Modeling of starch retrogradation onset in its aqueous solution using thermoreversible gelation concept

A model was developed to predict starch retrogradation onset in its aqueous solution and verified with the selected literature data. The most probable chain helix distribution was first estimated via minimizing the system free energy with respect to chain helix length. Later, the calculation was extended to double helix formation among single polymer chains with zeta 2 = 10 as the retrogradation criterion zeta 2 is the average double helix length usually equals 10 implying the number of participating residues in the thickness of the thinnest reported starch lamella in the literature. The model prediction namely the retrogradation onset temperature, showed quite reasonable agreement with the selected literature data. Equal chain conformational entropy loss, Delta s/kB approximate to -0.7, was inferred for various starch aqueous solutions due to the double helix kind of associations. Nonetheless, the studied systems showed distinct restrictions, sigma = 9 x 10(-4)-4.7 x 10(-3), against association. (C) 2013 Elsevier Ltd. All rights reserved.