Abstract: To understand the optical properties of fruit and their relationships with soluble solids content (SSC) and moisture content, an optical properties measurement system based on single integrating sphere technology was established and validated. Furthermore, the absorption coefficient μa and reduced scattering coefficient μ's of strawberry samples, varieties of ‘Hongyan’, ‘Tianxiang’ and ‘Zhangji’, were measured over the wavelength range of 950-1 650 nm. The relationships between optical properties and SSC and moisture content were analyzed, and the partial least squares models to predict SSC and moisture content based on the spectra of optical properties were established. The results showed that the average relative errors of the system for μa and μ's were 8.23% and 3.71%, respectively. Over the investigated wavelength range, μa had peaks at 975, 1 197 nm and 1 411 nm, and μ's generally decreased with increased wavelength. The μa had negative correlation with SSC, while had positive correlation with moisture content. Moreover, the extreme correlation coefficients were observed at the absorption peaks. The models based on the spectra of μa had the best ability in predicting SSC (Rp = 0.815, RMSEP = 1.153%) and moisture content (Rp = 0.757, RMSEP = 1.280%), indicating that SSC and moisture content mainly affected the absorption property of strawberry and the absorption property could be used to predict the internal quality of strawberry well.

Key words: strawberry, absorption coefficient, reduced scattering coefficient, soluble solids content (SSC), moisture content