Physical modification of starch by high-pressure homogenization for improving functional properties of κ-carrageenan/starch blend film

Cornstarch granules were physically modified by high-pressure homogenizer at a pressure of 14 MPa (two and five passes) and 20 MPa (two passes). Then, the modified starches were blended with κ-carrageenan and functional properties of κ-carrageenan/starch films were investigated. Upon homogenization, X-ray diffraction pattern of native starch changed and relative crystallinity reduced. Differential scanning calorimetry showed that melting-point peaks of native starch were shifted to lower temperature after homogenization process. The modified starch granules preserved their integrity, while several micro-pores appeared on their surfaces. In order to study the impact of modified starches on κ-carrageenan film, morphological properties, mechanical parameters, contact angle, water solubility and water vapor permeability of blend films were evaluated. Scanning electron microscopy micrographs of cross-sectional view revealed a good level of miscibility between κ-carrageenan and modified starches. Κ-carrageenan films containing pressured starches showed the highest surface hydrophobicity and tensile strength. Water barrier property and water resistance of κ-carrageenan film were found to improve after addition of modified starches. These changes were more marked when the starch was modified with high level of homogenization pressure.