Effect of CPPU on bulk optical properties of kiwifruit during storage in near-infrared range.

Background: Investigating the effect of N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU) on the bulk optical properties of postharvest kiwifruit is helpful in understanding the mechanism of identification of CPPU-treated kiwifruit using spectroscopy and to develop effective optical sensing techniques. In this study, the absorption coefficient μ and reduced scattering coefficient of flesh and skin of kiwifruit treated with CPPU solutions at CPPU concentration levels (CCLs) of 0, 5, 10 and 15 mg L were measured by using a single integrating sphere setup over the range 950-1650 nm during 12 weeks' storage.

Results: Generally, at the same storage period, there was no significant difference (P ≤ 0.05) on flesh's μ among the kiwifruit treated with different CCLs at absorption peaks of 970, 1190, and 1390 nm. The average flesh's of kiwifruit treated with higher CCLs at 1190 nm were larger than those treated with lower CCLs, and there was a significant difference (P ≤ 0.05) between the kiwifruit treated with 0, 5 and 15 mg L CPPU solutions except for week 6. Contrasted with the μ and of kiwifruit flesh, the μ and of skin had bigger standard deviations and larger fluctuations with storage time. Additionally, the CPPU-treated kiwifruit had higher moisture content, lower firmness, and larger cells than CPPU-untreated kiwifruit.

Conclusions: This study indicates that the of flesh has potential in identifying kiwifruit treated with different CCLs during storage. © 2020 Society of Chemical Industry.