Application of Thyme-Orange Essential Oils to Reduce Salmonella and Campylobacter on Processed Broiler Chicken

Poultry meat is often linked to human illness outbreaks caused by Salmonella and Campylobacter. Natural antimicrobial interventions are gaining interest among consumers. Essential oils are plant-derived compounds that have a potential to be used as natural antimicrobials in food. Preliminary studies were conducted to screen the oils of thyme, orange, rosemary, clove, and thyme-orange oil combination (TOC) against Salmonella and Campylobacter using disc diffusion and macro broth dilution techniques. A concentration of 0.14% v/v of TOC was found to be effective against both pathogens. Two separate experiments were conducted to evaluate the effect of TOC on reducing S. enteritidis (SE) and C. coli numbers on inoculated broiler breast fillets and on whole wings dipped or marinated with TOC. Three independent trials were conducted for the dip study and two independent trials for the marination study. In the dip study, each part was dipped in a mixture of inoculum containing SE and C. coli and then subjected to a dip treatment in one of four solutions: 0.25% TOC; 0.5% TOC; DMSO (Dimethyl sulfoxide used as emulsifier for the essential oils) or control (only water) for one minute. In the marination study, 12 breast fillets or wings were vacuum tumbled for 20 min with the marination solution either with or without 0.5% TOC. Results from the three replicate trials of the dip study showed that 0.5% TOC significantly reduced (P < 0.05) SE by 2.4 and 4.1 log cfu/mL on breast fillets and whole wings, respectively, and C. coli by 4.5 log cfu/mL on breast fillets. Although 0.5% TOC resulted in 4.80 log cfu/mL reduction of C. coli on the wings, compared to 2.2 logs for control, results were not significant due to variation between different trials. TOC at 0.25% level performed similar to the DMSO and control treatments. Results from the two replicate trials of the marination study indicated that TOC at 0.5% in the marinade solution applied by vacuum tumbling significantly reduced (P < 0.05) numbers of viable SE on broiler breast fillets by 2.6 and 2.3 log10 cfu/ml, respectively, and C. coli on whole wings by 3.6 and 3.1 log10 cfu/ml The un-inoculated chicken parts were positive after marination with inoculated parts, indicating cross-contamination. However, the numbers of bacterial cells recovered from the TOC-treated samples were significantly lower (P < 0.05) than the numbers recovered from the untreated samples. A third experiment was conducted to evaluate the effect of 0.5% TOC-containing marinade on the shelf life of broiler breast fillets and whole wings. The total aerobic and facultative mesophiles (TAM) occurring naturally on these products during refrigerated storage for 14 d (at 1, 7, 10, and 14 d) were enumerated. One set of duplicate plates were incubated at 35°C and another set at room temperature (20--25°C) for 48h. TOC marinade was able to significantly (P < 0.05) reduce TAM numbers on the breast fillets on days 1, 7 and 10 compared to the controls, with a log reduction of 0.3, 0.9--1.4, and 0.7--1.1 on d 1, 7, and 10, respectively, at both incubation temperatures. The difference in TAM between the treated and untreated whole wings was not significant.;In conclusion, 0.5% TOC applied on broiler breast fillets and whole wings by dip or marination can be successfully used as natural antimicrobial to reduce Salmonella and Campylobacter numbers on the products. Marination with 0.5% TOC can also be used to reduce TAM on skinless breast fillets; however, higher concentration may be required for skin-on poultry products.