Novel Soy Protein Isolate Films Incorporated with Phage CAM-21 Show Strong Antimicrobial Effects Against E. coli O157:H7

Due to their specificity, bacteriophages are becoming more widely used as antibacterial agents in the food industry. However, their effectiveness in food is often compromised by food components that can lead to a loss of their biological activity. In this study, soy protein isolate (SPI)-based packaging films incorporated with Escherichia phage CAM-21 were developed using a solution casting method. CAM-21 was relatively stable at pH 3-11 and temperatures up to 55 °C after 1 h of incubation. It remained active on the surface of raw beef, ground beef, and baby spinach after 36 h at 4 °C. The distribution of CAM-21 in the films was uniform, and its incorporation did not affect the film microstructure. No significant impact on the color, water vapor permeability, opacity, and mechanical properties of the films was observed. The antimicrobial activity of CAM-21-incorporated films was significantly enhanced in beef products inoculated with E. coli O157:H7. CAM-21-containing films significantly decreased the number of bacteria on raw beef samples by up to 1.5 and 2.0 log CFU/g after 3 and 5 days of refrigerated storage, respectively. These findings suggest that SPI films containing Escherichia phage CAM-21 have potential as antimicrobial packaging materials for preserving meat products.