Effects of hot water treatment on electrical properties, cell membrane structure and texture of potato tubers

• We obtained equivalent circuit parameters from heated potato tubers.
• These parameters changed with heating time at high temperature.
• Damaged cell membranes were observed by CLSM.
• Changes in electrical properties were caused by membrane damage.
• The electrical properties were also correlated with texture.

Hot water treatment is a common procedure during the processing and cooking of fruit and vegetables. To establish a technique that enables quality estimation during processing, we investigated the effects of hot water treatment on the electrical properties, cell membrane structure and texture of potato tubers. After hot water treatment at 50, 60, 70, 80 and 90 °C, electrical impedance spectroscopy (EIS), confocal laser scanning microscopy (CLSM) and penetration tests were conducted. In addition, the EIS results were analyzed by use of an equivalent circuit. Obtained equivalent circuit parameters (intracellular resistance, extracellular resistance and cell membrane capacitance) increased or decreased with immersion time at high temperatures. CLSM images indicated that electrical changes were caused by cell membrane damage. Textural changes were strongly correlated with the equivalent circuit parameters. We suggest that EIS is useful to assess the degree of softening of potato during heating.