Optical properties of healthy and bruised blueberry tissues in the near-infrared spectral region

Abstract.

One of the issues of fresh blueberry production is the excessive bruises caused by mechanical impact during harvesting and packaging, which lower the fruit quality and cause commercial losses. Spectroscopy or imaging techniques such as hyperspectral imaging have great potential to detect and quantify internal bruises in fruite. It is important to measure the fundamental optical properties of blueberry tissues to better employ spectroscopy or imaging techniques. The aim of this study was to obtain the absorption coefficient (μ_a), reduced scattering coefficient (μ_s‘), and scattering anisotropy (g) of healthy and bruised blueberry tissues at the spectral range of 925-1400nm. For this purpose, the total reflectance, total transmittance, and collimated transmittance of the flesh were collected using a spectrometer. A single integrating sphere with fiber optic guide was implemented for diffusing and receiving light. Using the collected spectra, the inverse adding-double (IAD) method was applied to calculate the μ_a, μ_s‘, and g. The results indicated that it is feasible to identify healthy and bruised blueberry tissues using μ_s‘ and g. Furthermore, these measurements can be used to investigate the light propagation model of blueberries using simulation methods for developing more efficient systems to inspect blueberry internal bruising.