OCT based investigation of post harvest sub-peel microstructural changes in Mango (Mangifera indica): ethylene-induced vs. natural ripening

Optical coherence tomography (OCT) is a high-resolution, non-destructive imaging modality gaining attention in agricultural research. With growing concerns about harmful chemicals like calcium carbide and acetylene gas used for artificial fruit ripening, especially in India, rapid assessment techniques for fruit health are needed. In this work, we used OCT to examine microstructures in the sub peel region of mango (Mangifera indica) ripened artificially (with ethylene gas) and naturally (in paddy straw). Qualitative analysis of OCT images showed distinct sub-peel microstructural changes. In ethylene based ripened mangoes, randomly shaped void spaces resembling intercellular spaces were formed in the parenchyma cell region. This is due to the early cell wall disintegration indicating the faster tissue ripening. Also, irregular spacing (∆t) between two distinct regions (exocarp and mesocarp) was evident as early as day 4. Conversely, naturally ripened mangoes exhibited only few irregularly shaped microcrack-like features in the outer mesocarp region only by day six, reflecting a more gradual transformation.