Optimization and kinetics of lavender essential oil extraction: Effects of flower pretreatment, salt solutions, and hydrolat reuse

This study aimed to optimize lavender flower pretreatment, assess the effects of different salt concentrations, and evaluate the use of hydrolat from previous hydro-distillation on essential oil yield and composition. Whole flowers produced as much oil as wet-ground or freshly ground flowers. Contrary to previous studies, NaCl and KCl solutions (3-10%) did not affect maximum oil yield but did alter hydrodistillation kinetics, reducing washing rates and enhancing diffusion by disrupting oil glands and raising the boiling point. Using a mix of recycled hydrolat and fresh water increased oil yield and improved kinetics by enhancing internal oil extraction. The process was successfully modeled using distinct washing and diffusion mechanisms. Both pretreatments of lavender flowers have a significant impact on the essential oil composition. Salt pretreatment enhances the extraction of oxygenated monoterpenes compounds and monoterpenes, while hydrolat addition negatively affects the solubility and volatility of oxygenated monoterpenes. In conclusion, soaking whole lavender flowers in hydrolat-water mixture is an efficient method, reducing both energy and water usage, and lowering operational costs, while simultaneously requiring attention to its impact on the composition.