Model 7890a

The extract samples obtained by SFE at 30 MPa and 40 °C (based on the high yields and AA; Sections 3.2 and 3.3) and SOX extraction with hexane were selected for GC-MS analysis. The samples were subjected to methylation fractionation reaction (FAME) to assist the analysis of the compounds by GC-MS (O’Fallon, Busboom, Nelson, & Gaskins, 2007 (link)). The identification and relative quantification of the volatile compounds in the soursop seed extract were performed using a gas chromatography system equipped with a mass spectrophotometer (GC-MS, model 7890 A, mass detector 5975C, Agilent Technologies, USA), attached to an HP-5MS column (30 m × 0.32 mm (internal diameter) with a film thickness of 0.25 µm, Agilent Technologies, USA), following the method described by Mazzutti et al. (2018) (link). Helium was used as a carrier gas with a flow rate of 4 mL∙min⁻¹, split ratio of 5:1, injector temperature of 250 °C, and Thermal Aux 2 (MSD Transfer Line). The column temperature was increased from 60 °C to 230 °C at a rate of 3 °C∙min⁻¹, in a total time of 55.56 min, and a quadrupole detector temperature of 150 °C was used. The major components of the selected extracts were identified by comparing the mass spectra and retention times of the compounds to those available in the NIST 11 Mass Spectral Library.

Fatty acid methyl esters were separated and quantified by gas-liquid chromatography (Model 7890A, Agilent Technologies, USA) using a 30 m×0.32 mm i.d. capillary column (SP-2330, Supelco, Inc., Bellefonte, PA, USA). The hydrogen was used as the carrier gas at 40 mL/min. The injector temperature was programmed at 240°C and the detector temperature was 250°C. The column temperature program started to run at 140°C, for 2 min, warmed to 158°C at 1°C/min, held for 28 min, warmed to 220°C at 1°C/min and then held for 20 min to achieve satisfactory separation. The identification of the peaks was made by comparison of equivalent chain lengths with those of authentic fatty acid methyl esters (37 Component FAME mix, Supelco, Bellefonte, PA). Peak areas were determined automatically using the Agilent gas chromatography chemstation software (Agilent Technologies, USA). The fatty acid concentrations are expressed as percentage of the sum of total identified peaks measured in each sample.

The fatty acid composition was determined by gas chromatography (GC) as described previously (Hao et al., 2020 ). First, the LDM samples were extracted with a mixture of chloroform and methanol (2:1; vol/vol). Approximately 20 g of each LDM sample was weighed and dried in an oven at 105 °C for 1 h, and then 1 g of each dried sample was weighed and leached with petroleum ether for 3 h. A total of 60 mg of the extracted fat was placed in a test tube, 4 mL of isooctane was added to fully dissolve the sample, and then 200 μL potassium hydroxide-methanol and 1 g of sodium bisulfate were added. After salt precipitation, the solution containing the methyl esters was drawn into the upper layer and stored in a refrigerator at 4 °C. Each sample was filtered through a 0.22-nm filter membrane before GC detection (Model 7890 A, Agilent Technologies, Palo Alto, CA, USA). Finally, the fatty acid concentration was analyzed by GC ChemStation software (Agilent Technologies, Palo Alto, CA, USA).