30E-5 |
Effect of sugars on rheological properties of corn starch paste |
Y. H. Chang, Dept. of Food Science and Technology, Dongguk University, 3 Pil-dong, Chung-gu, Seoul, 100-715, South Korea, S. T. Lim, Graduate School of Biotechnology, Korea University, 1, 5-ka, Anam-dong, Sungbuk-ku, Seoul, 136-701, South Korea, and B. YOO, Dept. of Food Science and Technology, Dongguk Univeristy, 3 Pil-dong, Chung-gu, Seoul, 100-715, South Korea. Sugars have been known to play an important role of the gelation and retrogradation of starch paste. In order to understand the effect of sugars on gelation and retorgradation, several researchers studied rheological properties of starch-sugar composites. However, little information is available on the effect of various sugars on gelation properties of corn starch pastes in the cooling and the ageing processes by small-deformation oscillatory measurements. The overall objectives of this study were to examine the effect of sugars on the rheological properties of corn starch pastes as a function of the type of sugar and sugar concentration by measuring dynamic moduli during cooling and ageing. Starch dispersions (5% w/w) were prepared by mixing with distilled water, and sugars (sucrose, glucose, and xylose) were added to obtain 10, 20, and 30% sugar levels. The starch-sugar dispersions were held to 95C in a jacketed vessel for 30min. Each starch paste was transferred to a TA AR1000 rheometer plate (plate-plate geometry) set at 95C. They were then cooled down to 4C at a rate of 1C/min and held at 4C for 10hr with measurements of storage moduli (G') at 1 Hz and 3% strain. Magnitudes of G' increased sharply during cooling and moved to progressively lower temperature as the concentration of sugar was increased. G' values as a function of aging time were found to increase rapidly initially and showed pseudoplateau values after a few hours. The structure development rate constant (k) of gelation during ageing was described by an apparent first-order kinetics. G' and k values in corn starch-sugar composites were significantly reduced in the presence of sugars, and decreased in the following order: xylose > sucrose > glucose > control (no sugar). From these results, it was found that on cooling and ageing, the gelation of corn starch paste was significantly affected by the addition of sugars and was apparently dependent on the type of sugar and sugar concentration.
Session 30E, Food Engineering: Rheology and texture
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