Abstract
Hyperspectral imaging is a non-destructive method for the detection of chilling injury in fruit. However, the limitation of this technique is the lacking of an appropriate working parameters and a feasible discriminating model for chilling on-line sorting. This research was aimed to select the optimal spectral resolution, scanning speed, and classification model for green jujube chilling injury detection based on hyperspectral reflectance imaging. Criminisi algorithm was firstly carried out to reconstruct the specular reflection region in spectral images before deriving mean spectra, and thus the optimal wavelengths were selected by random frog. Results showed that the Criminisi algorithm presented a desirable ability of spectral image inpainting. The linear discriminant analysis (LDA) achieved overall accuracies of 98.3% and 93.3% for two-class and three-class classification, respectively, at the speed of 20 mm/s with the spectral resolution of 5.03 nm based on selected spectral features. The results demonstrated that 20 mm/s with the spectral resolution of 5.03 nm was more feasible for the detection of green jujube chilling injury in hyperspectral imaging system due to a higher scanning efficiency, but a less data size.
Highlights
Green jujube (Zizyphus mauritiana) is becoming a popular fruit with a lot of vitamin C, B complexes, calcium, and carotenoids, and it is admired for its high nutritional value contributing to promoting health [1]
It was found that rectangle mask did not show a desirable inpainting performance because the pixels that are located along boundary still presented difference of image texture from source region with sound pixels, which indicated that pixels that are distributing along boundary had influence on image inpainting
Apart from visual evaluation, it displays a highest peak signal-to-noise ratio (PSNR) value of 51.08 based on ellipse when compared with that of original and rectangle ones (Figure 2b), demonstrating that the ellipse mask was more feasible for spectral image inpainting for green jujube
Summary
Green jujube (Zizyphus mauritiana) is becoming a popular fruit with a lot of vitamin C, B complexes, calcium, and carotenoids, and it is admired for its high nutritional value contributing to promoting health [1]. The main limited factor to its growth is temperature. The leaves and fruits will undergo chilling stress when temperature is lower than 4 ◦ C and 0 ◦ C, respectively. Like many other agricultural products, the external and internal quality of green jujube fruit needs to be inspected, such as the shape, size, surface condition, and nutrition content. Chilling stress causes adverse impacts on fruit quality, such as surface blemish and internal defects [2], which makes chilled samples decay quickly and contaminate other fruit during the process of harvest, transport, and storage. It is essential to identify defective green jujubes with chilling injury and remove them
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