Research on the Firmness of Persimmon by Near_Infrared Diffuse Reflectance Spectroscopy

The purpose of this study is to establish the mathematical relationship between visible and Near_ Infrared (Vis_NIR) Diffuse Reflectance Spectroscopy and firmness of persimmon in order to evaluate the applicability of Vis_NIR Spectroscopy technique for non-destructive measurement of the firmness of persimmon. The FieldSpec 3 spectroradiometer was used to collect 22 samples spectra data of the three kinds of persimmon in same position of the equatorial position separately. Then a fruit sclerometer was used to measure the firmness of samples in the same position. The principal component regression (PCR) and partial least square (PLS) regression were used to establish mathematical model for analyzing the firmness of persimmon with three kinds of spectral data which were pretreated by absorbency log(1/R), the first derivative D1log(1/R) and the second derivative D1log(1/R) first. The results showed that the best prediction results were obtained, which is based on absorbency log(1/R) at equatorial position of persimmon with PLS model. The correlation coefficient of calibration set is 0.8929, and the root mean standard error of correction (RMSEC) is 0.4398N. The principal component regression (PCR) and partial least square (PLS) regression were used to analyze the firmness of persimmon using the pretreated absorbency log(1/R) data. The results also showed that the fine prediction results were obtained, which is based on the absorbency log(1/R) data of persimmon with PLS model. The correlation coefficient of prediction set is 0.9682, and the root mean standard error of correction (RMSEC) is 0.2776N. Vis_NIR spectroscopy is a fast and available method for non-destructive of firmness of persimmon.