Determination of Pears Ripening Stages Based on Electrochemical Ethylene Sensor

Fruit firmness and color as simple, and ethylene emission as more sophisticated, are indicators of fruit maturity. Many studies have reported that 'William' pears generally ripen within 7 days at 20 °C after purchase. Usually, this information is based on experiments that were performed in a controlled environment. In reality, at the point of sale, storage time and conditions are not known, neither commercial handling procedures implemented to extend the shelf life after storage. The objective of this study is to implement and evaluate the electrochemical sensor system as a non-destructive approach to measure ethylene, which might be a reliable indicator of overall fruit maturity. Three experiments were performed during 9 days of shelf life at a temperature of 25 °C to obtain firmness (N), color parameters (L*, a*, b*), calculate hue angle (h°), and ethylene emission of 'William' pears purchased at the local store. Based on firmness, we have defined three ethylene concentration stages (ECS) with distinct ethylene emission rates that were determined by our sensor system (ECS1 - underripe, not ready to eat, ECS2 - ripe, ready to eat, ECS3 - overripe, senescent). The system gives good reproducibility and good correlation to the firmness stages as defined from related work. In general, the employed sensor system can determine ripening stages based on ethylene emission rate that also includes other volatile compounds.