Effect of osmotic dehydration on Actinidia deliciosa kiwifruit: A combined NMR and ultrastructural study

The effects of individual osmotic dehydration processes (OD) on kiwifruit outer pericarp tissue were studied as reliant on treatment temperature (25, 35 and 45 °C) and extent (0–300 min). Macro (Low Frequency Nuclear Magnetic Resonance, LF-NMR), micro (Light Microscopy, LM) and ultrastructural (Transmission Electron Microscopy, TEM) measurements were performed to evaluate modifications of three cellular compartments, namely vacuole, cytoplasm – extracellular space and cell wall. Both LF-NMR relaxometry and LM observations highlighted shrinkage of the vacuole compartment along the OD. Intercellular space formations, observed at TEM, were in agreement with LF-NMR results. Cell walls of outer pericarp showed considerable changes in size, structure and stain uptake during OD, at both LM and TEM. Furthermore cell walls showed extensive swelling, which intensity varied from cell to cell and even within the same cell. The proposed multianalytical approach should enable both better designs of combined processing technologies and estimations of their effects on tissue response.