Hyperspectral Laser-induced Fluorescence Imaging for Nondestructive Assessing Soluble Solids Content of Orange

Abstract

Laser-induced fluorescence imaging is a promising technique for assessing quality of fruit. This paper reports on using a hyperspectral laser-induced fluorescence imaging technique for measurement of laser-induced fluorescence from orange for predicting soluble solids content (SSC) of fruit. A laser (632 nm) was used as an excitation source for inducing fluorescence in oranges. Fluorescence scattering images were acquired from ‘Nanfeng’ orange and navel orange by a hyperspectral imaging system at the instance of laser illumination. Subsequent analysis of Fluorescence scattering images consisted in selecting regions of interest (ROIs) of 100 50 pixels, and ROIs were segment around the laser illumination point from Fluorescence scattering images. The hyperspectral fluorescence image data in the wavelength range of 700-1100 nm were represented by mean grey value of the ROIs. The fruit soluble solids content were measured using hand-held refractometer. A line regressing method was used for developing prediction models to predict fruit soluble solids content. Excellent predictions were obtained for soluble solids content with the correlation coefficient of prediction of 0.998 (‘Nanfeng’ orange) and 0.96 (navel orange). The results show that hyperspectral laser-induced fluorescence imaging is a very good method for nondestructive assessing soluble solids content of orange.