Preparing water-resistant films using partially debranched potato starch and oleic acid

Improvement in film-forming properties of starch is critical for the wide application of environmentally friendly starch film. To enhance moisture barrier and mechanical properties of starch films, the formation of starch-lipid inclusion complex was promoted by partial debranching of starch and reaction at various temperature. The partially debranched potato starch was initially prepared with pullulanase, and the starch-lipid inclusion complex was subsequently produced with oleic acid at various reaction temperatures of 30, 50, and 70 °C. The partial debranching combined with oleic acid addition induced characteristic V-type crystalline peaks in the X-ray diffraction (XRD) patterns. The highest reaction temperature, of 70 °C, induced more apparent XRD peaks and higher thermal transition temperatures and enthalpy. The partially debranched starch film with oleic acid at 70 °C showed a smooth and uniform surface with a more rigid and condensed network. The high content of starch-lipid inclusion complexes in a partially debranched starch film with oleic acid at 70 °C significantly reduced water vapor permeability (from 162.22 to 65.99 g∙mm∙m^-2∙day^-1∙atm^-1) and increased both the contact angle (from 61.08 to 74.55°) and tensile strength (from 2.126 to 5.473 MPa) compared to a native starch film. Therefore, the formation of more abundant starch-lipid inclusion complexes at relatively high reaction temperatures with partial debranched starch can effectively enhance the moisture barrier properties of starch films for industrial application as biodegradable film.