On-spot Evaluation of Maturity Stage of Fruits Based on 655 nm Laser-induced Photoluminescence of Chlorophyll-α

A technique to evaluate maturity stage of fruits, measured nondestructively and in situ by laser-induced photoluminescence of chlorophyll-α, was successfully developed. Using 655 nm laser diode as a new kind of light source to stimulate fluorescence as well as combining fiber and spectrum technique, various spectrums from 500 to 900 nm were recorded for different ripening stages of fruits. Experiments revealed that the content of chlorophyll-α decreases significantly with the fruit ripening. This method is completely feasible to give a visual judgment for chlorophyll-α content, according to the fluorescence emission spectrum of chlorophyll-α, and can be applied in a conveyor belt system using sorting criteria such as concentration of the chlorophyll-α.