Microemulsions of cinnamon and orange oils as an antimicrobial delivery system for Salmonella biofilms on stainless steel

Essential oils (EOs) are natural antimicrobials that can be used to develop intervention strategies to inhibit pathogens, but EOs are lipophilic. Colloidal systems, such as microemulsions, are needed for food industry applications. This dissertation focused on the development and characterization of a microemulsion composed of cinnamon oil (CO, Cinnamomum zeylanicum) and orange oil (OO, Citrus sinensis) to be used against Salmonella Enteritidis H4267 biofilms formed on stainless steel disc surfaces. First, the antimicrobial activity of CO and OO against S. Enteritidis H4267, either used in combination or in a microemulsion system, was determined. CO had a greater antimicrobial effect on S. Enteritidis H4267 when used in combination with OO than when individually (p® 20, 1% and 5% CO-OO (9:1) were transparent, thermodynamically stable microemulsions that had bactericidal activity on S. Enteritidis H4267. The second objective investigated the biofilm forming ability of S. Enteritidis H4267 and determined a method to remove biofilms on stainless steel disc surfaces. S. Enteritidis H4267 was determined to produce curli and cellulose indicative of biofilm development, and biofilms were formed on stainless steel disc surfaces. Sonication in 0.1% (w/v) peptone water for 30 sec effectively dislodged biofilms from disc surfaces without causing extensive cell death. Biofilms were treated with microemulsions and emulsion controls for 5 minutes to determine the antimicrobial activity in the third objective. The 2% SL, 5% CO-OO (9:1) microemulsions displayed the greatest antimicrobial activity against biofilms. This study demonstrated that OO enhances the bactericidal activity of CO when in an oil or microemulsion system, and co-encapsulated oils in microemulsions could be developed for antimicrobial delivery systems. Further research into developing microemulsions with positively charged droplets and with greater microemulsion exposure time should be investigated