Incorporation of partially purified hen egg white lysozyme into zein films for antimicrobial food packaging

Lysozyme, partially puriWed from hen egg white by precipitation of non-enzyme protein with ethanol and lyophilized after dialysis, was incorporated into zein Wlms. The recovery and speciWc activity of the enzyme after partial puriWcation varied between 45% and 72% and 2173 and 3448 U/mg, whereas the activity of the lyophilized enzyme varied between 2900 and 3351 U/mg. The partially puriWed enzyme was very stable and lost almost no activity in lyophilized form or in zein Wlms stored at i18 and 4 °C for up to 8 and 4 months, respectively. During partial puriWcation and in zein Wlm preparation, ethanol treatment caused 123–137% and 132–315% activation of the enzyme, respectively. In zein Wlms incorporated with 187–1318 U/cm 2 (63–455g/cm 2 ) lysozyme, the release rates at 4 °C, changed between 7 and 29 U/cm 2 /min, increased at high lysozyme concentrations. Zein Wlms incorporated with partially puriWed lysozyme showed antimicrobial eVect on Bacillus subtilis and Lactobacillus plantarum. By the addition of disodium EDTA, the Wlms also became eVective on Escherichia coli. The results of this study showed that the partially puriWed lysozyme may be used in antimicrobial packaging to increase food safety.  2005 Elsevier Ltd. All rights reserved.