Evaluation of the Changes in Optical Properties of Peaches with Different Maturity Levels during Bruising

The main objective was to measure the optical coefficients of peaches after bruising at different maturity levels and detect bruises. A spatially resolved method was used to acquire absorption coefficient (μ_a) and the reduced scattering coefficient (µ_s') spectra from 550 to 1000 nm, and a total of 12 groups (3 maturity levels * 4 detection times) were used to assess changes in µ_a and µ_s' resulting from bruising. Maturation and bruising both caused a decrease in µ_s' and an increase in µ_a, and the optical properties of immature peaches changed more after bruising than the optical properties of ripe peaches. Four hours after bruising, the optical properties of most samples were significantly different from those of intact peaches (p < 0.05), and the optical properties showed damage to tissue earlier than the appearance symptoms observed with the naked eye. The classification results of the Support Vector Machine model for bruised peaches showed that μ_a had the best classification accuracy compared to μ_s' and their combinations (µ_a × µ_s', µ_eff). Overall, based on μ_a, the average detection accuracies for peaches after bruising of 0 h, 4 h, and 24 h were increased.