Abstract
Apple is one of the most valuable cash crops in Italy, due to its great economic importance in the European market, and driven by consumer preferences. In this region, a wide variety of apple cultivars are grown; among them, some are susceptible to internal browning during cold storage and postharvest management. Currently, there is no specific method capable of directly analyzing internal browning in apples. This study aims to develop an efficient, low-cost cost and non-destructive technique to estimate internal browning in apples after seven months of postharvest storage using the electrical impedance spectroscopy (EIS) technique and compare with other well-investigated optical non-destructive, using a delta absorbance meter (DA) and near-infrared spectroscopy (NIR), and destructive (refractometer) quality analysis techniques. The quality parameters, including dry matter, chlorophyll, and total soluble solids, as well as the ripening stages, age, and texture condition of the fruits, were used to validate the bioimpedance results. In the low and mid-frequency region of the bioimpedance spectrum, good discrimination was observed between healthy and internally browned samples, with statistically significant differences (p-values ≤0.01). The frequency points (40 Hz and 10 kHz) efficiently investigate the physicochemical changes produced during the development of internal browning in apples, while the high-frequency region (2.5 MHz) was not significant (p-values ≥0.05). The dry matter and sugar content measurements of fruit on the sunny and shaded sides were also short of discriminating between healthy and internally browned apples (p-values ≥0.05). However, chlorophyll content on the sunny side of the fruit discriminates between healthy and internal browned apples, with statistically significant differences (p-values ≤0.05), while it proved to be insignificant for the shady side (p-values ≥0.05). This real-time, optimized, user-friendly, and cost-effective technique will help reduce postharvest loss and contribute to sustainable agriculture and food security in the future.