*2.7. Naturally Occurring Microorganisms*

Each sample treated with chitosan EC containing cinnamon oil underwent microbiological analysis after 0, 4, 8, 12, and 16 days of storage. For the analysis, potato cubes were disrupted in a sterile blender containing 90 mL of 0.1% peptone water.

Suspensions of 0.1 mL from the potato cubes were cultured and counted on plate count agar (PCA) for total plate counts at 37 ◦C for 48 h, on potato dextrose agar (PDA) at 28 ◦C for 48–96 h for yeast and mould counts, on violet-red bile dextrose agar (VRBDA) at 37 ◦C for 24 h for total coliform counts, and on Lactobacilli MRS agar at 37 ◦C for 48 h for *Lactobacillus* counts [41,42]. All culturing media were purchased from Qingdao Hopebio Giotechnology Co., Ltd. (Qingdao, China).

### *2.8. Inoculation and Analysis of Listeria monocytogenes*

The potatoes were cut into cubes (approximately 10 g per cube) and uniformly inoculated in petri dishes. The entire top surface of the potato cubes was inoculated with suspensions of LM (8.84 log cfu/mL, 500 μL each cube) for a challenge study. In a biosafety cabinet, the samples were air-dried at 25 ◦C for 1 h. Then, the samples were coated with EC or EC containing cinnamon oil as previously described. The control group consisted of fresh-cut potatoes without a coating. Each potato cube was placed in a blender bag and stored at 4 ◦C for 16 days. A triplicate of each experiment was conducted, with samples being analysed every 4 days for 16 days. The population of LM inoculated into fresh-cut potatoes was counted on an Oxford agar base (Qingdao Hopebio Giotechnology Ltd. Company, Qingdao, China). All the plates were incubated at 37 ◦C for 24 h. The number of microorganisms is expressed as log cfu/g [43].

### *2.9. Statistical Analysis*

All experiments were performed in triplicate, and the data are presented as mean ± standard deviation. SPSS software was used to analyse the data (Version 14.0; SPSS, Chicago, IL, USA). The significance of the differences between variables was tested using one-way

ANOVA (between groups) and repeated-measures ANOVA (within group). The means were compared using Duncan's multiple range test. The statistical significance was determined at *p* < 0.05.
