On-line Fusion of Colour Camera and Spectrophotometer for Sugar Content Prediction of Apples

Abstract

Current grading lines for fresh fruit use sensors that measure weight, size, and sometimes colour or firmness. However, none of them measures so far an important organoleptic criteria for the consumer: sugar content. Image analysis can provide colour information on the fruit, while near-infrared spectrophotometric data can be used in order to determine sugar content. Sensor fusion methodology is aimed at improving the sugar content prediction by combining both these on-line non-destructive sensors. The fusion process began by a diagnosis of each sensor, followed by the development of a neural network model that uses the information provided by the sensors. It was found that the repeatability of the classification of the fruits based on sugar content was improved when the two sensors were combined. The sensors and the fusion process were implemented on-line within a robotic device currently running at 3·5 s per fruit.