Food-Safe Bioimpedance Monitoring of Table Grapes and Their Post-Harvest Aging

Abstract

The integration of digital technologies into agriculture is reshaping post-harvest monitoring, enabling sustainable, non-destructive fruits and vegetables quality assessment methods. Electrochemical Impedance Spectroscopy (EIS) constitutes a powerful tool to evaluate physicochemical changes in fruits and their quality during ripening and rotting. However, its widespread application is limited by the use of non-biodegradable, short-term adhesive electrodes and low-throughput, contact-inconsistent setups. Here, we present an EIS platform combining edible adhesive electrodes and a food-safe sensorized soft gripper for monitoring fruit without damage. The electrodes are fabricated from food-derived materials such as zein and activated carbon (E153) and are key to allow safe and reproducible access to fruit bioimpedance. The soft gripper, coated with food-contact safe conductive materials including gold foil (E175), polydimethylsiloxane, and activated carbon, allows reliable electrical probing. Table grapes were selected as a non-climacteric study case crop to evaluate post-harvest physiological changes under different storage temperatures. Our system enabled continuous monitoring over several days and detected significant impedance changes within the first 24 h, with refrigerated grapes showing a slower spectral variation with respect to those stored at room temperature. These findings demonstrate the potential of the proposed food-compatible EIS platform for real-time fruit quality monitoring in sustainable post-harvest supply chains.