Resumen:
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Effects of plasticizers (glycerol, sorbitol, and 1:1 mixture of glycerol and sorbitol) on moisture sorption characteristics of hydrophilic soyprotein isolate (SPI) films were investigated at three levels of plasticizer concentration (0.3, 0.5, and 0.7 g plasticizer/g SPI). The combined effects of relative humidityand plasticizer on mechanical properties of soy protein films were also examined. Moisture affinities of soyprotein films were affected byhy drophilicityof plasticizer and its concentration. Under given RH conditions, films with higher glycerol ratio absorbed more moisture with higher initial adsorption rate, and films with higher plasticizer contents exhibited higher equilibrium moisture contents. Monolayer moisture contents of SPI films increased as glycerol ratio in a plasticizer mixture and plasticizer concentration increased. Plasticizer and absorbed water loosened the film synergistically, resulting in higher elongation but lower tensile strength. RH effects on mechanical properties of SPI films were varied with plasticizers and their concentration. Films of lower glycerol contents were more sensitive to RH variation as compared to the higher glycerol samples, whereas sorbitol concentration affected the RH region where a sharp decrease in TS value occurred.
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