RESUMO
Combinations of ethylenediaminetetraacetic acid (EDTA) or apo-lactoferrin (Apo-Lf) and lysozyme were evaluated for their antimicrobial effectiveness in ultra-high temperature pasteurized milk against Pseudomonas fluorescens , Salmonella typhimurium , Escherichia coli O157:H7, and Listeria monocytogenes . Neither P. fluorescens nor S. typhimurium growth was influenced by EDTA, Apo-Lf or lysozyme alone or in combinations. Escherichia coli O157:H7 was inhibited by EDTA alone, but no increase in antimicrobial effectiveness was noted in the presence of lysozyme. In contrast, EDTA and lysozyme had a significant interactive antimicrobial effect against L. monocytogenes . Apo-Lf, at concentrations up to 2.5 mg/ml, displayed similar inhibition patterns with lysozyme against the E. coli O157:H7 and L. monocytogenes however, the magnitude of inhibition was much less and of little practical significance. When evaluated over time, EDTA (1.5-2.5 mg/ml)-lysozyme (150 µg/ml) slowed growth of E. coli and was bactericidal to L monocytogenes . Apo-lactoferrin (15 mg/ml)-lysozyme (150 µg/ml) had little practical effect on E. coli growth but did slow growth of L. monocytogenes .
RESUMO
The influence of bovine lactoferrin (LF) and Apo-LF on growth of Listeria monocytogenes in Ultra-High Temperature (UHT) 2% fat milk was determined. The effect of LF was dependent upon both the degree of iron saturation and concentration. Before iron removal, LF was found to be approximately 52% saturated with iron; and at 23 and 46 mg/ml LF, minimal growth inhibition of L. monocytogenes was observed. Following dialysis, Apo-LF iron saturation was reduced to approximately 18%. At 15 and 30 mg/ml Apo-LF, a bacteriostatic effect against L. monocytogenes was observed. Inhibition of growth associated with Apo-LF was abolished when ferric ammonium citrate was added to saturate the iron binding sites of the Apo-LF.
