74 Novel food packaging techniques Innoculum level PS-PEG-Peptide 5505.56.06.57.0 ph Fig. 5.3 Antimicrobial activity of a small synthetic peptide against E coli 0157: H7 in 0. IM citrate buffer from pH 3.5 to 7.0. Activity is shown for the native peptide( ) and peptide attached to a PS surface through a PEG spacer(). Equivalent peptide concentrations were used in each determination. Adapted from Appendini(1999) Mabrouk. 1997: Panza et al. 1997: Veronese. 2001: Yang et al. 1995a: Yang et al., 1995b: Zaks and Klibanov, 1984). This enhanced stability to organic solvents is useful in allowing a broader range of solvents and chemicals to be used in casting, cleaning/sterilising or treating polymer films prior to package filling without damaging the functional characteristics of immobilised bioactive constituents The long-term stability of immobilised peptides and proteins is generally enhanced compared to the native compounds(Katchalski-Katzir, 1993; Panza et al, 1997). The improved stability will help ensure the activity of bioactive packaging is retained for the shelf-life of the packaged food product. Long-term stability is also important in ensuring adequate shelf-life of the NMBP packages before filling, packaging materials are often warehoused for extended periods prior to use; any modifications need to remain active after storage The second technical benefit is concentration of the activity at a specific locus within the package and/or the food. This allows the activity to be concentrated where it will be most effective. For many minimally processed food products, such as fresh meat and fresh-cut fruit and vegetables, the majority of contaminating bacteria are located on the surface of the product( Collins-Thompson and Cheng An, 2000, Hotchkiss, 1995). Concentrating antimicrobials on the surface of the product, as occurs with antimicrobial packaging, allows minimal amounts of the(Mabrouk, 1997; Panza et al., 1997; Veronese, 2001; Yang et al., 1995a; Yang et al., 1995b; Zaks and Klibanov, 1984). This enhanced stability to organic solvents is useful in allowing a broader range of solvents and chemicals to be used in casting, cleaning/sterilising or treating polymer films prior to package filling without damaging the functional characteristics of immobilised bioactive constituents. The long-term stability of immobilised peptides and proteins is generally enhanced compared to the native compounds (Katchalski-Katzir, 1993; Panza et al., 1997). The improved stability will help ensure the activity of bioactive packaging is retained for the shelf-life of the packaged food product. Long-term stability is also important in ensuring adequate shelf-life of the NMBP packages before filling; packaging materials are often warehoused for extended periods prior to use; any modifications need to remain active after storage. The second technical benefit is concentration of the activity at a specific locus within the package and/or the food. This allows the activity to be concentrated where it will be most effective. For many minimally processed food products, such as fresh meat and fresh-cut fruit and vegetables, the majority of contaminating bacteria are located on the surface of the product (Collins-Thompson and Cheng￾An, 2000; Hotchkiss, 1995). Concentrating antimicrobials on the surface of the product, as occurs with antimicrobial packaging, allows minimal amounts of the Fig. 5.3 Antimicrobial activity of a small synthetic peptide against E.coli 0157:H7 in 0.1M citrate buffer from pH 3.5 to 7.0. Activity is shown for the native peptide ( ) and peptide attached to a PS surface through a PEG spacer ( ). Equivalent peptide concentrations were used in each determination. Adapted from Appendini (1999). 74 Novel food packaging techniques