Abstract
The study aimed to optimise the ultrasound-assisted aqueous extraction of oil, beta-carotene and lycopene from powdered microwave-dried gac arils. Ultrasound power, extraction time, powder particle size and the ratio of water to gac powder during the extraction, the centrifugal force used to recover the extracted components were investigated. Microwave-drying followed by aqueous extraction without ultrasound-assistance and air-drying followed by aqueous extraction with or without ultrasound-assistance was also carried out for comparisons. The gac material left behind after the extractions was also investigated using scanning electron microscopy (SEM). The results showed that ultrasound power of 32 W/g of aril powder, extraction time of 20 min, powder particle sizes of 0.3-0.5 mm, a ratio of water to powder of 9 g/g and a centrifugal force of 6,750 x g gave optimal extraction efficiencies for oil (90%), beta-carotene (84%) and lycopene (83%), and the oil had a low peroxide value (PV) of 2.2 meq/kg. The SEM analysis confirmed that the combination of microwave-drying followed by ultrasound-assisted aqueous extraction caused strong disruption of the gac aril cellular structures, which was consistent with the high extraction of oil, beta-carotene and lycopene obtained with the combination. It was concluded that gac oil containing high amounts of beta-carotene and lycopene and having a low PV could be extracted using microwave-drying and ultrasound-assisted aqueous extraction.
