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Antibacterial activity of pepsin-digested lactoferrin on foodborne pathogens in buffered broth systems and ultra-high temperature milk with EDTA

Murdock, C.A., Matthews, K.R.
Journal of applied microbiology 2002 v.93 no.5 pp. 850-856
EDTA (chelating agent), Escherichia coli O157, Gram-positive bacteria, Listeria monocytogenes, Salmonella Stanley, Staphylococcus aureus, UHT milk, UHT treatment, antibacterial properties, biopreservatives, food industry, food pathogens, glucose, hydrolysates, lactoferrin, milk, minimum inhibitory concentration, pH, pepsin, peptones, refrigeration, yeast extract
Aims: To evaluate the antimicrobial activity in peptone yeast extract glucose (PYG) broth and ultra-high temperature (UHT) milk of bovine lactoferrin hydrolysate (LFH) with pepsin against the foodborne pathogens Salmonella Stanley, Escherichia coli, Listeria monocytogenes and Staphylococcus aureus. Methods and Results: The LFH was suspended in PYG and the minimum inhibitory concentration for each pathogen determined. The LFH was also suspended in UHT milk adjusted to pH 4 or 7, samples incubated at 4 or 35 degrees C and the change in bacterial cell population determined. Experiments in UHT milk were conducted using L. monocytogenes and E. coli O157:H7. At pH 4 LFH reduced the population of E. coli O157:H7 and L. monocytogenes by approx. 2 log; however, only E. coli O157:H7 was inhibited in samples adjusted to pH 7. The addition of EDT A (10 mg ml-1) to UHT milk supplemented with LFH did not markedly influence the growth of E. coli O157:H7 or L. monocytogenes. Conclusions: The results suggest that, under low pH and refrigeration conditions, LFH can limit the growth or reduce the population of pathogenic bacteria in a dairy product. Significance and Impact of the Study: Natural preservatives that are active against Gram-negative and Gram-positive bacteria are desirable to the food industry. This study demonstrates that LFH is effective in a complex food system. Moreover, the LFH used was not purified, making its use by industry more attractive.