Film extrusion of sunflower protein isolate

Abstract

Film extrusion of sunflower protein isolate (SFPI) was studied. The influence of die temperature (85 to 160°C), water and glycerol contents were investigated through appearance, mechanical and thermo-mechanical properties and swelling behavior in water of films. It was demonstrated that highest temperature, well above SFPI denaturation temperature in the compound, highest glycerol content (70 parts for 100 parts of SFPI) and medium water content (20 parts for 100 parts of SFPI) gave the most regular and smoothest film (as seen on SEM micrographs). Its ultimate tensile strength, Young’s modulus and strain at break were respectively: 3.2 MPa, 17.7 MPa and 73%. Soaked in water, its swelling was about 186% w/w but the film was quiet insoluble. Effect of temperature and plasticizer content were discussed in relation to the kinetic of SFPI denaturation. These first results are very promising for the development of biodegradable protein-based films.