Improving properties of normal maize starch films using dual-modification: Combination treatment of debranching and hydroxypropylation.

Structure and properties of films made from native, debranched, hydroxypropylated and debranched/hydroxypropylated normal maize starches were determined and compared. The modified starch films were much smoother and more integrated than native starch film. Especially, the particles were not observed in dual-modified starch film but in debranched starch film, which might result from amylose recrystallization. Debranching substantially decreased elongation at break of starch films from 39.2% to 8.4% and hydroxypropylation decreased tensile strength from 4.82 to 2.92 MPa, indicating neither debranching nor hydroxypropylation could comprehensively improve the film properties. After dual-modification, elongation at break and tensile strength of the film were increased to 57.2% and 7.35 MPa, respectively. Moreover, the barrier performance of films was in the order of hydroxypropylated starch film < native starch film < dual-modified starch film < debranched starch film. It was suggested that dual-modification could be an effective approach to obtain starch films with tailor-made properties.