Abstract
Changes in electrical and rheological properties of agricultural products were investigated to clarify the softening mechanism of the organization in heating process. Potato, Japanese radish and carrot were used as the sample. These were heated in normal saline solution. Impedance was measured by LCR meter, and dynamic viscoelasticity was measured by the vibrating reed method. As a result, the impedance of potato tuber decreased gradually with an increase in temperature, then decreased rapidly at 65℃. Optical absorbance at 263 nm of the heating saline solution containing the test sample also rose drastically at this temperature, which suggested the release of intracellular nucleic acid related materials. Moreover, dynamic viscoelasticity decreased in the vicinity of this temperature, which suggested that the turgor pressure of the tissue cells was lost because of the cell membrane disruption. Similar phenomena were observed for Japanese radish and carrot although the temperature and the extent of the changes in physical properties were different depending on individuals. These results strongly suggest that the major softening mechanism of agricultural products in heating process exists in the thermal injury of cell membrane which caused the loss in turgor pressure of tissue.
