阅读说明：本技术 基于拉曼光谱检测小米类胡萝卜素的方法 (Method for detecting millet carotenoid based on Raman spectrum ) 是由 梁克红 赵欣 于 2021-07-01 设计创作，主要内容包括：本发明公开了一种基于拉曼光谱检测小米类胡萝卜素的方法,包括如下步骤：步骤一、称取原料；步骤二、确定类胡萝卜素的检测值；步骤三、确定原始拉曼光谱；步骤四、对拉曼光谱组中的168个小米样品以3:1的比例进行建模集和预测集划分；步骤五、采用小波变换法对原始拉曼光谱进行预处理；步骤六、建立PLS模型。本发明采用上述结构的基于拉曼光谱检测小米类胡萝卜素的方法,检测步骤简单,并有效降低了检测过程中对类胡萝卜素的破坏性。(The invention discloses a method for detecting millet carotenoid based on Raman spectrum, which comprises the following steps: step one, weighing raw materials; step two, determining the detection value of the carotenoid; step three, determining an original Raman spectrum; fourthly, modeling and predicting set division is carried out on 168-micron samples in the Raman spectrum group according to the proportion of 3: 1; step five, preprocessing the original Raman spectrum by adopting a wavelet transform method; and step six, establishing a PLS model. The method for detecting the carotenoid in the millet based on the Raman spectrum, which adopts the structure, has simple detection steps and effectively reduces the destructiveness of the carotenoid in the detection process.)

1. A method for detecting millet carotenoid based on Raman spectrum is characterized by comprising the following steps: the method comprises the following steps: step one, weighing raw materials: weighing two parts of raw materials with the same quantity from millets in the same batch, wherein one part is a Raman spectrum group, the other part is a measurement group, and numbering and marking the millets samples in the Raman spectrum group and the measurement group in a one-to-one correspondence manner, wherein the Raman spectrum group and the measurement group both comprise 168 millets samples;

step two, determining the detection value of the carotenoid: determining the concentration contents of lutein and zeaxanthin in the millet samples in the measurement group by using high performance liquid chromatography, and taking the sum of the concentration contents of lutein and zeaxanthin as a detection value of carotenoid;

step three, determining an original Raman spectrum: placing each sample in the Raman spectrum group on an optical detection platform, selecting 10 different positions for each sample to respectively collect a spectrum, and taking the average value of the 10 spectrums as the original Raman spectrum of each sample;

step four, carrying out modeling set and prediction set division on 168-micron samples in the Raman spectrum group according to the proportion of 3: 1: arranging the millet samples in the Raman spectrum groups from small to large according to the detection values of carotenoids of the millet samples in the measurement groups with the same number as the millet samples in the Raman spectrum groups, wherein the millet samples in each 8 Raman spectrum groups are taken as one group, selecting the 2 nd and 7 th millet samples from each group as a prediction set, and taking the rest millet samples as a modeling set to obtain 126 modeling set samples and 42 prediction set samples;

step five, preprocessing the original Raman spectrum by adopting a wavelet transform method;

step six, extracting the characteristic wave number in the full wave band of the 17 preprocessed Raman spectrums by adopting a continuous projection algorithm, further correspondingly extracting the 17 preprocessed Raman spectrum intensities, establishing a PLS model by taking the extracted preprocessed Raman spectrum intensities as independent variables and the corresponding detected values of the carotenoids as dependent variables, wherein the PLS model formula is as follows:

wherein Y is the predicted content of the millet carotenoid (mu g/g), and Xi is the Raman spectrum intensity after pretreatment when the wave number is i.

2. The method for detecting millet carotenoids based on raman spectroscopy as claimed in claim 1, characterized in that: in the process of collecting the Raman spectrum, the scanning frequency is 350 times, the scanning band is 200-3400cm < -1 >, the excitation wavelength is 532nm, the exposure time is 0.04s, and the magnification of the objective lens is 10 times.

3. The method for detecting millet carotenoids based on raman spectroscopy as claimed in claim 2, characterized in that: the method comprises the steps of taking an original spectrum and a preprocessed Raman spectrum as independent variables, taking a detected value of carotenoid corresponding to each spectrum as a dependent variable, preprocessing the original Raman spectrum by adopting five preprocessing methods of smooth denoising, normalization, multiple scattering correction, baseline correction and wavelet transformation respectively, establishing a preprocessing model, establishing a PLS modeling quantitative prediction result for the preprocessing model by adopting a full-interactive verification method, and selecting an optimal Raman spectrum data preprocessing method by taking a decision coefficient (R2c) and a Root Mean Square Error (RMSEC) of a modeling set as auxiliary judgment standards and taking a decision coefficient (R2p) and the RMSEP) of the prediction set as main judgment standards.

4. The method for detecting millet carotenoids based on raman spectroscopy as claimed in claim 3, characterized in that: the 17 characteristic wave numbers are 945, 1000, 1131, 1160, 1144, 1171, 1184, 1357, 1500, 1515, 1520, 1525, 1821, 2622, 2314, 2845 and 3062cm < -1 > respectively.

Technical Field

The invention relates to the technical field of carotenoid nondestructive detection, in particular to a method for detecting millet carotenoid based on Raman spectrum.

Background

Carotenoids are widely present in plants, fungi, algae and bacteria, and more than 700 species have been identified in nature. Carotenoids, as important natural pigments, play an important role in human health and have many physiological functions. The lutein and zeaxanthin have strong oxidation resistance, can eliminate the influence of free radicals, improve the immune function, reduce the risks of chronic diseases, cancers and the like, can prevent and treat diabetes, effectively reduce the damage of blue light to the retina, and prevent age-related macular degeneration and other diseases. Carotenoids are essential nutrient substances for health which cannot be synthesized by human bodies per se, and only can be supplied by depending on diet, and food crops are food which must be taken in a large amount every day, and the carotenoid content and the composition of the food crops have important significance for human health.

Millet is a crop rich in carotenoid in grain crops, and the determination of the carotenoid in the millet has important significance for the quality and the human health of the millet. The traditional carotenoid detection method comprises ultraviolet-visible spectrophotometry, high performance liquid chromatography, liquid chromatography-mass spectrometry, supercritical fluid chromatography, nuclear magnetic resonance method and the like. The traditional detection method has the defects of destructiveness and complicated detection steps, and online detection cannot be realized. Therefore, a method for rapidly and nondestructively detecting the carotenoid content of millet is needed.

Disclosure of Invention

The invention aims to provide a method for detecting millet carotenoid based on Raman spectrum, which has simple detection steps and effectively reduces the destructiveness of the carotenoid in the detection process.

In order to achieve the purpose, the invention provides a method for detecting millet carotenoid based on Raman spectrum, which comprises the following steps: step one, weighing raw materials: weighing two parts of raw materials with the same quantity from millets in the same batch, wherein one part is a Raman spectrum group, the other part is a measurement group, and numbering and marking the millets samples in the Raman spectrum group and the measurement group in a one-to-one correspondence manner, wherein the Raman spectrum group and the measurement group both comprise 168 millets samples;

step two, determining the detection value of the carotenoid: determining the concentration contents of lutein and zeaxanthin in the millet samples in the measurement group by using high performance liquid chromatography, and taking the sum of the concentration contents of lutein and zeaxanthin as a detection value of carotenoid;

step three, determining an original Raman spectrum: placing each sample in the Raman spectrum group on an optical detection platform, selecting 10 different positions for each sample to respectively collect a spectrum, and taking the average value of the 10 spectrums as the original Raman spectrum of each sample;

step four, carrying out modeling set and prediction set division on 168-micron samples in the Raman spectrum group according to the proportion of 3: 1: arranging the millet samples in the Raman spectrum groups from small to large according to the detection values of carotenoids of the millet samples in the measurement groups with the same number as the millet samples in the Raman spectrum groups, wherein the millet samples in each 8 Raman spectrum groups are taken as one group, selecting the 2 nd and 7 th millet samples from each group as a prediction set, and taking the rest millet samples as a modeling set to obtain 126 modeling set samples and 42 prediction set samples;

step five, preprocessing the original Raman spectrum by adopting a wavelet transform method;

step six, extracting the characteristic wave number in the full wave band of the 17 preprocessed Raman spectrums by adopting a continuous projection algorithm, further correspondingly extracting the 17 preprocessed Raman spectrum intensities, establishing a PLS model by taking the extracted preprocessed Raman spectrum intensities as independent variables and the corresponding detected values of the carotenoids as dependent variables, wherein the PLS model formula is as follows:

wherein Y is the predicted content of the millet carotenoid (mu g/g), and Xi is the Raman spectrum intensity after pretreatment when the wave number is i.

Preferably, in the process of collecting the Raman spectrum, the scanning frequency is 350 times, and the scanning waveband is 200-3400cm^-1The excitation wavelength is 532nm, the exposure time is 0.04s, and the magnification of the objective lens is 10 times.

Preferably, the original spectrum and the preprocessed Raman spectrum are used as independent variables, detection values of carotenoids corresponding to each spectrum are used as dependent variables, five preprocessing methods of smoothing denoising, normalization, multiple scattering correction, baseline correction and wavelet transformation are respectively adopted to preprocess the original Raman spectrum, a preprocessing model is established, a PLS modeling quantitative prediction result is established for the preprocessing model by adopting a full-interactive verification method, a decision coefficient (R2p) and a Root Mean Square Error (RMSEP) of a prediction set are used as main judgment standards, a decision coefficient (R2c) and a Root Mean Square Error (RMSEC) of the modeling set are used as auxiliary judgment standards, and an optimal Raman spectrum data preprocessing method is selected.

Preferably, 17 characteristic wave numbers are 945, 1000,1131，1160，1144，1171， 1184，1357，1500，1515，1520，1525，1821，2622，2314，2845，3062 cm^-1。

therefore, the method for detecting the carotenoid in the millet based on the Raman spectrum, which adopts the structure, has simple detection steps and effectively reduces the destructiveness of the carotenoid in the detection process.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

FIG. 1 is the original Raman spectrum of a Raman acquisition of a millet sample in step three.

Detailed Description

Embodiments of the present invention will be further described with reference to the accompanying drawings.

A method for detecting millet carotenoid based on Raman spectrum comprises the following steps: the method comprises the following steps: step one, weighing raw materials: weighing two parts of raw materials with the same quantity from millets in the same batch, wherein one part is a Raman spectrum group, the other part is a measurement group, and numbering and marking the millets samples in the Raman spectrum group and the measurement group in a one-to-one correspondence manner, wherein the Raman spectrum group and the measurement group both comprise 168 millets samples;

step two, determining the detection value of the carotenoid: determining the concentration contents of lutein and zeaxanthin in the millet in the measurement group by using high performance liquid chromatography, and taking the sum of the concentration contents of lutein and zeaxanthin as the detection value of carotenoid;

step three, determining an original Raman spectrum: each sample in the Raman spectrum group is placed on an optical detection platform, and in the Raman spectrum collection process, the scanning times are 350 times, and the scanning wave band is 200-3400cm^-1The excitation wavelength is 532nm, the exposure time is 0.04s, and the magnification of the objective lens is 10 times. Each sample is collected at 10 different positions, and the average value of the 10 spectra is used as the original Raman spectrum of each sample. The raw raman spectrum of a millet sample raman collected is shown in figure 1.

Step four, carrying out modeling set and prediction set division on 168-micron samples in the Raman spectrum group according to the proportion of 3: 1: arranging the millet samples in the Raman spectrum groups from small to large according to the detection values of carotenoids of the millet samples in the measurement groups with the same number as the millet samples in the Raman spectrum groups, wherein the millet samples in each 8 Raman spectrum groups are taken as one group, selecting the 2 nd and 7 th millet samples from each group as a prediction set, and taking the rest millet samples as a modeling set to obtain 126 modeling set samples and 42 prediction set samples;

and step five, preprocessing the original Raman spectrum by adopting a wavelet transform method. The wavelet transform method is most accurate in preprocessing results of original Raman spectra, and the specific selection process is as follows: the original spectrum and the preprocessed Raman spectrum are used as independent variables, the detection value of carotenoid corresponding to each spectrum is used as a dependent variable, five preprocessing methods of smooth denoising, normalization, multiple scattering correction, baseline correction and wavelet transformation are respectively adopted to preprocess the original Raman spectrum, a preprocessing model is established, and a PLS modeling quantitative prediction result is established for the preprocessing model by adopting a full-interactive verification method, which is shown in Table 1. The wavelet transform method is the optimal Raman spectrum data preprocessing method according to the data result in the table 1, namely, the decision coefficient (R2p) and the Root Mean Square Error (RMSEP) of the prediction set are used as main judgment standards, the decision coefficient (R2c) and the Root Mean Square Error (RMSEC) of the modeling set are used as auxiliary judgment standards, the higher the decision coefficient is, the higher the interpretation degree of independent variables to dependent variables is, the smaller the root mean square error value is, and the higher the prediction accuracy is.

TABLE 1 PLS modeling quantitative prediction results obtained by different spectral preprocessing methods

Sixthly, extracting the characteristic wave numbers in the 17 preprocessed Raman spectrum full wave bands by adopting a continuous projection algorithm, wherein the 17 characteristic wave numbers are 945, 1000, 1131, 1160, 1144, 1171, 1184, 1357, 1500, 1515, 1520, 1525, 1821, 2622, 2314, 2845 and 3062cm respectively^-1. Further, 17 preprocessed Raman spectrum intensities are extracted correspondingly to extract preprocessed Raman lightThe spectrum intensity is an independent variable, the detection value of the corresponding carotenoid is used as a dependent variable, a PLS model is established, and the PLS model formula is as follows:

wherein Y is predicted millet carotenoid content (mug/g), X_iIs the intensity of the raman spectrum after pretreatment at wavenumber i.

The PLS modeling quantitative prediction result established for the PLS model by adopting the full-interactive verification method is shown in Table 2, and the PLS model can accurately predict the content of the carotenoid in millet according to the data result in Table 2 by taking the decision coefficient (R2p) and the Root Mean Square Error (RMSEP) of the prediction set as main judgment standards and taking the decision coefficient (R2c) and the Root Mean Square Error (RMSEC) of the modeling set as auxiliary judgment standards.

TABLE 2 PLS modeling quantitative prediction results

Therefore, the method for detecting the carotenoid in the millet based on the Raman spectrum, which adopts the structure, has simple detection steps and effectively reduces the destructiveness of the carotenoid in the detection process.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the invention without departing from the spirit and scope of the invention.