Cereal Chem 68:245-248   |  VIEW ARTICLE

Gelatinization of Wheat Starch in the Presence of Sucrose and Sodium Chloride: Correlation Between Gelatinization Temperature and Water Mobility as Determined by Oxygen-17 Nuclear Magnetic Resonance.

P. Chinachoti, M.-S. Kim-Shin, F. Mari, and L. Lo. Copyright 1991 by the American Association of Cereal Chemists, Inc. 

The inhibitory effect of sucrose and NaCl on starch gelatinization was investigated by differential scanning calorimetry and nuclear magnetic resonance (NMR) spectroscopy. The increase in gelatinization temperature (Tp) resulting from added solutes was correlated to various physical properties, such as water activity, solute-solvent average molecular weight, and 17O NMR D2O mobility. As the solute concentration increased, 17O relaxation time (T2) decreased, indicating that D2O mobility decreased. This reduced the plasticizing effect, leading to an increased Tp. However, the dependency of Tp on D2O mobility was limited to only some solute concentrations. At a sucrose concentration above 20% (starch basis), Tp increased with solute content, but T2 remained relatively constant, resulting in a negative correlation. A decrease in free volume by added solutes also played an important role. A balance between both of these factors was proposed to be responsible for the final Tp. The Tp-T2 relationship for NaCl was complicated by ionic properties, which resulted in a much higher Tp at a given T2 than for sucrose, regardless of its smaller molecular weight.