Food Structure


The microstructure of potato starch pastes and gels in the concentration range 5-10% (w/w) was studied as a function of shear and heat treatment usi.ng light microscopy. Heating induced extensive swelling of potato starch granules, and the swollen granules filled the whole volume of the starch pastes that were subjected to a minimum of shear. The volume of the aqueous phase outside and in the center of the swollen granules is practically negligible compared to the volume occupied by the walls of the swollen granules. The granules with the lowest gelatinization temperatures swelled quickly without restrictions, so that less water was available for the leakage of amylose and for the swelling of the granules with higher gelatinization temperatures. The swelling and the contents of amylose and amylopectin differed between granules of different gelatinization temperatures.

Shearing during heating altered the structure completely. The granules were broken down into fragments, and an extensive solubilization of the granules took place. Amylopectin, as well as amylose, was solubilized and formed a continuous phase containing dispersed fragments of granules. Demixing of amylose and amylopectin was observed within the phase of starch in macromolecular solution. The separation into amylopectin-rich and amylose-rich domains within the solubilized starch increased with the heating time.

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