Effect of drying pre-treatments on the yield and bioactive content of oil extracted from Gac Aril

Gac fruit (Momordica cochinchinensis Spreng) aril contains high levels of bioactive compounds including β-carotene, lycopene and fatty acids. Therefore, it is important to find an extraction method of Gac oil resulting in the highest content of bioactive compounds. The effects of microwave and air-drying pre-treatments of Gac aril prior to hydraulic pressing and Soxhlet extraction on the oil yield, nutrients and chemical properties of the oil were compared. Results showed that the highest oil yield could be obtained when the aril was microwave-dried before Soxhlet extraction. This finding was explained by microstructural changes of the dried arils. Microwave-drying prior to pressing resulted in the highest content of β-carotene (174 mg/100 mL) and lycopene (511 mg/100 mL) in the oil extract. Oleic acid (48%) and linoleic acid (18%) were found to be the dominant fatty acids in the oil extracts. Gac oil with the lowest acid (0.69 mg KOH/g) and peroxide values (1.80 meq O2/kg) was extracted when microwave-drying was applied prior to pressing. It can be concluded that the microwave drying pre-treatment before pressing was better than the air-drying pre-treatment for extracting Gac oil of high quality.