A method for annealing high amylose starch at 40-45% moisture content

Abstract

The application discloses a method for annealing treatment of high amylose starch under 40%-45% high moisture content, 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 40%-45%, annealing for 20-30 minutes in a constant humidity environment with a temperature of 45-55 DEG C and a relative humidity of 75%-85%, and then rapidly cooling to 25 DEG C or below within 90 seconds by using a fluidized bed with cold air at-5 to 0 DEG C to lock the RS3 crystal lattice structure. In the 40%-45% interval which is higher than the conventional moisture content (20%-35%), the method prevents excessive hydration of starch particles under high moisture conditions by reducing the annealing temperature (45-55 DEG C) and reducing the relative humidity (75%-85% RH), the obtained RS3 resistant starch content is greater than or equal to 12% (determined according to the AOAC 2002.02 standard method), and the RS3 melting temperature 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 40%-45% high moisture interval.

Description

Technical Field

[0001] This invention belongs to the field of starch deep processing technology, specifically relating to a method for purely physical annealing modification of high amylose starch under conditions of 40%-45% higher than conventional moisture content. This method locks in the patent's peripheral parameters (moisture content 20%-35%) by extending the upper boundary of moisture content to 45%, thus blocking competitors' room for maneuver in the high moisture gray area. Background Technology The core patent for purely physical annealing modified RS3 resistant starch discloses an annealing moisture content window of 20%-35%, using a temperature of 50-58℃ and a relative humidity of 80%-95%. Competitors may attempt annealing in the 40%-45% range, exceeding 35%, and claim non-infringement on the grounds that "the moisture content is not within the patentee's required range." Therefore, it is essential to apply for this patent to lock in the parameter boundary of the 40%-45% high moisture range. Annealing under high moisture conditions of 40%-45% faces key technical challenges: the risk of overhydration of starch granules and microbial growth. When the moisture content exceeds 40%, the starch granules swell sufficiently, leading to accelerated molecular chain migration. However, excessively high moisture content means that the granules are more prone to overhydration and localized gelatinization in prolonged warm environments. Furthermore, the warm, high-moisture environment (45-55℃) is a suitable breeding ground for heat-resistant Bacillus subtilis. Therefore, it is necessary to reduce the annealing temperature (45-55℃ vs. the conventional 50-58℃) and the relative humidity (75%-85%RH vs. the conventional 80%-95%RH) to prevent overhydration and microbial growth under high moisture conditions. Lowering the annealing temperature slows down the water absorption and swelling rate of starch granules and the rate of molecular chain movement, preventing excessive hydration and gelatinization under high moisture conditions. Lowering the relative humidity reduces the transfer of moisture from the environment to the surface of the starch granules, further inhibiting the continuous water absorption of the granules. The synergistic effect of these two factors ensures that the RS3 content is ≥12% and the RS3 melting temperature is ≥120℃ under high moisture conditions of 40%-45%. Summary of the Invention Purpose of the invention A method for annealing high amylose under high moisture conditions of 40%-45% is provided. By reducing the annealing temperature and relative humidity, the method prevents overhydration and microbial growth caused by high moisture content and locks in the upper limit of moisture content. Technical solution High-amylose corn starch (amylose content ≥ 55%) was adjusted with water to a moisture content of 40%-45%, and then annealed in a constant temperature and humidity environment at 45-55℃ and 75%-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 lattice 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 protection scope of this method is defined by five parameters: moisture content controlled at 40%-45%, annealing temperature controlled at 45-55℃, relative humidity controlled at 75%-85%, annealing time controlled at 20-30 minutes, and amylose content in the starch raw material controlled at ≥55%. If the moisture content is below 40% or above 45%, the annealing temperature is below 45℃ or above 55℃, the relative humidity is below 75% or above 85%, the annealing time is less than 20 minutes or more than 30 minutes, or the amylose content is below 55%, the RS3 content and / or RS3 melting temperature will not reach the standards of ≥12% and ≥120℃, respectively. Specifically: when the moisture content is below 40%, the annealing temperature needs to be increased to above 55℃ (falling within the protection range of the conventional 20%-35% / 50-58℃ annealing process); when the moisture content is above 45%, the risk of overhydration increases significantly, and the RS3 content decreases instead (e.g., the RS3 content is only about 9.0% at 50% moisture); when the annealing temperature is below 45℃, the molecular thermal motion kinetic energy is insufficient under high moisture conditions, resulting in low annealing efficiency; when the annealing temperature is above 55℃, starch granules are prone to overgelatinization under high moisture conditions; when the relative humidity is above 85%, the humidity in the high moisture environment further promotes overhydration; when the amylose content is below 55%, the amylose template is insufficient. Core Mechanism The parameter linkage mechanism of high-moisture annealing is based on the triple coupling relationship of moisture, temperature, and humidity. Under high moisture conditions of 40%-45%, starch granules have sufficient internal moisture and abundant molecular chain migration media, but the risk of overhydration also increases. To suppress this overhydration, the annealing temperature must be lowered—from the conventional 50-58℃ to 45-55℃—to slow down the water absorption and swelling rate of the starch granules. Simultaneously, the relative humidity must be reduced from the conventional 80%-95%RH to 75%-85%RH—to reduce the rate of moisture transfer from the environment and prevent further water absorption by the high-moisture granules. The triple coupling relationship between moisture, temperature, and humidity can be quantitatively described as follows: for every 2 percentage point increase in moisture content (within the 40%-45% range), to maintain an RS3 content ≥12%, the annealing temperature needs to be reduced by approximately 2-3℃, or the relative humidity needs to be reduced by approximately 2%-3%RH. For example, under 40% moisture conditions, an annealing temperature of approximately 52-55℃ and a humidity of approximately 82%-85%RH can achieve an RS3 ≥12%; under 42% moisture conditions, an annealing temperature of approximately 48-52℃ and a humidity of approximately 78%-82%RH can achieve the same RS3 level; and under 45% moisture conditions, an annealing temperature of approximately 45-48℃ and a humidity of approximately 75%-78%RH can achieve the same RS3 level. This quantitative parameter linkage is the core technical characteristic of the high-moisture annealing process. Detailed Implementation Example 1 (High Moisture Annealing at 50°C) High-amylose corn starch (amylose content approximately 58%) was added to water and adjusted to a moisture content of approximately 42%. It was then placed in a constant temperature and humidity apparatus and annealed for 25 minutes at 50℃ and 80%RH. After annealing, the mixture 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℃ high moisture annealing + high linear chain ≥70%) Take extra-high amylose corn starch (amylose content approximately 72%), with a moisture content of 44%, and anneal it at 45℃ and 78%RH for 30 minutes. The RS3 content is 16.5%±0.8% (≥15%), and the RS3 melting temperature is 127±1℃ (≥122℃). Example 3 (Boundary Validation with 55% Amylose Content) Take high amylose corn starch (amylose content exactly 55%), add water to adjust to a moisture content of about 42%, and anneal at 50℃ and 82%RH for 28 minutes. The RS3 content is 12.1%±0.5% (just ≥12%), and the RS3 melting temperature is 121±2℃ (≥120℃). Comparative Example 1 (moisture content above 45% - RS3 not up to standard) Using the same raw materials and process as in Example 1, with a moisture content of 50% (>45%), an annealing temperature of 50°C, and an annealing time of 25 minutes, the RS3 content was 9.0% ± 0.5% (<12%). Excessive moisture content led to overhydration of the starch granules and localized gelatinization. Comparative Example 2 (moisture content below 40% - falls within the range of conventional annealing processes) Using the same raw materials and process as in Example 1, the moisture content was 28% (<40%), 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 20%-35% / 50-58°C annealing process). 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 40°C (<45°C) and the annealing time was 25 minutes. The RS3 content was 8.5% ± 0.5% (<12%). Comparative Example 4 (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 8.8% ± 0.5% (<12%). Overhydration was carried out under high moisture and high humidity conditions. Comparative Example 5 (Conventional annealing process window: 55℃ / 18 minutes / 88%RH / 28% moisture) Using the same high-amylose corn starch as in Example 1, a conventional annealing process window was employed: annealing for 18 minutes at 55°C and 88% RH with a moisture content of 28%. 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 moisture content (28%) was 14 percentage points lower than that in Example 1 (42%). This demonstrates that the high-moisture annealing process of this patent increases the moisture content by 14 percentage points while maintaining a essentially unchanged RS3 content. Comparative Example 6 (relative humidity below 75% - 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 70% (<75%). The RS3 content was 9.2% ± 0.5% (<12%). Under high moisture conditions, the relative humidity was too low, the transfer of environmental moisture was insufficient, the evaporation of moisture on the particle surface was too fast, and the RS3 formation efficiency could not meet the standard. Comparative Example 7 (annealing time less than 20 minutes - RS3 not up to standard) Using the same raw materials and process as in Example 1, the annealing temperature was 50°C and the annealing time was 16 minutes (<20 minutes). The RS3 content was 9.5% ± 0.5% (<12%). Insufficient annealing time under high moisture conditions resulted in inadequate molecular chain rearrangement. Comparative Example 8 (Moisture content 38% - falls into the gray area and does not meet the standard) Using the same raw materials and process as in Example 1, with a moisture content of 38% (between the conventional upper limit of 35% and the lower limit of the present invention of 40%), and an annealing temperature of 50°C, the RS3 content was 10.5% ± 0.5% (< 12%), and did not fall within the protection scope of any existing patent. This demonstrates that 40% is a clear lower limit for the usability of this method—below 40%, the RS3 content cannot be met unless conventional annealing temperature conditions are used (falling within the scope of conventional patents). Industrial applications This method locks in the parameter boundaries of purely physically annealed modified RS3 resistant starch within the 40%-45% high moisture range. Moisture content controlled at 40%-45%, annealing temperature controlled at 45-55℃, relative humidity controlled at 75%-85%, annealing time controlled at 20-30 minutes, and amylose content in the starch raw material controlled at ≥55%—these five parameter windows together constitute the protection scope of this method. This method, together with the conventional 20%-35% moisture annealing method and the separately applied 15%-20% low moisture hydrothermal treatment method and 35%-40% medium moisture hydrothermal treatment method, forms a complete protection loop in terms of moisture content—15%-20% (low moisture hydrothermal treatment) → 20%-35% (conventional annealing) → 35%-40% (medium moisture hydrothermal treatment) → 40%-45% (this method), providing comprehensive coverage across the entire moisture 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 high-amylose starch under high moisture content conditions of 40%-45%, 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 40%-45%; b. High moisture annealing: The conditioned material is annealed in a constant humidity environment with an annealing temperature of 45-55℃ and a relative humidity of 75%-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 78%-82%, 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 42%-44%; 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.