Raman Spectroscopy of Fish Oil Capsules: Polyunsaturated Fatty Acid Quantitation Plus Detection of Ethyl Esters and Oxidation.

Fish oils are the primary dietary source of ω-3 polyunsaturated fatty acids (PUFA), but these compounds are prone to oxidation, and commercial fish oil supplements sometimes contain less PUFA than claimed. These supplements are predominantly sold in softgel capsules. In this work, we show that Fourier transform (FT)-Raman spectra of fish oils (n = 5) and ω-3 PUFA concentrates (n = 6) can be acquired directly through intact softgel (gelatin) capsules. These spectra could be used to rapidly distinguish supplements containing ethyl esters from those containing triacylglyceride oils. Raman spectroscopy calibrated with partial least-squares regression against traditional fatty acid methyl ester analyses by gas chromatography-mass spectrometry could be used to rapidly and nondestructively quantitate PUFA and other fatty acid classes directly though capsules. We also show that FT-Raman spectroscopy can noninvasively detect oxidation with high sensitivity. Oils with peroxide values of as low as 10 mequiv kg-1, which are on the cusp of falling outside of specification, could be readily distinguished from oils that were within specification (7 mequiv kg-1).

[1]  G. Ghesti,et al.  FT-Raman Spectroscopy Quantification of Biodiesel in a Progressive Soybean Oil Transesterification Reaction and Its Correlation with 1H NMR Spectroscopy Methods , 2007 .

[2]  W. Connor,et al.  Absorption of the n-3 eicosapentaenoic and docosahexaenoic acids as ethyl esters and triglycerides by humans. , 1991, The American journal of clinical nutrition.

[3]  Lawrence J Appel,et al.  Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. , 2002, Arteriosclerosis, thrombosis, and vascular biology.

[4]  F. Shahidi,et al.  Oxidative stability of oil from blubber of harp seal (Phoca groenlandica) as assessed by NMR and standard procedures , 1994 .

[5]  R. G. Ackman,et al.  EPA and DHA contents of encapsulated fish oil products , 1989 .

[6]  D. Marais,et al.  Analysis of omega-3 fatty acid content of South African fish oil supplements , 2011, Cardiovascular journal of Africa.

[7]  F. Shahidi,et al.  Comparison of standard and NMR methodologies for assessment of oxidative stability of canola and soybean oils , 1995 .

[8]  Elling-Olav Rukke,et al.  Quantitative determination of saturated-, monounsaturated- and polyunsaturated fatty acids in pork adipose tissue with non-destructive Raman spectroscopy. , 2007, Meat science.

[9]  M. Zou,et al.  Rapid authentication of olive oil adulteration by Raman spectrometry. , 2009, Journal of agricultural and food chemistry.

[10]  Joseph Maria Kumar Irudayaraj,et al.  Comparison of near-infrared, fourier transform-infrared, and fourier transform-raman methods for determining olive pomace oil adulteration in extra virgin olive oil , 2001 .

[11]  A. M. Calderón de la Barca,et al.  Seasonal variation in the fatty acid composition and quality of sardine oil from sardinops sagax caeruleus of the gulf of California , 1999, Lipids.

[12]  K. Gordon,et al.  Quantitative Raman spectroscopy for the analysis of carrot bioactives. , 2013, Journal of agricultural and food chemistry.

[13]  M. Dorgan,et al.  Effect of fish oil on arrhythmias and mortality: systematic review , 2008, BMJ : British Medical Journal.

[14]  Vincent Baeten,et al.  Oil and Fat Classification by FT-Raman Spectroscopy , 1998 .

[15]  M. Metian,et al.  Global overview on the use of fish meal and fish oil in industrially compounded aquafeeds: Trends and future prospects , 2008 .

[16]  Vincent Baeten,et al.  Detection of the presence of hazelnut oil in olive oil by FT-raman and FT-MIR spectroscopy. , 2005, Journal of agricultural and food chemistry.

[17]  J. Hansen,et al.  Effects of highly purified eicosapentaenoic acid and docosahexaenoic acid on fatty acid absorption, incorporation into serum phospholipids and postprandial triglyceridemia , 1998, Lipids.

[18]  J. Pierna,et al.  Assessment of the discrimination of animal fat by FT-Raman spectroscopy , 2009 .

[19]  M. Garg,et al.  Fish oil supplements in New Zealand are highly oxidised and do not meet label content of n-3 PUFA , 2015, Scientific Reports.

[20]  Isabel Jaime,et al.  Production of omega-3 polyunsaturated fatty acid concentrates: A review , 2010 .

[21]  G. Arhonditsis,et al.  Modelling the role of highly unsaturated fatty acids in planktonic food web processes: a mechanistic approach , 2012 .

[22]  L. Rodriguez-Saona,et al.  Application of Infrared Spectroscopy for Characterization of Dietary Omega-3 Oil Supplements , 2015 .

[23]  A. Kaczor,et al.  Raman spectroscopy of proteins: a review , 2013 .

[24]  H. Rice,et al.  Oxidation in EPA‐ and DHA‐rich oils: an overview , 2016 .

[25]  M. Toborek,et al.  Omega-3 fatty acid oxidation products prevent vascular endothelial cell activation by coplanar polychlorinated biphenyls. , 2011, Toxicology and applied pharmacology.

[26]  Bjørn Grung,et al.  Determination of Omega-3 Fatty Acids in Fish Oil Supplements Using Vibrational Spectroscopy and Chemometric Methods , 2014, Applied spectroscopy.

[27]  Rapid quantitation of fish oil fatty acids and their ethyl esters by FT‐NIR models , 2010 .

[28]  V. Christensen,et al.  Valuing seafood: The Peruvian fisheries sector , 2014 .

[29]  Neil Mann,et al.  Origins and evolution of the Western diet: health implications for the 21st century. , 2005, The American journal of clinical nutrition.

[30]  P. Nichols,et al.  Australian and New Zealand Fish Oil Products in 2016 Meet Label Omega-3 Claims and Are Not Oxidized , 2016, Nutrients.

[31]  A. Ruiz,et al.  Monitoring the oxidation of unsaturated oils and formation of oxygenated aldehydes by proton NMR , 2005 .

[32]  C. Barrow,et al.  Rapid Determination of Protein Contents in Microencapsulated Fish Oil Supplements by ATR-FTIR Spectroscopy and Partial Least Square Regression (PLSR) Analysis , 2013, Food and Bioprocess Technology.

[33]  Kamila Kochan,et al.  Raman spectroscopy of lipids: a review , 2015 .

[34]  M. T. Arts,et al.  Essential fatty acids in the planktonic food web and their ecological role for higher trophic levels , 2004 .

[35]  R. Ackman,et al.  The absorption of fish oils and concentrates , 1992, Lipids.

[36]  D. Cameron-Smith,et al.  Oxidation of Marine Omega-3 Supplements and Human Health , 2013, BioMed research international.

[37]  Ermias A. Haile,et al.  Rapid Prediction of Fatty Acid Content in Marine Oil Omega-3 Dietary Supplements Using a Portable Fourier Transform Infrared (FTIR) Device and Partial Least-Squares Regression (PLSR) Analysis. , 2017, Journal of agricultural and food chemistry.

[38]  K. Gordon,et al.  Rapid Quantitative Determination of Squalene in Shark Liver Oils by Raman and IR Spectroscopy , 2015, Lipids.

[39]  C. Barrow,et al.  Stabilization of highly unsaturated fatty acids and delivery into foods , 2007 .

[40]  Pavel Zemánek,et al.  Characterization of oil-producing microalgae using Raman spectroscopy , 2011 .

[41]  A. Simopoulos.  Omega-3 fatty acids in health and disease and in growth and development. , 1991, The American journal of clinical nutrition.

[42]  H. Bays.  Safety considerations with omega-3 fatty acid therapy. , 2007, The American journal of cardiology.