Abstract
The properties of mungbean protein film plasticized with glycerol have been previously shown to have a low tensile strength (TS) and high water vapor permeability (WVP) making the film unsuitable for commercial usage as a packaging material. In this study, improvement of these properties of mungbean protein film and soy protein film was carried out by two methods: incorporation of starch (tapioca, corn, wheat and potato) and also by using various other types of plasticizer than glycerol [sorbitol, ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG)]. TS of the protein films mixed with starch were improved for all the starches tested; TS of mungbean protein film was increased from 0.244 to a range of 2.55-3.32MPa and TS of soy protein film was increased from 0.921 to a range of 4.91-6.53MPa. The decrease of WVP value which indicates an improvement of the film's barrier properties, of the mungbean protein-tapioca starch film was decreased from 22.1 to 5.63×10-11g/m.s.Pa. WVP of the soy protein-wheat starch film decreased from 10.7 to 7.01×10-11g/m.s.Pa. The elongation of film was not improved by this method. The TS and WVP of films were improved by using sorbitol as a plasticizer. TS of sorbitol-plasticized film increased from 0.921 to 3.52MPa for soy protein and increased from 0.264 to 0.95MPa for mungbean protein film. WVP of sorbitol-plasticized film decreased from 8.96×10-11 to 1.16×10-11g/m.s.Pa for soy protein. WVP of mungbean protein film plasticized with sorbitol decreased from 15.05×10-11 to 1.9×10-11g/m.s.Pa. EG, DEG and TEG also can improve TS but WVP of film plasticized with these plasticizers is high.
