Method for evaluating quality of rice and application thereof

Abstract

The invention relates to the technical field of food quality control, in particular to a method for evaluating rice quality and application thereof. The method comprises the following steps: obtaining a chromatic value of to-be-detected rice; judging the quality of the rice to be detected according to the chromatic value; the chromatic values include an L * value, an a * value, and a b * value. Researches find that the taste quality and key physicochemical property indexes of the rice are related to the chromatic value of the rice, the quality of the rice can be directly judged by detecting the chromatic value of the rice, the quality identification efficiency of rice products is remarkably improved, and the method has important significance in the field of quality detection of the rice.

Description

Technical Field

[0001] The invention relates to the technical field of food quality control, and in particular to a method for evaluating rice quality and application thereof. Background Art

[0002] Rice is a common food and a staple food for many people. In recent years, with the continuous improvement of people's living standards, people's demand for rice has also shifted from quantity to quality, and high-quality rice has become the main choice of consumers. However, the evaluation of rice quality is currently mainly through sensory evaluation, physical and chemical analysis or instrumental analysis, but these methods either require a lot of sample manpower and material resources or require complex instruments and equipment. There is a lack of convenient, fast and effective quality evaluation methods for rice products currently sold on the market to protect consumer rights and ensure food quality safety.

[0003] The sensory evaluation of rice quality is the most direct way to reflect the quality of rice. A professional tasting panel scores the appearance, smell, taste, palatability, cold rice texture and other aspects of the rice to determine its taste value. However, this method requires a large amount of rice samples, time, manpower and material resources, and is not suitable for the rapid evaluation of the quality of a small amount of rice samples. The physical and chemical analysis method mainly uses the content of amylose and crude protein as indirect evaluation indicators of taste quality. The starch and protein content in rice can reach 90%. The content of amylose in starch is significantly correlated with the hardness, cohesion, viscosity and resilience of rice. When the content of amylose is high, the rice is hard, the color is dull, the rice grains are dry and fluffy, and the taste quality is poor; when the content of amylose is low, the rice tastes softer and the rice grains are crystal clear and shiny. Protein content affects the water absorption of rice grains during cooking and is negatively correlated with the taste of rice. High protein content leads to a too tight structure of rice grains, small gaps between starch grains, which hinders the rice from absorbing water, increases the gelatinization temperature, increases hardness, reduces viscoelasticity, dulls color, and reduces taste. However, the determination of these two indicators requires experienced operators, complex operating steps, expensive instruments and equipment, and a large number of Yangping, and is not suitable for rapid on-site testing.

[0004] Rice quality is closely related to its variety, origin, cultivation conditions, processing and storage. There are large differences between different varieties or the same variety. Whether it is through sensory evaluation, physical and chemical analysis, or instrumental analysis to evaluate rice quality, it is difficult to represent the real-time changes in rice quality on the market. When the tested sample is not from the same batch of rice as the product of the same brand and specification sold, the test result cannot represent the quality of the rice product. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a method for evaluating rice quality and its application. Based on the correlation between the chromaticity value of rice and its taste quality and physical and chemical properties, the present invention establishes a method for directly judging the quality of rice by detecting the chromaticity value of rice, which has a high rice quality detection efficiency.

[0006] In a first aspect, the present invention provides a method for evaluating rice quality, comprising: Obtaining a chromaticity value of the rice to be tested; and judging the quality of the rice to be tested according to the chromaticity value; The chromaticity value includes L* value, a* value and b* value.

[0007] Further, judging the quality of the rice to be tested according to the chromaticity value includes: The chromaticity index, taste value and physicochemical property index of the rice to be tested are judged according to the chromaticity value; the quality of the rice to be tested is judged according to the chromaticity index, taste value and physicochemical property index of the rice to be tested; the physicochemical properties include: one or more of amylose content, protein content, lipid content, water content or viscosity.

[0008] Furthermore, the physicochemical properties are amylose content and protein content.

[0009] Furthermore, the chromaticity index is calculated by the following method: WI=100-[(100-L*) 2 +a* 2 +b* 2 ] 0.5 ; The taste value is calculated by the following method: For japonica rice, N 1 =71.85+0.2555×L*-0.2603×a*-0.3247×b*, for indica rice, it is N 1 =101.4-0.06014×L*-0.1155×a*-0.7792×b*; The index of the amylose content is calculated by the following method: For japonica rice, N 2 =57.12-0.3424×L*+0.5150×a*-0.9128×b*, for indica rice, it is N 2 =-0.6210+0.2130×L*-0.2735×a*-0.008783×b*, according to N 2 The calculation result is used to determine the index of amylose content; The protein content index is calculated by the following method: For japonica rice, N3 =3.039+0.0004746×L*-0.3556×a*+0.06670×b*, for indica rice, it is N 3 =14.12-0.09323×L*+0.06509×a*-0.02579×b*, according to N 3 The calculated results are used to determine the protein content index.

[0010] Further, according to N 2 The calculation results of the index for judging the content of amylose include: N 2 The index for values ​​between 13.5% and 16.0% is 5, N 2 The index for values ​​between 16.1% and 18.0% is 4, N 2 The index for values ​​greater than 18.0% or less than 13.5% is 3; According to N 3 The calculation results of protein content include: N 3 The index for values ​​less than 6% is 10, N 3 The index for values ​​between 6.0% and 6.5% is 8, N 3 Values ​​greater than 6.5% are given an index of 6.

[0011] The invention provides a calculation method of an amylose content index value and a protein content value based on the correlation between a rice taste value, a chromaticity value and an amylose content / protein content, so as to directly reflect the taste and quality of rice through the chromaticity value.

[0012] Further, a comprehensive evaluation index is calculated according to the chromaticity index, taste value and physicochemical property index of the rice to be tested, and rice with a higher comprehensive evaluation index has better quality; The comprehensive evaluation index is calculated by the following method: Comprehensive quality index = 0.05 × chromaticity index WI + 0.8 × taste value N 1 + Index of amylose content + Index of protein content.

[0013] Furthermore, the chromaticity value also includes: L* value, a* value and b* value detected after the rice to be tested is steamed; they are respectively recorded as cookL*, cooka* and cookb*.

[0014] Furthermore, the rice quality can be evaluated for cookL*, cooka* and cookb* in the same manner as the aforementioned L*, a* and b* values. For example, the color index after cooking, cookWI = 100 - [(100 - cookL*) 2 +cooka* 2 +cookb*2 ] 0.5 The rice with a larger chromaticity index cookWI has better quality. The chromaticity value after cooking can be a further supplement to the evaluation results of the chromaticity value of uncooked rice.

[0015] Furthermore, the steaming includes: steaming the rice to be tested and water in a ratio of (1:1.3) to (1:1.4) for 30 to 50 minutes.

[0016] Furthermore, the rice is one or more of Wuyoudao No. 4, Jiyuanxiang No. 1, Suijing 18 or Longjing 31.

[0017] In a second aspect, the present invention provides application of the method in determining the storage time of rice.

[0018] The present invention has found that as the storage time increases, the WI value of rice gradually decreases, and accordingly the quality of rice also gradually decreases. Therefore, the storage time of rice can be determined by detecting the chromaticity value of rice.

[0019] The present invention has the following beneficial effects: The present invention has found that the taste quality and key physical and chemical property indicators of rice have a certain correlation with its chromaticity value, and thus proposed a technical solution for judging the quality of rice by its chromaticity value. By detecting the chromaticity value of commercial rice, a preliminary judgment of its quality can be achieved, which can significantly improve the efficiency of rice quality detection.

[0020] The present invention can more intuitively reflect the quality of rice by establishing the relationship between rice chromaticity and quality, is more convenient for monitoring the change of rice quality, takes active and effective solutions and preventive measures, reduces manpower, material and economic costs, can timely and effectively monitor the deterioration of rice quality, and provide a reference for consumers to purchase polished round-grained rice products. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 The embodiment 1 of the present invention provides the appearance of japonica rice and indica rice under different water-rice ratios; the upper figure is japonica rice, and the lower figure is indica rice.

[0023] Figure 2 It is the chromaticity value of polished round-grained rice and indica rice under different qualities and different water-rice ratios provided by Example 1 of the present invention.

[0024] Figure 3 It is a schematic diagram of the correlation between the chromaticity value and the taste value and the taste-related physical and chemical indicators of the Wuyoudao No. 4 rice variety provided in Example 1 of the present invention.

[0025] Figure 4 It is a schematic diagram of the multiple regression analysis results of the chromaticity value and taste value, amylose content, and protein content of the polished round-grained rice varieties provided in Example 2 of the present invention.

[0026] Figure 5 It is a schematic diagram of the multiple regression analysis results of the chromaticity value and taste value, amylose content, and protein content of the indica rice varieties provided in Example 2 of the present invention.

[0027] Figure 6 This is the variation law of the taste values ​​of four japonica rice varieties in three forms of polished rice, brown rice and paddy rice at different storage times provided by Example 3 of the present invention; the varieties are Wuyoudao No. 4 (WYD4), Longjing 31 (LJ31), Suijing 18 (SJ18) and Jiyuanxiang No. 1 (JYX1).

[0028] Figure 7 This is the variation pattern of the amylose content in three forms of polished rice, brown rice and paddy rice of four japonica rice varieties provided in Example 3 of the present invention at different storage times; the varieties are Wuyoudao No. 4 (WYD4), Longjing 31 (LJ31), Suijing 18 (SJ18) and Jiyuanxiang No. 1 (JYX1).

[0029] Figure 8 This is the law of protein content change in three forms of polished rice, brown rice and paddy rice of four japonica rice varieties provided in Example 3 of the present invention at different storage times; the varieties are Wuyoudao No. 4 (WYD4), Longjing 31 (LJ31), Suijing 18 (SJ18) and Jiyuanxiang No. 1 (JYX1).

[0030] Fig. 9 This is the variation pattern of fatty acid values ​​of four japonica rice varieties in three forms of polished rice, brown rice and paddy rice at different storage times provided by Example 3 of the present invention; the varieties are Wuyoudao No. 4 (WYD4), Longjing 31 (LJ31), Suijing 18 (SJ18) and Jiyuanxiang No. 1 (JYX1). DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The experimental methods involved in the following examples, unless otherwise mentioned, are all conventional methods in the art, for example, reference may be made to experimental manuals in the art, or the conditions recommended in the manufacturer's instructions.

[0033] Unless otherwise specified, the experimental materials and reagents involved in the following examples can be obtained from commercial sources.

[0034] Example 1

[0035] This embodiment provides a method for evaluating rice quality by rice chromaticity, which specifically includes the following process: 1. Determine the optimal rice-water ratio

[0036] The rice cooking experiment was carried out in a Panasonic HI rice cooker. 200g of polished japonica rice and indica rice were cooked at different water-to-rice ratios, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5 for polished japonica rice and 1:0.9, 1:1.0, 1:1.2, 1:1.3, 1:1.4 for indica rice. The chromaticity was measured when the mass of polished japonica rice or indica rice was 200g. The results are as follows: Figure 1 As shown. The rice was cooked with different weights of 160g, 180g, 200g, 240g, and 260g of japonica rice and indica rice, with a rice-water ratio of 1:1.35, and the color was measured. The results showed that the whiteness of the rice was the highest when 200g of japonica rice or indica rice was used.

[0037] Rice whiteness determination method: The color L*, a*, and b* values ​​of polished rice were measured using a Konica Minolta CR-310 colorimeter (Konica Minolta, Toyku, Japan), and each sample was repeated three times. The calibration standard values ​​of L*, a*, and b* were 97.97, -5.30, and +6.92, respectively, and the color index (whiteness index, WI) was calculated: WI = 100-[(100-L*) 2 +a* 2 +b* 2 ] 0.5 (The method can be referred to Pongthorn Leelayuthsoontorn, Aluck Thipayarat. Texturaland morphological changes of Jasmine rice under various elevated cooking conditions. FOOD CHEMISTRY, 2006, 96(4): 606-613). Figure 2As shown, it can be seen that the rice-water ratio of both japonica rice and indica rice is higher at 1:1.3. Therefore, the rice colorimetry method is determined as follows: the mass of japonica rice or indica rice is 200g, and the water-rice ratio is 1:1.3-1:1.4.

[0038] 2. Relationship between rice quality and its color

[0039] Wuyoudao No. 4 is a representative japonica rice variety with excellent taste quality in the rice-growing areas of Northeast China. 23 rice materials of Wuyoudao No. 4 newly harvested in the first and second accumulated temperature zones of Heilongjiang Province were collected. The content of amylose, crude protein, crude fat, moisture content, polished rice whiteness, cooked rice whiteness, RVA spectrum were measured and correlation analysis was performed. The specific methods and standards are as follows: i) Processing and appearance quality determination: For brown rice rate and polished rice rate, refer to GB / T 21719-2008 “Test method for polished rice rate of rice”; for chalkiness, refer to GB / T 1354-2018 “Rice”.

[0040] ii) Determination of physical and chemical properties: The determination of amylose content shall refer to GB / T 15683-2008 “Determination of amylose content in rice”.

[0041] iii) The moisture content shall be determined in accordance with GB 5009.3-2016.

[0042] iv) The crude protein content (dry basis) was determined according to NY / T 3-1982 “Determination of crude protein in cereal and legume seeds (semi-micro Kjeldahl method)”.

[0043] v) The analysis of gelatinization characteristics shall refer to NY / T 1753-2009 "Rapid Viscosity Analyzer Method for Determination of Gelatinization Characteristics of Rice Flour".

[0044] vi) Crude protein content determination shall refer to GB 5009.6-2016 “National Food Safety Standard - Determination of Fat in Foods”.

[0045] vii) Taste quality determination: The sensory taste evaluation of rice shall refer to GB / T 15682-2008 "Sensory Evaluation Method for Edible Quality of Paddy and Steamed Rice for Inspection of Cereals and Oils" and DB23 / T 2687-2020 "Management Procedure for Evaluation of Rice Taste Quality".

[0046] This study further conducted correlation analysis on the polished rice color, rice color, polished rice whiteness, rice taste, and taste-related physical and chemical indicators of Wuyoudao No. 4. The results are as follows: Figure 3As shown: the chromaticity of polished rice is significantly correlated with the chromaticity of cooked rice; the chromaticity value of cooked rice is significantly correlated with the protein content, as shown by the significant negative correlation between L* and crude protein content, with a correlation coefficient of -0.472; a* is significantly positively correlated with crude protein content, with a correlation coefficient of 0.505; the taste quality of rice is significantly positively correlated with the content of amylose, with correlation coefficients of 0.488; the protein content is significantly negatively correlated with viscosity characteristics such as polished rice chromaticity, peak viscosity, minimum viscosity, and final viscosity.

[0047] Example 2

[0048] 1. The present invention further collects high-quality rice varieties at home and abroad, evaluates the taste quality, screens out the top 50 indica and japonica rice samples in terms of taste value, and measures the rice chromaticity, rice chromaticity, and main physical and chemical indicators closely related to the taste quality, including amylose content, protein content, and viscosity characteristics. The specific method is the same as in Example 1. GraphPad software and Excel are used for data processing and multivariate linear statistical analysis to establish a prediction relationship between the chromaticity of japonica rice and the taste value, amylose content, and protein content ( Figure 4 ), the formula is as follows: Japonica rice taste value = 71.85 + 0.2555 × L* - 0.2603 × a* - 0.3247 × b*,

[0049] Japonica rice amylose content = 57.12-0.3424×L*+0.5150×a*-0.9128×b*,

[0050] Japonica rice protein content = 3.039 + 0.0004746 × L* - 0.3556 × a* + 0.06670 × b*.

[0051] Establish prediction of color and taste value, amylose content and protein content of indica rice ( Figure 5 ), the formula is as follows: Indica rice taste value = 101.4-0.06014×L*-0.1155×a*-0.7792×b*,

[0052] Indica rice amylose content = -0.6210 + 0.2130 × L* - 0.2735 × a* - 0.008783 × b*,

[0053] The protein content of indica rice = 14.12-0.09323×L*+0.06509×a*-0.02579×b*.

[0054] As shown in Table 1, domestic high-quality rice with good taste was analyzed. After preliminary evaluation, re-evaluation and final evaluation, the top 20 japonica rice and indica rice samples were selected according to the comprehensive score ranking to analyze their appearance characteristics. The higher the taste value, the better. In japonica rice, the protein content ranges from 5.1% to 8.8%, and the quality is better if it is close to 6.2%. The amylose content ranges from 8.9% to 19.3%, and the quality is better if it is close to 16.6%. In indica rice, the protein content ranges from 5.3% to 8.0%, and the quality is better if it is close to 6.8%. The amylose content ranges from 13.1% to 17.9%, and the quality is better if it is close to 15.4%.

[0055] Table 1 Variation range and average value of appearance quality and taste quality of high-quality rice

[0056] 2. Based on the above results, the present invention provides a formula for determining the comprehensive quality index: According to N 2 The calculation result is used to judge the index of amylose content, N 2 The index for values ​​between 13.5% and 16.0% is 5, N 2 The index for values ​​between 16.1% and 18.0% is 4, N 2 A value greater than 18.0% or less than 13.5% is assigned an index of 3.

[0057] According to N 3 The calculated result is used to judge the protein content index, N 3 The index for values ​​less than 6% is 10, N 3 The index for values ​​between 6.0% and 6.5% is 8, N 3 Values ​​greater than 6.5% are given an index of 6.

[0058] Combined with the chromaticity index calculation formula WI = 100-[(100-L*) 2 +a* 2 +b* 2 ] 0.5 Finally, the following comprehensive quality index is calculated: Comprehensive quality index = 0.05 × chromaticity index WI + 0.8 × taste value N 1 + Index of amylose content + Index of protein content.

[0059] In comparison, rice with a higher comprehensive quality index has higher quality.

[0060] 3. In order to further verify the effect of the calculation formula of the aforementioned comprehensive quality index, the present invention randomly selected 14 polished rice samples and 4 indica rice samples to predict the quality index. The results showed that the relative bias ranged from -1.00% to -3.32% (Table 2), indicating that the method has a relatively high accuracy.

[0061] Table 2 Prediction and analysis of rice quality index

[0062] Example 3

[0063] This example further performs quality testing on the Wuyoudao No. 4 polished rice under different storage forms and times, and the specific process is as follows: The present invention packages the rice varieties Wuyoudao No. 4 (first accumulated temperature zone), Jiyuanxiang No. 1 (first accumulated temperature zone), Suijing 18 (second accumulated temperature zone), and Longjing 31 (third accumulated temperature zone) newly harvested from the most suitable planting accumulated temperature zone in Heilongjiang Province in the form of polished rice, brown rice, and paddy rice, and stores them at room temperature and low temperature (cold storage at about 10°C). The taste value, amylose content, crude protein content, and moisture content are measured every 20 days until the storage time reaches 200 days. The measurement results are as follows: Figure 6-Figure 9 As shown in Table 3, the rice taste value, amylose content and moisture content showed a downward trend, the protein content did not change significantly, and the fatty acid value measurement results showed that the fatty acid value reached the highest at 140 days, indicating that the rice quality deteriorated seriously at 140 days. After 40 days, 60 days, 80 days, 100 days, 120 days and 140 days of storage, the brown rice and paddy were processed into polished rice to measure their chromaticity values, and the measurement method was the same as that of the second embodiment. By comparing the chromaticity values ​​of rice under three storage forms, the results shown in Table 3 were obtained: the chromaticity values ​​showed a downward trend with the extension of storage time. Whether the polished rice, brown rice and paddy stored under normal temperature or low temperature conditions had a WI value lower than -30 when it exceeded 140, so it can be used for preliminary judgment of the storage time of Wuyoudao No. 4 (Daohuaxiang No. 2), Longjing 31, Suijing 18, Jiyuanxiang No. 1 rice varieties or rice commodities.

[0064] Table 3 Rice chromaticity parameters of main japonica rice varieties under different storage forms and time conditions - Part I

[0065] Table 4 Rice chromaticity parameters of main japonica rice varieties under different storage forms and time conditions - Part II

[0066] Table 5 Rice chromaticity parameters of main japonica rice varieties under different storage forms and time conditions - Part III

[0067] Table 6 Rice chromaticity parameters of main japonica rice varieties under different storage forms and time conditions - Part IV

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating rice quality, characterized in that: include: Obtaining the chromaticity value of the rice to be tested; judging the quality of the rice to be tested according to the chromaticity value; the chromaticity value includes L* value, a* value and b* value.

2. The method according to claim 1, characterized in that The method of judging the quality of the rice to be tested according to the chromaticity value comprises: The chromaticity index, taste value and physicochemical property index of the rice to be tested are judged according to the chromaticity value; the quality of the rice to be tested is judged according to the chromaticity index, taste value and physicochemical property index of the rice to be tested; the physicochemical properties include: one or more of amylose content, protein content, lipid content, water content or viscosity.

3. The method according to claim 2, characterized in that The physicochemical properties are amylose content and protein content.

4. The method according to claim 3, characterized in that The chromaticity index is calculated by the following method: WI = 100 - [(100 - L*) 2 +a* 2 +b* 2 ] 0.5 ; The taste value is calculated by the following method: For japonica rice, N1=71.85+0.2555×L*-0.2603×a*-0.3247×b*, and for indica rice, N1=101.4-0.06014×L*-0.1155×a*-0.7792×b*; The index of the amylose content is calculated by the following method: For japonica rice, N2=57.12-0.3424×L*+0.5150×a*-0.9128×b*, and for indica rice, N2=-0.6210+0.2130×L*-0.2735×a*-0.008783×b*. The index of amylose content is determined based on the calculation result of N2. The protein content index is calculated by the following method: For japonica rice, N3=3.039+0.0004746×L*-0.3556×a*+0.06670×b*, and for indica rice, N3=14.12-0.09323×L*+0.06509×a*-0.02579×b*. The protein content index is determined based on the calculation result of N3.

5. The method according to claim 4, characterized in that The index for judging the content of amylose according to the calculation result of N2 includes: an index of 5 when the N2 value is 13.5% to 16.0%, an index of 4 when the N2 value is 16.1% to 18.0%, and an index of 3 when the N2 value is greater than 18.0% or less than 13.5%; The index for judging the protein content according to the calculation result of N3 includes: an index of 10 when the N3 value is less than 6%, an index of 8 when the N3 value is 6.0% to 6.5%, and an index of 6 when the N3 value is greater than 6.5%.

6. The method according to any one of claims 2 to 5, characterized in that: Calculating a comprehensive evaluation index according to the chromaticity index, taste value and physicochemical property index of the rice to be tested, wherein the rice with a higher comprehensive evaluation index has better quality; The comprehensive evaluation index is calculated by the following method: Comprehensive quality index = 0.05 × chromaticity index WI + 0.8 × taste value N1 + index of amylose content + index of protein content.

7. The method according to claim 1, characterized in that The chromaticity value also includes: the chromaticity index L* value, a* value and b* value detected after the rice to be tested is cooked; they are recorded as cookL*, cooka* and cookb* respectively.

8. The method according to claim 7, characterized in that The steaming comprises: steaming the rice to be tested and water at a ratio of (1:1.3) to (1:1.4) for 30 to 50 minutes.

9. The method according to any one of claims 1 to 8, characterized in that: The rice is one or more of Wuyoudao No. 4, Jiyuanxiang No. 1, Suijing 18 or Longjing 31.

10. Use of the method according to any one of claims 1 to 9 in determining the storage time of rice.

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