(262d) Prediction of Storage Modulus of Starch Suspensions during Granule Swelling

We present a methodology to predict the storage modulus (G') of starch paste due to granule swelling, given the physical properties of the starch granule and temperature history. This was tested on experimental measurements of G' for 8% w/w suspensions of waxy maize, normal maize, waxy rice, normal rice, and maize cross-linked with STMP– all heated to different temperatures (65 to 90 ⁰C) and holding times (2 to 60 min). Experimental data of storage modulus G' versus volume fraction φ fall onto a master curve when G' is normalized by its limiting value G₀', the latter of which can be estimated through measurements of granule-solvent interfacial energy using a theory that examines the surface forces in closed-packed system. This master curve, coupled with previously developed theories that predict the granule size distribution over time, allows one to semi-empirically predict the storage modulus due to swelling for a wide range of starch compositions and temperature history profiles. We will demonstrate this theory on real food systems like soups and gravies under various processing conditions. The talk will conclude with a discussion on how to extend such ideas to include other effects such starch-oligosaccharide interactions, as well as develop theories to examine other aspects of starch rheology such as loss moduli (G'') and yield stress (nonlinear response).