Non-migratory bioactive polymers(NMBP)in food packaging &1 The activity of chitosan has been tested against a broad range of microorganisms by researchers in many different fields, including dentistry and pharmaceuticals (Ikinci et al, 2002), textiles(Takai et al., 2002)and food packaging(Oh et al, 2001; Paulk et al, 2002; Tanabe et al, 2002). In microbial growth broths, chitosan has been found effective against gram-positive and gram-negative bacteria, along with some moulds and yeasts(Oh et al., 2001 Tsai and Su, 1999, Tsai et al., 2002). The minimum inhibitory concentration varies with organism and increases as the chitosan degree of deacetylation decreases. Chitosan activity has also been tested in mayonnaise against Z. bailin and L. fructivorans(Oh et al, 2001). The addition of chitosan to the mayonnaise formulation increased the bacterial inhibition compared to the control mayonnaise, although bacteria numbers also decreased in the control. Higher concentrations of chitosan were required for a significant inhibitory effect in mayonnaise than in growth broth. Tsai and colleagues(2000)investigated the antimicrobial efficacy of chitosan in milk, although strict milk composition regulations and the significant solubility of chitosan in milk mean that this application is unlikely to be commercially viable. At this stage, it is important to note that most research on chitosan activity has been conducted in solution, not with chitosan films, so extrapolation to packaging applications is difficult Additionally, the high solubility of chitosan makes its use in liquid packaging applications unlikely, as it would dissolve into the food over time, violating the non-migratory principle far as pac carin uses go, chitosan activity has been investigated edible antimicrobial film for fish fillets (Tsai et al., 2002). The indigenous microflora of fish was inhibited by films formed from 0.5% and 1. 0% chitosan solutions. After ten days of storage, mesophilic and psychrotrophic bacteria were reduced compared to control samples. For both types of organism, counts were reduced by approximately 1 log. Additionally, volatile basic nitrogen evolution was decreased and pH increase was suppressed compared to the controls. Coliforms were inhibited throughout a 14-day storage trial, while Aeromonas and Vibrio species showed negligible initial inhibition but slower growth and decreased numbers during the second half of storage. Pseudomonas spp. were initially inhibited on the dipped fillets, but increased after five days to the same levels as the control fillets. Overall, chitosan appeared to be an effective antibacterial coating, it may be suitable for use as an antimicrobial edible film for processed fish products In another edible film application, the antimicrobial effect of edible 98% deacetylated chitosan films was investigated against Listeria spp. on agar media and cheese. Significant anti-listerial activity was found in an agar plate assay reductions of 5-8 log cycles were observed. The effect was also significant on the chitosan coated cheese samples. No viable cells were detected three and five days after dipping the cheese samples first in an inoculating solution of 10" cells/ ml and then in a chitosan film-forming solution. These results are promising for the application of chitosan edible films to help control pathogenic contamination on the surfaces of solid food products. Similarly, the antifungal properties ofThe activity of chitosan has been tested against a broad range of microorganisms by researchers in many different fields, including dentistry and pharmaceuticals (Ikinci et al., 2002), textiles (Takai et al., 2002) and food packaging (Oh et al., 2001; Paulk et al., 2002; Tanabe et al., 2002). In microbial growth broths, chitosan has been found effective against gram-positive and gram-negative bacteria, along with some moulds and yeasts (Oh et al., 2001; Tsai and Su, 1999; Tsai et al., 2002). The minimum inhibitory concentration varies with organism and increases as the chitosan degree of deacetylation decreases. Chitosan activity has also been tested in mayonnaise against Z. bailii and L. fructivorans (Oh et al., 2001). The addition of chitosan to the mayonnaise formulation increased the bacterial inhibition compared to the control mayonnaise, although bacteria numbers also decreased in the control. Higher concentrations of chitosan were required for a significant inhibitory effect in mayonnaise than in growth broth. Tsai and colleagues (2000) investigated the antimicrobial efficacy of chitosan in milk, although strict milk composition regulations and the significant solubility of chitosan in milk mean that this application is unlikely to be commercially viable. At this stage, it is important to note that most research on chitosan activity has been conducted in solution, not with chitosan films, so extrapolation to packaging applications is difficult. Additionally, the high solubility of chitosan makes its use in liquid packaging applications unlikely, as it would dissolve into the food over time, violating the non-migratory principle. As far as packaging uses go, chitosan activity has been investigated as an edible antimicrobial film for fish fillets (Tsai et al., 2002). The indigenous microflora of fish was inhibited by films formed from 0.5% and 1.0% chitosan solutions. After ten days of storage, mesophilic and psychrotrophic bacteria were reduced compared to control samples. For both types of organism, counts were reduced by approximately 1 log. Additionally, volatile basic nitrogen evolution was decreased and pH increase was suppressed compared to the controls. Coliforms were inhibited throughout a 14-day storage trial, while Aeromonas and Vibrio species showed negligible initial inhibition but slower growth and decreased numbers during the second half of storage. Pseudomonas spp. were initially inhibited on the dipped fillets, but increased after five days to the same levels as the control fillets. Overall, chitosan appeared to be an effective antibacterial coating; it may be suitable for use as an antimicrobial edible film for processed fish products. In another edible film application, the antimicrobial effect of edible 98% deacetylated chitosan films was investigated against Listeria spp. on agar media and cheese. Significant anti-listerial activity was found in an agar plate assay: reductions of 5–8 log cycles were observed. The effect was also significant on the chitosan coated cheese samples. No viable cells were detected three and five days after dipping the cheese samples first in an inoculating solution of 104 cells/ ml and then in a chitosan film-forming solution. These results are promising for the application of chitosan edible films to help control pathogenic contamination on the surfaces of solid food products. Similarly, the antifungal properties of Non-migratory bioactive polymers (NMBP) in food packaging 81