Abstract
The objective of this study was to evaluate the use of hyperspectral near-infrared (NIR) reflectance imaging techniques for detecting cuticle cracks on tomatoes. A hyperspectral NIR reflectance imaging system that analyzed the spectral region of 1000–1700 nm was used to obtain hyperspectral reflectance images of 224 tomatoes: 112 with and 112 without cracks along the stem-scar region. The hyperspectral images were subjected to partial least square discriminant analysis (PLS-DA) to classify and detect cracks on the tomatoes. Two morphological features, roundness (R) and minimum-maximum distance (D), were calculated from the PLS-DA images to quantify the shape of the stem scar. Linear discriminant analysis (LDA) and a support vector machine (SVM) were then used to classify R and D. The results revealed 94.6% and 96.4% accuracy for classifications made using LDA and SVM, respectively, for tomatoes with and without crack defects. These data suggest that the hyperspectral near-infrared reflectance imaging system, in addition to traditional NIR spectroscopy-based methods, could potentially be used to detect crack defects on tomatoes and perform quality assessments.
Highlights
Tomatoes are the most popular vegetable by volume with world-wide production of approximately162 million tons in 2012 [1]
The relative reflectance spectra of the specular, crack, stem scar, and sound regions of tomatoes obtained in the spectral region between
The mean reflectance spectra were calculated from the pixel values of the regions of interest (ROI) in the reflectance images
Summary
162 million tons in 2012 [1] They are considered to be healthy because they contain high levels of lycopene, which is a natural antioxidant, as well as β-carotene, vitamin C, and vitamin E [2]. The United States Center for Disease Control (CDC) reported that tomatoes have been associated with 12 outbreaks of food poisoning in North America between 1990 and 2007 [3]. In 2000, a Salmonellae javiana infection occurred in 174 patients in four states after the consumption of raw tomatoes, and a Shigella flexneri outbreak affected 886 people in North America in 2001 [4]. Additional multistate outbreaks of Salmonellae typhimurium in the United States were associated with the consumption of raw tomatoes [5]
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