Fruit Ripeness Determination by Electronic Sensing of Aromatic Volatiles

A sniffer for determining fruit ripeness nondestructively, based on electronic sensing of gas emissions, was developed. The sensing head consists of a semiconductor gas sensor located within a small cup that is placed on the fruit surface, in this study, for a period of up to 30 seconds. Natural gases emitted by the ripening fruit accumulate in the cup and cause a change in the sensors conductivity. The sensor was tested on three muskmelon cultivars over two growing seasons. The overall Bayesian maximum likelihood classification accuracy was 90.2% when separating unripe from ripe fruit (two-way classification), and 83.0% for sorting into three ripeness categories (unripe, half-ripe, and ripe). Comparison of sniffer performance with traditional methods of ripeness determination, including flesh firmness, stem detachment force, percent soluble solids, and ethylene emissions, demonstrated that performance of the electronic sniffer had a higher degree of accuracy than all other destructive and nondestructive methods evaluated. Classification accuracy of fruit growing in the field under ambient conditions were comparable to fruit measured in the laboratory: 88.0% and 78.3% for two-way and three-way classification, respectively.