A TRANSIENT METHOD FOR DETERMINING DYNAMIC VISCOELASTIC PROPERTIES OFSOLID FOODS

This article describes a transient dynamic method for measuring the co mplex modulus of solid foods over a range of frequencies from one sing le loading test. Mathematical justifications for the proposed method a re given and the instrumentation system for performing the transient d ynamic tests is described in the article. Experiments were conducted t o measure the complex modulus of apples and potatoes and its relations hip with initial stress and vibration input. The magnitudes of the com plex modulus increased by 50% for the apples and 80% for the potatoes as the frequency increased from 0 to 800 Hz. The phase angle generally decreased with frequency. As expected, initial stress had a significa nt effect on the magnitude of the complex modulus, but not on the phas e angle. Vibration amplitude had little effect on the magnitude and ph ase angle. The values of the complex modulus for apples and potatoes m easured from the transient dynamic tests were not significantly differ ent at the 0.05 level from the steady-state sinusoidal rests at freque ncies of 200, 400, and 600 Hz.