Effects of acid solvents on properties of kudzu starch/chitosan composite edible films

In order to evaluate the effects of acid solvents on antibacterial, physical and mechanical properties of composite edible films, the kudzu starch-chitosan composite film-forming solutions were prepared by tape casting with mass fraction 1% of acetic acid, lactic acid and malic acid as solvents. For the film, 0.5g/L of ascorbic acid as the active additive, 0.6g/L of glycerol as the plasticizer and 0.1g/L of Tween 20 as the surfactant were added into the solutions. It was found that there was certain surface activity for film-forming solution, and acid solvent had no obvious impact on the surface tension of each solution. The types of acid solvents had obvious impact on the performance of composite films, in which the film with acetic-acid solvent had best mechanic strength, the mean tensile strength and puncture strength were 5.73 MPa and 8.63 N, respectively, and its solubility was the smallest, which was about 34%. The film made from lactic acid solution displayed the greatest flexible property, which mean elongation and puncture distance were 71.5% and 6.05 mm, respectively. The composite film using malic acid as solvent showed the best antibacterial activity against escherichia coli and staphylococcus aureus, which were 98.9% and 81.2%, respectively, and its water-tightness was best, which the water vapor permibility was 4.82×10-11 g/(m·s·Pa). So different acid solvents can be selected to prepare films according to different requirements. The study results can provide theoretical references for the application of edible films.