Modifications of protein-based films using cold plasma

In this research, the influence of different cold plasma treatments was investigated as a novel method for modification of protein film properties. The films were prepared from whey and gluten proteins using solvent casting method and then treated with vacuum low-pressure glow plasma using air and argon gases at 50 KW for 5, 10, and 15 min and further analyzed mechanically and physicochemically. The images of atomic force microscopy (AFM) revealed a significant increase in roughness of whey protein films after plasma treatment, while the roughness of treated gluten films diminished dramatically. Furthermore, the tensile strength of films improved significantly after 10 min of process, from 6.902 to 10.772 MPa and from 1.854 to 2.571 MPa for whey protein and gluten films, respectively. Introduction of functional groups such as C-O and O=C bonds plus cross link creation was observed by FTIR which could lead to changes in different film features. Although gas permeability of both edible polymers decreased significantly, other parameters including solubility and water vapor permeability of control and plasma treated (PT) films did not show dramatic differences. Therefore, the optimum condition and time of low-pressure glow plasma has the potential for modifying protein films. (C) 2019 Published by Elsevier B.V.