You can consider absorbing of these material with TGA but on silica because chitosan has organic structure and the temperature degradation of it with Essential are the same.
But in the case of silica you should be consider the TGA of silica and the mixture of it with Esdential separately.
After 200 C in the case of mixture you can see a step combine exothermic peak related to degradation essential which there is not in pure silica.