Degradation profiles of potato starch melts through a capillary tube viscometer

The effects of time-temperature and strain history on potato starch melts at 150 °C were investigated by use of a capillary tube viscometer. Reciprocating and single extrusions were performed in this study. Shear stress at single extrusion decreased gently as initial heating time increased, while shear stress at reciprocating extrusion decreased rapidly as the number of extrusion strokes increased. A high degree of cold water solubility was obtained by reciprocal extrusion at lower moisture content. From the results of gel filtration it could be concluded that starch molecules were depolymerized by high and reciprocal shear stress. According to these results time-temperature history was more effective on the depolymerization of starch molecules and degradation of starch granules at higher moisture content, while strain history was more effective at lower moisture content.