Exploring the Potential of Electrical Impedance Spectroscopy for Predicting Internal Browning in Apples

Internal browning-related disorders in apple flesh and core can cause significant economic losses by undermining consumer trust and market acceptability, particularly in susceptible cultivars. The comprehensive assessment of apple internal browning across the whole supply chain is crucial for meeting consumer demand, reducing food waste, and improving the profit margins of producers. To address these objectives, there is an urgent need for fast, reliable, and portable non-destructive technique that enable real-time decision-making. In this preliminary study, non-destructive bio-impedance spectroscopy was employed to analyze internal browning in apples which was assessed through expert evaluation, enabling the discrimination of samples into healthy, slightly browned, and severely browned categories. Fruit firmness, the quality parameter which represents the state-of-the-art approach for determining ripening stage, age and texture condition, was used to validate the bio-impedance results. The lower frequency dataset (40 Hz and 600 Hz) of bioimpedance exhibited promising results, with statistically significant differences observed in impedance magnitude (p-values of 0.0016 and 0.0017, respectively) and phase (p-values of 0.099 (p≥0.05) and 0.012, respectively). Additionally, at the middle frequency of 10 kHz, highly significant results were obtained for both magnitude and phase, with p-values of 0.0036 and 0.0029, respectively. These specific frequency points (40 Hz, 600 Hz, and 10 kHz) demonstrate suitability for detecting changes in fruit physiochemical properties during the development of internal browning. In contrast, firmness measurement did not exhibit promising discrimination between healthy and internally browned apples, with a p-value of 0.21 (p≥0.05).