Abstract:

In order to develop a new technology to extract onion essential oil, a 2-L equipment of subcritical water extraction （SWE） suitable for industrial production was designed and used to extract the essential oil from the red onion peculiar in Lingnan. The effects of extraction mode, extraction time, temperature and pressure on the yield and the sulphur compounds content were then analyzed, and different extraction solvents and extraction times were investigated in the liquid-liquid extraction procedure. The optimal conditions of subcritical water extraction of onion essential oil were finally determined as follows ： a static extraction at 5 MPa for 30min, with a sequential programed temperature increasing from 100 to 150℃, and with petroleum ether as the extraction solvent for two extractions successively. The results indicate that （ 1 ） in the optimal conditions, the extraction yield of onion essential oil and the content of sulphur compounds respectively reach 0. 362% and 97.36g/kg; （2） as compared with the conventional steam distillation and ultrasonic-assisted extraction, the subcritical water extraction costs less extraction time, and possesses high efficiency, low energy consumption and high product quality, etc. ; and （3） the designed 2-L equipment of SWE is highly automatic and is convenient to operate.

Key words: subcritical water extraction, equipment, essential oil, steam distillation, ultrasonic-assisted extraction