Effect of agar on the microstructure and performance of potato starch film

Films made of agar and potato starch were elaborated and tested for a potential use as food packaging. Fourier-transform infrared spectroscopy (FT-IR) confirmed that starch and agar were compatible and inter-molecular hydrogen bonds existed between them. Scanning electron microscopy (SEM) of composite film with 15% content of agar showed a compact and homogeneous structure. X-ray diffraction (XRD) indicated the composite films were amorphous. At 50% relative humidity (RH), the addition of agar could enhance the tensile strength (TS) from 5.33 to 11.76 MPa. At high moisture environment (75% RH), the addition of agar could also enhance TS value from 0.84 to 3.36 MPa. Fortunately, the addition of 5% agar increased the elongation (E) from 32.5% to 58.33%. Water vapor permeability (WVP) decreased from 6.29 to 4.60 × 10−10 g Pa−1 s−1 m−1. In conclusion, the addition of agar improved microstructure of starch film, and then meliorated mechanical properties and WVP at high moisture environment. It widened the application of potato starch film in food packaging films as expected.