刘云宏, 王庆庆, 石晓微, 高秀薇. 金银花贮藏过程中绿原酸含量的高光谱无损检测模型研究[J]. 农业工程学报, 2019, 35(13): 291-299. DOI: 10.11975/j.issn.1002-6819.2019.13.035
    引用本文: 刘云宏, 王庆庆, 石晓微, 高秀薇. 金银花贮藏过程中绿原酸含量的高光谱无损检测模型研究[J]. 农业工程学报, 2019, 35(13): 291-299. DOI: 10.11975/j.issn.1002-6819.2019.13.035
    Liu Yunhong, Wang Qingqing, Shi Xiaowei, Gao Xiuwei. Hyperspectral nondestructive detection model of chlorogenic acid content during storage of honeysuckle[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2019, 35(13): 291-299. DOI: 10.11975/j.issn.1002-6819.2019.13.035
    Citation: Liu Yunhong, Wang Qingqing, Shi Xiaowei, Gao Xiuwei. Hyperspectral nondestructive detection model of chlorogenic acid content during storage of honeysuckle[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2019, 35(13): 291-299. DOI: 10.11975/j.issn.1002-6819.2019.13.035

    金银花贮藏过程中绿原酸含量的高光谱无损检测模型研究

    Hyperspectral nondestructive detection model of chlorogenic acid content during storage of honeysuckle

    • 摘要: 绿原酸(chlorogenic acid, CGA)是评价金银花品质的重要指标。为了实现金银花贮藏期间CGA含量变化的快速有效检测,该文采集了500个不同贮藏时间(0~20 d)的金银花高光谱图像,构建CGA含量的高光谱检测模型。为了提高模型性能,采用savizky-golay卷积平滑(SG),移动窗口平滑(moving average),标准正态变量(standard normal variable,SNV),基线校正(baseline correction,BC),多元散射校正(multiplicative scatter correction,MSC),正交信号校正(orthogonal signal correction,OSC)6种预处理方法并建立偏最小二乘回归(partial least squares regression,PLSR)模型,确定SNV方法为最佳预处理方法,其预测集的R2为0.976 6,RMSE为0.271 1%。为了简化校准模型,利用无信息变量消除(uninformative variable elimination,UVE),连续投影算法(successive projections algorithm,SPA),竞争性自适应加权算法(competitive adaptive reweighted sampling,CARS)以及UVE-CARS、UVE-SPA等方法对SNV预处理后的光谱提取特征波长。然后,分别基于全光谱数据和所选特征变量数据,建立线性偏最小二乘回归(PLSR)和非线性BP神经网络模型。结果表明:UVE-CARS算法可以有效地减少提取变量个数(共提取26个,仅占全光谱范围的3.2%),PLSR和BP模型的预测集R2分别为0.974 6和0.978 4,RMSE分别为0.286 3%和0.250 3%。非线性BP模型预测结果整体优于线性PLSR模型,在BP模型中,UVE-CARS-BP预测精度最高,预测集的R2和RMSE的值分别为0.978 4, 0.250 3%。综上,基于高光谱成像技术建立的SNV-UVE-CARS-BP模型,可以实现金银花贮藏过程中CGA含量变化的快速无损预测。

       

      Abstract: Abstract: During the storage process, honeysuckle easily undergoes discoloration and mildew under the influence of temperature, humidity and microorganisms, which leads to a significant decrease of its medicinal efficacy and economic value, and even harms the health of consumers. Hence, it is necessary to monitor the quality of honeysuckle during storage. Chlorogenic acid (CGA), as the main active ingredient, is an important indicator to evaluate the quality of honeysuckle. In order to realize rapid and effective detection of CGA content in honeysuckle, 500 hyperspectral images of honeysuckle during different storage periods were collected by hyperspectral imaging (HSI) system, and then CGA content values were measured by high performance liquid chromatography (HPLC) method. Average spectral information extracted from the hyperspectral images and corresponding CGA values were used to build HSI detection models. Because of the non-uniformity of sample surface, baseline drift of instrument, random noise and light scattering, the collected hyperspectral images contained some redundant information, which could reduce the accuracy of modeling. In order to improve the prediction accuracy and efficiency of the model, six spectral preprocessing methods were used to improve the signal-to-noise ratio of the original spectrum, including Savizky-Golay filter (SG), moving average, standard normal variable (SNV), baseline correction (BC), multiplicative scatter correction (MSC), orthogonal signal correction (OSC). Comparing the effects of different pretreatment methods by establishing partial least squares regression (PLSR) models, the SNV-PLSR model obtained the best prediction accuracy with determination coefficient (R2) of 0.976 6 and root mean square error (RMSE) of 0.271 1% in prediction set, and SNV was identified as the best pretreatment method for further analysis. In order to simplify the calibration model, the uninformative variable elimination (UVE), successive projections algorithm (SPA), competitive adaptive reweighted sampling (CARS), the combination of UVE and CARS (UVE-CARS), and the combination of UVE and SPA (UVE-SPA) were used to extract characteristic wavelengths from the pre-processed spectrum by SNV method. And UVE, CARS, SPA, UVE-CARS and UVE-SPA selected 192, 51, 17, 26, 9 characteristic wavelengths from the full spectrum. Then, based on the full spectrum data and the selected characteristic variables by five variable screening methods, the linear PLSR and the non-linear BP neural network model were established. The performance of all the models were evaluated by the index of R2 for calibration set and prediction set, (RMSE) for calibration set and prediction set. The results showed that UVE-CARS algorithm could effectively eliminate useless information variables from full spectrum, and 26 characteristic wavelengths were selected from full spectrum by UVE-CARS algorithm, and the established model based on UVE-CARS algorithm had high accuracy, which was considered as the best feature wavelength screening method. The prediction results of the non-linear BP model were better than that of the linear PLSR model. In all BP model, the prediction accuracy of UVE-CARS-BP was the highest with R2 of 0.978 4 and RMSE of 0.250 3% in prediction set, respectively, and it was proved that the non-linear model was more suitable for the prediction of CGA content in honeysuckle. In conclusion, HSI technology combined with SNV-UVE-CARS-BP model can realize the rapid and non-destructive prediction of CGA content in honeysuckle during storage.

       

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