CN108918449B - Rice yellow-change degree detection method based on ultraviolet-visible spectrophotometry - Google Patents
Rice yellow-change degree detection method based on ultraviolet-visible spectrophotometry Download PDFInfo
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- 235000007164 Oryza sativa Nutrition 0.000 title claims abstract description 230
- 235000009566 rice Nutrition 0.000 title claims abstract description 230
- 238000001514 detection method Methods 0.000 title claims abstract description 37
- 238000000870 ultraviolet spectroscopy Methods 0.000 title claims abstract description 14
- 240000007594 Oryza sativa Species 0.000 title 1
- 241000209094 Oryza Species 0.000 claims abstract description 229
- 235000013312 flour Nutrition 0.000 claims abstract description 57
- 238000004383 yellowing Methods 0.000 claims abstract description 42
- 238000002791 soaking Methods 0.000 claims abstract description 22
- 238000012360 testing method Methods 0.000 claims abstract description 18
- 239000002904 solvent Substances 0.000 claims abstract description 11
- 238000010521 absorption reaction Methods 0.000 claims abstract description 10
- 238000012417 linear regression Methods 0.000 claims abstract description 5
- 238000000862 absorption spectrum Methods 0.000 claims abstract description 4
- 239000006228 supernatant Substances 0.000 claims abstract description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 47
- 238000002386 leaching Methods 0.000 claims description 39
- 230000000694 effects Effects 0.000 claims description 35
- BNIILDVGGAEEIG-UHFFFAOYSA-L disodium hydrogen phosphate Chemical compound [Na+].[Na+].OP([O-])([O-])=O BNIILDVGGAEEIG-UHFFFAOYSA-L 0.000 claims description 26
- 235000019799 monosodium phosphate Nutrition 0.000 claims description 25
- 229910000403 monosodium phosphate Inorganic materials 0.000 claims description 25
- AJPJDKMHJJGVTQ-UHFFFAOYSA-M sodium dihydrogen phosphate Chemical compound [Na+].OP(O)([O-])=O AJPJDKMHJJGVTQ-UHFFFAOYSA-M 0.000 claims description 25
- 230000031700 light absorption Effects 0.000 claims description 19
- 235000019441 ethanol Nutrition 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 238000002835 absorbance Methods 0.000 claims description 7
- 238000000227 grinding Methods 0.000 claims description 7
- 239000012153 distilled water Substances 0.000 claims description 6
- 238000003801 milling Methods 0.000 claims description 3
- 238000007427 paired t-test Methods 0.000 claims description 2
- 238000000034 method Methods 0.000 abstract description 14
- 239000000843 powder Substances 0.000 abstract description 9
- 230000008859 change Effects 0.000 abstract description 5
- 238000011161 development Methods 0.000 abstract description 2
- 238000012545 processing Methods 0.000 abstract description 2
- 235000014113 dietary fatty acids Nutrition 0.000 description 12
- 229930195729 fatty acid Natural products 0.000 description 12
- 239000000194 fatty acid Substances 0.000 description 12
- 150000004665 fatty acids Chemical class 0.000 description 12
- 229910019142 PO4 Inorganic materials 0.000 description 10
- 238000007619 statistical method Methods 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 229910000397 disodium phosphate Inorganic materials 0.000 description 5
- 235000012054 meals Nutrition 0.000 description 5
- 239000007788 liquid Substances 0.000 description 4
- 229910000162 sodium phosphate Inorganic materials 0.000 description 4
- 238000011160 research Methods 0.000 description 3
- 239000011734 sodium Substances 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000010828 elution Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000002798 spectrophotometry method Methods 0.000 description 2
- 229920000856 Amylose Polymers 0.000 description 1
- 102000004190 Enzymes Human genes 0.000 description 1
- 108090000790 Enzymes Proteins 0.000 description 1
- 239000004480 active ingredient Substances 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000006701 autoxidation reaction Methods 0.000 description 1
- 235000013339 cereals Nutrition 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000004737 colorimetric analysis Methods 0.000 description 1
- 235000019800 disodium phosphate Nutrition 0.000 description 1
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
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- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
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Abstract
The invention discloses a paddy yellow degree detection method based on an ultraviolet-visible spectrophotometry, which comprises the following steps: preparing 14 parts of rice samples, processing the rice into rice, measuring the yellowness index by using a color difference meter, and taking out a part of each sample to be crushed into the rice powder; soaking rice and rice flour in 4 different solvents respectively, standing for 2 hr, centrifuging with centrifuge, collecting supernatant, detecting, and measuring the absorption spectrum of each leachate with ultraviolet-visible spectrophotometer; and (3) analyzing results, detecting that the maximum absorption wavelengths of the rice and rice flour leachate are 305.2nm, 533.2nm and 595.2nm respectively by using a spectrophotometer, establishing a linear regression model to obtain a predicted value of the rice sample index, and performing matched T-test with the actual value. The invention has the advantages that: through a spectrophotometric color development method, the quality change condition of the stored rice can be known in time, and the method is better than a rice yellowing detection method of a color difference meter.
Description
Technical Field
The invention relates to a detection technology for researching rice yellowing, in particular to a rice yellowing detection method based on an ultraviolet-visible spectrophotometry.
Background
During the storage process of the rice, due to the difference of physical and chemical characteristics of the rice, the interaction of different enzymes, autoxidation, storage condition differences and the like, the stored rice is changed differently. The quality change of the stored rice can be known in time by a spectrophotometric color development method. Visual colorimetry is frequently used in the early stage, and the accuracy of a resolution result is low due to the difference of human perception abilities. The basic principle of spectrophotometry is that the absorbance of a solution should be measured at the maximum absorption wavelength because the absorption degree of light is different at different absorption wavelengths for the same substance due to different contents.
In practical application, the method is mainly used for measuring the content of active ingredients such as amylose in the grain quality detection by adjusting the proper pH value of a system and selecting a high-efficiency extraction solvent. The absorbance may be measured, and the concentration or content of the sample component may be converted by a standard curve to perform quantitative analysis.
Compared with a color difference meter, the spectrophotometer has the advantages that the determination method is simple and convenient, the accuracy is high, the equipment is cheap, the light absorption value of the leachate under the maximum absorption wavelength is determined by establishing a standard curve equation, and the yellowness index of the rice can be obtained by substituting the equation, so that the position of the spectrophotometer in food analysis is more and more important. The invention soaks rice or rice flour in different solvents (distilled water, absolute ethyl alcohol, 95% ethyl alcohol, 0.1-0.5mol/L sodium dihydrogen phosphate and 0.1-0.5mol/L disodium hydrogen phosphate), and utilizes a spectrophotometer to detect the maximum absorption wavelength (305.2nm, 533.2nm and 595.2nm) of the leachate, optimizes the absorption and elution effects, establishes a linear regression model, takes another batch of samples, measures the yellowness index, then processes the samples under the same conditions, measures the light absorption value of the samples, substitutes the light absorption value into the established linear equation to obtain the predicted value of the rice sample index, and performs matched T-test with the actual value to verify the feasibility of the model.
Disclosure of Invention
The invention aims to provide a paddy yellowing degree detection method based on an ultraviolet-visible spectrophotometry, which can timely know the quality change condition of stored paddy through a spectrophotometry developing method and is better than a paddy yellowing degree detection method of a color difference meter.
The technical scheme adopted by the invention is as follows: a method for detecting the yellow degree of paddy based on an ultraviolet-visible spectrophotometry is characterized by comprising the following steps:
(1) preparing 14 parts of rice samples, hulling and milling the rice to obtain national standard third-level rice, measuring a yellowness index by using a colorimeter, and taking out a part of each sample to be crushed into rice flour;
(2) soaking rice and rice flour in 4 different solvents, respectively, such as distilled water, ethanol, sodium dihydrogen phosphate and disodium hydrogen phosphate, standing for 2 hr, centrifuging with a centrifuge, collecting supernatant, detecting, and measuring the absorption spectrum of each leachate with an ultraviolet-visible spectrophotometer;
(3) and (3) analyzing results, detecting that the maximum absorption wavelengths of the rice and rice flour leachate are 305.2nm, 533.2nm and 595.2nm respectively by using a spectrophotometer, establishing a linear regression model (linear relation between the yellowness index and absorbance), obtaining a predicted value of the rice sample index, and performing matched T-test with the actual value (performing variance analysis on the predicted value and the actual value of the model).
The ethanol is absolute ethanol and 95% ethanol, and the content of sodium dihydrogen phosphate and disodium hydrogen phosphate is 0.1-0.5 mol/L.
When the wavelengths are 305.2nm and 533.2nm, the detection effect of the rice flour absolute ethyl alcohol leaching solution is best, and the correlation coefficient R is the best20.884 and 0.840, respectively, and the linear equations y 0.010x +0.453 and y 0.009x-0.198, respectively. Wherein Y is the absorbance and X is the yellowness index.
When the wavelengths are 305.2nm and 595.2nm, the detection effect of 0.2mol/L rice sodium dihydrogen phosphate leaching solution is the best, and the correlation coefficient R is20.818 and 0.871 respectively, and the linear equations are y-0.013 x-0.181 and y-0.005 x +0.234 respectively.
When the wavelengths are 305.2nm and 533.2nm, the detection effect of 0.5mol/L rice meal sodium dihydrogen phosphate leaching solution is the best, and the correlation coefficient R is the best20.856 and 0.847 respectively, and the linear equations are-0.021 x +1.491 and-0.008 x +0.326 respectively.
When the wavelengths are 533.2nm and 595.2nm, the detection effect of 0.3mol/L rice disodium hydrogen phosphate leachate is best, and the correlation coefficient R is20.839 and 0.859, respectively, and the linear equations-0.010 x +0.459 and-0.009 x +0.4101, respectively.
When the wavelengths are 305.2nm and 595.2nm, the detection effect of 0.4mol/L rice flour disodium hydrogen phosphate leachate is best, and the correlation coefficient R is20.804 and 0.810 respectively, and the linear equations are-0.028 x +1.443 and-0.010 x +0.391 respectively.
The invention has the advantages that: the rice or rice flour is soaked in different solvents, the maximum absorption wavelength of a leaching solution is detected by using a spectrophotometer, the leaching solution is optimized, the elution effect is compared, a linear regression model is established, another batch of samples are taken, the yellowness index is measured, the light absorption value of the samples is measured by processing under the same condition, the light absorption value is substituted into the established linear equation, the predicted value of the rice sample index is obtained, and the predicted value and the actual value are subjected to matched T-test to verify the feasibility of the model.
Drawings
FIG. 1 is a schematic view showing a method of soaking rice in distilled water according to the present invention.
FIG. 2 is a schematic view showing a model of soaking rice flour in distilled water according to the present invention.
FIG. 3 is a schematic representation of a 95% ethanol soaked rice model of the present invention.
Fig. 4 is a model diagram of 95% ethanol-soaked rice flour according to the present invention.
FIG. 5 is a schematic diagram of an absolute ethanol-soaked rice model of the present invention.
Fig. 6 is a model view of the absolute ethyl alcohol-soaked rice flour of the present invention.
FIG. 7 shows the 305.2nm NaH of the present invention2PO4Model graph of concentration soaked rice.
FIG. 8 shows 533.2nm NaH of the present invention2PO4Model graph of concentration soaked rice.
FIG. 9 shows 595.2nm NaH of the present invention2PO4Model graph of concentration soaked rice.
FIG. 10 shows the 305.2nm NaH of the present invention2PO4Concentration soaking rice flour model chart.
FIG. 11 shows 533.2nmNaH of the present invention2PO4Concentration soaking rice flour model chart.
FIG. 12 shows 595.2nmNaH according to the present invention2PO4Concentration soaking rice flour model chart.
FIG. 13 shows 305.2nmNa according to the present invention2HPO4Model graph of concentration soaked rice.
FIG. 14 shows 533.2nmNa of the present invention2HPO4Model graph of concentration soaked rice.
FIG. 15 shows 595.2nmNa according to the present invention2HPO4Model graph of concentration soaked rice.
FIG. 16 shows 305.2nmNa according to the present invention2HPO4Concentration soaking rice flour model chart.
FIG. 17 shows 533.2nmNa of the present invention2HPO4Concentration soaking rice flour model chart.
FIG. 18 shows 595.2nmNa according to the present invention2HPO4Concentration soaking rice flour model chart.
Detailed Description
1. The technical scheme adopted by the invention is as follows: a method for detecting the yellow degree of paddy based on an ultraviolet-visible spectrophotometry is characterized by comprising the following steps:
(1) as shown in table 1, table 2, table 3, table 4, 14 parts of rice samples were prepared, and the rice was subjected to husking, rice milling to state standard three-grade (GB1354-2009) rice, yellowness index was measured with a color difference meter, and a part of each sample was taken out and pulverized into rice flour (80 mesh).
(2) Soaking rice and rice flour in 4 different solvents (distilled water, ethanol, sodium dihydrogen phosphate and disodium hydrogen phosphate), standing for 2 hr, centrifuging, collecting supernatant, detecting, and measuring the absorption spectrum of each leachate with ultraviolet-visible spectrophotometer. The reason for adopting the four solvents is that water and ethanol are common polar solvents, some substances are soluble in water, some substances are soluble in ethanol, the fatty acid value content is increased and the pH value is reduced after the rice is yellowed, and the sodium dihydrogen phosphate and the disodium hydrogen phosphate respectively show weak acidity and weak alkalinity, so that the four solvents can be used for analyzing and researching whether the materials after the rice is yellowed are neutral, weak acidity or weak alkalinity.
TABLE 1 Rice sample information
TABLE 2 yellowness index test results
TABLE 3 Experimental instrumentation
TABLE 4 reagents used in the experiment
2. Rice detection results with different yellowing degrees
As can be seen from FIGS. 1 to 6 and Table 5, the detection effect of the rice absolute ethyl alcohol extract was the best at wavelengths of 305.2nm, 533.2nm and 595.2nm, and the correlation coefficient R was found to be the best20.880, 0.792, and 0.807, respectively; the same method can obtain the rice flour absolute ethyl alcohol leaching solution with best detection effect and correlation coefficient R under the wavelength of 305.2nm, 533.2nm and 595.2nm20.884, 0.840 and 0.816 respectively. From the above analysis results, it is presumed that most of the substances after yellowing of rice are alcohol-soluble substances. The detection effect of each solvent leaching solution of the rice flour is better than that of the rice leaching solution. The reason may be that the yellowing material is more easily dissolved in the solvent after grinding the rice into powder. In summary of the above results, the rice meal absolute ethanol leachate has the best detection effect at the wavelengths of 305.2nm and 533.2nm, and the correlation coefficient R20.884 and 0.840, respectively, and the linear equations y 0.010x +0.453 and y 0.009x-0.198, respectively.
And predicting the established model, selecting 10 rice with different yellowing degrees, measuring X, Y, Z tristimulus values of a rice sample by using a colorimeter, calculating a yellowness index serving as a reference true value, grinding the rice into rice flour, soaking the rice flour by using absolute ethyl alcohol, measuring light absorption values of solutions at 305.2nm and 533.2nm, substituting the light absorption values into a constructed linear equation to obtain a predicted value, and performing matched T test with an actual value, wherein the result is shown in a table 6.
TABLE 5 yellowness index model prediction values and reference truth values for the rice flour absolute ethanol leachate
TABLE 6 yellowness index model prediction values and reference truth T-test of rice meal absolute ethanol leachate at 305.2nm
TABLE 7 yellowness index model prediction values and reference truth T-test for rice meal absolute ethanol leachate at 533.2nm
As can be seen from tables 5-7, under 305.2nm and 533.2nm, the predicted value of the yellowness index model of the rice flour absolute ethyl alcohol leaching solution is not significantly different from the reference true value (P is more than 0.05, the confidence interval is 95%), which indicates that the model is reliable.
As can be seen from FIGS. 7 to 12, the detection effect of 0.2mol/L rice sodium dihydrogen phosphate leachate was the best at wavelengths of 305.2nm, 533.2nm and 595.2nm, and the correlation coefficient R was the best20.818, 0.798 and 0.871, respectively; the same method can obtain the rice flour sodium dihydrogen phosphate leaching solution with 0.5mol/L of best detection effect and correlation coefficient R at the wavelength of 305.2nm, 533.2nm and 595.2nm20.856, 0.847 and 0.815, respectively. In summary of the above results, 0.2mol/L of rice sodium dihydrogen phosphate leachate was detected best at 305.2nm and 595.2nm, and the correlation coefficient R was determined20.818 and 0.871, respectively, and the linear equations are y ═ 0.013x-0.181 and y ═ 0.005x +0.234, respectively; the detection effect of 0.5mol/L rice meal sodium dihydrogen phosphate leaching solution is best under the wavelength of 305.2nm and 533.2nm, and the correlation coefficient R is the best20.856 and 0.847 respectively, and the linear equations are-0.021 x +1.491 and-0.008 x +0.326 respectively. From the graph, the detection effect of the 0.2mol/L rice sodium dihydrogen phosphate leaching liquid is better than that of the rice flour leaching liquid, and the detection effect of the 0.5mol/L rice sodium dihydrogen phosphate leaching liquid is not as good as that of the rice flour leaching liquid.
Predicting the established model as shown in tables 8 and 9, selecting 10 rice with different yellowing degrees, measuring X, Y, Z tristimulus values of rice samples by using a colorimeter, calculating a yellowness index, grinding the rice into big rice flour, soaking the rice with 0.2mol/L sodium dihydrogen phosphate, and measuring light absorption values of leachate at 305.2nm and 595.2 nm; soaking rice flour in 0.5mol/L sodium dihydrogen phosphate, measuring light absorption values of leachate at 305.2nm and 533.2nm, substituting into the established equation to obtain predicted value, and performing paired T test with the actual value.
TABLE 8 0.2mol/L of rice NaH2PO4Statistical analysis of prediction value and reference truth value of leaching solution yellowness index model
TABLE 9 Rice flour NaH at 305.2nm0.5mol/L2PO4T-test of prediction value and reference truth value of leaching solution yellowness index model
TABLE 10 595.2.2nm0.2mol/L rice NaH2PO4T-test of prediction value and reference truth value of leaching solution yellowness index model
As is clear from tables 9 and 10, 0.2mol/L of rice NaH was observed at 305.2nm and 595.2nm2PO4The predicted value of the yellowness index model of the leachate has no significant difference with the reference true value (P is more than 0.05, and the confidence interval is 95 percent), which indicates that the model is reliable.
TABLE 11 0.5mol/L Rice flour NaH2PO4Statistical analysis of prediction value and reference truth value of leaching solution yellowness index model
TABLE 12 Rice flour NaH at 305.2nm0.5mol/L2PO4Statistical analysis of prediction value and reference truth value of leaching solution yellowness index model
TABLE 13, 533.2nm0.5mol/L Rice flour NaH2PO4Statistical analysis of prediction value and reference truth value of leaching solution yellowness index model
As is clear from tables 11 to 13, 0.5mol/L of NaH was obtained at 305.2nm and 595.2nm2PO4The predicted value of the yellowness index model of the leachate has no significant difference with the reference true value (P is more than 0.05, and the confidence interval is 95 percent), which indicates that the model is reliable.
3. As can be seen from FIGS. 13-18, at wavelengths of 305.2nm, 533.2nm and 595.2nm, 0.3mol/L of rice disodium hydrogen phosphate leachate showed the best detection effect, and the correlation coefficient R was determined20.725, 0.839 and 0.859, respectively; the same method can obtain the rice flour disodium hydrogen phosphate leaching solution with 0.4mol/L best detection effect and correlation coefficient R under the wavelength of 305.2nm, 533.2nm and 595.2nm20.804, 0.789 and 0.810, respectively. In summary of the above results, 0.3mol/L of rice disodium hydrogen phosphate leachate was detected best at wavelengths of 533.2nm and 595.2nm, and the correlation coefficient R was found to be20.839 and 0.859, respectively, and the linear equations-0.010 x +0.459 and-0.009 x +0.4101, respectively; the detection effect of 0.4mol/L rice flour disodium hydrogen phosphate leachate is best under the wavelength of 305.2nm and 595.2nm, and the correlation coefficient R is20.804 and 0.810 respectively, and the linear equations are-0.028 x +1.443 and-0.010 x +0.391 respectively. From the chart, the detection effect of the rice disodium hydrogen phosphate leaching agent with the concentration of 0.3mol/L is better than that of the rice flour, and the rice is 0.4mol/L based on the concentration of the sodium hydrogen phosphate leaching agentThe detection effect of the rice disodium hydrogen phosphate leaching solution L is not as good as that of rice flour.
Predicting the established model, selecting 10 rice with different yellowing degrees, measuring X, Y, Z tristimulus values of a rice sample by using a colorimeter, calculating a yellowness index, grinding the rice into big rice flour, soaking the rice with 0.3mol/L disodium hydrogen phosphate, and measuring light absorption values of leachate at 533.2nm and 595.2 nm; after 0.4mol/L disodium hydrogen phosphate is used for soaking rice flour, light absorption values of the leachate at 305.2nm and 595.2nm are measured, the light absorption values are substituted into a built equation to obtain a predicted value, and the predicted value and an actual value are subjected to matching T test.
TABLE 14, 0.3mol/LNa2HPO4Statistical analysis of the predicted value and the reference true value of the yellowness index model of the rice leaching solution
TABLE 15, 533.2nm0.3mol/L rice Na2HPO4T-test of prediction value and reference truth value of yellowness index model of leachate
TABLE 16 595.2nm0.3mol/L rice Na2HPO4T-test of prediction value and reference truth value of yellowness index model of leachate
As is clear from tables 14 to 16, 0.3mol/L of rice Na was observed at 533.2.2nm and 595.2nm2HPO4The predicted value of the yellowness index model of the leachate has no significant difference with the reference true value (P is more than 0.05, the confidence interval is 95 percent), which indicates thatThe model is reliable.
TABLE 17 0.4mol/L rice flour Na2HPO4Statistical analysis of prediction value and reference truth value of yellowness index model of leachate
TABLE 18, 305.2nm0.4mol/L rice flour Na2HPO4T-test of prediction value and reference truth value of leaching solution yellowness index model
TABLE 19 rice flour Na of 595.2nm0.4mol/L2HPO4T-test of prediction value and reference truth value of leaching solution yellowness index model
As is clear from tables 17 to 19, 0.4mol/L of rice flour Na was obtained at 305.2.2nm and 595.2nm2HPO4The predicted value of the yellowness index model of the leachate has no significant difference with the reference true value (P is more than 0.05, and the confidence interval is 95 percent), which indicates that the model is reliable.
The research and discussion result of the invention shows that under the wavelength of 305.2nm and 533.2nm, the rice powder absolute ethyl alcohol leaching solution has the best effect of detecting the yellow stain of the rice, and the correlation coefficient R20.884 and 0.840, respectively, and the linear equations Y0.010X +0.453 and Y0.009X-0.216, respectively (X is rice yellowness index and Y is leachate absorbance).
Under the wavelength of 305.2nm and 595.2nm, the rice sodium dihydrogen phosphate leaching solution of 0.2mol/L rice has the best yellowing effect, and the correlation coefficient R20.818 and 0.871, respectively, and the linear equations are y ═ 0.013x-0.181 and y ═ 0.005x +0.234, respectively; the rice powder sodium dihydrogen phosphate leaching solution with the concentration of 0.5mol/L has the best yellowing effect when used for detecting rice at the wavelengths of 305.2nm and 533.2nm, and the correlation coefficient R20.856 and 0.847 respectively, and the linear equations are-0.021 x +1.491 and-0.008 x +0.326 respectively. From the chart, the yellowing effect of the rice detected by 0.2mol/L of the rice sodium dihydrogen phosphate leaching solution is better than that of the rice powder, and the yellowing effect of the rice detected by 0.5mol/L of the rice sodium dihydrogen phosphate leaching solution is not as good as that of the rice powder.
The rice yellowing effect is best detected by 0.3mol/L rice disodium hydrogen phosphate leachate under the wavelength of 533.2nm and 595.2nm, and the correlation coefficient R is20.839 and 0.859, respectively, and the linear equations are-0.010 x +0.459 and-0.009 x +0.411, respectively; the rice powder disodium hydrogen phosphate leaching solution with the concentration of 0.4mol/L has the best yellowing effect when being used for detecting the rice at the wavelengths of 305.2nm and 595.2nm, and the correlation coefficient R20.804 and 0.810 respectively, and the linear equations are-0.028 x +1.443 and-0.010 x +0.391 respectively. From the chart, the yellowing effect of the rice detected by 0.3mol/L of the rice disodium hydrogen phosphate leaching solution is better than that of the rice powder, and the yellowing effect of the rice detected by 0.4mol/L of the rice disodium hydrogen phosphate leaching solution is not as good as that of the rice powder.
4. Rice yellow grade.
4. 1, determining a rice yellowing threshold and grading; the quality of the rice and the yellowing of the rice can be simultaneously carried out during the storage period, the yellowing grade of the rice is comprehensively considered according to the quality change and the storage quality change of the rice, and whether the rice is reduced or not and the storage quality condition are taken as the basis for grading the yellowing grade. Therefore, indexes such as the fatty acid value, the polished rice rate, the yield and the like of the rice are measured at different stages of the rice yellowing, and the rice yellowing grade is determined. The rice quality indexes in the national standards are shown in table 20.
TABLE 20 Rice quality index
The yellowing of the rice is graded according to the yellowing degree, the fatty acid value and the quality index of the rice, and the statistical result is shown in table 21.
TABLE 21 grading of yellowing of unhulled rice
Since the fatty acid value is one of important indexes for judging whether the quality of the rice is deteriorated and the roughness and the polished rice percentage are indexes for judging whether the quality of the rice is changed, the rice is classified into 5 grades according to the fatty acid value, the roughness and the polished rice percentage, wherein the grades are respectively yellow to five grades, and the degree of yellow is gradually increased, and the obtained results are shown in table 48. When the fatty acid value is less than or equal to 12.38mg/100g, the roughness yield is greater than or equal to 75.032, the polished rice rate is greater than or equal to 44.231, the rice is defined as first-grade yellow stain, the storage state of the rice is in a suitable storage range, and the grade of the rice is 3 grade; when the fatty acid value is less than or equal to 29.92mg/100g, the roughness yield is greater than or equal to 73.754, the polished rice rate is greater than or equal to 41.238, and the grade of the rice is reduced to 4 grade, namely secondary yellowing, although the rice is in a proper storage range; when the fatty acid value is less than or equal to 35.75mg/100g, the roughness yield is greater than or equal to 73.043, the polished rice rate is greater than or equal to 41.015, and the quality of the rice is grade 4, but the storage state of the rice is light and is not easy to store, and the rice is defined as third-level yellowing; when the fatty acid value is less than or equal to 36.96mg/100g, the roughness yield is greater than or equal to 72.850, the polished rice rate is greater than or equal to 38.891, the quality of the rice is grade 5, and the storage state of the rice is not easy to store, which is defined as four-grade yellowing; when the fatty acid value is more than 37.64mg/100g, the roughness yield is more than or equal to 71.754, the polished rice rate is more than or equal to 38.002, although the quality of the rice is 5 grade, the storage state of the rice is hard to store, the rice is defined as five-grade yellowing, and a theoretical basis is provided for field detection and research of the rice yellowing.
With the standard of the rice yellowing grade, a collector can obtain the yellowness index by substituting the absorbance of an unknown sample measured by an ultraviolet-visible spectrophotometry into an established model in the research, preliminarily determine the yellowing grade, and further accurately determine the rice yellowing grade by measuring the fatty acid value, the roughness and the polished rice rate, so that whether the rice is easy to store and has edible value can be judged.
After the yellowing of the rice is detected by adopting an ultraviolet-visible spectrophotometry detection technology, the yellowing degree (yellowness index) of the rice is divided into five grades according to the fatty acid value (suitable for storage, mild unsuitable for storage and severe unsuitable for storage) and the quality index (roughness and polished rice rate) of the rice, and the index threshold value is determined, and specific results are shown in table 22. This study is of great importance in the food sector.
TABLE 22 grade of yellowing of rice
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (1)
1. A paddy yellow degree detection method based on an ultraviolet-visible spectrophotometry is characterized by comprising the following steps:
(1) preparing 14 parts of rice samples, hulling and milling the rice to obtain national standard third-level rice, measuring a yellowness index by using a colorimeter, and taking out a part of each sample to be crushed into rice flour;
(2) soaking rice and rice flour in 4 different solvents, respectively, such as distilled water, ethanol, sodium dihydrogen phosphate and disodium hydrogen phosphate, standing for 2 hr, centrifuging with a centrifuge, collecting supernatant, detecting, and measuring the absorption spectrum of each leachate with an ultraviolet-visible spectrophotometer;
(3) analyzing results, detecting that the maximum absorption wavelengths of the rice and rice flour leachate are 305.2nm, 533.2nm and 595.2nm respectively by using a spectrophotometer, establishing a linear regression model to obtain a predicted value of the rice sample index, and performing matched T-test with an actual value;
the ethanol is absolute ethanol and 95 percent ethanol, and the content of sodium dihydrogen phosphate and disodium hydrogen phosphate is 0.1-0.5 mol/L;
the detection effect of the rice flour absolute ethyl alcohol leaching solution is best when the wavelengths are 305.2nm and 533.2nm, and the correlation coefficient R is the best2 0.884 and 0.840, respectively, and linear equations Y =0.010X +0.453 and Y =0.009X-0.198, respectively, where Y is absorbance and X is yellowness index;
predicting the established model, selecting 10 rice with different yellowing degrees, measuring X, Y, Z tristimulus values of a rice sample by using a colorimeter, calculating a yellowness index as a reference true value, grinding the rice into rice flour, soaking the rice flour by using absolute ethyl alcohol, measuring light absorption values of solutions at 305.2nm and 533.2nm, substituting the light absorption values into the established linear equation to obtain a predicted value, and performing matched T test with an actual value;
the rice has the best detection effect on 0.2mol/L sodium dihydrogen phosphate leaching solution at the wavelength of 305.2nm and 595.2nm, and the correlation coefficient R2 0.818 and 0.871, respectively, and the linear equations y =0.013x-0.181 and y = -0.005x +0.234, respectively;
when the wavelength is 305.2nm and 533.2nm, the detection effect of 0.5mol/L sodium dihydrogen phosphate leaching solution of rice flour is the best, and the correlation coefficient R is2 0.856 and 0.847, respectively, and the linear equations y = -0.021x +1.491 and y = -0.008x +0.326, respectively;
predicting the established model, selecting 10 rice with different yellowing degrees, measuring X, Y, Z tristimulus values of a rice sample by using a colorimeter, calculating a yellowness index, grinding the rice into big rice flour, soaking the rice with 0.2mol/L sodium dihydrogen phosphate, and measuring light absorption values of leachate at 305.2nm and 595.2 nm; soaking rice flour in 0.5mol/L sodium dihydrogen phosphate, measuring light absorption values of leachate at 305.2nm and 533.2nm, substituting into the established equation to obtain predicted value, and performing paired T test with the actual value;
the rice has the best detection effect of 0.3mol/L disodium hydrogen phosphate leachate at the wavelengths of 533.2nm and 595.2nm, and the correlation coefficient R2 0.839 and 0.859, respectively, and linear equations of y = -0.010x +0.459 and y =, respectively-0.009x+0.4101；
The rice flour has the best detection effect of 0.4mol/L disodium hydrogen phosphate leachate at the wavelength of 305.2nm and the wavelength of 595.2nm, and the correlation coefficient R2 0.804 and 0.810 respectively, and y = -0.028x +1.443 and y = -0.010x +0.391 respectively;
predicting the established model, selecting 10 rice with different yellowing degrees, measuring X, Y, Z tristimulus values of a rice sample by using a colorimeter, calculating a yellowness index, grinding the rice into big rice flour, soaking the rice with 0.3mol/L disodium hydrogen phosphate, and measuring light absorption values of leachate at 533.2nm and 595.2 nm; after 0.4mol/L disodium hydrogen phosphate is used for soaking rice flour, light absorption values of the leachate at 305.2nm and 595.2nm are measured, the light absorption values are substituted into a built equation to obtain a predicted value, and the predicted value and an actual value are subjected to matching T test.
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