Abstract: In this research, it was performed the measurement of apple’s sugar content and acidity by using CCD-NIR spectroscopy system, with the Y-type fiber acquiring the reflectance spectra of 120 Fuji apples. Partial least squares regression was applied to construct the model between measured values and spectral signals. It was performed different methods of data pretreatment such as S-G smoothing, first derivative and second derivative in order to reduce the CCD spectrum noise. The results show that the best models of the sugar content and acidity are obtained after preprocessing of S-G smoothing. The calibration model gives the correlation coefficients of 0.9240 and 0.8151 respectively, with the standard error of calibration of 0.9254 and 0.0120 respectively, and the standard error of prediction of 0.9407 and 0.0204 respectively. The study showes that it is feasible to nondestructively measure the sugar content and acidity of apple using CCD-NIR system in 6301030 nm.

Key words: apple, sugar content, acidity, near infrared, CCD, spectral pretreatment, partial least squares