Testing the Freshness of Marine Oils
Posted by Dr. Theo Kapanadze, D.Sc., Ph.D. on Fri, Apr 27, 2012
Modification of low density lipoproteins (LDL) by oxidation of their polyunsaturated lipid components has been implicated in the etiology of atherosclerosis. Oxidation proceeds by interaction of polyunsaturated fatty acids (PUFA) with active oxygen species or with lipid oxidation products. Moreover, there are indications that lipid oxidation promotes pre-mature coronary atherosclerosis since susceptibility to LDL oxidation has been associated with the severity of coronary heart disease. Protection against oxidation can come from antioxidants, antioxidant enzymes and co-factors. The use of antioxidants to inhibit LDL oxidation has been reviewed extensively. Under in vivo conditions, there exists a competition between oxidative and protective processes that depend on PUFA composition and on antioxidant levels. Therefore, it is important to properly assess the oxidation of the fatty acids in marine oils.
The traditional analytical tequniques available to test the freshness of marine oils are:
|
Test
|
Method
|
Specification
|
Results
|
|
Acid Value
|
AOCS Method
Cd 3d-63
|
< 3 KOH/g
|
KOH/g
|
|
Anisidine Value
|
AOCS Method
Cd 18-90
|
< 20 meq/kg
|
meq/kg
|
|
Peroxide Value
|
AOCS Method
Cd 8-53
|
< 5 meq/kg
|
meq/kg
|
|
EFA Analysis
Marine Oils
|
AOCS Method
CE 1b-89
|
EE mg/gram
|
EPA: 441.31 mg/g
DHA: 221.07 mg/g
|
In our case studies section, we describe a method using headspace Gas Chromatography (GC-FID) for the determination of important decomposition products in n-6 PUFA peroxidation. This method has been used to examine rat liver and other tisue samples.
With the increasing importance of marine oils and their feect as antioxidants, new methodologies are required to address the question whether LDL composition does affect the oxidative stability of lipoprotein particles. GC-FID can be used to test the effect of marine oil supplementation on the susceptibility of LDL fractions to oxidation. Appearance of specific volatile peroxidation products can be found that are correlated with the fatty acid profile but not with the tocopherol content of LDL.
