## 3 Impact of Cold Plasma on Packaging Properties
### Antimicrobial Properties  
A novel cold plasma technique is applied to modify polymer surface attributes, the decontamination of packaging surfaces and food processing instruments, and to enhance the safety level of several food products [52, 114]. The active packaging films loaded with bioactive compounds like essential oils, peptides, or functional components when exposed to cold plasma show higher antimicrobial activity. [PERSON], [PERSON] [45] prepared active packaging film from cold plasma treated low-density polyethylene (LDPE) coated with carboxymethyl cellulose (CMC) or collagen (COL) containing cinnaldehyde (CMAL). The application of cold plasma enhanced the attachments between the LDPE and CMC/CMAL or COL/CMAL and showed strong antibacterial activity against _S. aureus_ and _E. coli_. The composite film LDPE/COL/CMAL demonstrated a strong antimicrobial effect against both these bacteria when compared to LDPE/CMC/CMAL due to the COL's higher retention capability. Further, the LDPE/COL films containing 0, 2.0, 4.0, 6.0, and 8.0% CMAL were used for packaging tilapia fillets and stored for 14 days. The total plate count (TPC) in the fish decreased with the increase in the CMAL concentration and the LDPE/COL film containing 6.0 and 8.0% CMAL enhanced the shelf life of fillet by at least three days. Also, the antimicrobial efficacy of the prepared LDPE/COL/CMAL film was tested against _V. parahaemolyticus_ in the packaged tilapia fillets stored at refrigerated temperatures (4 \({}^{\circ}\)C) and reported that the bacterial population at the end of the storage period was found to decrease by 1.27-1.92 log CFU/g for the film loaded with 6.0 and 8.0% CMAL as compared to the control film. The reduction in the microbial count can be attributed to the antimicrobial effect of CMAL during the storage period [45]. Similarly, plasma-treated polypropylene (PP) films coated with carboxymethyl cellulose (CMC) loaded with Zataria multiflora essential oil (ZEO) and showed the antimicrobial activity against Gram-positive (_S. aureus_) and Gram-negative (_E.coli_, _S. typhimurium_, and _P. aeruginosa_) bacteria [43]. As shown in Figure 61 the zone of inhibition increased with the increase in the concentration of ZEO. The antimicrobial activity of the PP/CMC/ZEO is higher when compared to the CMC/ZEO film [115] and this can be attributed to the PP layer that acts as a barrier against the loss of ZEO. The attachment between PP and CMC/ZEO is facilitated by plasma treatment [43]. Such antimicrobial activity on _S. aureus_, _B. subtilis_, and _E. coli_ was also reported for polyethylene terephthalate (PET)/polypropylene (PP) film assembled with chitosan loaded with sodium benzoate (1.0-5.0%), potassium sorbate (1.0-5.0%), calcium propionate (1.0-5.0%) and \(\varepsilon\)-poly-lysine (0.2-1.0%). All the plasma assembled films showed strong antimicrobial activity [44]. Although cold plasma treatment had no direct impact on the enhancement of antimicrobial activity, it increases adhesion between different layers and thereby protects antimicrobial components from loss resulting in higher antimicrobial activity. It is observed that plasma treatment facilitates the coating of functional components on the polymer layer and thereby increases antimicrobial efficacy. For instance, [PERSON], [PERSON] [116] prepared gallic acid (GA) coated polyethylene (PE) film applying plasma treatment (30 W for 60 s). The PE/GA active film reduced the growth of _E.coli_ and _S. aureus_ by 0.5-1.1 log reduction at a concentration above 1.0%. Such antimicrobial activity was also reported for plasma-treated polylactic acid (PLA) film coated with nisin where the active film showed a log reduction of 3.23 against _Listeria monocytogenes_, whereas pristine PLA film could not inhibit its growth. It was observed that with the increase in plasma treatment time (0-60 s) the microbial reduction increased and this could be ascribed to the content of nisin absorbed on the surface of the PLA.