Effect of CPPU on optical properties of strawberry in near-infrared range during growth

To investigate the effect of CPPU (forchlorfenuron) on optical properties of strawberry during growth, the optical properties (absorption coefficient (μ_a) and reduced scattering coefficient (μ_s')) of strawberry treated with CPPU solutions at different concentrations (0, 2.5, 5.0 and 7.5 mg/L) were measured in white, color turning and red stages by using a single integrating sphere system over near-infrared wavelength range of 900-1700 nm. The physicochemical properties, i.e., single fruit weight, soluble solids content, firmness and moisture content, as well as microstructure of strawberry were also investigated. The results showed that in white stage, the μ_a of strawberry treated with 7.5 mg/L CPPU was significantly (p ≤ 0.05) lower than that of untreated strawberry at absorption peak of 1411 nm. In color turning stage, the μ_s' of strawberry treated with 5 mg/L CPPU was significantly lower than that of treated with 2.5 mg/L at absorption peaks of 975, 1197 and 1411 nm. In red stage, the μ_a of strawberry treated with 2.5 mg/L CPPU was significantly (p ≤ 0.05) different from that of treated with 7.5 mg/L at 1197 nm. The study indicates that the optical properties of strawberry were affected by CPPU, and it provides useful information for identifying CPPU treated strawberry.