The cooking temperature required to alter the structure of apple sticks was investigated by NMR (magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS)) to detect the thermal degradation of the vacuolar membrane, and by puncture tests to detect tissue softening due to heating. Both NMR methods evidenced the pivot temperature of 53 °C at which the apple parenchyma switches from “fresh” to “cooked” state, i.e. loses its cellular and subcellular structuration. At the tissue scale, the puncture tests performed on apple sticks also showed a shift in firmness at 53 °C. At the molecular scale, the NMR measurements converged with both MRI and MRS, evidencing a thermal degradation of the cell membranes leading to a change in vacuole water chemical exchanges and distribution throughout the cells, cell walls and intercellular spaces. These phenomena lead to a tissue homogenization with heating, which is reflected by a single T2 after cooking.