*2.1. Bacterial Strains and Preparation of Bacterial Inoculum*

*Salmonella typhimurium* (ST, CICC 21484), *Staphylococcus aureus* (SA, CICC 21600), *Listeria monocytogenes* (LM, CICC 21633), and *Escherichia coli* O157:H7 (EC O157:H7, CICC 21530) were obtained from China Center of Industrial Culture Collection (CICC, Beijing, China). LM was cultured in tryptic soy broth with yeast extract (TSB-YE) for 12 h at 37 ◦C. ST, EC O157:H7, and SA were cultured in tryptic soy broth (TSB) for 12 h at 37 °C. The suspension of LM was centrifuged at 2795× *g* for 5 min at 4 ◦C and washed with 0.1% (*w*/*v*) peptone water (Aobox Biotechnology, Beijing, China) three times. The suspension was diluted 1:10 with 0.1% (*w*/*v*) peptone water to obtain the proper inoculum. The bacterial counts are represented as log cfu/mL [31].
