Abstract
The effects of citric acid and acetic acid on the rheological properties of corn starch pastes were studied by steady and dynamic viscoelasticity and intrinsic viscosity measurements, and by microscopic observation. The pH value of corn starch dispersion was arbitrarily adjusted to between 6.0and 3.0. The viscosity of the pastes was increased by decreasing pH value (between 5.5 and 3.8), while the viscosity of samples with a pH value below 3.5 was lower than that of the control (pH =6.3). Many glucose chains were leached out from the starch granules by adding acid, which led to hydrolysis of glucose chains. No decrease in the viscoelasticity of the corn starch pastes was apparent from adding acid at 25°C after gelatinization, indicating that the degree of this hydrolysis was low.
