A method for annealing starch under long time conditions of 20-30 minutes

Abstract

The application discloses a method for annealing treatment of starch under a long-time condition of 20-30 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 (the content of amylose is greater than or equal to 55%) to adjust the moisture content to 20%-30%, annealing the high-amylose corn starch in a constant humidity environment with a temperature of 45-55 DEG C and a relative humidity of 70%-85% for 20-30 minutes, and then rapidly cooling the high-amylose corn starch to below 25 DEG C by using a fluidized bed with cold air at-5 to 0 DEG C within 90 seconds to lock the RS3 crystal lattice structure. In the 20-30 minute interval which is longer than the conventional annealing time (15-20 minutes), the method prevents the risk of excessive hydration of starch particles and breeding of microorganisms caused by long-time annealing by reducing the annealing temperature (45-55 DEG C) and the relative humidity (70%-85% RH), 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 20-30 minute long-time interval.

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 annealing time of 20-30 minutes, which is longer than the conventional annealing time. This method locks in the peripheral parameters of the core underlying patent (annealing time of 15-20 minutes), and by extending the upper limit of the annealing time from 20 minutes to 30 minutes, it blocks the room for competitors to maneuver in the long-term gray area. Background Technology The core patent for purely physical annealing modified RS3 resistant starch discloses an annealing time window of 15-20 minutes. Competitors may attempt to anneal within a 20-30 minute range, slightly longer than 20 minutes, and claim non-infringement on the grounds that "the annealing time is not within the patent holder's required range." Therefore, this patent must be applied for to lock in the parameter boundary of the 20-30 minute long time range. Annealing for 20-30 minutes presents two major technical challenges: overhydration of starch granules and the risk of microbial growth. During prolonged annealing, starch granules are exposed to a warm and humid environment for an extended period, causing them to continuously absorb water and swell, potentially leading to overhydration or even localized gelatinization. Simultaneously, the warm and humid environment of 45-55℃ provides a suitable breeding range for heat-resistant Bacillus species (such as Bacillus subtilis), and extending the annealing time to 20-30 minutes increases the risk of microbial growth. Therefore, it is necessary to reduce the annealing temperature (45-55℃ vs. the conventional 50-58℃) and the relative humidity (70%-85%RH vs. the conventional 80%-95%RH) to prevent overhydration and microbial growth caused by prolonged annealing. Lowering the annealing temperature slows down the rate of water absorption and swelling of starch granules and the rate of molecular chain movement, reducing the risk of overhydration. Lowering the relative humidity reduces the water activity on the surface of starch granules, slowing down the rate of water penetration into the granules. At the same time, the low-humidity environment inhibits the metabolic activity of heat-resistant Bacillus. The synergistic effect of these two factors ensures that the RS3 content is ≥12% and the RS3 melting temperature is ≥120% under long-term conditions of 20-30 minutes. Summary of the Invention Purpose of the invention A method for annealing starch under a long annealing time of 20-30 minutes is provided. This method prevents overhydration and microbial growth caused by prolonged annealing by reducing the annealing temperature and relative humidity, thereby locking in the upper limit of the annealing time. Technical solution High-amylose corn starch (amylose content ≥ 55%) was adjusted with water to a moisture content of 20%-30% and then annealed in a constant temperature and humidity environment at 45-55℃ and 70%-85% relative humidity for 20-30 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 20-30 minutes, the annealing temperature at 45-55℃, the relative humidity at 70%-85%, 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 20 minutes or more than 30 minutes, annealing temperature below 45℃ or above 55℃, relative humidity below 70% or above 85%, 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 20 minutes, the annealing temperature needs to be increased to above 55℃ (falling within the protection range of 50-58℃ / 15-20 minutes for conventional annealing processes); when the annealing time is more than 30 minutes, the risks of overhydration and microbial growth increase significantly, and the RS3 content decreases (e.g., at 35 minutes, the RS3 content is only about 9.2%); when the annealing temperature is below 45℃, the molecular thermal kinetic energy is insufficient, and even if the annealing time is extended, the dissolution and ordered rearrangement of the amylose molecular chains are still insufficient, and the RS3 content cannot meet the standard (e.g., at 42℃, the RS3 content is...). (Approximately 8.8%); when the annealing temperature is above 55℃, the annealing time can be shortened to less than 20 minutes (falling within the 15-20 minute protection range of conventional annealing processes); when the relative humidity is below 70%, the water activity is too low, and the dissolution and migration rate of amylose is insufficient under long-term conditions, resulting in low RS3 formation efficiency; when the relative humidity is above 85%, the starch granules are overhydrated under long-term conditions, and the RS3 content decreases instead; 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 7.2%). Core Mechanism The parameter linkage mechanism of long-term annealing is based on a triple coupling relationship of time, temperature, and humidity. Under long-term conditions of 20-30 minutes, starch granules are exposed to a warm and humid environment for an extended period, gradually accumulating the risk of overhydration. To suppress this overhydration, the annealing temperature must be reduced—from the conventional 50-58℃ to 45-55℃—to slow down the rate of water absorption and swelling of the starch granules and the rate of molecular chain movement. Simultaneously, the relative humidity must be reduced from the conventional 80%-95%RH to 70%-85%RH—lowering water activity slows the rate of water penetration into the granules, avoiding overhydration caused by prolonged high humidity, while the low-humidity environment inhibits the metabolic activity of heat-resistant Bacillus. The triple coupling relationship of time, temperature, and humidity can be quantitatively described as follows: for every 5-minute extension of the annealing time (within the range of 20-30 minutes), to maintain an RS3 content ≥12%, the annealing temperature needs to be reduced by approximately 3-5℃, or the relative humidity needs to be reduced by approximately 3%-5%RH. For example, under 20-minute conditions, an annealing temperature of approximately 52-55℃ and a humidity of approximately 80%-85%RH can achieve an RS3 ≥12%; under 25-minute conditions, an annealing temperature of approximately 48-52℃ and a humidity of approximately 75%-80%RH can achieve the same RS3 level; under 30-minute conditions, an annealing temperature of approximately 45-48℃ and a humidity of approximately 70%-75%RH can achieve the same RS3 level. This quantitative parameter linkage is the core technical feature of the long-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 a long annealing time of 20-30 minutes, producing unexpected technical effects—even with an annealing time 5-10 minutes longer than conventional annealing, it still achieves the same RS3 content and melting point levels as conventional annealing processes through parameter linkage compensation (reducing temperature + reducing humidity). Comparative Example 5 (annealed with the same raw material at 55℃ / 18 minutes / 88%RH) has an RS3 content of approximately 13.5%, while Example 1 of this patent (50℃ / 25 minutes / 78%RH) has an RS3 content of approximately 13.3%—under the premise of essentially the same RS3 content, the annealing temperature was reduced by 5℃ (from 55℃ to 50℃). This technical effect of "not reducing quality over a long period of time, achieving RS3 compliance through parameter linkage, and being more energy-efficient" is something that those skilled in the art could not have anticipated from conventional annealing processes. When faced with the technical problem of "extending annealing time," those skilled in the art, following conventional testing methods, would simply extend the time while maintaining the same temperature and humidity as conventional processes (50-58℃ / 80-95%RH), without anticipating the need to simultaneously reduce the annealing temperature and relative humidity to prevent overhydration and achieve RS3 content compliance. Detailed Implementation Example 1 (50°C long-term annealing) High-amylose corn starch (amylose content approximately 58%) was added to water and adjusted to a moisture content of approximately 25%. It was then placed in a constant temperature and humidity apparatus and annealed at 50℃ and 78%RH for 25 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 13.3%±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 (45℃ long-term annealing + high straight chain ≥70%) Take extra-high amylose corn starch (amylose content approximately 72%) with a moisture content of 28%, and anneal it at 45℃ and 72%RH for 30 minutes. The RS3 content is 16.2%±0.8% (≥15%), and the RS3 melting temperature is 127±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 25% and annealed at 50°C and 80% RH for 28 minutes. The RS3 content was 12.1% ± 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 25 minutes in Example 1 to 28 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 more than 30 minutes - RS3 not up to standard) Using the same raw materials and process as in Example 1, the annealing time was 35 minutes (>30 minutes). The RS3 content was 9.2% ± 0.5% (<12%), and the RS3 melting temperature was 116 ± 2℃ (<120℃). Excessive annealing time led to overhydration of the starch granules, localized gelatinization, and a decrease in the RS3 content. This demonstrates that 30 minutes is the upper limit for RS3 formation. Comparative Example 2 (annealing for less than 20 minutes - falling within the range of conventional annealing processes) Using the same raw materials and process as in Example 1, the annealing time was 16 minutes (<20 minutes) and the annealing temperature was 58°C (>55°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 shorter than 20 minutes fall within the protection range of conventional annealing processes, and this method clearly demarcates itself from conventional annealing processes at the 20-minute boundary. Comparative Example 3 (Temperature below 45℃ - RS3 fails to meet standard) Using the same raw materials and process as in Example 1, the annealing temperature was 42°C (<45°C), and the annealing time was 25 minutes. The RS3 content was 8.8% ± 0.5% (<12%). Under prolonged conditions, the temperature was too low, resulting in insufficient molecular thermal kinetic energy and inadequate dissolution and orderly rearrangement of the amylose molecular chains. Even with extended annealing time, the RS3 content could not meet the target. Comparative Example 4 (linear chain content < 55% - RS3 not up to standard) Ordinary corn starch (amylose content approximately 27%, <55%) was used, annealed at 50°C for 25 minutes, and at 78% RH. The RS3 content was 7.2% ± 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 / 88%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 88% 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 (13.3%), but the annealing temperature (55°C) was 5°C higher than that in Example 1 (50°C), and the humidity (88% RH) was 10 percentage points higher than that in Example 1 (78% RH). This demonstrates that the long-time annealing process of this patent, while maintaining a essentially unchanged RS3 content, reduces the annealing temperature by 5°C and the relative humidity by 10 percentage points—resulting in greater energy efficiency and lower microbial risk. This "long-time annealing without quality reduction, greater energy efficiency, and greater safety" technical effect is something that those skilled in the art could not anticipate from conventional annealing processes. Comparative Example 6 (relative humidity below 70% - RS3 not up to standard) Using the same raw materials and process as in Example 1, the annealing temperature was 50°C, the annealing time was 25 minutes, and the relative humidity was 65% (<70%). The RS3 content was 9.0% ± 0.5% (<12%). Under long-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 85% - RS3 not up to standard) Using the same raw materials and process as in Example 1, the annealing temperature was 50°C, the annealing time was 25 minutes, and the relative humidity was 90% (>85%). The RS3 content was 8.5% ± 0.5% (<12%). Under prolonged conditions with excessively high relative humidity, the starch granules continuously absorbed water and became overhydrated, resulting in localized 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 long annealing time range of 20-30 minutes. Annealing time is controlled at 20-30 minutes, annealing temperature at 45-55℃, relative humidity at 70%-85%, and 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 20 minutes or more than 30 minutes, temperature below 45℃ or above 55℃, humidity below 70% or above 85%, 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 separately applied 10-15 minute short-time annealing method, constitutes a complete protection loop in the annealing time dimension—10-15 minutes (short-time method) → 15-20 minutes (conventional method) → 20-30 minutes (this 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 a long-term condition of 20-30 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 20%-30%; b. Long-term annealing: The conditioned material is annealed in a constant humidity environment at an annealing temperature of 45-55℃ and a relative humidity of 70%-85% for 20-30 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 48-52℃, the annealing time is 22-26 minutes, the relative humidity is 75%-80%, 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 22%-28%; the annealing time in step b is 25-30 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.