2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

New methodology for small strain oscillatory shear testing using a vane sensor is needed to fill a current void in viscoelastic characterization of 'problematic' food including starch-based thixotropic materials. To overcome the difficulties associated with traditional sensors, a semi-empirical method was developed to allow the use of a 4-bladed vane sensor (height = 0.0580 m and radius = 0.02005 m) with a 0.02170 m radius cup in oscillatory testing. It was assumed that the vane sensor acted as a bob with an acting radius (R(V)) different from the actual radius of vane. To solve for R(V), the complex modulus (G*, Pa) of reference viscoelastic fluids obtained using a concentric cylinder sensor was set equal to the complex modulus equation, which was based on bob geometry, for the vane sensor. R(V) values were grouped into phase shift ranges (delta(d)) of 5° smaller than or equal to (<) (d) < 16°, 16° < (d) < 60°, and 60° < (d) < 90° and were 0.01883, 0.01869, and 0.01850 m, respectively. These values were used in the calculation of viscoelastic properties of eight commercial food products, and resulted in G* values within 15% to those obtained using a concentric cylinder sensor. Results shown that this particular vane and cup system can be used to directly measure the storage and loss moduli of viscoelastic material, and phase shift angles within the frequency range of 0.63 - 6.28 rad/s. The method developed provides a new approach to viscoelastic testing and gives insight to viscoelastic behavior of complex phenomena occuring in food systems such as 1) recrystallization and retrogredation of starch systems, 2) ingredient functionality, and 3) ingredient interaction.