A method for annealing starch under short time conditions of 10-15 minutes

Abstract

The application discloses a method for annealing treatment of starch under short-time condition of 10-15 minutes, and belongs to the technical field of deep processing of starch. The method comprises the following steps: adding water to high-amylose corn starch (amylose content is greater than or equal to 55%) to adjust the moisture content to 25%-35%, annealing the high-amylose corn starch in a constant humidity environment with a relative humidity of 88%-98% and at a temperature of 58-68 DEG C for 10-15 minutes, and then rapidly cooling the high-amylose corn starch to below 25 DEG C by using a fluidized bed with cold air at a temperature of-5 to 0 DEG C within 90 seconds to lock the RS3 crystal lattice structure. In the method, the annealing temperature (58-68 DEG C) and the relative humidity (88%-98% RH) are increased to compensate for the decrease in RS3 generation efficiency caused by short time in the 10-15 minute interval which is shorter than the conventional annealing time (15-20 minutes), the content of RS3 type resistant starch obtained is greater than or equal to 12% (determined according to the standard method AOAC 2002.02), and the melting temperature of RS3 is greater than or equal to 120 DEG C (determined according to the differential scanning calorimetry method). The method locks the parameter boundary of the pure physical annealing modification process in the short-time interval of 10-15 minutes.

Description

Technical Field

[0001] This invention belongs to the field of starch deep processing technology, specifically involving a method for purely physical annealing modification of high amylose starch under a shorter annealing time of 10-15 minutes than conventional annealing. This method locks in the peripheral parameters of the core underlying patent (annealing time of 15-20 minutes), extending the lower boundary of the annealing time from 15 minutes to 10 minutes, thus blocking the room for competitors to maneuver in the short-term gray area. Background Technology Annealing under short 10-15 minute conditions faces a key technical hurdle: insufficient time for the dissolution and ordered rearrangement of amylose molecular chains. Within the conventional 15-20 minute annealing window, sufficient time is required for the migration of amylose molecular chains from the interior of the starch granule to the surface microcrystalline template and for their ordered arrangement along the template. When the annealing time is shortened to 10-15 minutes, the amount of molecular chain dissolution and the degree of ordered rearrangement may be insufficient, leading to a decrease in RS3 content. This decrease in RS3 formation efficiency due to the short annealing time needs to be compensated for by increasing the annealing temperature (58-68℃ vs. the conventional 50-58℃) and the relative humidity (88%-98%RH vs. the conventional 80%-95%RH). Increasing the annealing temperature is the main means of compensating for the decrease in efficiency during short-term annealing. At 58-68℃, the thermal kinetic energy of amylose molecules is significantly enhanced, accelerating the migration rate from the interior of the granules to the surface microcrystalline template, allowing for complete dissolution and ordered rearrangement in a shorter time. Increasing relative humidity increases the water activity on the starch granule surface, increasing the driving force for water penetration into the granules, further accelerating the dissolution rate of amylose molecules. The synergistic effect of these two factors ensures that the RS3 content is ≥12% and the RS3 melting temperature is ≥120℃ within a short time of 10-15 minutes. Summary of the Invention Purpose of the invention A method for annealing starch under short-time conditions of 10-15 minutes is provided. The method compensates for the decrease in RS3 formation efficiency caused by the short annealing time by increasing the annealing temperature and increasing the relative humidity, thereby locking the lower boundary of the annealing time. Technical solution High-amylose corn starch (amylose content ≥ 55%) was adjusted with water to a moisture content of 25%-35% and then annealed in a constant temperature and humidity environment at 58-68℃ and 88%-98% relative humidity for 10-15 minutes. During annealing, amylose molecules rearranged orderly along the surface of residual microcrystals to form RS3-type resistant starch. After annealing, the starch was rapidly cooled to below 25℃ within 90 seconds using cold air at -5 to 0℃ in a fluidized bed to lock the RS3 crystal structure, and then dried at a low temperature not exceeding 50℃ until the moisture content was ≤ 13%. The resulting RS3-type resistant starch had a content ≥ 12% (determined according to the AOAC 2002.02 standard method) and an RS3 melting temperature ≥ 120℃ (determined by differential scanning calorimetry). The annealing time is controlled at 10-15 minutes, the annealing temperature at 58-68℃, the relative humidity at 88%-98%, and the amylose content in the starch raw material is controlled at ≥55%. These four parameter windows together constitute the protection range of this method. Under the conditions of annealing time less than 10 minutes or more than 15 minutes, annealing temperature below 58℃ or above 68℃, relative humidity below 88% or above 98%, and amylose content below 55%, the RS3 content and / or RS3 melting temperature will not be able to reach the standards of ≥12% and ≥120℃. Specifically: When the annealing time is less than 10 minutes, even with increased temperature and humidity, the dissolution and ordered rearrangement of the amylose molecular chains are still insufficient, and the RS3 content cannot meet the standard (e.g., at 8 minutes, the RS3 content is only about 9.0%); when the annealing time is more than 15 minutes, the annealing temperature can be reduced to below 58℃ (falling within the core patent's 50-58℃ / 15-20 minute protection range); when the annealing temperature is below 58℃, the molecular thermal kinetic energy is insufficient, and sufficient rearrangement cannot be completed in a short time, resulting in the RS3 content not meeting the standard; when the annealing temperature is higher than... At 68℃, starch granules begin to over-gelatinize at high temperatures, and the RS3 content decreases (e.g., at 72℃, the RS3 content is only about 8.5%). When the relative humidity is below 88%, the water activity is insufficient, and the amylose dissolution rate is not fast enough in a short time. When the relative humidity is above 98%, it is close to saturation humidity, making it difficult to guarantee the accuracy of humidity control in the equipment, and free water condenses on the surface of the starch granules. When the amylose content is below 55%, the amylose template is insufficient, and the RS3 content cannot meet the standard (e.g., when the amylose content is 27%, the RS3 content is only about 7.5%). Core Mechanism The parameter linkage mechanism of short-time annealing is based on a triple coupling relationship of time, temperature, and humidity. Under short-time conditions of 10-15 minutes, the time window for the dissolution and ordered rearrangement of amylose molecules is significantly shortened. To compensate for this insufficient time, the annealing temperature must be increased—from the conventional 50-58℃ to 58-68℃—utilizing higher thermal kinetic energy to accelerate the migration of molecular chains from the interior of the granules to the surface microcrystalline template and their ordered arrangement along the template. Simultaneously, the relative humidity must be increased from the conventional 80%-95%RH to 88%-98%RH—increasing water activity increases the water concentration gradient on the starch granule surface, amplifies the driving force for water penetration into the granule interior, and further accelerates the dissolution of amylose molecules. The triple coupling relationship of time, temperature, and humidity can be quantitatively described as follows: for every 2 minutes the annealing time is shortened (within the range of 10-15 minutes), to maintain an RS3 content ≥12%, the annealing temperature needs to be increased by approximately 3-5℃, or the relative humidity needs to be increased by approximately 3%-5%RH. For example, under 15-minute conditions, an annealing temperature of approximately 58-62℃ and a humidity of approximately 88%-92%RH can achieve an RS3 ≥12%; under 13-minute conditions, an annealing temperature of approximately 62-65℃ and a humidity of approximately 92%-95%RH can achieve the same RS3 level; under 10-minute conditions, an annealing temperature of approximately 65-68℃ and a humidity of approximately 95%-98%RH can achieve the same RS3 level. This quantitative parameter linkage is the core technical feature of the short-time annealing process and the essential difference between this method and the conventional 50-58℃ / 15-20 minutes / 80%-95%RH annealing process. This method achieves an RS3 content ≥12% and a melting point ≥120℃ under short-time conditions of 10-15 minutes, producing unexpected technical effects—under conditions shorter than conventional annealing times of 5-10 minutes, it still achieves the same RS3 content and melting point levels as conventional annealing processes through parameter linkage compensation (increasing temperature + increasing humidity). Comparative Example 5 (annealed with the same raw materials at 55℃ / 18 minutes / 90%RH) has an RS3 content of approximately 13.5%, while Example 1 of this patent (65℃ / 13 minutes / 94%RH) has an RS3 content of approximately 13.6%—under the premise of essentially the same RS3 content, the annealing time is shortened by approximately 28% (from 18 minutes to 13 minutes). This technical effect of "short time without quality reduction and achieving RS3 compliance through parameter linkage" is something that those skilled in the art could not have anticipated from conventional annealing processes. When faced with the technical problem of "shortening annealing time", those skilled in the art, according to conventional testing methods, would simply shorten the time while keeping the temperature and humidity consistent with conventional processes (50-58℃ / 80-95%RH), and would not have anticipated that it would be necessary to simultaneously increase the annealing temperature and increase the relative humidity to achieve RS3 content compliance. Detailed Implementation Example 1 (Short-time annealing at 65°C) High-amylose corn starch (amylose content approximately 58%) was added to water and adjusted to a moisture content of approximately 30%. It was then placed in a constant temperature and humidity apparatus and annealed at 65℃ and 94%RH for 13 minutes. After annealing, the starch was rapidly cooled to below 25℃ within 90 seconds using a fluidized bed with -5℃ cold air to lock the RS3 lattice structure. It was then dried at 45℃ to a moisture content of approximately 12%. Three batches were tested (n=3): RS3 content 13.6%±0.5% (≥12%, determined according to AOAC 2002.02 standard method), RS3 melting temperature 125±2℃ (≥120℃, determined by DSC, heating rate 10℃ / min, nitrogen atmosphere, sample amount 3-5mg, temperature range 30-180℃, recording the peak temperature of the endothermic peak). Example 2 (68℃ short-time annealing + high straight chain ≥70%) Take extra-high amylose corn starch (amylose content approximately 72%), with a moisture content of 32%, and anneal it at 68℃ and 96%RH for 10 minutes. The RS3 content is 16.8%±0.8% (≥15%), and the RS3 melting temperature is 128±1℃ (≥122℃). Example 3 (Boundary verification with 55% amylose content) High-amylose corn starch (amylose content exactly 55%) was added to adjust the moisture content to approximately 30% and annealed at 65°C and 96% RH for 14 minutes. The RS3 content was 12.2% ± 0.5% (just ≥ 12%), and the RS3 melting temperature was 121 ± 2°C (≥ 120°C). This example verifies that an amylose content of 55% is the lower limit for this method—when the amylose content is exactly 55%, the annealing time needs to be extended from 13 minutes in Example 1 to 14 minutes to compensate for the relative deficiency of the amylose template, and the resulting RS3 content just reaches the threshold of ≥ 12%. Comparative Example 1 (annealing for less than 10 minutes - RS3 not up to standard) Using the same raw materials and process as in Example 1, the annealing time was 8 minutes (<10 minutes). The RS3 content was 9.0% ± 0.5% (<12%), and the RS3 melting temperature was 114 ± 2℃ (<120℃). The annealing time was too short, resulting in insufficient dissolution and ordered rearrangement of the amylose molecular chains. Even with increased temperature to 65℃ and humidity to 94% RH, the RS3 formation efficiency still could not meet the target. This demonstrates that 10 minutes is the absolute lower limit for RS3 formation time. Comparative Example 2 (annealing for more than 15 minutes - falling within the range of conventional annealing processes) Using the same raw materials and process as in Example 1, the annealing time was 18 minutes (>15 minutes) and the annealing temperature was 55°C (<58°C). The RS3 content was 13.5% ± 0.5% (meets the standard, but falls within the protection range of the conventional 50-58°C / 15-20 minute annealing process). This demonstrates that annealing processes longer than 15 minutes fall within the protection range of conventional annealing processes, and this method clearly demarcates itself from conventional annealing processes at the 15-minute boundary. Comparative Example 3 (Temperature below 58℃ - RS3 not up to standard) Using the same raw materials and process as in Example 1, the annealing temperature was 52°C (<58°C), and the annealing time was 13 minutes. The RS3 content was 8.8% ± 0.5% (<12%). Under short-term conditions, the temperature was too low, resulting in insufficient molecular thermal kinetic energy, inadequate dissolution and orderly rearrangement of the amylose molecular chains, and the RS3 content could not meet the standard. Comparative Example 4 (linear chain content < 55% - RS3 not up to standard) Ordinary corn starch (amylose content approximately 27%, <55%) was used, annealed at 65°C for 13 minutes, and at 94% RH. The RS3 content was 7.5% ± 0.5% (<12%). Due to insufficient amylose template, the RS3 content could not be met even when the annealing temperature, time, and humidity were within the specified range. Comparative Example 5 (Conventional annealing process window annealing - 55℃ / 18 minutes / 90%RH) Using the same high amylose corn starch as in Example 1 (amylose content approximately 58%), a conventional annealing process window was employed: annealing at 55°C and 90% RH for 18 minutes. The RS3 content was 13.5% ± 0.5%, and the RS3 melting temperature was 126 ± 2°C. The RS3 content (13.5%) in this comparative example was not significantly different from that in Example 1 (13.6%), but the annealing time (18 minutes) was approximately 38% longer than that in Example 1 (13 minutes). This demonstrates that the short-time annealing process of this patent reduces the annealing time by approximately 28% while maintaining a substantially similar RS3 content—a technical effect that would not be expected by those skilled in the art from conventional annealing processes. Comparative Example 6 (relative humidity below 88% - RS3 not up to standard) Using the same raw materials and process as in Example 1, the annealing temperature was 65°C, the annealing time was 13 minutes, and the relative humidity was 84% ​​(<88%). The RS3 content was 9.2% ± 0.5% (<12%). Under short-term conditions, the relative humidity was too low, the water activity was insufficient, the dissolution and migration rate of the amylose molecular chains were insufficient, and the RS3 formation efficiency could not meet the standard. Comparative Example 7 (relative humidity above 98% - equipment humidity control is difficult and RS3 does not meet the standard) Using the same raw materials and process as in Example 1, the annealing temperature was 65°C, the annealing time was 13 minutes, and the relative humidity was 99% (>98%). The RS3 content was 8.8% ± 0.5% (<12%). Under near-saturated humidity conditions, the humidity control accuracy of the equipment was difficult to guarantee, and free water condensed on the surface of the starch granules. Local overhydration led to gelatinization, and the RS3 content actually decreased. Industrial applications This method locks in the parameter boundaries of purely physically annealed modified RS3 resistant starch within a short time range of 10-15 minutes. Annealing time is controlled at 10-15 minutes, annealing temperature at 58-68℃, relative humidity at 88%-98%, and the amylose content in the starch raw material is controlled at ≥55%. These four parameter windows together constitute the protection range of this method. Any deviation of parameters from the above windows (time less than 10 minutes or more than 15 minutes, temperature below 58℃ or above 68℃, humidity below 88% or above 98%, amylose content below 55%) will result in the RS3 content and / or RS3 melting temperature failing to reach the standards of ≥12% and ≥120℃. This method, together with the conventional 15-20 minute annealing method and the 20-30 minute long-time annealing method in another application, forms a complete protection loop in the annealing time dimension—10-15 minutes (this method) → 15-20 minutes (conventional method) → 20-30 minutes (long-time method), providing comprehensive coverage across the entire time range. The resulting RS3 type resistant starch is suitable for low-GI foods, pharmaceutical excipients, industrial raw materials, or pet food.

Claims

1. A method for annealing starch under short-time conditions of 10-15 minutes, characterized in that, Includes the following steps: a. Conditioning: Add water to high amylose corn starch (amylose content ≥55%) and condition to a moisture content of 25%-35%; b. Short-time annealing: The conditioned material is annealed in a constant humidity environment at an annealing temperature of 58-68℃ and a relative humidity of 88%-98% for 10-15 minutes, so that the amylose molecules rearrange in an orderly manner along the surface of the residual microcrystals to generate RS3 type resistant starch. c. Rapid cooling and crystal locking: The annealed material is rapidly cooled to below 25°C within 90 seconds using a fluidized bed with cold air at -5 to 0°C to lock the RS3 lattice structure. d. Drying: Dry the rapidly cooled material at a temperature not exceeding 50°C until the moisture content is ≤13%; The obtained RS3 resistant starch content is ≥12% (determined according to AOAC 2002.02 standard method), and the melting temperature of RS3 resistant starch is ≥120℃ (determined by differential scanning calorimetry, heating rate 10℃ / min, nitrogen atmosphere, sample amount 3-5mg, temperature range 30-180℃, and the peak temperature of the endothermic peak is recorded).

2. The method according to claim 1, characterized in that, The annealing temperature in step b is 62-66℃, the annealing time is 12-14 minutes, the relative humidity is 92%-96%, and the resulting RS3 type resistant starch has a melting temperature ≥122℃.

3. The method according to claim 1, characterized in that, The high amylose corn starch in step a has an amylose content of ≥70% and a moisture content of 28%-33%; the annealing time in step b is 10-12 minutes, and the resulting RS3 resistant starch content is ≥15%.

4. The application of RS3 resistant starch prepared according to claim 1 in low-GI foods, pharmaceutical excipients, industrial raw materials or pet foods.