Starch edible films loaded with donut-shaped starch microparticles

This paper describes the preparation of thermoplastic starch edible films (TPS) loaded with donut-shaped starch microparticles from two different botanical origins. The microparticles were produced by a simple thermal aqueous-alcoholic treatment. The average size was 14.01 ± 2.65 μm and 28.61 ± 6.84 μm for the microparticles from corn and pea starch, respectively. The double helical A-type and C-type crystallinity of corn and pea starch granules, respectively were converted to single helix V-type crystalline structure during the donut-shaped microparticles preparation. This crystalline distortion was revealed by X-ray diffraction, differential scanning calorimetry (DSC) and the enhanced swelling properties of the microparticles. The starch films were produced using the solution casting method with glycerol as plasticizer. The X-ray diffraction patterns showed both residual and processing induced crystallinity of the TPS films. The starch films were found to be more thermally stable by increasing the donut-shaped microparticles percentage as confirmed by the thermogravimetric analysis (TGA). The water vapour and the oxygen transmission rates through the TPS films can be modified by changing the microparticle content. The TPS films are intended mainly for food packaging applications.