Effect of the Addition of Citric Acid and Whey Protein Isolate in Canna indica L. Starch Films Obtained by Solvent Casting

In this study, the effect of the addition of citric acid (CA) and whey protein isolate (WPI) on film properties of the starch extracted from the achira rhizome (Canna indica L.) was evaluated. For this purpose, starch films were prepared by solvent casting with different CA and WPI concentrations. Starch granules were fully characterized and the chemical and thermal behavior of the obtained starch films were also studied. The retrogradation phenomenon was analyzed in films from 1 week to 1 year of preparation. Maximum tensile strength (max) and maximum elongation at break (max), as well as water vapor permeability, were measured for all films. It was found that both molecules, CA and WPI, show a plasticizing effect on starch films, favoring the formation of a more uniform and resistant material by means of hydrogen bonding. A partial crosslinking between CA and starch was found by Fourier transform infrared, which is coherent with a higher degradation temperature peak found by thermogravimetric analysis. It was also observed that starch retrogradation was affected by the presence of both molecules, CA and WPI. The highest max (5.7 ± 0.1 N/mm2) and max (35%) values were achieved at the eighth weeks when both CA (6%) and WPI (11%) were used. Addition of CA and WPI did not show a significant difference in permeability values of starch films (1.40 × 10−9 ± 0.10 g/m s Pa).