In recent years، natural biopolymers such as starch have been paid more attention as alternatives to the petroleum-derived plastics for packaging films production. Nowadays، different modified starches with novel characteristics were proposed to the market and could be used in producing edible films. In this study، four corn-based edible films namely corn starch، pregelatinized starch، oxidized starch and corn flour were compared in all their physical and mechanical properties. Results showed that films obtained from oxidized starch have good appearance and transparency but because of high solubility and water vapor permeability (WVP) besides poor mechanical properties، is not much favorable candidate. Pregelatinized corn starch films were similar in many characteristics to simple corn starch but their WVP were high and did not have appropriate tensile strength. Films from corn flour were compatible in many functional aspects to simple corn starch films. However، all four type films exhibit highly biodegradable property.

This study aimed to the native starch modification with α-amylase enzyme and compare it with oxidized starch for surface sizing of paper. Native starch was prepared under different temperature and time conditions by addition of alpha-amylase enzyme to achieve viscosity proportional to oxide starch for base paper surface sizing. Then, the basic industrial paper was subjected to surface sizing by immersion with enzymatic starch and oxidized starch prepared. The papers physical and mechanical properties were measured and evaluated after drying. Based on the results of this study, oxidized starch viscosity at a concentration of 5 % at 95 °C reached 17.51 cp during preparation and to achieve this amount of enzymatic starch viscosity, native starch was prepared at 85 °C using 0.005 % enzyme. The results also showed starch modification with the enzyme by varying the temperature, cooking duration, and concentration of the enzyme and native starch, it is possible to achieve a spectrum of viscosity. Evaluation of the physical and mechanical properties showed greater improvement in paper properties including indices of transverse and longitudinal tensile strength (20% and 30% respectively), transverse and longitudinal tear strength (7% and 15% respectively), burst strength (15%), CMT (7%), and RCT (30%) using enzymatic modified starch compared to oxidized starch for surface sizing. In general, the use of α-amylase enzyme in comparison with oxidized starch enables the economical preparation of starch with a spectrum of viscosity for different conditions for a certain improvement in paper properties can be considered for industrial application.