[Study on synchronous correlation between fruit characteristic spectrum and the parameter of internal quality for Hamlin sweet orange fruit].

The purpose of our study is to study the relationship between the reflective spectrum of fruit and the internal quality of the orange fruit and find the suitable mark spectrum that can synchronously measure the several fruit quality index at same time to lay a foundation for the development of a rapid and nondestructive field fruit quality analysis technique by analyzing the visible-near infrared spectrum. Mature Hamlin orange (Citrus sinensis (L)cv. Hamlin sweet orange) fruits were individually mensurated for their reflective spectrum by using FieldSpec-HH spectrometer and for their contents of total soluble solid (TSS), citric acid and vitamin C (Vc) by chemistry analysis. The experiment results showed that the fruit reflectivity values (x) at 988 nm was significantly correlated to both TSS (y)(r = 0.387* *, y = 13. 957x + 5.405), TSS/acid ratio(y)(r = 0. 440* *, y = 75.120x + 37.256), and Vc(r = 0.309*). Both of TSS and Vc contends were positively correlated with the second derivatives of the reflective spectrum at 943 nm, with correlation coefficients of 0.339* and 0.355*. TSS/acid ratio was positively correlated only with the reciprocal log values of the reflective spectrum at 944 nm (r = 0.304*). The results in this study indicated that fruit quality indexes TSS, Vc and TSS/acid can be synchronously, rapidly and nondestructively field measured at the same time by the 988 or 429 nm reflective spectrum test and special regress equation operation.