Effects of CaCl2, HCl, acetic acid or citric acid on dynamic mechanical performances and physicochemical properties of sodium alginate edible films

The effects of CaCl2, HCl, acetic acid or citric acid on dynamic mechanical performances and physicochemical properties of sodium alginate (SA) edible films are investigated. The results showed that the storage or loss modulus of the films were greater at 33 % relative humidity (RH) and decreased much slower with temperature (30–90 ℃) at 57 % or 75 % RH after different treatments, with their glass transition temperatures shifting higher. All the treatments improved the water resistance and mechanical properties of SA films. Specifically, CaCl2-treated films had the lowest solubility, and highest water contact angle and tensile strength. Acetic acid-treated films had the highest elongation at break. Citric acid-treated films had the lowest equilibrium moisture content and water vapor permeability. Film surface morphology kept dense and compact after various treatments. FT-IR spectra revealed that all the acid treatments increased hydrogen-bond interaction. This work provides new information for SA edible film modification.