Listeria monocytogenes and Escherichia coli O157:H7 inhibition in vitro by liposome-encapsulated nisin and ethylene diaminetetraacetic acid

Encapsulation technologies that effectively reduce antimicrobial interaction with food components or protect antimicrobial compounds from food processing measures have the potential to improve the microbiological safety of ready-to-eat foods. Recent application of liposomes for the preservation of cheese has spurred research into their utility in other food matrices. To ascertain the feasibility of encapsulated antimicrobial for the control of Listeria monocytogenes and Escherichia coli O157:H7 growth in a model system, nisin (5.0 and 10.0 μg/mL) and the chelator ethylene diaminetetraacetic acid were entrapped in phospholipid liposomes. While phosphatidylcholine (PC) liposomes did not produce significant inhibition of target pathogens, PC/phosphatidylglycerol 8/2 and 6/4 (mol%) produced significant inhibition of pathogens. Near-complete inhibition of E. coli O157:H7 with liposomal antimicrobials at concentrations below those reported necessary for unencapsulated antimicrobial and chelator suggests that liposomes may represent a powerful technology for the encapsulation of antimicrobials and the control of foodborne pathogens. The activity of many antimicrobials is abolished in many food products for a variety of reasons. Interference and cross-reactions of the antimicrobial and various food constituents, such as protein and fat, are difficult to overcome and often require large amounts of antimicrobial in order to gain significant reductions in the pathogen load in a product. Loss of solubility of some antimicrobials based on pH or ionic strength will negatively affect the antimicrobial potential of a compound like nisin. Liposome encapsulation technologies, such as that reported here, may allow for the maintenance of antimicrobial activity by protecting the antimicrobial against cross-reactions with food components. Additionally, the liposome core represents a microenvironment which can be manipulated by the manufacturer in order to preserve optimal antimicrobial solubility and stability conditions until the time of release.