Paper Number
SC17 

Session
Suspensions, Colloids, and Granular Materials

Title
A first-principles approach toward characterizing the rheology of starch granules during granule swelling

Presentation Date and Time
October 12, 2021 (Tuesday) 10:40

Track / Room
Track 5 / Ballroom 6

Authors (Click on name to view author profile)

  1. Narsimhan, Vivek (Purdue University, Davidson School of Chemical Engineering)
  2. Desam, Gnana P. (Purdue University, Agricultural and Biological Engineering)
  3. Li, Jinsha (Archer Daniels Midland Company)
  4. Dehghani, Nader L. (Purdue University, Davidson School of Chemical Engineering)
  5. Narsimhan, Ganesan (Purdue University, Agricultural and Biological Engineering)

Author and Affiliation Lines (in printed abstract book)
Vivek Narsimhan1, Gnana P. Desam2, Jinsha Li3, Nader L. Dehghani1 and Ganesan Narsimhan2
1Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907; 2Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907; 3Archer Daniels Midland Company, Decatur, IL 62526

Speaker / Presenter 
Narsimhan, Vivek

Keywords
experimental methods; theoretical methods; computational methods; applied rheology; foams; gels; non-Newtonian fluids; suspensions

Text of Abstract
Starch pasting is the process by which starch granules swell irreversibly in hot water and thicken. This process confers texture to many foods, and controls the flow behavior of starches in pharmaceuticals, biomaterials, and consumer products. Currently, the bioprocess industry spends considerable resources to chemically modify starches for the sole purpose of tailoring their swelling in order to control their flow behavior. Despite the importance of starch swelling, there is a surprising lack of first-principles theories that can offer physical guidance on how to design these processes given the chemical makeup of starch and the heating profile. In this talk, we will discuss our recent developments in first-principles modeling to describe starch rheology during the initial stages of swelling. The first part of the talk will discuss a recently-developed polymer swelling model based on Flory-Rehner theory that predicts how the size distribution of starch granules change during swelling, given the physical properties of the granule (gelatinization temperature and enthalpy, fraction of network that is cross-linked, and second virial coefficient between water and starch). In the second part of the talk, we will discuss how to connect the volume fraction from this theory to the linear viscoelasticity of the starch dispersion. For volume fractions ?<0.5, we show through experiments and Stokesian dynamics simulations that the starch rheology behaves similarly to a rigid particle dispersion. For volume fractions above this limit, the rheology depends on the granule contact mechanics. In particular, we find that the storage modulus G' vs volume fraction ? fall onto a master curve when G' is normalized by ?/R, where ? is the granule-solvent interfacial energy and R is the average swollen granule size. We demonstrate that both the swelling and rheology theories discussed here allow one to forecast the time dependent storage modulus for many starches and certain food products under arbitrary heating profiles.