Freeze–thaw enhanced stability and mechanical strength of polysaccharide‐based sodium alginate/hyaluronic acid films

Abstract An edible polysaccharide film with high tensile strength and biodegradability was prepared by freeze–thaw treatment with sodium alginate (SA) and hyaluronic acid (HA) and cross‐linking with calcium lactate. The SA/HA ratio, the calcium concentration, the number of freeze–thaw cycles, and the calcification time all have significant effects on the tensile strength of SA/HA films. An increase in tensile strength was obtained due to the reaction of 3% calcium lactate with 60% SA. Compared with the control group, the tensile strength of the SA/HA films developed in this study increased by 214% from 3.188 to 10.02 MPa. The compatibility of films was evaluated by Fourier transform infrared spectroscopy; the absorption peaks of SA and sodium hyaluronate had shifted to a wavelength of 3,403 ~ 3,411 cm −1 after freeze–thaw treatment, and a strong interaction occurred at a wavelength of 1,328 cm −1 . In addition, the swelling and solubility of the SA/HA film decreased by half during the freeze–thaw period. Further, scanning electron microscopy showed that the cross sections of the films were uniform and compact after two freeze–thaw treatments. SA/HA films that exhibited increased tensile strength and that had the potential to overcome the poor water vapor barrier problems traditionally experienced with these films were developed in this study.