Ultrasound-assisted hydrodistillation for extraction of essential oil from clove buds - A step towards process improvement and sustainable outcome

Ultrasound-assisted hydrodistillation was selected for the extraction of essential oil from clove buds. The essential oil yield, eugenol content, and total phenolic content (TPC) were considered the critical response parameters during the parametric study. The effect of various process parameters on the responses has been studied using a one-factor-at-a-time approach followed by optimization of processing conditions using Box-Behnken design (BBD). The proposed model has shown good prediction capability. For the highest essential oil yield (15.23%, w/w), the optimum conditions were achieved at 50 min extraction time, 15 g solid loading, 500 W heating mantle power, 40% amplitude, and 20:40 pulse interval. Under these conditions, the residual water has 101.21 mg GAE/g phenolic compounds and exhibited 85.68% antioxidant activity. The incorporation of sonication in hydrodistillation has substantially improved the process by shrinking the carbon footprint by 25%, reducing the utility consumption to similar to 42%, and increasing the oil yield. The outcomes of the present study suggest that ultrasound-assisted hydrodistillation can be considered a sustainable and greener option for hydrodistillation.