Effect of mild heat treatments on the antimicrobial activity of essential oils of Curcuma longa, Xylopia aethiopica, Zanthoxylum xanthoxyloides and Zanthoxylum leprieurii against Salmonella enteritidis

The antimicrobial activity of essential oils (EOs) from spices and medicinal plants or their constituents has gained increasing interest. However, studies on their use in combination with other antimicrobials or technologies are still scarce. In this paper, the survival of Salmonella enteritidis exposed to a combined effect of four EOs (from Xylopia aethiopica, Curcuma longa, Zanthoxylum leprieurii and Zanthoxylum xanthoxyloides) and mild heat treatments (55° and 60°C) were assessed. Salmonella enteritidis demonstrated a biphasic inactivation curve at 55°C in the absence of EOs, while in the presence of EOs the Weibull model was used. The combination of temperature and EOs reduced the treatment time needed to inactivate 7 log cfu/mL of S. enteritidis: this reduction ranged, with respect to the control, from 92.6% to 96.4% when the treatment was performed at 55°C, and from 20.5% to 27. 5% at 60°C. The efficiency of the interaction of the combination of EOs and mild thermal treatment is related to increased vapor pressure of EO constituents, which became more soluble in the membrane of stressed cells