Abstract
Chitosan nanoparticles (CsNp) at varying concentrations (0.5, 1%, and 2%) were tested for their antibacterial properties on the shelf life and sensory characteristics (taste, texture, colour, odour, and overall acceptability) of fish fillets while they were being chilled. Additionally, three studies were conducted to examine the antibacterial properties of CsNp on fish fillets contaminated with Salmonella enteritidis and Staph aureus, two food poisoning pathogens, during chilling storage. Dipping in varying concentrations of CsNp (0.5, 1%, and 2%), according to microbial study, significantly reduces bacterial growth over a 12-day period at 4ºC and prolongs the shelf life of fish fillets more than untreated samples. The overall bacterial count should not be more than 1×106 cfu/g (6 log10 cfu/g) in fish muscle according to (EOS No. 3494 / 2020). At day 5, APC count for the control samples was 5.36±0.45, while at day 7 was 6.72±0.04 which was over the maximum recommended limit and indicated that the untreated control fish fillets samples had a shelf-life of less than 5 days. The treated samples exhibited a delayed growth for APC till day 12, and a larger decreasing impact in APC was noted in group treated with CsNp 2% where it was within the permissible limit (4.92±0.24), this indicates that under chilled storage, the fish fillets samples' shelf life was extended to 12 days. While the APC values for the samples of fish fillets treated with CsNp1% suitable for eating until day nine of storage, while the samples treated with CsNp 0.5%, remained valid until day seven of storage. Both Salmonella enteritidis and Staph. aureus, which are food-borne pathogens, are inhibited by CsNp in fish fillets; however, the protective effect against Salmonella enteritidis is dose-dependent. CsNp 2% was found to have the strongest effect on the two microorganisms examined, followed by CsNp 1% and CsNp 0.5%. Fish fillets' shelf life can be increased and microbiological proliferation inhibited by these CsNp. The results of this study demonstrated that dipping fish fillets in a solution of CsNp could be a potential technique for managing unwanted microbiological and sensory changes in the fish fillet sector.

Key words: Chitosan Nanoparticles, fish fillets, Salmonella enteritidis, Staph. aureus, Antimicrobial activities and Shelf life.