Characteristics of rice starch film blended with sugar (trehalose/allose) and oil (canola oil/coconut oil): Part I - Filmogenic solution behavior and mechanical properties.

The concentrations effects of sugars (trehalose and allose) and oils (canola and coconut oil) on the characteristics of rice starch suspension and mechanical properties of rice starch film were studied. The samples were prepared using 3% (w/w) rice starch, with 10% or 30% (w/w) sugar (trehalose or allose) added and 10% or 30% (w/w) oil (canola or coconut). The droplet size of the film suspension increased with increasing oil concentration both in trehalose and allose, which blended with oil. The flow behavior of the film suspensions showed shear-thinning behavior as calculated by the Power Law model. The apparent viscosity tended to increase with the addition of sugar and oil. The breaking stress of the films blended with sugar and oil was less than that of control. On preparation day and after 7 days' storage, the breaking strain tended to increase more with the addition of coconut oil than with that of canola oil. However, breaking stress and breaking strain decreased after 28 days' storage. Adding sugar had correlation with mechanical properties whereas adding oil had correlation with film suspension characteristics, allowed the sugar and oil to interact and inhibited starch chain mobility due to concentration, sugar type, and oil type. PRACTICAL APPLICATION: Trehalose, allose, canola oil, and coconut oil could be used as a plasticizer in a starch edible/biodegradable film system. The preparation process of filmogenic solution was depended on the combination of sugar and oil that could change the flow behavior and affected the mechanical properties of the edible film. The sugar and oil might improve the mechanical properties of the film by a hydroxyl group of sugar and lubricating properties of the oil.