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Plasticizing—Antiplasticizing Effects of Water on Physical Properties of Tapioca Starch Films in the Glassy State
Author(s) -
Chang Y.P.,
Cheah P.B.,
Seow C.C.
Publication year - 2000
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.2000.tb16025.x
Subject(s) - starch , food science , materials science , chemical engineering , chemistry , polymer science , engineering
The effects of moisture sorption on physical properties of native and cross‐linked starch films in the glassy state were studied. Water played a dual role as a plasticizer or an antiplasticizer, depending on the physical property measured. Plasticizing effects were clearly evident in the case of the calorimetric glass transition temperature ( T g ), tensile modulus, linear expansion, and water vapor permeability. In contrast, antiplasticization by water resulted in maxima in tensile strength, strain‐at‐break, and toughness of films that were observed at an intermediate moisture content ranging from 4% to 8% (RVP 0.1 to 0.4). The seemingly contradictory effects of water on mechanical properties associated with lower and higher deformation of starch films were reconciled by assigning different roles to water operating primarily via opposite entropic/free volume effects. Relationships, if any, between DSC thermal events and mechanical antiplasticization were not apparent.