Critical analysis of microwave hydrodiffusion and gravity as a green tool for extraction of essential oils: Time to replace traditional distillation

Background: In the recent year's essential oils has found profound use in agriculture industry, food and beverage industry, flavor and fragrance industry, furniture industry and undoubtedly pharmaceutical industry and is currently an important entity for commerce and business around the globe. In this context a green extraction technology suitable for large scale extraction of essential oil with increased yield becomes the need of the hour. Scope and approach: This review article is an amalgamation of all research registered in Scopus till 2018 pertaining to extraction of essential oil using microwave hydrodiffusion and gravity. The technique is a solvent free extraction method based on puncturing of oil glands and subsequent drainage of oil by the action of gravity. The article critically analyzes the factors affecting extraction performance and takes detailed note on the quality of essential oil extracted using the proposed technique and its comparison with traditional methods. A work model has been proposed and key takeaways are presented as concentrate of the researches done so far on MHG. Key findings and conclusions: With the growing concerns on environmental issues and climate change it is highly important to switch to greener mode of operation for industrial sustainability. The key takeaways suggested shall serve as vital leads for researchers and act as statutory guidelines for method development and scale up. The article also intends to promote capacity building in this filed to popularize adoption of greener methods.