Starch content affects physicochemical properties of corn and cassava starch-based films

Biodegradable starch-based film has been widely used as alternative to packaging derived from fossil sources. The composition, structural and morphological properties of starch granules vary with plant source, contributing to significant differences in properties and desired functionality. The objective of this work was to evaluate the starch content influence on physicochemical properties of corn (Zea mays L.) and cassava (Manihot esculenta L.) starch-based films manufactured by casting. Different starch contents (20-60 g kg(-1)), glycerol (9 g kg-1) and xanthan gum (0.05 g kg(-1)) were used. From Scanning Electron Microscopy (SEM) analysis, it can be seen that corn and cassava native starches exhibited polyhedral and oval shape, respectively. The Principal Component Analysis (PCA) results showed that higher biopolymer content promoted an increase in thickness (ranging between 0.07 and 0.17 mm) and a reduction in water vapor permeability (ranging between 0.42 and 0.15 g mm h(-1) M-2 kPa(-1)) of the starch-based films. Moreover, increased starch content in the films promoted improved mechanical properties. For the same starch content, cassava starch based films presented higher water solubility than corn films, approximately 22% and 16%, respectively. Mechanical properties of the starch (40 g kg(-1)) based films as tensile strength, (3.9 MPa), maximum elongation (120%) and elastic modulus (65 MPa) were comparable to LDPE (low density polyethylene) based films used as food packaging currently marketed. From the results obtained, corn and cassava starch may be considered promising alternatives for the food packaging development.