Application of nondestructive impedance spectroscopy to determination of the effect of temperature on potato microstructure and texture

The objective of this study was to use impedance spectroscopy to evaluate microstructural changes in potato tissue caused by heat treatments. Potato samples were subjected to 30 min treatments at room temperature, 30, 40, 50, 60 and 70 C. Changes in microstructure were evaluated by texture, electrolyte leakage and color measurements, and confocal laser scanning microscopy (CLSM). Samples processed at 60 and 70 C showed significantly different module of impedance and phase values than those processed at ≤50 C. Texture decreased and electrolyte leakage increased after treating potato at temperatures above 60 C, indicating loss of turgor pressure and rupture of both membranes and cell walls. Significant changes in tissue microstructure and progressive cell wall degradation as temperature increased were visualized using CLSM. Real-time nondestructive impedance spectroscopy proved to be a quantitative means of following the effects of process temperature on potato cell walls and starch, and subsequently on textural properties.