73D-32 |
Heat curing of SPI films at atmospheric and sub-atmospheric conditions |
K. M. KIM1, C. L. Weller, M. A. Hanna, and A. Gennadios4. (1) Industrial Agricultural Products Center, University of Nebraska, 233 LW Chase Hall, Lincoln, NE 68583-0730, (2) Materials Science Research and Development, Banner Pharmacaps Inc., 4125 Premier Dr., High Point, NC 27265-8144 Soy protein films have poor moisture barrier properties due to the hydrophilic nature of the protein and the substantial amounts of hydrophilic plasticizer(s) used in film preparation. Previous studies have observed improved barrier properties with heat curing. This study showed moisture barrier properties improved by heat curing at elevated temperatures and sub-atmospheric pressures. Our objective was to determine the effect of heat curing under various time, temperature and pressure conditions on soy protein isolate (SPI) film properties. The effect of heat curing at atmospheric or sub-atmospheric conditions on selected properties (moisture content, water vapor permeability (WVP), color, tensile strength (TS), elongation (E), and soluble solids content) of cast SPI films was investigated. SPI films were heat-cured at 85 oC for 6, 12, 18, or 24 h, heat-cured at 60, 72.5 or 85 °C and at pressures of 101.3, 81.32, and 61.32 kPa for 24 h. Heat-cured films had increased (P<0.05) TS and decreased (P<0.05) WVP and E compared to control, unheated films. Heat treatment under vacuum had a more prominent effect of lowering WVP of films than heat curing at atmospheric pressure. High TS values, low E values, and low soluble solids content values were also reached within shorter heating times under vacuum than those at atmospheric pressure. However, vacuum treatment increased the size and number of cavities in cured films as evidenced by scanning electron micrographs. Moisture content, WVP, E, and SS decreased, and total color difference and TS increased as temperature increased. Pressure, individually and interactively with temperature, significantly affected film moisture content, TS and SS. Improved moisture barrier properties and packaging functionality for SPI films in edible packaging applications may be obtained through heat-curing at sub-atmospheric pressures.
Session 73D, Food Packaging
|