Effect of different extraction methods on physicochemical properties of gac fruit (Momordica cochinchinensis) pulp and peel oil

Gac fruit (Momordica cochinchinensis) is an underutilized fruit where its pulp and peel are often discarded. Fewer studies were conducted on its pulp and peel than on its arils and seeds. This study provides insights into the comparison of crude oil yield and compositions of palmitic and stearic acid of the crude oil extracted using three different extractions, including maceration, ultrasound-assisted extraction (UAE), and enzymatic-assisted extraction (EAE). The pH, refractive index, color measurement, total phenolic content (TPC), DPPH radical scavenging activity, and iron-reducing antioxidant power of FRAP assay were also studied. Results showed that different extraction methods might have significant differences in the yield of crude oil, palmitic and stearic acid compositions, pH, refractive index, color measurement, TPC, DPPH, and FRAP values at p<0.05. Crude oil samples for pulp and peel extracted using the UAE method have the highest yield at 7.81±1.84% and 4.24±0.20%, respectively, as compared to other methods. As for concentrations of palmitic in the sample, crude pulp oil extracted using UAE showed the highest concentration (0.792±0.102 ppm) in comparison to other methods. However, no significant difference was observed in stearic acid concentration. Crude oil extracted using UAE method also showed a significant difference in pH for pulp (6.24±0.05), refractive index for pulp (20.27±0.15) and peel (18.50±0.35), TPC for pulp (6.51±0.04 mg GAE/g) and peel (6.65±0.07 mg GAE/g) and percentage of DPPH radical scavenging from pulp (41.09±0.24%) and peel (68.75±0.09%). In conclusion, UAE was a more efficient extraction method for extracting the highest oil yield, free fatty acid content, and antioxidant activity. In contrast, the physicochemical properties of pulp and peel are comparable.