Physicochemical characteristics, antibacterial effect and application in beef preservation of a novel...

Nisin, a natural food preservative, is widely used in food preservation. However, it has the drawbacks of poor antibacterial stability and a restricted antibacterial spectrum. In this study, a novel ternary complex of nisin/rhamnolipid (RL)/chitosan (CS) was prepared based on complex coacervation, and its antibacterial effects and application in beef preservation was investigated. The results demonstrate that the particle size of the complex was uniform within 682.5-744.4 nm under pH 2-8. At the pH_opt (pH = 4.5), the encapsulation efficiency of nisin was 59.17% and the loading capacity was 29.58%. In vitro release experiments showed the total release rate of nisin in nisin/RL/CS complex was only 39.55% with good sustained release performance at 72 h. Moreover, nisin/RL/CS complex had broad-spectrum antibacterial activity, where the minimum inhibitory concentration and minimum bactericidal concentration against Staphylococcus aureus were 0.5 and 1.0 mg/mL, and 0.25 and 0.5 mg/mL for Escherichia coli, respectively. Further beef preservation experiments confirmed that the nisin/RL/CS complex could effectively inhibit the proliferation of microorganisms on the surface of beef, reduce the rate of lipid oxidation, maintain pH and texture quality, and significantly prolong the shelf life. This study provides theoretical and technical support for the development of nisin-based broad-spectrum antibacterial preservatives and their application in food preservation.