Abstract: To understand the effect of 1-(2-chloropyridin-4-yl)-3-phenylurea (CPPU) on the optical parameters and internal quality of ‘Xuxiang’ kiwifruit during growth and the relationship between optical parameters and internal quality. Growing ‘Xuxiang’ kiwifruits treated with 0, 10 and 20 mg/L CPPU solutions were measured for absorption coefficient μa and reduced scattering coefficient μs’ using single integrating sphere system (950–1 650 nm). The internal quality indices, such as soluble solid content (SSC), moisture content and firmness, were also measured. Partial least squares regression (PLSR) was used to build an internal quality prediction model based on optical parameters. The results showed that CPPU reduced the firmness and increased the moisture content, but had no significant effect on the SSC of kiwifruits (P > 0.05). CPPU led to changes in the optical parameters of kiwifruits. μa and μs’ showed different correlations with the same internal quality attribute of kiwifruits, the correlation coefficients changed with wavelength, and there was a good correlation in a certain band. The PLSR model based on μa had the best prediction effect on the SSC and moisture content with correlation coefficient of prediction (Rp) of 0.709 and 0.790 and root mean square error of prediction (RMSEP) of 0.579% and 0.408%, respectively, while the model based on μa + μs’ had the best performance in predicting the hardness (Rp = 0.796, RMSEP = 7.890 N). This study provides a theoretical basis for predicting the internal quality of kiwifruits based on spectral technology.

Key words: kiwifruit; 1-(2-chloropyridin-4-yl)-3-phenylurea; growth stage; optical parameters; internal quality; correlation