Fatty Acid Determination in Human Milk Using Attenuated Total Reflection Infrared Spectroscopy and Solvent-Free Lipid Separation

• Published in: Applied spectroscopy Vol. 76; no. 6; p. 730
• Main Authors: Akhgar, Christopher K, Nürnberger, Vanessa, Nadvornik, Marlene, Ramos-Garcia, Victoria, Ten-Doménech, Isabel, Kuligowski, Julia, Schwaighofer, Andreas, Rosenberg, Erwin, Lendl, Bernhard
• Format: Journal Article
• Language: English
• Published: United States 01.06.2022
• Subjects: Animals; Fatty Acids - analysis; Humans; Milk - chemistry; Milk, Human - chemistry; Solvents - analysis; Spectrophotometry, Infrared - methods; Spectroscopy, Fourier Transform Infrared - methods; partial least squares regression; fatty acids; Mid-infrared spectroscopy; attenuated total reflection; human milk; PLSR; ATR
• ISSN: 1943-3530
• DOI: 10.1177/00037028211065502

This study introduces the first mid-infrared (IR)-based method for determining the fatty acid composition of human milk. A representative milk lipid fraction was obtained by applying a rapid and solvent-free two-step centrifugation method. Attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy was applied to record absorbance spectra of pure milk fat. The obtained spectra were compared to whole human milk transmission spectra, revealing the significantly higher degree of fatty acid-related spectral features in ATR FT-IR spectra. Partial least squares (PLS)-based multivariate regression equations were established by relating ATR FT-IR spectra to fatty acid reference concentrations, obtained with gas chromatography-mass spectrometry (GC-MS). Good predictions were achieved for the most important fatty acid sum parameters: saturated fatty acids (SAT, R = 0.94), monounsaturated fatty acids (MONO, R = 0.85), polyunsaturated fatty acids (PUFA, R = 0.87), unsaturated fatty acids (UNSAT, R = 0.91), short-chain fatty acids (SCFA, R = 0.79), medium-chain fatty acids (MCFA, R = 0.97), and long-chain fatty acids (LCFA, R = 0.88). The PLS selectivity ratio (SR) was calculated in order to optimize and verify each individual calibration model. All mid-IR regions with high SR could be assigned to absorbances from fatty acids, indicating high validity of the obtained models.