61A-35 |
Characterization of the effect of starch damage on rheological properties of maize starch pastes |
X. Z. HAN1, O. H. Campanella2, and B. R. Hamaker1. (1) Department of Food Science and Whistler Center for Carbohydrate Research, Purdue University, West Lafayette, IN 47907, (2) Department of Agricultural and Biological Engineering and Whistler Center for Carbohydrate Research, Purdue University, West Lafayette, IN 47907 Starch damage causes significant changes in starch granular structure and amylopectin molecules. Starch damage was found by others to decrease the viscosity of pastes. However, information regarding how the extent of damage affects rheological properties under different shear conditions and on viscoelastic properties of starch pastes was unknown. In-depth characterization of the effect of starch damage on rheological properties of starch pastes will aid in understanding rheological changes caused by starch damage and will permit better prediction of final product quality. The objectives of this study were: 1) to determine the effects of starch damage on shear stress and viscosity of starch pastes during pasting and under different shear rates, 2) to investigate the viscoelastic properties of starch pastes in relation to starch damage, and 3) to study rheological differences between normal and waxy maize starches after starch damage. Starches were ball-milled to create different extents of starch damage. Steady shear measurements were conducted at a range of shear rates using a controlled stress rheometer with a cone and plate system. Dynamic measurements were performed over a frequency sweep in the linear viscoelastic range. Starch damage caused decreases in viscosity in both waxy and normal maize starches. Viscosity decreases were much higher in waxy than in normal maize starches after the same ball milling times. The viscosity decrease caused by starch damage was also shear dependent in waxy starch; high shear caused greater decrease in viscosity. Storage moduli of pastes decreased, and loss modulus increased with increase in starch damage in both waxy and normal maize starches, indicating increase of liquid behavior. The study showed that starch damage caused shear-dependent decrease in viscosity and elastic property of starch pastes. The results aid in understanding and controlling variations caused by starch damage in processing starch-containing foods.
Session 61A, Carbohydrate
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