Page 29 - Summer 2019 Journal

METHODS FOR COD LIVER OIL TESTING
NMR: High-resolution nuclear magnetic resonance (NMR) spectroscopy is a state-of-the-art technique that involves the exposure of samples to an intense magnetic field causing the nuclei of the molecules to respond by producing an elec- tromagnetic signal with a frequency characteristic of the magnetic field at the nucleus, allowing researchers to identify various components of the sample. NMR offers many advantages over alternative analytical techniques, since it allows the rapid, simultaneous, non-invasive and non-destructive analysis of a wide range of agents present in complex, multi- component samples such as foods, oils, pharmaceutical formulations, health care products and biological fluids such as blood plasma and urine. Data acquired through NMR testing are presented as what is known as a spectrum consisting of a plot of signal intensity versus resonance frequency in parts per million (ppm, a dimensionless unit).
HPLC: High-performance liquid chromatography (HPLC), formerly referred to as high-pressure liquid chromatography, is a technique in analytical chemistry used to separate, identify and quantify each component in a mixture. It relies on pumps to pass a pressurized liquid solvent containing the sample mixture through a column filled with a solid adsorbent material. Each component in the sample interacts slightly differently with the adsorbent material, causing different flow rates for the different components and leading to the separation of the components as they flow out of the column. For oils, HPLC provides readings for peroxide value (PV) or primary oxidation and anisdine value (PA) or secondary oxida- tion. Another measurement of oxidation is thiobarbituric acid (TBA) and TBARS (a more involved version of the TBA test). The TBARS test is especially problematic for omega-3 oils as the method requires heating the samples for periods of about fifteen minutes. Heating causes peroxidation of polyunsaturated fatty acids, and hence all results derived from this heat-dependent test system are suspect. In addition, the TBARS is not a good technique for products containing phenols or residual proteins.
SPECTROPHOTOMETRY
Spectrophotometry is a tool that provides a quantitative analysis of molecules depending on how much light is absorbed by colored compounds. Spectrophotometry uses photometers, known as spectrophotometers, which can measure a light beam's intensity as a function of its color (wavelength). The spectrophotometer can generate a beam that goes through the sample (mainly transparent liquids). The colored compound in the sample will absorb the energy of the light, then the photometer can detect the absorption level of the light at a certain frequency on the other side. Based on the absorption level of the compound, the quantity of this compound can be calculated. As with HPLC, the sample must be heated to ascertain a TBARS value, so values obtained by spectrophotometry are considered less than reliable.
SPECTROPHOTOMETRY RESULTS FOR FERMENTED COD LIVER OIL14
PV Peroxide Value:
PA Anisdine Value:
TBA Thiobarbituric Acid: TBARS:
Free Fatty Acids:
Very low Very low Low High High
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