Fatty acid evaluation of seeds and nuts by spectroscopy and chromatography

Abstract

The study aimed to determine the oil content and identify fatty acid methyl esters such as stearate, palmitate, linolenate, linoleate, and oleate in seeds and nuts like candlenut, peanut, sesame, sunflower, and sacha inchi. Oil extraction was carried out using Soxtec 8000™ and n-hexane solvent. The samples were dried at 50oC. The extraction conditions optimized were temperature 135oC, n-hexane 50 mL, boiling time 40 min, and total extraction time 115 min. Identification of fatty acids was carried out using Attenuated Total Reflection (ATR), Nuclear Magnetic Resonance (NMR), and Gas Chromatography-Flames Ionization Detector (GC-FID). The oil percentage detected in each sample was candlenut (59.95%), peanut (40.08%), sesame (57.06%), sunflower (43.97%), and sacha inchi (51.71). The ATR results show that the flour of nuts and seeds has a strong vibrational frequency of the O−H molecule. Linolenate was detected at a chemical shift of 0.975 ppm in NMR spectra and was found in sacha inchi and candlenut. The ATR, NMR, and GC-FID results showed that all samples contained unsaturated fatty acids. Candlenut, peanut, sesame, and sacha inchi were rich in linoleate (ω-6) as much as 25.68%, 20.15%, 26.38%, and 20.73%, respectively. Oleate was abundant in sesame (21.87%) and sunflower (16.78%). Linolenate was found only in sacha inchi (22.88%). The maximum percentage of stearate was found in sunflower (4.02%) followed by sesame (2.96%), candlenut (1.81%), sacha inchi (1.52%), and peanut (0.71%). This research provides useful information on fatty acid profiles beneficial for health, especially stearic acid, which can substitute trans fatty acids harmful to health.