2009 Volume 13 Issue 3 Pages 197-206
he Line Spread Test（LST）is known as a simple method for measuring the rheological properties of thickened liquid foods. However, the applicability of these methods has not been thoroughly examined. Therefore, we assessed various thickened liquid foods prepared with instant food thickeners by a modified LST method by which the measured value is more precise than the original ring method. We then measured the rheological properties of thickened liquid foods and analyzed the relationships between the various properties with the LST values. First, we measured the properties of three thickened liquid foods, water, milk, and orange juice, in which three xanthan gum-based thickeners, commercially available, were dissolved. The correlations between the LST values and other physical properties such as viscosity, hardness, and adhesive energy, were analyzed. The LST values were correlated linearly with the viscosities and with the hardness, but logarithmically with the adhesive energy. The range of viscosities practically measurable by LST was from 1,000 to 7,000 mPa・s. In addition, we measured the properties of thickened milk in which xanthan gum, starch, or guar gum-based thickeners were dissolved and evaluated by the simple linear regression analysis between the LST value and each of other physical properties. We found that the lower the rotor rotating speed for the viscosity measurements, the higher the contribution ratio between the LST values and the viscosity. We then performed multiple linear regression analysis with the LST value as an objective variable, and with the other physical properties as explanatory variables. The LST values without the starch-based thickeners match a good multiple linear regression model which comprises three factors including viscosity, hardness, and adhesive energy. In conclusion, the LST value reflects multiple physical properties, and it is important to set up appropriate measuring conditions and evaluation indices for practical application.
