Abstract In this study, a composite coating (CS-PUL-A) which based on chitosan-pullulan and contained antibacterial agent (0.3% lysozyme and 0.18% ε-polylysine hydrochloride) was prepared. The amount of each antibacterial agent was determined by analyzing the effects of agent’s additive amount on physicochemical properties of the composite coating. Then, property differences were compared between CS-PUL-A and composite coating without antibacterial agent (CS-PUL). The results showed that antibacterial agents improved toughness and barrier properties of gas and water of the composite coating, but had little effect on tensile strength and light transmission. Further, antibacterial activity of the composite coatings on Pseudomonas fluorescens which is one of specific spoilage organisms was analyzed. The results showed that CS-PUL-A had stronger antibacterial activity than CS-PUL. Furthermore, CS-PUL-A possessed bactericidal activity at the initial cultured 12h. Compared with CS-PUL, CS-PUL-A led to more leakage of nucleotide and electrolytes and higher conductivity of samples, indicated that CS-PUL-A increased the damage of cell membrane integrity and permeability. Treatment with coatings also reduced activity of alkaline phosphatase in samples. SDS-PAGE electrophoresis indicated that CS-PUL mainly affected proteins with small molecular weight, while CS-PUL-A affected proteins with small and also large molecular weight. Scanning electron microscopy further confirmed the damage of bacteria caused by CS-PUL-A. In summary, CS-PUL-A exerted batter physicochemical properties and antibacterial properties than CS-PUL, which was expected to be used in food preservation.
Received: 17 October 2018
Published: 25 October 2019