If too little essential oil is released, it should be inefficacious
whereas if released excessively, it should cause unpleasant odor.
Thus, controlling the release rate by microencapsulation could
be the best way. Sustained release is a one mode of controlled
release system. It can maintain constant concentration of active
compounds at target (Lakkis 2007). In initial stage, the amount of
released oil is large and then slowly become constant (Chang and
Dobashi 2003; Chang and others 2006). Release rate of encapsulated
volatile essential oils depends on component materials of
microcapsules (encapsulated material, emulsifier, and coating material)
and various environment conditions such as temperature,
pH, and humidity.