive annealing time led to excessive starch crystallization, resulting in a deteriorated texture. Detection methods Amylose content was determined by iodine colorimetric method, gelatinization degree was determined by enzymatic hydrolysis method, GI value was determined by ISO26642:2010 standard method, RS3 melting temperature was determined by differential scanning calorimetry, and resistant starch content was determined by AOAC 2002.02 standard method. Industrial applications This invention can be implemented on existing continuous pre-cooking-annealing-cooling-drying production lines. The core equipment includes a steam pre-cooking machine, a closed continuous annealing tower with a temperature control accuracy of ±0.5℃ across the entire range, a cold water spray quenching system, and a low-temperature airflow drying device.

Claims

1. A method for strengthening high-amylose rice through annealing and crystallization, characterized in that, Includes the following steps: a. Moist heat precooking: High amylose rice with an amylose content ≥28% is precooked in a moist heat environment until the starch gelatinization degree is 45%-65%; b. Isothermal annealing: The pre-cooked rice is kept in a constant humidity environment with a relative humidity of 80%-95% for 10-15 minutes within a temperature window of 65-70℃. The temperature window is higher than that of ordinary rice annealing temperature window, which is adapted to the high amylose content of high amylose rice. This allows the gelatinized amylose molecules to fully and orderly attach and rearrange the crystal lattice along the surface of the residual natural microcrystals, forming high melting point RS3 type resistant starch with a melting temperature ≥120℃. c. Forced rapid cooling: Cool the annealed rice to a core temperature of ≤25℃ within 50-120 seconds to terminate the gelatinization reaction; d. Low-temperature drying: Dry the cooled rice at a temperature not exceeding 50℃ until the moisture content reaches 11%-13%; e. Sealed packaging: The dried rice is sealed in packaging.

2. The method according to claim 1, characterized in that, The gelatinization degree of the wet heat precooking in step a is preferably 50%-60%.

3. The method according to claim 1, characterized in that, The annealing temperature in step b is 67-68℃, and the annealing time is 12-13 minutes.

4. The method according to claim 1, characterized in that, The forced rapid cooling described in step c uses cold water spray or cold air blast cooling, with a cooling time of 60-90 seconds and a cooling medium temperature ≤25℃.

5. The method according to claim 1, characterized in that, The drying temperature in step d is 40-45℃, and the total drying time is 2.5-3.5 hours.

6. A pre-cooked rice with high amylose content, low glycemic index, and high resistant starch, characterized in that: The rice is prepared by the method described in any one of claims 1-5, and the rice simultaneously meets the following requirements: GI value ≤ 55, resistant starch content ≥ 10%, RS3 type resistant starch melting temperature ≥ 120℃, and resistant starch retention rate ≥ 75% after secondary cooking.

7. The rice according to claim 6, characterized in that, The rice has a GI value ≤ 50 and a resistant starch content ≥ 12%.

8. The application of the rice described in claim 6 or 7 in the preparation of sugar-controlled staple foods, functional food ingredients, meal replacement powders, and biodegradable packaging materials.