Cereal Chem 72:64-69  |  VIEW ARTICLE

Dielectric Properties and Water Mobility for Heated Mixtures of Starch, Milk Protein, and Water.

M. N. Tsoubeli, E. A. Davis, and J. Gordon. Copyright 1995 by the American Association of Cereal Chemists, Inc. 

The dielectric properties of hydrated whey protein isolate (WPI), Ca-caseinate, and wheat starch, alone or in combination, were measured at ambient temperature and during heating to 90 C. At lower moisture contents and ambient temperature, WPI exhibited higher dielectric properties than starch, whereas Ca- caseinate had a lower dielectric constant than either WPI or starch. At higher moisture contents, the dielectric properties were similar. At moisture contents of 30-80%, WPI showed increasing microwave absorption properties with increasing temperature; at higher moisture contents, microwave absorption by Ca-caseinate decreased with temperature. Adding WPI affected the dielectric loss and absorptivity of starch during heating but such an effect was not evident with Ca-caseinate. The dielectric properties of these systems were compared with their hydration properties by electron spin resonance using TEMPO, a water and oil-soluble noninteractive probe to correlate water mobility results to dielectric relaxation phenomena. All systems were equally effective in slowing the motion of TEMPO. However, their dielectric properties differed, indicating that the dielectric properties are not only influenced by the water but by the macromolecules present as well.