Olá Jackline. Podes encontrar muitas referências no lattes de uma colega de trabalho (http://lattes.cnpq.br/0820396530673217). Ela trabalha com óleos essenciais.

I don't have experience in the area but I can tell you confidently that the Journal of Essential Oil Research will be a great place to search for references in methodology. See if your university has access...

http://www.tandfonline.com/toc/tjeo20/current#.U_9yUqO5LKc

please refer

http://agritech.tnau.ac.in/horticulture/extraction_methods_natural_essential_oil.pdf

http://www.naha.org/explore-aromatherapy/about-aromatherapy/how-are-essential-oils-extracted

http://www.experience-essential-oils.com/methods-of-extracting-essential-oils.html