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23 April 2010 Characterization of the optical properties of normal and defective pickling cucumbers and whole pickles
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Internal defect in pickling cucumbers can cause bloater damage during brining, which lowers the quality of final pickled products and results in economic loss for the pickle industry. Hence it is important to have an effective optical inspection system for detection and segregation of defective pickling cucumbers. This research was intended to measure the spectral absorption and scattering properties of normal and internally defective pickling cucumbers and whole pickles, using hyperspectral imaging-based spatially-resolved technique. Spatially-resolved hyperspectral scattering images were acquired from 50 freshly harvested 'Journey' pickling cucumbers in the summer of 2008. The cucumbers were then subjected to rolling under mechanical load to induce internal damage. The damaged cucumbers were imaged again one hour and one day after the mechanical stress treatment. In addition, 20 whole pickles each of normal and defective (bloated) class were also measured by following the same procedure as that for pickling cucumbers. Spectra of the absorption and reduced scattering coefficients for pickling cucumbers and whole pickles were extracted from the spatially-resolved scattering profiles, using an inverse algorithm for a diffusion theory model, for the spectral range of 700-1,000 nm. It was found that within one hour after mechanical damage, changes in the absorption and reduced scattering coefficients for the cucumbers were minimal. One day after mechanical damage, the absorption coefficient for the cucumbers increased noticeably for the wavelengths of 700-920 nm, whereas the reduced scattering coefficient decreased more significantly for the wavelengths of 700-1,000 nm. Overall mechanical damage had greater impact on the scattering properties than on the absorption properties. After brining, pickles became translucent and scattering was greatly diminished. Thus the diffusion theory model was no longer valid for determining the optical properties of whole pickles. This research suggests that effective defect detection may be achieved by enhancing scattering features in the optical evaluation of cucumbers.
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Renfu Lu, Diwan P. Ariana, and Haiyan Cen "Characterization of the optical properties of normal and defective pickling cucumbers and whole pickles", Proc. SPIE 7676, Sensing for Agriculture and Food Quality and Safety II, 76760G (23 April 2010);

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