Breakthroughs in extraction and encapsulation of volatile oil and essential oil for superior functionalities

Volatile oils (also called essential oils (EO) in some studies) are rich in terpenoids, alcohols and other bioactive components, and are widely used in medicine, food, cosmetics and agriculture. However, their high volatility, low water solubility and photo-thermal sensitivity have greatly restricted practical applications. This review systematically analyzed nearly 200 related literatures, and clarified that Rutaceae, Labiatae and Cruciferae are the common sources of plant volatile oils, and terpenoids are their main components. More than 10 traditional and emerging extraction and separation techniques, such as supercritical fluid extraction, were investigated, moreover, solvent-free microwave extraction combined with ultrasonic pretreatment increased the yield of essential oil from the rutaceae pericarp by 26%. Meanwhile, more than 10 encapsulation forms, such as nanocapsules and liposomes, which can effectively improve the stability and bioactivity of volatile oils, were summarized. At the level of multiple applications, nanoemulsions and pickering emulsions are outstanding in skin care, nano-particles and nano-capsules are widely used in textiles and food flavouring, and nano hydrogels have become a new type of carrier for drug delivery, and the multiple forms break the limitations of the application of essential oils in an all-round way. However, the new extraction and separation technologies have the problems of high cost, complicated operation, and difficult to be adapted to industrial production; and the encapsulation technologies face the challenges of easy essential oil dispersion, difficult to be adapted to the substrate, doubtful material safety, and lack of monitoring means. This paper breaks through the limitation of traditional single research by constructing a multi-dimensional research framework of ‘chemical composition-extraction technology-encapsulation process-diversified applications’, which provides a new perspective and theoretical support for the research and industrial development in the field of volatile oils and EO.