Rapid iodine colorimetric identification method for retrogradation degree of rice

Abstract

The invention discloses a rapid iodine colorimetric identification method for the retrogradation degree of rice, and relates to the technical field of plant detection, and the rapid iodine colorimetric identification method comprises the following steps: respectively processing different varieties of rice to obtain rice flour solutions of the different varieties of rice; adding an iodine solution into the rice flour solutions of different varieties of rice, and carrying out a chromogenic reaction to obtain a chromogenic solution; determining a starch iodine absorption parameter OD550 of the color developing solution; and predicting the retrogradation degrees of different varieties of rice according to the starch iodine absorption parameter OD550. According to the invention, rice varieties with different retrogradation degrees can be quickly screened.

Description

Technical Field

[0001] The invention relates to a rapid iodine colorimetric identification method for rice retrogradation degree, belonging to the technical field of plant detection. Background Art

[0002] Rice is one of my country's staple crops. As people's living standards improve, rice quality has become increasingly important. Over 85% of the rice endosperm is starch, and the composition and structure of starch are closely related to rice quality. Gelatinization and retrogradation are key evaluation indicators of rice's cooking and flavor quality. Gelatinization primarily refers to the destruction of the crystalline structure of rice starch during heating, while retrogradation is the formation of recrystallizations of gelatinized starch during low-temperature storage. Retrogradation causes rice to become hard and deteriorate in flavor; however, retrogradation can increase the resistant starch content of rice, which is beneficial for the health of people with overweight, obesity, and diabetes. Therefore, cultivating rice with varying degrees of retrogradation can meet the needs of different populations.

[0003] Currently, rice retrogradation is commonly determined using differential scanning calorimetry (DSC). Retrogradation is calculated by measuring the gelatinization enthalpy (∆H) of raw rice flour and the ∆H of retrograded rice flour. However, direct DSC screening of rice varieties with varying degrees of retrogradation from a large sample size presents challenges such as low efficiency, high cost, and stringent sample preparation requirements. Rice retrogradation is influenced by the amylose content and amylopectin chain length distribution. Both amylose and amylopectin can bind to iodine, with varying binding properties. Therefore, the absorption spectral parameters of starch and iodine can reflect the amylose content and amylopectin structure. The starch-iodine colorimetric method offers advantages such as ease of use, low cost, and sensitivity to changes in amylose content and amylopectin structure. However, a rapid iodine colorimetric method for predicting rice retrogradation has yet to be established. Therefore, it is necessary to establish a rice retrogradation identification method that is simple to operate and can meet the needs of most laboratories for experiments, so as to provide technical support for the rapid screening of rice varieties with different retrogradation degrees from a large number of rice varieties. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a rapid iodine colorimetric identification method for rice retrogradation, which can realize rapid screening of rice varieties with different retrogradation degrees.

[0005] To achieve the above object, the present invention is implemented by adopting the following technical solutions: The present invention provides a rapid iodine colorimetric identification method for rice retrogradation, comprising: Processing different varieties of rice separately to obtain rice flour solutions of different varieties of rice; Adding iodine solution to rice flour solutions of different rice varieties to perform color development reaction to obtain color development solutions of different rice varieties; Determine the starch iodine absorption parameter OD550 of the colorimetric solution of different rice varieties; The retrogradation degree of different rice varieties was predicted based on the starch iodine absorption parameter OD550, and the retrogradation degree ranking of different rice varieties was obtained.

[0006] Furthermore, the rice varieties include japonica rice and indica rice.

[0007] Furthermore, the different varieties of rice are processed separately to obtain rice flour solutions of different rice varieties, comprising: For each rice variety: The rice is roughened and ground, and then sieved through a 100-mesh sieve to obtain refined rice flour; After adding anhydrous ethanol to the refined rice flour for dispersion, sodium hydroxide solution is added for alkaline hydrolysis to obtain a rice flour solution.

[0008] Furthermore, the amount of anhydrous ethanol added is 0.01 mL / mg; and / or the concentration range of the sodium hydroxide solution is 0.95~1.05 mol / L; and / or the amount of sodium hydroxide solution added is 0.09 mL / mg.

[0009] Furthermore, the alkaline hydrolysis treatment includes vortex mixing for 5-10 s every 1-2 minutes in a time period of 0-5 minutes at 90-100° C., and then vortex mixing for 5-10 s every 5-10 minutes in a time period of 6-60 minutes.

[0010] Furthermore, before adding iodine solution to the rice flour solution of different rice varieties for color development reaction to obtain the color development solution, the rice flour solution needs to be diluted with water and neutralized with acetic acid aqueous solution until the solution becomes acidic.

[0011] Furthermore, the iodine solution comprises an iodine aqueous solution with a mass volume ratio of 0.18-0.22% and a potassium iodide aqueous solution with a mass volume ratio of 1.8-2.2%; and / or the concentration range of the acetic acid aqueous solution is 0.95-1.05 mol / L; and / or the volume ratio of the rice flour solution to water is 1:90-110.

[0012] Furthermore, the color development reaction time is 10 to 15 minutes.

[0013] Furthermore, the starch iodine absorption parameter OD550 is measured by a spectrophotometer at 550 nm.

[0014] Furthermore, the starch iodine absorption parameter OD550 is positively correlated with the retrogradation degree.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention utilizes the correlation between the starch iodine absorption parameter OD550 and the rice retrogradation degree to quickly screen out rice varieties with different retrogradation degrees from a large number of rice varieties. The method is simple to operate, does not require starch extraction, is low in cost, and does not require complex instruments and equipment. It is suitable for routine laboratory testing and large-scale sample analysis, and is particularly suitable for scientific research or production environments with limited resources, and can be promoted on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a graph showing the DSC analysis results of raw rice flour and retrograded rice flour of 14 rice varieties in Comparative Example 1 of the present invention; Figure 2 These are correlation analysis results of the starch iodine absorption parameter OD550 measured in Example 1 of the present invention and the retrogradation degree measured in Comparative Example 1, wherein (a) is a correlation analysis result of the starch iodine absorption parameter OD550 and retrogradation degree 1, (b) is a correlation analysis result of the starch iodine absorption parameter OD550 and retrogradation degree 2, and (c) is a correlation analysis result of the starch iodine absorption parameter OD550 and total retrogradation degree; Figure 3 This is a graph showing the DSC analysis results of raw rice flour and retrograded rice flour of a rice variety with low retrogradation degree (Ruihua 220) and a rice variety with high retrogradation degree (Yangjing M2118) screened by iodine colorimetry in Example 2 of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Example 1

[0018] The embodiment of the present invention provides a rapid iodine colorimetric identification method for rice retrogradation, which specifically includes the following steps: Fourteen rice varieties were obtained, including W220116-Huaian low, Hongnongjing 5, Huaidao 5, Nanjing 24054, Ning 21016, Sidao 119-Huaian low, Tianfengjing 164, Tianfengjing 177, Wuxiangjing 243, Wuyujing 187, Yangjing 158, Yangjing 339, Yangxiangyu 200, and Zhendao 6081 mature rice grains.

[0019] For each rice variety: The first step is to use a BLH-3250B electric rice huller to hull the rice to obtain mature brown rice. About 100 g of mature brown rice is put into a BLH-3500 rice polishing machine and milled for 30 s to obtain polished rice.

[0020] Polished rice was ground into powder using a JFS-13A cyclone mill, passed through a 100-mesh sieve, placed on an A4 paper, and evenly spread with a weighing spoon. The powder was then placed in a 40°C drying oven for 2–3 days and then sealed for storage.

[0021] Weigh 50 mg (±3 mg) of refined rice flour into the bottom of a dry 10 mL screw-top glass test tube with a cap. Write the number on the test tube in advance and record the corresponding sample name to ensure the accuracy of the sample later.

[0022] Use a 1 mL pipette to remove 0.5 mL of anhydrous ethanol solution to rinse any rice flour stuck to the sides of a 10 mL screw-top glass test tube. Use an MX-S variable speed vortexer to mix and disperse the rice flour.

[0023] Prepare 1 mol / L NaOH solution: a. Weigh 40 g of solid NaOH into a 500 mL beaker containing 300 mL to 400 mL of deionized water. b. Stir with a glass rod until dissolved and free of solid particles, then transfer to a 1 L volumetric flask. c. Cool the NaOH solution to room temperature. Rinse the beaker 3-4 times with a small amount of deionized water, transfer the solution to a volumetric flask, and dilute to 1 L with deionized water to obtain a 1 mol / L NaOH solution.

[0024] 4.5 mL of 1 mol / L NaOH solution was pipetted into a 10 mL screw-top glass test tube using a 5 mL pipette. The tube cap was tightened and the rice flour was dispersed using an MX-S adjustable speed vortexer.

[0025] Place the threaded glass test tube in a water bath at 95°C for 1 hour. Starting from the 0-5 minute stage, take it out every 1-2 minutes and immediately mix it in a vortex for 5-10 seconds. Then, during the 6-60 minute alkaline hydrolysis stage, take it out every 5-10 minutes and mix the rice flour solution for 5-10 seconds. After the alkaline hydrolysis treatment, the rice flour solution is obtained.

[0026] The second step is to add iodine solution to the rice flour solution for color development and measure the absorbance at 550 nm.

[0027] Prepare 1 mol / L acetic acid solution: Use a 5 mL pipette to pipette 5.75 mL of glacial acetic acid into a 100 mL volumetric flask in two portions and dilute to 100 mL with deionized water.

[0028] Prepare an iodine solution with a mass volume ratio of 0.2% I2 and 2% KI: a. I2 is readily soluble in a saturated KI solution. First, weigh 10 g of solid KI into a 500 mL beaker, add a small amount of deionized water, and stir with a glass rod to ensure that the KI is not completely dissolved. b. Weigh 1 g of solid I2 into the above beaker and stir with a glass rod to ensure that the I2 is dissolved. Continue to add deionized water to fully dissolve it and transfer it to a 500 mL volumetric flask. c. Rinse the beaker 2-3 times with deionized water, transfer the solution to a volumetric flask, and dilute to 500 mL. Store in a dark place until ready for use.

[0029] Take out the screw-top glass test tube and let it cool at room temperature for 20-30 minutes.

[0030] Prepare a dry 20 mL glass test tube and add 9.3 mL of water. Pre-number the tube and record the corresponding sample name. Add 0.1 mL of the rice flour solution, 0.2 mL of 1 mol / L acetic acid solution, and 0.4 mL of iodine solution.

[0031] Vortex mix and let stand in the dark at room temperature for 10-15 min.

[0032] The absorbance at a wavelength of 550 nm was measured using a Thermo BIOMATE 3S spectrophotometer.

[0033] The OD550 values ​​of starch iodine absorption parameters of 14 rice varieties are shown in Table 1: Table 1: OD550 values ​​of starch iodine absorption parameters of 14 rice varieties

[0034] The data in Table 1 are the mean ± standard deviation of three replicates, and Sig. indicates the significance of the normal distribution of the mean data by the Shapiro-Wilk test of SPSS.

[0035] The data in Table 1 show that the starch iodine absorption parameter OD550 of refined rice flour from 14 rice varieties presents a normal distribution and can be used for correlation analysis.

[0036] Comparative Example 1: In this comparative example 1, differential scanning calorimetry (DSC) was used to analyze the retrogradation characteristics of refined rice flour of 14 rice varieties in Example 1. The specific steps were as follows: (1) Sample preparation: Accurately weigh 5 mg of refined rice flour into an aluminum crucible, add 2 μL of deionized water per mg of refined rice flour, seal the sample using a DSC press, and let it equilibrate at room temperature for 2 h.

[0037] (2) Sample testing: First, use a differential scanning calorimeter to test the enthalpy of each sample of raw rice flour ( ), the operating program is as follows: the heating rate is 10℃ / min, the heating range is 20-120℃, such as Figure 1 The black line shows the gelatinization thermogram of raw rice flour. The thermal enthalpy of raw rice flour of each rice variety sample ( ) as shown in Table 2: Table 2: Enthalpy values ​​of raw rice flour from 14 rice varieties

[0038] Among them, the data in Table 2 are the mean ± standard deviation of two repetitions, Sig. is the significance of the normal distribution of the mean data by the Shapiro-Wilk test of SPSS, Enthalpy 1 is the gelatinization enthalpy value of the first gelatinization peak, and Enthalpy 2 is the gelatinization enthalpy value of the second gelatinization peak.

[0039] The gelatinized rice flour samples were then placed in a 4°C refrigerator for 10 days for retrogradation treatment, and then the retrogradation characteristics of the rice flour were measured. The test conditions were as follows: the heating rate was 10°C / min, the heating range was 15~120°C, and the Figure 1 The red line shows the gelatinization thermogram curve of retrograded rice flour. The thermal enthalpy of retrograded rice flour of each rice variety sample ( ) as shown in Table 3.

[0040] Table 3: Thermal enthalpy and degree of retrogradation of gelatinized rice flour of 14 rice varieties after 10 days of retrogradation

[0041] Among them, the data in Table 3 are the mean ± standard deviation of two repetitions, Sig. is the significance of the normal distribution of the mean data by the Shapiro-Wilk test of SPSS, enthalpy 1 is the enthalpy value of the first gelatinization peak, enthalpy 2 is the enthalpy value of the second gelatinization peak, retrogradation degree 1 is the percentage of the two average enthalpy values ​​of the first gelatinization peak of retrograded rice flour and uncooked rice flour, retrogradation degree 2 is the percentage of the two average enthalpy values ​​of the second gelatinization peak of retrograded rice flour and uncooked rice flour, and the total retrogradation degree is the percentage of the total enthalpy value of retrograded rice flour and uncooked rice flour (the sum of the two average enthalpy values ​​of the first and second gelatinization peaks).

[0042] The OD550 in Example 1 and the retrogradation degree of Comparative Example 1 were subjected to correlation analysis. The results are shown in FIG. Figure 2 . It was found that OD550 had a very significant positive correlation with the degree of retrogradation 1 ( p = 0.003), OD550 also had a very significant positive correlation with the total recovery degree ( p =0.001), while OD550 had no significant correlation with the degree of rejuvenation 2 ( p= 0.503). Therefore, OD550 parameters can be used to predict rice retrogradation degree 1 and total retrogradation degree. Example 2

[0043] The embodiment of the present invention uses a rapid iodine colorimetric identification method to predict the degree of retrogradation based on multiple rice varieties, which specifically includes the following steps: The rice varieties in this embodiment include Hongnongjing 203, Huai 2311, Huai 2391-Huai'an high, Huai 6728, Huaijing 618, Huaiyang 919, Jindi 802, Kendao 88, Kenxiangdao 215, Kenxiangyu 198, Lian 639, Lian 640, Ningjing 6201, Nongjing 2046-Gaoyou low, Qianjing 22127, Qianliangyou 216, Quanyou 822, Ruihua 220, Runyangjing 205, Shenzhoudao 211, Su 1619-Huai'an low, Tianfengjing 146, and Wuxiangjing 299. Mature rice grains of 46 rice varieties, including Wuxiangjing 99, Wuyujing No. 3, Wuyun 2207, Wuyunjing 23, Wuyunjing 399, Xiayou 100, Yanjing 1359, Yanjing 19272, Yanjing 2200, Yangfujing 1288, Yangjing M2118, Yangjing M2120, Yangliangyou 2019, Yangliangyou 3968, Yangliangyoukang 319, Yuanliangyou 2120, Yuanliangyou 819, Yuanliangyou 968, Yueguang, Zhendao 26, Zhendao 37, Zhendao 39, and Zhendao 6080.

[0044] For each rice variety: The first step is to use a BLH-3250B electric rice huller to hull the rice to obtain mature brown rice. About 100 g of mature brown rice is put into a BLH-3500 rice polishing machine and milled for 30 s to obtain polished rice.

[0045] Polished rice was ground into powder using a JFS-13A cyclone mill, passed through a 100-mesh sieve, placed on an A4 paper, and evenly spread with a weighing spoon. The powder was then placed in a 40°C drying oven for 2–3 days and then sealed for storage.

[0046] Weigh 50 mg (±3 mg) of refined rice flour into the bottom of a dry 10 mL screw-top glass test tube with a cap. Write the number on the test tube in advance and record the corresponding sample name to ensure the accuracy of the sample later.

[0047] Use a 1 mL pipette to remove 0.5 mL of anhydrous ethanol solution to rinse any rice flour stuck to the sides of a 10 mL screw-top glass test tube. Use an MX-S variable speed vortexer to mix and disperse the rice flour.

[0048] Prepare 1 mol / L NaOH solution: a. Weigh 40 g of solid NaOH into a 500 mL beaker containing 300 mL to 400 mL of deionized water. b. Stir with a glass rod until dissolved and free of solid particles, then transfer to a 1 L volumetric flask. c. Cool the NaOH solution to room temperature. Rinse the beaker 3-4 times with a small amount of deionized water, transfer the solution to a volumetric flask, and dilute to 1 L with deionized water to obtain a 1 mol / L NaOH solution.

[0049] 4.5 mL of 1 mol / L NaOH solution was pipetted into a 10 mL screw-top glass test tube using a 5 mL pipette. The tube cap was tightened and the rice flour was dispersed using an MX-S adjustable speed vortexer.

[0050] Place the threaded glass test tube in a water bath at 95°C for 1 hour. Starting from the 0-5 minute stage, take it out every 1-2 minutes and immediately mix it in a vortex for 5-10 seconds. Then, during the 6-60 minute alkaline hydrolysis stage, take it out every 5-10 minutes and mix the rice flour solution for 5-10 seconds. After the alkaline hydrolysis treatment, the rice flour solution is obtained.

[0051] The second step is to add iodine solution to the rice flour solution for color development and measure the absorbance at 550 nm.

[0052] Prepare 1 mol / L acetic acid solution: Use a 5 mL pipette to pipette 5.75 mL of glacial acetic acid into a 100 mL volumetric flask in two portions and dilute to 100 mL with deionized water.

[0053] Prepare an iodine solution with a mass volume ratio of 0.2% I2 and 2% KI: a. I2 is readily soluble in a saturated KI solution. First, weigh 10 g of solid KI into a 500 mL beaker, add a small amount of deionized water, and stir with a glass rod to ensure that the KI is not completely dissolved. b. Weigh 1 g of solid I2 into the above beaker and stir with a glass rod to ensure that the I2 is dissolved. Continue to add deionized water to fully dissolve it and transfer it to a 500 mL volumetric flask. c. Rinse the beaker 2-3 times with deionized water, transfer the solution to a volumetric flask, and dilute to 500 mL. Store in a dark place until ready for use.

[0054] Take out the screw-top glass test tube and let it cool at room temperature for 20-30 minutes.

[0055] Prepare a dry 20 mL glass test tube and add 9.3 mL of water. Pre-number the tube and record the corresponding sample name. Add 0.1 mL of the rice flour solution, 0.2 mL of 1 mol / L acetic acid solution, and 0.4 mL of iodine solution.

[0056] Vortex mix and let stand in the dark at room temperature for 10-15 min.

[0057] The absorbance at a wavelength of 550 nm was measured using a Thermo BIOMATE 3S spectrophotometer.

[0058] The OD550 values ​​of starch iodine absorption parameters of 46 rice varieties are shown in Table 4: Table 4: OD550 values ​​of starch iodine absorption parameters of 46 rice varieties

[0059] The data in Table 4 are the mean ± standard deviation of three replicates, and rice varieties are arranged from small to large according to OD550 values.

[0060] Comparative Example 2: In this comparative example 2, the retrogradation of the rice with the lowest OD550 value (Ruihua 220) and the highest OD550 value (Yangjing M2118) measured by starch iodine colorimetry in Example 2 was measured. The operation steps are as follows: (1) Sample preparation: Accurately weigh 5 mg of refined rice flour into an aluminum crucible, add 2 μL of deionized water per mg of refined rice flour, seal the sample using a DSC press, and let it equilibrate at room temperature for 2 h.

[0061] (2) Sample testing: First, the gelatinization enthalpy of each sample of raw rice flour was tested using a differential scanning calorimeter ( ). The operating procedure is as follows: the heating rate is 10℃ / min, and the heating range is 20~120℃. Then the gelatinized rice flour sample is placed in a 4℃ refrigerator for 10 days for retrogradation treatment, and then the retrogradation characteristics of the rice flour are measured. The test conditions for the retrogradation sample are as follows: the heating rate is 10℃ / min, and the heating range is 15~120℃. Figure 3 The black line is the gelatinization thermogram of raw rice flour, and the red line is the gelatinization thermogram of gelatinized rice flour after 10 days of retrogradation. The test results of the retrogradation degree are shown in Table 5.

[0062] Table 5: Retrogradation parameters of Ruihua 220 and Yangjing M2118 rice

[0063] The data in Table 5 are the mean ± standard deviation of two replicates. Enthalpy 1 and Enthalpy 2 are the enthalpy values ​​of the first and second gelatinization peaks, respectively. Retrogradation 1 is the percentage of the average enthalpy values ​​of the first gelatinization peak of retrograded rice flour and uncooked rice flour. Retrogradation 2 is the percentage of the average enthalpy values ​​of the second gelatinization peak of retrograded rice flour and uncooked rice flour. Total retrogradation is the percentage of the total enthalpy value of retrograded rice flour and uncooked rice flour (the sum of the average enthalpy values ​​of the first and second gelatinization peaks).

[0064] As can be seen from the data in Table 5, the degree of retrogradation 1 and the total degree of retrogradation of Ruihua 220 (minimum OD550) are significantly lower than those of Yangjing M2118 (maximum OD550), which is consistent with the extremely significant positive correlation between OD550 and the degree of retrogradation 1 and the total degree of retrogradation, indicating that the iodine colorimetric method provided by the present invention can quickly identify rice varieties with different degrees of retrogradation.

[0065] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A rapid iodine colorimetric identification method for rice retrogradation, characterized in that: include: Processing different varieties of rice separately to obtain rice flour solutions of different varieties of rice; Adding iodine solution to rice flour solutions of different rice varieties to perform color development reaction to obtain color development solutions of different rice varieties; Determine the starch iodine absorption parameter OD550 of the colorimetric solution of different rice varieties; The retrogradation degree of different rice varieties was predicted based on the starch iodine absorption parameter OD550, and the retrogradation degree ranking of different rice varieties was obtained.

2. The rapid iodine colorimetric identification method for rice retrogradation according to claim 1, wherein The rice varieties include japonica rice and indica rice.

3. The rapid iodine colorimetric identification method for rice retrogradation according to claim 1, wherein The method of processing different varieties of rice to obtain rice flour solutions of different rice varieties comprises: For each rice variety: The rice is de-roughened, ground, and sieved through a 100-mesh sieve to obtain refined rice flour; After adding anhydrous ethanol to the refined rice flour for dispersion, sodium hydroxide solution is added for alkaline hydrolysis to obtain a rice flour solution.

4. The rapid iodine colorimetric identification method for rice retrogradation according to claim 3, wherein: The amount of anhydrous ethanol added is 0.01 mL / mg; and / or the concentration range of the sodium hydroxide solution is 0.95~1.05 mol / L; and / or the amount of sodium hydroxide solution added is 0.09 mL / mg.

5. The rapid iodine colorimetric identification method for rice retrogradation according to claim 3, wherein: The alkaline hydrolysis treatment includes vortex mixing for 5-10 s every 1-2 minutes within a time period of 0-5 minutes at 90-100° C., and then vortex mixing for 5-10 s every 5-10 minutes within a time period of 6-60 minutes.

6. The rapid iodine colorimetric identification method for rice retrogradation according to claim 1, wherein: Before adding iodine solution to the rice flour solution of different rice varieties to carry out color development reaction to obtain color development solution, the rice flour solution needs to be diluted with water and neutralized with acetic acid aqueous solution until the solution becomes acidic.

7. The rapid iodine colorimetric identification method for rice retrogradation according to claim 6, characterized in that: The iodine solution comprises an iodine aqueous solution with a mass volume ratio of 0.18-0.22% and a potassium iodide aqueous solution with a mass volume ratio of 1.8-2.2%; and / or the concentration range of the acetic acid aqueous solution is 0.95-1.05 mol / L; and / or the volume ratio of the rice flour solution to water is 1:90-110.

8. The rapid iodine colorimetric identification method for rice retrogradation according to claim 1, characterized in that: The color development reaction time is 10 to 15 minutes.

9. The rapid iodine colorimetric identification method for rice retrogradation according to claim 1, wherein: The starch iodine absorption parameter OD550 is measured by a spectrophotometer at 550 nm.

10. The rapid iodine colorimetric identification method for rice retrogradation according to claim 1, characterized in that: The OD550 is positively correlated with the degree of retrogradation.

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