Identification of Kiwifruits Treated with Exogenous Plant Growth Regulator Using Near-Infrared Hyperspectral Reflectance Imaging

The goal of this study was to explore the potential of using near-infrared (NIR) hyperspectral imaging in combination with multivariate analysis for the identification of kiwifruits treated with exogenous plant growth regulator (EPGR). One hundred twenty kiwifruits, variety ‘Xixuan,’ treated with EPGR and another 120 ‘Xixuan’ kiwifruits without EPGR (named as normal ones) were used in the study. Hyperspectral images were acquired using a near-infrared hyperspectral imaging system in the spectral range of 865.11–1,711.71 nm. Based on the Kennard-Stone method, the samples were divided into two sets: 180 samples in calibration set and 60 samples in validation set. Standard normal variate transformation was used to preprocess obtained spectra. Principal component analysis (PCA) and successive projections algorithm (SPA) were used to select principal components and characteristic wavelengths. Partial least square (PLS) regression and support vector machine (SVM) modeling methods were used to establish models for identifying EPGR-treated kiwifruits and normal ones. The results indicated that average correct identification rates of all models were higher than 98.9 and 96.7 % for the calibration set and validation set, respectively. The identification performance of PLS was better than that of SVM, and the best model was PLS-SPA, whose average accuracy rate reached 100 % for the calibration set and 98.4 % for the validation set. The results demonstrated that NIR hyperspectral imaging technique can be used as a noninvasive method for distinguishing kiwifruits treated with EPGR from normal ones.