Microstructure and Rheological Properties of Composites of Potato Starch Granules and Amylose: A Comparison of Observed and Predicted Structures

Potato starch granules were gelatinised in amylose solution to study the effect of adding amylose to a highswelling granular starch system. The effects of varying the amount of potato starch from 1-10% , added to a solution of 2% amylose, were studied by means of dynamic viscoelastic measurements and light microscopy. The granules gelatinised in amylose solution had a lower degree of swelling than those gelatinised in water. The restricted swelling in amylose was reflected in a decrease in the complex shear modulus (G*) at 75\u27C. GeJatinisation in 2% amylopectin also caused a decrease in G*, but gelatinisation in 2% 0-glucose did not affect the rheological behaviour. Microstructural analysis showed that the added amylose was present outside the granules after swelling, whereas the inherent amylose from the potato starch seemed to have diffused main] y to the inner aqueous centre of the granules. The mixed potato starch/amylose systems showed a fast gelation comparable to that of cereal starch. The results were analysed by a model predicting the shear modulus of aqueous biphasic gels. When the system is regarded as a continuous network of added amylose with dispersed potato starch granules, the results from both microscopy and rheology are in excellent agreement with the model at potato starch concentrations below 6%. As the potato starch concentration was raised, the high swelling potential of the potato starch granules led to partial disruption of the continuous amylose network. The results imply that the inherent amylose from potato starch did not contribute to the gel strength caused by the added solubilised amylose

Distribution of Amylose and Amylopectin in Potato Starch Pastes: Effects of Heating and Shearing

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

Comparison of potato amylopectin starches and potato starches - influence of year and variety

Starches from three potato varieties and their respective transformants producing amylopectin starch were studied over a period of 3 years. The gelatinisation, swelling and dispersion properties were studied using differential scanning calorimetry (DSC), X-ray diffraction, swelling capacity measurements and a Brabender Viscograph. The potato amylopectin starches (PAP) exhibited higher endothermic temperatures as well as higher enthalpies than the normal potato starches (NPS). PAP samples gave rise to an exceptionally sharp viscosity peak during gelatinisation and a relatively low increase in viscosity on cooling. Swelling capacity measurements showed that PAP granules swelled more rapidly, and that the dispersion of the swollen granules occurred at a lower temperature (85 degreesC). Analysis of variance (ANOVA) also revealed that the year influenced the DSC results, and that both year and variety affect some of the Brabender parameters. Furthermore, the PAP and NPS samples were subjected to heat-moisture treatment at three different moisture levels, and the Brabender viscosity properties were studied. (C) 2002 Elsevier Science Ltd. All rights reserved