Method and system for evaluating freshness of unhulled rice in grain purchase

Abstract

The invention relates to the technical field of grain purchase quality detection, in particular to a method and system for evaluating the freshness of rice in reserve grain alternate warehousing. In order to solve the problem that the rice freshness cannot be accurately and scientifically evaluated in grain purchasing and warehousing, the invention provides a rice freshness N evaluation method and system in alternate purchasing. According to national standards, industrial standards and enterprise purchase and warehousing requirements, a mathematical model # imgabs0 # is established, the fresh degree N of rice in the warehousing process is determined by measuring the content H of yellow rice grains, the fatty acid value S, the freshness value Y and the tasting score value P, and new grains and old grains are comprehensively judged. According to the invention, whether the stored grains are new grains is determined through the HSYP evaluation model system for the first time, and a powerful technical support is provided for a stored grain storage enterprise and a grain inspection and detection mechanism to determine the new degree of rice in government stored grain alternate storage.

Description

Technical Field

[0001] The present invention relates to the technical field of grain purchase quality inspection, and specifically to a method and system for evaluating the freshness of paddy during the rotation and storage of reserve grain in storage. Background Art

[0002] With the increasing living standards of modern people, consumers are paying more and more attention to the quality of rice. However, in the process of rotation and purchase of government reserve grain, the problem of replacing new grain with old grain often occurs, resulting in unqualified quality of the reserve grain in storage. Therefore, accurately determining the freshness of paddy during the rotation and storage of government reserve grain is crucial for reserve grain storage enterprises at all levels and grain inspection and testing institutions. At present, there is no specific detection method and standard for judging the freshness of paddy in the country. During the process of grain storage inspection, storage enterprises mainly use the sensory detection method to preliminarily judge the freshness. New grain usually has a bright appearance color, good transparency, an inherent rice fragrance and a special grass fragrance, has a slightly sweet taste when chewed, and has no peculiar smell; while old grain has a yellowish color, poor transparency, an unclear fragrance, and seriously has an "old smell", and has a sour or bitter taste when chewed. Judging solely by sensory identification sometimes has a large error and lacks scientificity. In the laboratory, chemical colorimetric methods are commonly used to judge the freshness of paddy. For example, the acidity of paddy is evaluated through a mixed indicator of methyl red - bromothymol blue. The leaching solution of new grain shows green, while that of old grain shows yellow. The longer the storage time of paddy, the yellower the color; the freshness of paddy is judged by detecting the change in enzyme activity of paddy. The fresher the paddy, the higher the activity of catalase, which can oxidize guaiacol into red 4 - guaiacol, and the deeper the red color of the reaction product. The detection results of such methods are greatly affected by the storage years of paddy, with poor repeatability and low accuracy. Therefore, there is an urgent need for a method and system for evaluating the freshness of paddy during rotation and purchase to solve the technical problem that the freshness of paddy during the rotation and storage of reserve grain cannot be accurately and scientifically evaluated in the prior art, provide strong technical support for reserve grain storage enterprises and grain inspection and testing institutions to judge the freshness of paddy during the rotation and storage of government reserve grain, thereby ensuring the storage safety of government reserve grain and safeguarding the safety of the people's food on the tip of their tongues. Summary of the Invention

[0003] The present invention provides a method and system for evaluating the freshness of paddy during grain purchase, which can accurately and scientifically evaluate the freshness of paddy during the rotation and storage of reserve grain, provide strong technical support for reserve grain storage enterprises and grain inspection and testing institutions to judge the freshness of paddy during the rotation and storage of government reserve grain, ensure the storage safety of government reserve grain, and safeguard the safety of the people's food on the tip of their tongues.

[0004] To solve the above technical problems, an embodiment of the present invention provides a method and system for evaluating the freshness degree (N) of paddy rice in rotation purchase. According to national and industry standards, the freshness of new grains and old grains is comprehensively judged by measuring the yellow rice content, fatty acid value, freshness value and taste score value. The method is characterized by including the following steps.

[0005] Step 1: Measure the yellow rice content of the paddy rice in rotation purchase, and the yellow rice content is H. The higher the moisture content of the paddy rice, the more times of heating, the more yellow rice appears, and the more yellow rice there is with the longer storage years. Yellow rice directly affects the color, smell and edible quality of grains. The presence of yellow rice seriously affects the edible quality and commercial appearance of rice. Compared with normal rice grains, the nutritional components of yellow rice are reduced, and it affects the color, aroma and taste of rice. Therefore, the inspection of yellow rice in paddy rice during rotation into storage is particularly important.

[0006] The detection method of the yellow rice index in Step 1 of the present invention: Measure according to the method of "Inspection of Grain and Oil - Inspection of Yellow Rice and Cracked Grains" (GB / T 5496 - 1985). The specific steps are as follows.

[0007] (1) Sample preparation: After removing impurities from the evenly mixed paddy rice, and after dehusking the paddy rice with a rice huller to obtain brown rice, the brown rice sample is milled into rice with an accuracy approximately equivalent to standard second - grade rice using a small rice milling machine.

[0008] (2) Weighing and calculation: Remove the bran powder from the above - mentioned rice, weigh the mass of the sample (W), and then pick out the yellow rice that is significantly different in color from normal rice grains and weigh it (W 1 ) That's it.

[0009] Calculate the yellow rice content as H, and the formula is: .

[0010] Step 2: Measure the fatty acid value content of the paddy rice in rotation purchase, and the fatty acid value content is S. The fatty acid value is an important index for judging the suitable storage quality of paddy rice. During long - term storage, the lipids in paddy rice are easily affected by factors such as oxygen, temperature and humidity, and are hydrolyzed by lipase to generate linoleic acid, oleic acid, etc. Therefore, by measuring the fatty acid value, the change of lipids in paddy rice can be effectively reflected to evaluate the freshness degree. The higher the fatty acid value, the lower the freshness degree of paddy rice.

[0011] The detection method of the fatty acid value index in Step 2 of the present invention: Measure according to Appendix A of the "Rules for Judging the Storage Quality of Paddy Rice" (GB / T20569 - 2006). The specific steps are as follows.

[0012] (1) Sample preparation: Take a uniformly mixed sample, dehusk it with an experimental rice huller and crush the brown rice with a hammer - type cyclone mill. After the crushed sample is fully mixed, it is filled into a ground - glass stoppered bottle for standby.

[0013] (2) Sample treatment: Weigh about 10 g of the prepared sample (with moisture content w), with a mass of m, accurate to 0.01 g. Place it in a 250 mL stoppered conical flask with ground glass joints, add 50.0 mL of absolute ethanol, shake it on a reciprocating shaker for 10 min, with a shaking frequency of 100 times / min. Let it stand for 2 min, filter it through a folded filter paper placed in a glass funnel, discard the first few drops of the filtrate, and collect more than 25 mL of the filtrate.

[0014] (3) Experimental determination: Pipette 25.0 mL of the filtrate into a 150 mL conical flask, add 50 mL of distilled water without CO 2 After adding 3 drops of phenolphthalein indicator, titrate the solution with a potassium hydroxide standard (concentration c) titrant until it turns slightly pink and does not fade within 30 s. Record the volume of the KOH standard titrant consumed (V 1 ).

[0015] (4) Blank test: Pipette 25.0 mL of absolute ethanol into a 150 mL conical flask, add 50 mL of distilled water without CO 2 After adding 3 drops of phenolphthalein indicator, titrate the solution with a KOH standard titrant until it turns slightly pink and does not fade within 30 s. Record the volume of the KOH standard titrant consumed (V 0 ).

[0016] The ambient temperature during the extraction and titration processes should be controlled at 15 °C - 25 °C.

[0017] (5) Calculate the fatty acid value content as S, formula: 。

[0018] Step 3: Determine the freshness value of the paddy rice in the rotation purchase, and the freshness value is Y. After the paddy rice is dehulled, it is milled into rice with the processing precision specified in Grade 3 rice in GB 1354-2018. It reacts with the color developer. According to the different amounts of aldehyde and ketone substances contained in the rice with different freshness levels, different color characteristics are shown. By analyzing the color difference through spectroscopy, the freshness value of the paddy rice is obtained.

[0019] The detection method of the freshness value in Step 3 of the present invention: It is determined according to the method of "Grain and Oil Inspection - Determination and Differentiation of Paddy Rice Freshness" (LS / T 6118-2017), and the specific steps are as follows.

[0020] (1) Sample preparation: Weigh about 25 g of paddy rice, hull it into brown rice with an experimental hulling machine, and pick out the unhulled paddy rice; the brown rice is milled into rice with the processing precision specified in Grade 3 rice in the GB 1354-2009 rice standard with an experimental rice milling machine.

[0021] The processed rice is uniform, the grain surface is clean, and there is basically no residual bran powder.

[0022] (2)Sample staining: The milled rice is tested after removing broken rice. Weigh 2.0 g of the rice sample to be tested and place it in a 15 mL centrifuge tube. Use a pipette to accurately transfer 10.0 mL of the color reagent and add it along the tube wall to the centrifuge tube containing the sample. Tighten the tube cap and place it parallel on the shaker. Shake for 1 minute. After shaking, pour the upper layer liquid into a 2 mL centrifuge tube and place it in the centrifuge for 1 minute of centrifugation.

[0023] The above staining operation needs to be completed within 10 minutes.

[0024] (3)Instrument calibration: Preheat the instrument according to the instrument operation regulations, and then select the calibration line according to the type of the sample to be tested. Empty the sample detection chamber, calibrate the instrument according to the instrument operation regulations, and then put in the color reagent for blank calibration.

[0025] (4)On-machine detection: Pour the upper clear liquid in the centrifuge tube into a cuvette and conduct on-machine detection. Put the test solution into the detection chamber, press the "Test" button to start the detection, and the instrument automatically gives the freshness value Y of the paddy sample.

[0026] Step 4: Determine the tasting score value of the paddy in the rotation purchase, and the tasting score value is P. The paddy is shelled and milled into rice, and after cooking, the tasting score value is obtained by scoring according to the color, smell, appearance structure, taste of the cooked rice and the control reference sample, which is used to evaluate the quality of the paddy.

[0027] The detection method of the tasting score value in Step 4 of the present invention: It is determined according to the method in Appendix B of "Rules for Judging the Storage Quality of Paddy" (GB / T 20569-2006), and the specific steps are as follows.

[0028] (1)Specimen preparation: Take 500 g of the well-mixed net paddy sample, dehull it into brown rice by a hulling machine, and then make it into standard first-class precision rice by a rice milling machine.

[0029] (2)Cooking the rice: Weigh 10 g of the prepared rice above into a lunch box, stir and wash it once with 30 mL of water, then rinse it once with 30 mL of distilled water, and finally add 30 mL of distilled water, cover the lunch box and cook for 40 minutes, stop heating, and let it stand for 10 minutes before tasting.

[0030] (3)Tasting and scoring: Score according to the smell, taste, color, and appearance of the rice grains of the cooked rice, compared with the reference sample, and the sum of the scores for each item is the tasting score value P.

[0031] The present invention is based on the fact that the longer the storage period of the paddy, the higher the content of yellow rice grains; the higher the fatty acid value, the less suitable the paddy is for storage; the higher the freshness of the paddy, the higher the freshness degree; the higher the tasting score value, the better the quality of the paddy; and a mathematical model for evaluating the freshness degree N of the paddy is established: , where H is the content of yellow rice grains, S is the fatty acid value, Y is the freshness value, P is the taste score value, and k 1 and k 2 are correction factors.

[0032] According to the regulations in the national standards "Paddy" (GB 1350-2009) and "Rice" (GB / T 1354-2018), the content of yellow rice grains H shall not exceed 1.0%. The "Rules for Judging the Storage Quality of Paddy" (GB / T 20569-2006) stipulates that the fatty acid value S ≤ 30.0 mg / 100 g, the taste score value P ≥ 70 points, and the storage quality of early indica rice is good and suitable for continued storage. The Hunan Branch of China National Grain Reserves Corporation stipulates that the yellow rice grain content of newly purchased grains for rotation in the reserves is ≤ 0.3%, and the fatty acid value S ≤ 18 mg / 100 g. The "Inspection of Grain and Oil - Determination and Difference of Paddy Freshness" (LS / T 6118-2017) stipulates that when the freshness value Y ≥ 85 points, it is judged as fresh paddy; when the freshness Y is between 75 and 85 points, it is judged as sub - fresh paddy; when the freshness Y < 75 points, it is judged as non - fresh paddy.

[0033] Set the yellow rice grain content H to 0.1%, the fatty acid value S to 12 mg / 100 g, the freshness value Y to 100 points, the taste score value P to 100 points, and the freshness degree N in the model to 100, which is the highest value for new grains; set the yellow rice grain content H to 0.3%, the fatty acid value S to 18 mg / 100 g, the freshness value Y to 85 points, the taste score value P to 70 points, and the freshness degree N in the model to 60, which is the critical value between new grains and old grains.

[0034] Through mathematical formula calculation, the correction factors k 1 = 0.37 and k 2 = 2.89 are calculated. The mathematical model for evaluating the freshness degree of paddy in the present invention is: .

[0035] Based on the existing national and industry standard methods, the present invention comprehensively determines the freshness degree N of the paddy to be detected by detecting the content of yellow rice grains H, the fatty acid value S, the freshness value Y, and the taste score value P of the paddy, so as to judge the freshness degree evaluation of the paddy to be detected. It can accurately and scientifically evaluate the freshness degree of paddy in the rotation of government - reserved grains into storage, providing strong technical support for reserve - grain storage enterprises and grain inspection and testing institutions to judge the freshness degree of paddy in the rotation of government - reserved grains into storage, thus ensuring the storage safety of government - reserved grains and safeguarding the safety of the people's food on the tip of the tongue. Description of the Drawings

[0036] Figure 1 It is a HSYP evaluation simulation judgment diagram for the freshness degree N of paddy.

[0037] Figure 2For the new and old degree N of paddy stored in warehouse P1 of a certain reserve grain storage enterprise for one month 1 HSYP evaluation simulation determination diagram of

[0038] Figure 3 For the new and old degree N of paddy stored in warehouse P2 of a certain reserve grain storage enterprise for half a year 2 HSYP evaluation simulation determination diagram of

[0039] Figure 4 For the new and old degree N of paddy stored in warehouse P3 of a certain reserve grain storage enterprise for one year 3 HSYP evaluation simulation determination diagram of

[0040] Figure 5 For the new and old degree N of paddy stored in warehouse P4 of a certain reserve grain storage enterprise for two years 4 HSYP evaluation simulation determination diagram of

[0041] Figure 6 For the new and old degree N of paddy stored in warehouse P5 of a certain reserve grain storage enterprise for three years 5 HSYP evaluation simulation determination diagram of Specific implementation mode

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] Example 1 For the paddy stored in warehouse P1 for one month, in strict accordance with the provisions of the "Measures for Sampling and Inspection Management of Quality Inspection of Government Reserve Grain and Oil" (Guoliangbiaogui

[2023] No. 60), sampling is carried out layer by layer from bottom to top by area, layer, and point. According to the size of the grain surface area in the warehouse, the area is divided into zones with an area of 350㎡. Each zone has a total of 5 points at the center and four corners. Each point is set at about 0.5m from the edge of the grain pile. The sampling quality ratio of the center point to the four corner points is 1:1, forming the test sample P1.

[0044] For the above test sample P1, according to the detection method of the yellow rice index in step 1: the method of "Inspection of Grain and Oil - Inspection Method for Yellow Rice and Cracked Grains" (GB / T 5496 - 1985), the content of yellow rice H is determined 1 。

[0045] For the above test sample P1, according to the detection method of the fatty acid value in step 2: the method in Appendix A of the "Rules for Determining the Storage Quality of Paddy" (GB / T 20569 - 2006), the fatty acid value S is determined 1 。

[0046] For the above test sample P1, determine the freshness value Y according to the detection method of the freshness value in Step 3: "Grain and Oil Inspection - Determination and Differentiation of Paddy Freshness" (LS / T 6118-2017). 1 。

[0047] For the above test sample P1, determine the taste score value P according to the detection method of the taste score value in Step 4: Appendix B of "Rules for Judging the Storage Quality of Paddy" (GB / T 20569-2006). 1 。

[0048] The yellow rice content H of P1 1 is 0.1%, and the fatty acid value S 1 is 16.5 mg / 100 g, the freshness value Y 1 is 90 points, the taste score value P 1 is 88 points, and the calculated freshness degree N of the model 1 is 84, determining P1 as new grain. The storage years of paddy are consistent with the evaluation results of this example.

[0049] Example 2: For the paddy stored in Warehouse P2 for half a year, in strict accordance with the provisions of the "Measures for Sampling and Inspection Management of Quality Inspection of Government Reserve Grain and Oil" (Guo Liang Biao Gui

[2023] No. 60), sample layer by layer from bottom to top by area, layer, and point. According to the size of the grain surface area in the warehouse, divide the area into sections of 350 ㎡, and set a total of 5 points at the center and four corners in each section. Each point is set about 0.5 m from the edge at the edge of the grain pile, and the sampling mass ratio of the center point to the four corner points is 1:1 to form the test sample P2.

[0050] For the above test sample P2, determine the yellow rice content H according to the detection method of the yellow rice index in Step 1: "Inspection of Grain and Oil - Inspection Method for Yellow Rice and Cracked Grains" (GB / T 5496-1985). 2 。

[0051] For the above test sample P2, determine the fatty acid value S according to the detection method of the fatty acid value in Step 2: Appendix A of "Rules for Judging the Storage Quality of Paddy" (GB / T 20569-2006). 2 。

[0052] For the above test sample P2, determine the freshness value Y according to the detection method of the freshness value in Step 3: "Grain and Oil Inspection - Determination and Differentiation of Paddy Freshness" (LS / T 6118-2017). 2 。

[0053] For the above test sample P2, determine the taste score value P according to the detection method of the taste score value in Step 4: Appendix B of "Rules for Judging the Storage Quality of Paddy" (GB / T 20569-2006). 2 。

[0054] The yellow rice content H of P2 2 is 0.2%, the fatty acid value S 2 is 17.6 mg / 100 g, and the freshness value Y 2 is 88 points, and the taste score value P 2 is 82 points. The freshness degree N calculated by the model 2 is 69, and it is determined that P2 is new grain. The storage years of paddy are consistent with the evaluation results of this example.

[0055] Example 3 For the paddy stored in Warehouse P3 for one year, in strict accordance with the provisions of the "Sampling Inspection and Management Measures for the Quality Inspection of Government Reserve Grain and Oil" (Guoliangbiaogui

[2023] No. 60), sampling is carried out layer by layer from bottom to top by area, layer, and point. According to the size of the grain surface area in the warehouse, the area is divided into zones of 200 ㎡. Each zone has a total of 5 points at the center and four corners. Each point is set about 0.5 m from the edge at the edge of the grain pile. The sampling mass ratio of the center point to the four corner points is 1:1 to form the test sample P3.

[0056] For the above test sample P3, the yellow rice content H is determined according to the detection method of the yellow rice index in Step 1: "Inspection of Grain and Oil - Inspection Method for Yellow Rice and Cracked Grains" (GB / T 5496 - 1985). 3 .

[0057] For the above test sample P3, the fatty acid value S is determined according to the detection method of the fatty acid value in Step 2: Appendix A of the "Rules for Judging the Storage Quality of Paddy" (GB / T 20569 - 2006). 3 .

[0058] For the above test sample P3, the freshness value Y is determined according to the detection method of the freshness value in Step 3: "Inspection of Grain and Oil - Determination and Difference of Paddy Freshness" (LS / T 6118 - 2017). 3 .

[0059] For the above test sample P3, the taste score value P is determined according to the detection method of the taste score value in Step 4: Appendix B of the "Rules for Judging the Storage Quality of Paddy" (GB / T 20569 - 2006). 3 .

[0060] The yellow rice content H of P3 3 is 0.6%, the fatty acid value S 3 is 22.5 mg / 100 g, and the freshness value Y 3 is 78 points, and the taste score value P 3 is 72 points. The freshness degree N calculated by the model 3 is 55, and it is determined that P3 is old grain. The storage years of paddy are consistent with the evaluation results of this example.

[0061] Example 4 For the paddy rice stored in Warehouse P4 for two years, in strict accordance with the provisions of the "Administrative Measures for Sampling and Inspection of the Quality of Government Reserves of Grain and Oil" (Guo Liang Biao Gui

[2023] No. 60), sampling is carried out layer by layer from bottom to top by area, layer, and point. According to the size of the grain surface area in the warehouse, the area is divided into zones of 350 ㎡. Each zone has a total of 5 sampling points, including the center and the four corners. Each point is set at about 0.5 m from the edge of the grain pile. The sampling mass ratio of the center point to the four corner points is 1:1, forming the test sample P4.

[0062] For the above test sample P4, according to the detection method of the yellow rice index in Step 1: "Inspection of Grain and Oil - Method for Inspection of Yellow Rice and Cracked Grains" (GB / T 5496 - 1985), the yellow rice content H is determined. 4 。

[0063] For the above test sample P4, according to the detection method of the fatty acid value in Step 2: Appendix A of the "Rules for Judging the Storage Quality of Paddy Rice" (GB / T 20569 - 2006), the fatty acid value S is determined. 4 。

[0064] For the above test sample P4, according to the detection method of the freshness value in Step 3: "Inspection of Grain and Oil - Determination and Differentiation of the Freshness of Paddy Rice" (LS / T 6118 - 2017), the freshness value Y is determined. 4 。

[0065] For the above test sample P4, according to the detection method of the taste score value in Step 4: Appendix B of the "Rules for Judging the Storage Quality of Paddy Rice" (GB / T 20569 - 2006), the taste score value P is determined. 4 。

[0066] The yellow rice content H of P4 4 is 0.8%, the fatty acid value S 4 is 24.8 mg / 100 g, the freshness value Y 4 is 75 points, the taste score value P 4 is 70 points, and the calculated freshness N by the model 1 is 52, determining P4 as old grain. The storage years of paddy rice are consistent with the evaluation results of this example.

[0067] Example 5 For the paddy rice stored in Warehouse P5 for three years, in strict accordance with the provisions of the "Administrative Measures for Sampling and Inspection of the Quality of Government Reserves of Grain and Oil" (Guo Liang Biao Gui

[2023] No. 60), sampling is carried out layer by layer from bottom to top by area, layer, and point. According to the size of the grain surface area in the warehouse, the area is divided into zones of 350 ㎡. Each zone has a total of 5 sampling points, including the center and the four corners. Each point is set at about 0.5 m from the edge of the grain pile. The sampling mass ratio of the center point to the four corner points is 1:1, forming the test sample P5.

[0068] For the above test sample P5, determine the yellow rice content H according to the detection method of yellow rice index in step 1: "Inspection of Grain and Oilseeds - Inspection Method for Yellow Rice and Cracked Grains" (GB / T 5496-1985). 5 .

[0069] For the above test sample P5, determine the fatty acid value S according to the detection method of fatty acid value in step 2: Appendix A of "Rules for Judging the Storage Quality of Paddy" (GB / T 20569-2006). 5 .

[0070] For the above test sample P5, determine the freshness value Y according to the detection method of freshness value in step 3: "Inspection of Grain and Oilseeds - Determination and Differentiation of the Freshness of Paddy" (LS / T 6118-2017). 5 .

[0071] For the above test sample P5, determine the taste score value P according to the detection method of taste score value in step 4: Appendix B of "Rules for Judging the Storage Quality of Paddy" (GB / T 20569-2006). 5 .

[0072] The yellow rice content H of P5 5 is 1.5%, the fatty acid value S 5 is 25.8 mg / 100 g, the freshness value Y 5 is 72 points, the taste score value P 5 is 65 points, and the freshness degree N calculated by the model 5 is 48. It is determined that P5 is old grain. The storage years of paddy are consistent with the evaluation results of this example.

Claims

1. A method and system for evaluating the freshness of rice in grain procurement, characterized in that: The following steps are included: Step 1: Determine the yellow rice content H of the rice purchased in rotation. Step 2: Determine the fatty acid value content S of the rice purchased in rotation. Step 3: Determine the freshness value Y of the rice purchased in rotation. Step 4: Determine the tasting score value P of the rice purchased in rotation.

2. The method and system for evaluating the freshness of rice during grain purchase according to claim 1, characterized in that: The longer the rice is stored, the higher the yellow rice content; the higher the fatty acid value, the less suitable the rice is for storage; the higher the freshness of the rice, the higher the staleness; the higher the tasting score, the better the rice quality; a mathematical model for evaluating the staleness N of rice is established: , where H is the yellow rice content, S is the fatty acid value, Y is the freshness value, P is the tasting score, and k1 and k2 are correction factors.

3. The method and system for evaluating the freshness of rice during grain purchase according to claim 2, characterized in that: According to national standards, industry standards and enterprise purchase and storage requirements, the yellow rice content H is set to 0.1%, the fatty acid value S is 12mg / 100g, the freshness value Y is 100 points, the tasting score value P is 100 points, and the freshness N in the model is 100, which is the highest value of new grain. The yellow rice content H is set to 0.3%, the fatty acid value S is 18mg / 100g, the freshness value Y is 85 points, the tasting score value P is 70 points, and the freshness N in the model is 60, which is the critical value of new and old grains. Through mathematical calculations, the correction factors k1= 0.37 and k2= 2.89 in the mathematical model are calculated.

4. The method and system for evaluating the freshness of rice during grain purchase according to claim 3, characterized in that: The mathematical model for evaluating the freshness of rice in grain procurement is: .

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