Lepidium perfoliatum seed gum (LPSG) film is brittle and permeable to water vapor. Therefore, in the present study different proportions of grass pea (Lathyrus sativus) protein isolate (LSPI) and glycerol (GLY) were used to improve the quality of the film. Fourier-transform infrared (FTIR) spectroscopy techniques were used to highlight the interactions between the two biopolymers. With addition of LSPI, the intensity and wave number of peaks changed, due to the interactions occurred between LPSG and LSPI. LPSG–LSPI blends had single glass transition temperature (Tg), meaning that LPSG and LSPI has formed a one phase blend. The moisture content, moisture absorption, water solubility and water vapor barrier of composite films significantly decreased with addition of LSPI to LPSG. Increasing LSPI to LPSG ratio led to a decrease in tensile strength (TS), young's modulus (YM) and melting point (Tm). Addition of LSPI to the composite films increased their transparency, whereas, elongation at break (EB) significantly increased when the LPSG ratio enhanced. The lightness of the composite film decreased and the film became greenish and bluish in color when the LSPI proportion increased. With incorporation of LSPI, the microstructure of films changed to a continuous and uniform network without any pores or cracks. As a result, the mechanical properties of LPSG film improved with addition of LPSI to the formulation and film made from 80:20 LPSG to LSPI ratio and 60% GLY could be used as a new biodegradable film with acceptable physical properties.

Keywords