In order to prolong the shelf life of freshwater fish at room temperature, an antibacterial coating consisting of ε-polylysine (ε-PL) and sodium bis (2-ethylhexyl) sulfosuccinate (AOT) was prepared by one-step electrostatic assembly, and its molecular structure, stability and antibacterial properties were studied. The effect of the antibacterial coating on preserving the quality of grass carp fillets was evaluated as well. The results showed that a stable ε-PL-AOT complex insoluble in water and soluble in ethanol was formed at pH 2, ε-PL concentration of 1.5 g/100 mL and AOT concentration of 3 g/100 mL. The complex at 2% in ethanol formed a stable coating on the surface of plastic wrap, which was effective against Escherichia coli and Staphylococcus aureus. The ε-PL-AOT antibacterial film had a higher antibacterial effect compared with ordinary commercial polyethylene (PE) film. After the ε-PL-AOT treated fish was kept at 37 ℃ for 24 h, the total number of bacterial colonies on the surface was 870 CFU/g, which meets the requirement of the Chinese national standard for the first freshness grade of meat products. The ε-PL-AOT composite coating has the advantages of simple preparation process, good stability and significant antibacterial effect and is promising for industrial production. The present study will hopefully promote the application of ε-PL-based coating in the preservation of freshwater fish products.

Foods are subject to deterioration caused by ice crystal formation and recrystallization during storage and transportation. At present, adding antifreeze is an effective means to delay the deterioration of frozen foods and maintain food quality. γ-Polyglutamic acid (γ-PGA) is an anionic polypeptide polymer whose molecular chain contains a large number of carboxyl groups connecting water molecules through hydrogen bonds, which can reduce water migration, inhibit the growth of ice crystals, and thus has excellent antifreeze effect. Additionally, γ-PGA has the advantages of low salt, low calorie, and promoting mineral absorption, and can better meet consumer demands for reduced sugar, reduced fat, reduced salt foods than traditional commercial antifreeze. Based on the current status of γ-PGA research, this paper reviews the basic structure and antifreeze mechanism of γ-PGA and its application in the food industry in order to provide a theoretical reference for the development and application of food-grade γ-PGA antifreeze in the food field.