ATR-FTIR and Raman Spectroscopies Associated with Chemometrics for Lipid Form Evaluation of Fish Oil Supplements: A Comparative Study

Abstract

Omega-3 fatty acids (FA) are mainly available as triacylglycerols (TAG) and ethyl esters (EE) in fish oils and it is known that EE are less bioavailable than TAG in the human body. This study applied ATR-FTIR and Raman associated with chemometrics to evaluate supplements lipid form. Representative products were firstly characterized by reference chromatographic methods. Subsequently, principal component analysis (PCA) and partial least square discriminant analysis were performed in the spectral wavenumber of 1700-1780 cm -1 (ATR-FTIR) and 1720-1770 cm -1 (Raman). TAG and EE were clearly distinguished along PC1 employing both techniques, but higher explained variance was obtained by ATR-FTIR. The prediction of TAG and EE fish oils samples was also better using ATR-FTIR (R-square = 0.99 versus 0.95 for Raman). However, both models classified correctly 100% of samples, which indicates the suitability of these approaches to be used in quality control laboratories aiming for fish oils lipid form evaluation.

Fatty acid composition and nutritional analysis of waste crude fish oil obtained by optimized milder extraction methods

“…Thus, MCFO and FCFO from the milder extraction methods have similar characteristic functional groups (Table S5). The band positions of =C-H (cis stretching), ̶ C=C ̶ (cis double bond stretching), =C ̶ H (cis bending out of plane), and =CH 2 (wagging) indicates the presence of unsaturated fatty acids in MCFO and FCFO, as also reported by Amorim et al [13]. The ratio between the bands due to =CH-cis group (3,012) and -CH 2 -group (2,920-2,925) can be used as a marker for analyzing PUFAs in fish oil samples.…”

“…Over the years, previous studies have enumerated the importance and applicability of fish oil in the food, cosmetic, pharmaceutical, and biofuel industries [10,13,14]. Although humans might not directly consume crude fish oils unless further purification is conducted, conserving their initial nutritional quality is critical.…”

Detection and Quantification of Adulteration in Krill Oil with Raman and Infrared Spectroscopic Methods

“…The associated loadings plots presented in Figure 3c provide insight into the spectral variances contributing to this separation. The main spectral contribution in the positive PC1 features were observed at 1735 cm −1 (C=O stretching, ethyl ester) and 1166 cm −1 (C-O stretching) [23,40], whereas the most spectral influence in the negative PC1 features were related to symmetric phosphate diester stretching in PO2 (1095 cm −1 ), asymmetric ester stretching in C-O-P (1060 cm −1 ) and various HC=CH vibration (980-950 cm −1 ) [40][41][42], indicating phospholipid signals. The second PC separated mostly the O3C adulterant samples, depending on characteristic ester shifting (1745 cm −1 ) and CH2 bending (1142 cm −1 ).…”

“…quantified total PUFA content and detected ethyl ester in intact fish oil capsules using Raman spectroscopy [22]. Both IR and Raman spectroscopic methods have been demonstrated to classify the lipid class (TAG, EE) in fish oil with 100% accuracy [23].…”

Quantum Cascade Laser Infrared Microscopy and In Situ Infant Formula Foam Wall Characterization

“…This rapid analysis is practically unfeasible with MIR microscopes based on a glow bar source. This is also a novel combination of MIR spectroscopy and multivariate analysis in the field of food analysis. − This combination is more often seen to be employed in a classification or a multivariate model-based assay role. − …”