Detection and visualization of soybean protein powder in ground beef using visible and near-infrared hyperspectral imaging

The undeclared addition of soybean proteins in meats is a serious problem due to health and economic reasons. This paper proposes a methodology for quantitative determination and rapid visualization of soybean protein powder (SPP) addition in ground beef using hyperspectral imaging (HSI). Hyperspectral images of a total of 256 samples with different SPP contents were acquired by HSI system in spectral range of 400-1000 nm. Regions of interest (ROIs) were identified to withstand interference of background and containers to extract spectra. Principal component analysis (PCA) of extracted spectra found that PC1 and PC2 were effective for grouping samples into different levels. Gray level co-occurrence matrix (GLCM) algorithm was thus applied on the corresponding first two PC score images to extract eight texture features. Partial least squares regression (PLSR) was used to establish quantitative models, yielding the optimal correlation coefficient in prediction (R-p) of 0.9979 and residual predictive deviation (RPD) of 14.48 using standard normal variate (SNV) followed by detrending preprocessed spectra. Deming and Passing-Bablok regression were also conducted, and HSI results revealed high model performance which can be interchanged with laboratory standard. Key wavelengths were selected using PC loadings, two-dimensional correlation spectroscopy (2D-COS) and regression coefficients (RC), respectively. After that, PLSR models were evaluated with various inputs, and results showed spectra played predominate role rather than texture. Consequently, simplified PLSR model based on six selected wavelengths from PC loadings was retained with R-p = 0.9933, RPD = 8.45 and limit of detection (LOD) of 0.74%. Colorful spatial distribution maps were successfully created to clearly observe SPP adulteration levels. Current study indicates that HSI has high potential for determining and visualizing SPP adulteration in ground beef.