Assessing firmness and SSC of pears based on absorption and scattering properties using an automatic integrating sphere system from 400 to 1150 nm

• An automatic integrating sphere system is proposed and calibrated.
• The μa and μ’s of the pear tissues were measured using the IAD method.
• The μa decreased with the increase of shelf-life time, the μ’s is the opposite.
• The relationships between SSC, firmness and the μa and μ’s were investigated.

It is important to understand the fundamental optical properties of fruit tissues when applying optical techniques for quality inspection of fruits. An automatic integrating sphere (AIS) system was used to measure the total reflectance and total transmittance of pear tissue in the wavelength range of 400–1150 nm. These two measurements were used to estimate the bulk optical properties (absorption coefficient μa and reduced scattering coefficient μ’s) of tissue samples using inverse adding-doubling (IAD) method. The accuracy of AIS system was verified by using both an INO solid phantom and a set of liquid phantoms. Relationships between soluble solids content (SSC), firmness and the optical properties were investigated, with coefficients of determination of 0.40 and 0.48 for validation, respectively. In addition, the μa decreased with the increase of shelf-life time, while the μ’s did just the opposite. This study demonstrated the feasibility of detecting multiple qualities of pears by investigating the tissue optical properties. For further research, the measured optical properties of pear tissues can be used for modeling and simulation of light-fruit interaction.