Relative humidity and temperature effects on mechanical and water vapor barrier properties of myofibrillar protein-based films

Fish mince-based films were studied as a function of equilibrium relative humidity and temperature conditions. The sigmoid-shape adsorption isotherm curves were typical of high protein content material and were adequately described, irrespective of temperature, by the Guggenheim-Anderson-de Boer equation. A plasticizing effect of water related to rapid changes in the functional properties was mainly noted at the highest a(w) and explained by the disruptive water-polymer hydrogen bonding theory. Relatively sharp decreases in force at break, elastic modulus and water vapor barrier properties, and increases in deformation at break were observed at temperature-dependent relative humidities; this relative humidity was reduced by increasing the temperature. The temperature dependence of the hydration effect on functional properties could be explained by the glass transition theory. (C) 1997 Elsevier Science Limited.