Between‐species Differences in Fracturability Loss: Comparison of the Thermal Behavior of Pectic and Cell Wall Substances in Potato and Chinese Waterchestnut1

This study was undertaken to determine how the mode of chemical changes taking place during the cooking of two chemically similar vegetables (potato and waterchestnut) might explain the tremendous between‐species differences in cooked tissue fractura bility as determined by Instron Texture Profile Analysis. Although pectin breakdown and depolymerization by heat weakens the cell wall structure, loss of cell wall physical strength does not necessarily coincide with pectin depolymerization. Potato phosphate‐soluble pectin (PSP) showed a more rapid rate of depolymerization than waterchestnut PSP as proven by both chemical and gel chromatographic studies. The unique composition (e.g., neutral sugar content) of the cell wall microstructure of a given vegetable species is the major determinant of the resistance of that plant tissue to fracturability loss during cooking. Based on GLC analyses of cell wall components, cell wall models have been proposed to illustrate the possible structural differences between potato and waterchestnut tissue. It appears that the cell wall character of edible plant tissue for a given species is determined genetically.