| Summary: | The Ultrasonic and Microwave-Assisted Hydro-Distillation (US-MAHD) method is a process combination of ultrasonic-assisted extraction (UAE) and microwave-assisted hydro-distillation (MAHD) carried out sequentially. This method aims to improve the UAE and MAHD methods in extracting citronella oil. This study evaluates the performance of US-MAHD in the extraction of citronella oil from the citronella plant. Extraction is conducted for 90 min at various solvent-plant ratios (v/m) (10:1, 12:1, 14:1), ultrasonic bath temperature (30 °C, 40 °C, 50 °C), and power of microwave oven (150 W, 300 W, 450 W). US-MAHD yields a maximum yield of citronella oil of 1.82 mg/g when extracting lemongrass plant with a combination of ultrasonic bath temperature of 30 °C, a solvent-plant ratio of 10:1, microwave power of 300 W, and time of 90 min. All quality parameters of the oil produced have met ISO 3848:1976 standard. Extraction of citronella oil using the US-MAHD method produces higher yields than the UAE and MAHD methods under the same operating conditions. The yields of citronella oil from the US-MAHD, UAE, and MAHD methods are 1.82, 0.92, and 1.48 mg/g, respectively. SEM analysis of residual lemongrass plant shows more cell wall damage which indicates more oil release from the plant matrix.
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