(440f) Predicting the Linear Viscoelasticity of Starch Dispersions during the Initial Stages of Granule Swelling

Starch pasting, i.e., the process by which aqueous dispersion of starch granules thicken upon heating, greatly influences the texture of a variety of consumer products. The current industrial paradigm is to use trial-and-error approaches to manipulate starch mechanics, which requires significant testing/investment when formulating new materials for the food and bioprocess industries. Here we discuss our progress in developing a first-principles approach to understand the linear viscoelasticity of starch during the initial stages of granule swelling. In the first part of the talk, we combine Stokesian dynamics simulations with rheology experiments to determine the conditions under which starch dispersions can be described using standard theories of rigid particle suspensions. In the second part of the talk, we invoke ideas from paste rheology to predict the rheology of starches in the high volume fraction limit when starch granules are highly deformed. In this limit, the experimental data of storage modulus G' vs volume fraction Φ fall onto a master curve when is normalized by γ/R, where γ is the granule-solvent interfacial energy and R is the average swollen granule size. These rigid particle and paste rheology theories allow one to employ our previously developed starch granule swelling models to predict how the volume fraction and rheology of starch dispersions evolve under arbitrary heating profiles. We see that these ideas can accurately forecast the time dependent storage modulus of many starches (different maize and rice varieties) and certain food products (soups and gravies). This work demonstrates how a first-principles approach can be helpful in many applications in the food processing industry.