Effectiveness of bacteriophage JN01 incorporated in gelatin film with protocatechuic acid on biocontrol of Escherichia coli O157:H7 in beef

A new gelatin-protocatechuic acid (PCA) film with Escherichia coli O157:H7 phage JN01 was developed and characterised. After incorporated with JN01, swelling value, water vapour permeability, water solubility and elongation at break of gelatin-PCA film were not significantly different. The addition of JN01 increased b value and transparency of film, while it decreased L value, a value and tensile strength of film. Moreover, the gelatin-PCA-JN01 film presented antioxidant activity of 60.07%. Furthermore, JN01 could be steadily released from gelatin-JN01 and gelatin-PCA-JN01 films in aqueous solution, and their release rates were 7.56% and 0.12% after 11 h, respectively. The microstructure analysis showed that JN01 particles were clustered and uniformly distributed in film, and the aggregation would be attenuated in the presence of PCA. Meanwhile, E. coli O157:H7 counts were 1.13 log(10)CFU mL(-1) and 0.45 log(10)CFU mL(-1) lower in gelatin-JN01 and gelatin-PCA-JN01 films compared with pure gelatin film in vitro at 4 degrees C for 24 h, respectively. After stored at 4 degrees C for 7 days, Escherichia coli O157:H7 counts were 1.00 log(10)CFU g(-1) and 0.80 log(10)CFU g(-1) lower in beef packed with these two gelatin films, compared with beef without gelatin film, respectively. In conclusion, the developed gelatin-PCA-JN01 film has potential application in food preservation.