Antimicrobial, physical and mechanical properties of kudzu starch–chitosan composite films as a function of acid solvent types

Kudzu starch–chitosan composite films were prepared by combining 2% (w/v) gelatinized kudzu starch and 2% (w/v) chitosan solution together. Effects of acids (acetic acid, lactic acid and malic acid) to dissolve chitosan on properties of the composite films were investigated. Fourier-transform infrared spectra showed that kudzu starch and chitosan could form miscible films. X-ray diffraction data indicated that the crystalline of each single component was suppressed after film forming process. The composite film using malic acid as solvent showed the best antimicrobial activity against Escherichia coli and Staphylococcus aureus, which may be due to the highest amount of dissolved amino group, the lowest water sorption ability and the best water barrier property. The film chose acetic acid as solvent presented the strongest mechanical property, the smallest solubility, the lightest yellowness and color. The film made from lactic acid solution displayed the greatest flexible property demonstrated by the maximum elongation.