## 3 Impact of Cold Plasma on Packaging Properties
### Antimicrobial Properties
This indicates that cold plasma treatment influences the absorption capacity of PLA film and thus the content of nisin thereby affecting the antimicrobial activity of the film [48]. The diffusion rate of antimicrobial compounds from the plasma-treated polymer matrices and its release rate can be a critical factor influencing the antimicrobial activity of the active films. [PERSON], [PERSON] [117] applied low-pressure aerosol-assisted plasma to prepare polycarbonate film coated with copper (organic-inorganic) and investigated the antimicrobial activity against (_P. fluorescens_ and _P. putida_). The authors reported a three-log reduction (from 108 to 105 CFU/mL) compared to the control polycarbonate film. The reduction in the microbial count was attributed to the release of Cu\({}^{2+}\) ions by coatings that penetrate the microbial cell resulting in their disruption [117]. Such results are consistent with other studies where [PERSON], [PERSON] [88] showed that DBD plasma treatment increased the diffusion rate of antimicrobial thym from zein matrix. This was ascribed to the etching effect that led to an increase in roughness and resulted in a decrease in the thickness [88]. [PERSON], [PERSON] [90] and [PERSON], [PERSON] [89] showed that plasma treatment enhanced the release of nisin from LDPE/nisin film and thus increased the microbial inhibition against _L. innocua_ as shown in Figure 6 II. Some studies demonstrated that plasma treatment had no significant effect on the inhibition of microbial growth. [PERSON], [PERSON] [81] showed that cold plasma had no significant effect on chitosan/ciprofloxacin hydrochloride antimicrobial film and further coating with zein had drastically reduced the release of ciprofloxacin hydrochloride resulting in reducing the antimicrobial effect. This could be attributed to the fact that plasma treatment may have enhanced intermolecular interaction (crosslinking) leading to firm adhesion between chitosan and zein, resulting in the increase in a barrier for the diffusion of ciprofloxacin hydrochloride [81]. Such reduction in the release of the antimicrobial compound due to cross-linking was also reported for sodium tripolymbosphate crossed linked chitosan film loaded with ciprofloxacin [118]. Overall, the impact of plasma treatment on the antimicrobial activity of the film containing functional compounds is critical. The strategic combination of polymers with antimicrobial substances treated with cold plasma can be a potential approach when preparing antimicrobial packaging materials suitable for food packaging applications. Figure 6: **(I)** Antimicrobial activity of cold plasma treated PP/CMC/ZEO film against _S. aureus_: **(a)** PP/CMC/1.0% ZEO: 9.24 \(\pm\) 0.1 mm; **(b)** PP/CMC/4.0% ZEO: 30.26 \(\pm\) 0.4 mm; against _E. coli_; **(c)** PP/CMC/1.0% ZEO: 8.71 \(\pm\) 0.0 mm; **(d)** PP/CMC/4.0% ZEO: 26.73 \(\pm\) 0.1 mm; against _S. typhimurium_; **(e)** PP/CMC/1.0% ZEO: 8.82 \(\pm\) 0.2 mm; **(f)** PP/CMC/4.0% ZEO: 24.94 \(\pm\) 0.1 mm. Reprinted with permission from Ref. [81], Elsevier, 2022; **(II)** antibacterial activity of plasma treated LDPE against _L. innocua_: **(a)** LDPE/nisin; **(b)** N\({}_{2}\) plasma treated LDPE/nisin; **(c)** acrylic acid treated LDPE/nisin; and **(d)** Ar/O\({}_{2}\) plasma treated LDPE/nisin. Reprinted with permission from Ref. [81], Elsevier, 2022.