WATER ACTIVITY RESTRICTION BY APPLICATION OF ESSENTIALS OILS

The antimicrobial activity of essential oils (EO) is mainly connected to the restriction of water distribution in reticular porous systems of bioactive matters, but the whole process is more complex. The reversibility of the EO desorption process in the water vapour environment of porous lignocellulosic materials, such as paper, is mainly controlled by the relative humidity (RH) of the atmosphere. At low RH, the reversibility is low in comparison with that at high RH. The reason of this behaviour is due to different diffusivity of penetrating water molecules at low RH and high RH, thus water diffusivity at low RH is higher and that at high RH is lower than EO diffusivity. During EO desorption process at low RH, e.g. of 49%, non-condensed water molecules spread rapidly through a porous material and the EO molecules do not have the time to escape from the non-uniform pores of lignocellulosic material. In contrast, the desorption process at high RH is more reversible.