Outbreaks of E. coli O157 infection, primarily transmitted through meat products, have increased in recent years. There are many methods of preserving food, but strong consumer demands currently seek effective but natural preservatives. One example of such a preservative is chitosan (Ch). Although shown to possess antimicrobial properties, the exact antimicrobial action of chitosan and its derivatives under different conditions remains unclear. Additionally, little research has been done on applications of chitosan as a packaging material and its optimization as an agent for food preservation and enhancing food safety. This was the focus of this PhD study. In the first experiment, the concentration of chitosan in solution and the pH values of its solvent were manipulated. Results showed that lower pH values exerted a stronger bactericidal effect against E. coli O157 under low chitosan concentration, with higher concentrations showing a stronger effect at more neutral pH. Chitosan only played a minor role in inhibition of the test pathogen, whilst pH exerted the predominant bactericidal influence. Further studies investigated chitosan-arginine (Ch-arg), a water-soluble derivative of chitosan. The second experiment showed that, when applied to meat juice, Ch-arg significantly reduced pathogen cell count and metabolic activity in a dosedependent manner, with greater inhibition at higher concentrations, and suppression of general food spoilage bacteria. Experiment three evaluated whether the age of pathogenic E. coli O157 cells altered the effectiveness of Ch-arg in meat juice. It was found that Charg was most bioactive against cells in the lag and exponential phases, significantly decreasing cell activity and density. In comparison, a reduced, although still significant, inhibitory effect was observed in the stationary phase. The final experiment investigated the use of cellulose chitosan arginine film (Ch-arg) as an antimicrobial additive to film packaging. High concentration of Ch-arg within film had a significant effect on cell count of E. coli O157 in chicken juice, but not in beef juice. Taken together, these studies suggest that Ch-arg may offer potential for limiting the growth of spoilage and pathogenic bacteria in food; however, further research is needed to establish the practicality and costs relative to other measures that are available to the food industry.