**2. Methods of application of essential oils**

## **2.1 Direct contact**

This method of application consists of adding the EO either in powder or liquid form, directly into food systems. However, their application is limited, due to the strong aroma and taste that EOs impart to food products, especially at concentrations at wich they can be considered antimicrobial agents. Therefore, very few EOs have the chemical (qualitative and quantitative composition, required concentration), physical (solubility, volatility), and sensory (strong flavors or aromas) characteristics required to be applied by direct contact [8].

*In-vitro* and *in-vivo* studies have reported that the antimicrobial effect of EOs is due to the presence of different active compounds that act synergistically [9, 10]. However, concentrations obtained under *in-vitro* conditions are not always effective when applied to foods [9], so the concentration of EO needed to observe the same effect could increase and thus affect acceptable sensory levels [8].
