柿子可溶性固形物含量的可见-近红外光谱检测

    Measurement of soluble solid content in persimmon using visible-near infrared spectroscopy

    • 摘要: 为了实现柿子(Diospyros kaki thunb)可溶性固形物含量的快速无损检测,提出了一种采用可见-近红外光谱分析技术无损检测柿子可溶性固形物含量的方法。采用Field Spec 3光谱仪对3种不同品种的柿子进行光谱分析,共获取66个样本数据。利用平均平滑法对样本数据进行预处理,再采用主成分分析法,依据可信度获取光谱的6个主成分数据。将样本随机分成51个建模样本(每种各17个)和15个验证样本(每种各5个),把6个主成分数据作为BP神经网络的输入变量,柿子的可溶性固形物含量作为输出变量,隐含层的节点数为11,建立3层BP神经网络检测模型,并用该模型对15个验证样本进行预测。结果表明,所建校正模型的校正标准差(SEC)为0.232,对预测集样本可溶性固形物含量的预测相对误差在3%以下,预测值和实测值的决定系数(R2)为0.99,预测标准差(SEP)为0.257。结果表明应用近红外光谱技术结合主成分分析和神经网络算法检测柿子的可溶性固形物含量是可行的。

       

      Abstract: To achieve fast and non-destructive measurement of soluble solid content (SSC) in persimmon, a new method based on visible-near infrared reflectance (NIR) spectroscopy was put forward. A Field Spec 3 spectroradiometer was used for collecting 66 sample spectra data of the three kinds of persimmon separately. Then principal component analysis (PCA) was used to process the spectral data after pretreatment using the average Smoothing method, and 6 principal components(PCs) were selected based on accumulative reliabilities. These selected PCs would be taken as the inputs of the three-layer back-propagation artificial neural network (BP-ANN). A total of 66 persimmon samples were divided into calibration sets including 51 samples(17 samples of each variety) and validation sets including 15 samples(5 samples of each variety) randomly. The three-layer BP-ANN model was established with 6 nodes being 6 principal components (PCs) in input layer, 1 node being soluble solid content (SSC) in persimmon in output layer and 11 nodes in hidden layer. Then the model was used to predict soluble solid content of persimmon for the sample in the validation set. The results showed that a standard error of calibration (SEC) of the calibration model was 0.232, its prediction relative error below 3% was achieved, the decision coefficient (R2) between the predicted value and the measurement value was 0.99, and the forecast standard deviation (SEP) was 0.257. It can be concluded that PCA combined with BP-ANN is an available method for soluble solid content measurement of persimmon based on NIR spectroscopy.

       

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