Rapid non-destructive detection and visualization of lard adulteration using hyperspectral imaging coupled with machine learning
摘要
To realize rapid and non-destructive detection of lard-palm oil adulteration, this study used Visible-Near Infrared (VNIR, 400–1000 nm) and Short-Wave Infrared (SWIR, 900–1700 nm) Hyperspectral Imaging (HSI) techniques, along with preprocessing, feature wavelength selection, and machine learning, to build an adulteration ratio quantitative model and achieve visual detection. Lard-palm oil samples with adulteration ratios of 0%-100% (10% intervals) were prepared. After spectral collection, preprocessing and feature selection were performed, followed by model construction using Partial Least Squares Regression (PLSR), Support Vector Regression (SVR), Random Forest (RF), and Extreme Gradient Boosting (XGBoost). Results showed SWIR outperformed VNIR significantly. This superiority is mainly attributed to lipid-related C–H overtone and combination absorptions in the SWIR region, which are more sensitive to compositional differences between lard and palm oil. The optimal model was SVR combined with Normalization (NOR) preprocessing and Iterative Variable Importance and Selection by Stability Analysis (iVISSA) feature selection, achieving R²P=0.9933, RMSEP = 2.5791, RRMSE = 0.0516, Bias = 0.0250, RPD = 12.3010 on the test set. For visualization, the established model was further applied in a pixel-wise manner to generate adulteration distribution maps, with colors transitioning from dark blue (0% adulteration) to dark red (100% adulteration). In conclusion, SWIR-HSI with nonlinear algorithms enables rapid, non-destructive, high-precision oil adulteration detection. The NOR-iVISSA-SVR scheme offers a reliable technical path for oil authenticity testing with great practical application potential.