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E. coli O157:H7 is one of the most important foodborne pathogens in the beef industry
and has resulted in a number of highly publicized and expensive recalls. Traditional
antimicrobial agents widely used in the beef processing plants include quaternary ammonium
compound, chlorine, acetic acid, and others. Many of these acidic and alkaline sanitizers are
corrosive, emit unpleasant odors, discolor surfaces, and are often vulnerable to harsh processing
conditions and abusive factors during transport and storage (high temperature, high pressure,
humidity), resulting in the loss of their antimicrobial properties due to decomposition or
sublimation of the antimicrobial agents.
<P> Novel inorganic antibacterial materials such as metal or metal oxides nanoparticles (NPs)
have received increasing attention in recent years because they are non-corrosive, odorless, and
stable under harsh processing conditions. Particularly, inorganic NPs made from metal oxides
with sizes less than 100 nm exhibit antimicrobial activities due to their special characteristics
such as small particle size and large surface area.
<P>With recent advances in film production and technology, there is growing interest in the
applications of novel antimicrobial films and coatings in microbial food safety. Yam (Dioscorea
alata) starch can form a transparent, colorless, odorless, and flexible film which is an excellent
oxygen and moisture barrier as a packaging material for food products. <P>
Objectives: The objectives of this study were to evaluate antimicrobial properties of novel inorganic
antimicrobial agents (zinc oxide nanoparticles (ZnO NPs) and calcium phosphate hydroxyapatite
(CaHA NPs)) against an important foodborne pathogen, E. coli O157:H7; study the mode of
action of NPs against bacteria and the development of bacterial biofilms on stainless steel; and
develop and use yam starch films containing antimicrobial NPs to inhibit the growth of E. coli
O157:H7 in beef products.
Findings: ZnO NPs showed strong antimicrobial activities with increasing inhibitory
effects on the growth of E. coli O157:H7 as the concentrations of ZnO NPs increased; while
CaHA NPs show mild antimicrobial activities against E. coli O157:H7. ZnO NPs could be used
to inhibit the development of E. coli O157:H7 biofilms on the surface of stainless steel and
incorporated into yam starch films to control the growth of E. coli O157:H7 on sirloin beef cuts.
Yam starch has long been used as a traditional medicine that provides great health benefits while
ZnO have excellent biocompatibility and bioactivity and are stable under harsh processing
conditions. Together, they could provide novel intervention strategies for pathogen control for
beef products.