Chemometric analysis applied to ¹H NMR and FTIR data for a quality parameter distinction of red fruit (Pandanus conoideus, lam.) oil products

Abstract

IntroductionRed fruit oil (RFO) is a natural product extracted from Pandanus conoideus Lam. fruit, a native plant from Papua, Indonesia. Recent studies indicate that RFO is popularly consumed as herbal medicine. Therefore, the quality of RFO must be assured.ObjectivesThis study aimed to develop a chemometric analysis applied to 1H nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) data for important quality parameter distinction of red fruit oil (RFO), especially regarding the degree of unsaturation and the amount of free fatty acids (FFA).Materials and methodsForty samples consisting of one crude RFO, thirty‐three commercial RFOs, and three oils as blends, including olive oil, virgin coconut oil, and black seed oil, were analysed by 1H NMR and FTIR spectroscopy. After appropriate preprocessing of the spectra, principal component analysis (PCA) and partial least squares regression (PLSR) were used for model development.ResultsThe essential signals for modelling the degree of unsaturation are the signal at δ = 5.37–5.27 ppm (1H NMR) and the band at 3000–3020 cm−1 (FTIR). The FFA profile represents the signal at δ = 2.37–2.20 ppm (1H NMR) and the band at 1680–1780 cm−1 (FTIR). PCA allows the visualisation grouping on both methods with > 98% total principal component (PC) for the degree of unsaturation and > 88% total PC for FFA values. In addition, the PLSR model provides an acceptable coefficient of determination (R2) and errors in calibration, prediction, and cross‐validation.ConclusionChemometric analysis applied to 1H NMR and FTIR spectra of RFO successfully grouped and predicted product quality based on the degree of unsaturation and FFA value categories.

A Comprehensive Study for Determination of Free Fatty Acids in Selected Biological Materials: A Review

“…It requires small amounts of sample for analysis, such as 0.10 mL, 1 drop of oil with the spectral area of 4000–600 cm −1 , which is almost same as MIR, and it also offers recording up to 128 scans of each spectrum [ 77 , 78 , 79 , 80 ]. Besides, Nascimento et al [ 78 ] propounded that FFA determination in commercial oil samples enforced minimal degradation by ATR-FTIR, better than 1 H NMR [ 78 ], and Triyasmono et al [ 81 ] agreed that the projection pattern of ATR-FTIR was more reliable than 1 H NMR over FFA determination of crude palm oil [ 81 ].…”

“…The absorption of cis-C=C bonds was observed related to the C-H absorption of bending vibrations of CH 2 and CH 3 bands from 1654 cm −1 to 1460 cm −1 , and weak absorption might be visible at ~962 cm −1 . The asymmetric C-O stretching vibrations (ester bonds) were detected at 1236, 1160, and 1117 cm −1 [ 70 , 77 , 81 , 83 , 84 , 85 ]. The specific peak at 725 cm −1 was identified as (-CH2) n- bending for sunflower, rapeseed, maize, palm, and coconut oils and their thermal exposure varieties, according to Mitrea et al [ 85 ].…”