A simple identification model for subtle bruises on the fresh jujube based on NIR spectroscopy

Visible–near infrared reflectance (NIR) spectroscopy was applied to identify the subtle bruise of fresh jujube. In this paper, 70 samples were selected randomly as a calibration set and 30 samples were selected as a prediction set. Multiplicative scatter calibration (MSC) was used to pre-process the spectra, 9 characteristic wavelengths were selected by successive projection algorithm (SPA) in the end. On the basis of spectroscopy theoretical analysis, the principal component analysis (PCA) was performed to analyze the spectral data of the characteristic wavelengths, and 4 principal components (PCs) data which were used as the input variables for the Least squares support vector machine (LS–SVM) model for identifying the subtle bruise of fresh Jujube fruits were picked up. Intact jujubes and bruise jujubes in prediction with code 1 and 2 respectively could be considered as the outputs. The identification accuracy rate of the MSC–SPA–PCA–LS–SVM model for subtle bruises of fresh jujube fruits could reach 100%, proving that the key information in spectral data could be effectively picked up by SPA and PCA combination methods. It is feasible to identify the subtle bruise of fresh jujube using visible–near infrared reflectance (NIR) spectroscopy.