Effect of Alternative Household Sanitizing Formulations Including: Tea Tree Oil, Borax, and Vinegar, to Inactivate Foodborne Pathogens on Food Contact Surfaces

Current trends indicate that American consumers are increasingly selecting products that they believe to be environmentally friendly or "natural." In the kitchen, this trend has been expressed through greater desire for using alternative or "green" sanitizers instead of bleach or other common chemical sanitizers. The purpose of this work was to evaluate the effectiveness of one suggested alternative, tea tree oil, as a food contact surface sanitizer. Three foodborne bacterial pathogens (Listeria monocytogenes N3-031 serotype 1/2a, Escherichia coli O157:H7 strain E009, and Salmonella Typhimurium ATCC 14028) were applied separately onto three different food contact surfaces (high density polyethylene, glass, and Formica® laminate). Tea tree oil (TTO), borax, and vinegar (5% acetic acid) were applied individually as well as in combination for a total of seven treatment solutions. In addition, household bleach (6.15% sodium hypochlorite), sterile reverse osmosis (RO) water, and no applied treatment were used as controls. Treatments were tested using an adaptation of the Environmental Protection Agency DIS/TSS-10 test method, whereby each contaminated surface was treated with 100 µl of test solution and held for 1 min followed by submersion in neutralizing buffer and microbiological plating. Samples (0.1 ml) were plated onto TSA and incubated at 35°C for 48 h prior to colony counting. Bleach reduced microbial populations significantly with greater than 5-log reduction reported for all surfaces (Formica® laminate, glass, and HDPE), against E. coli O157:H7, L. monocytogenes, and S. Typhimurium. TTO produced reductions between four and five logs for E. coli O157:H7, L. monocytogenes, and S. Typhimurium and was not statistically different from the vinegar treatment (P>0.05). All combination recipes, including the borax treatment, failed to produce reductions in microbial populations at levels considered to be appropriate for food contact surface sanitizers. Surface type did not play a significant role in the effectiveness of the treatment (P>0.05). Although TTO and vinegar did reduce pathogen populations on surfaces, reductions were not sufficient enough to be considered an equally effective alternative to household bleach.