Molecular Dynamics of Soy-Protein Isolate Films Plasticized by Water and Glycerol

Authors

S.-G. Choi, University of Georgia, Athens,
K. M. Kim
Milford Hanna, University of Nebraska-LincolnFollow
Curtis L. Weller, University of Nebraska-LincolnFollow
W. L. Kerr, University of Georgia, AthensFollow

Document Type

Article

Date of this Version

2003

Comments

Published in Journal of Food Science: Food Engineering and Physical Properties 68:8 (2003), pp. 2516–2522. Copyright © 2003 Institute of Food Technologists. Used by permission.

Abstract

The effects of water and glycerol on the molecular mobility of a soy-protein isolate (SPI)-based film were investigated using ¹H nuclear magnetic resonance (NMR). SPI-films were prepared with different glycerol contents and equilibrated to various levels of water activity (a_w). The distributed transverse relaxation of film samples showed 2 distinct components: a solid-like fraction (T_2s*) and a liquid-like fraction (T_2m*). The peak T_2s* values of films with lower glycerol concentration were more sensitive to variation in aw. As a_w increased, the change of solid-like to liquid-like fraction was observed in higher glycerol films. As glycerol content increased, a minimum longitudinal relaxation time (T₁) occurred at lower a_w. Our results suggest that NMR techniques can be used to quantify the plasticizing effects on biopolymer films.