posted on 2017-04-19, 00:00authored byDaniel P. Killeen, Susan N. Marshall, Elaine J. Burgess, Keith C. Gordon, Nigel B. Perry
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).