Stability of Egg White Lysozyme in Combination with Other Antimicrobial Substances

The effects of pH, ionic strength (I), and selected antimicrobial substances on the lytic activity of egg white lysozyme over an extended storage period of 30 d were studied by observing the rate of clearing of a cell suspension of Micrococcus lysodeikticus . During prolonged storage, lysozyme activity remained relatively stable at pH 7 and ionic strength <0.10, whereas lower activity (P < 0.05) was observed at pH 9 and ionic strength >0.14. Lysozyme activity was highly stable (i.e., maintained over 90% of lytic activity from day 1 to day 30) in solutions of 1.0% sodium chloride, 100 ppm sodium nitrite, 4.0% ethanol, and 100 ppm butylated hydroxytoluene. Lysozyme activity also was stable (i.e., retained over 80% of lytic activity) in solutions of 0.1% sodium benzoate and 100 ppm butylated hydroxyanisol. The lysozyme activity was relatively stable (i.e., retained over 70% of lytic activity) in Solutions of 0.3% calcium propionate, 0.1% potassium sorbate, and 0.1% propyl paraben. About half (50%) of the lysozyme activity was retained in solution of 0.5% EDTA. Activity was lost when lysozyme was combined with 0.5% lactic acid, 4% acetic acid, and 100 ppm chlorine water.