University of Arkansas, Fayetteville Division of Agriculture


Isomers, octodienoic acids


Dietary conjugated linoleic acid (CLA) is known to be effective in avoiding many obesity related diseases. Conjugated linoleic acid is a product of ruminant fermentation and 3.4 g/day are needed to obtain the clinical benefits. However, it is difficult to obtain sufficient CLA to realize these benefits from a healthy diet containing dairy and beef products, without increasing levels of dietary cholesterol and saturated fat. A 20% CLA soy oil with low saturated fat and no cholesterol has been produced by photoisomerization of linoleic acid in the triacylglyceride oil. Further increasing the CLA yields has been possible by addition of tocopherol antioxidants. The objectives of this research were to determine the effects of other natural phenolic antioxidants on CLA yield and oxidative stability during photoisomerization. Rosemary extract (RME), rosmarinic acid (RA), gallic acid (GA), caffeic acid (CA), and chlorogenic acid (CHA) were each added to refined bleached deodorized soy oil at levels they were reported to serve best as an antioxidant. The oil was then photoisomerized to produce CLA-rich oil. The CLA levels in soy oil were determined by gas chromatography - flame ionization detector (GC-FID) as fatty acid methyl esters (FAMES). The oxidative stability was determined by peroxide value (PV). The order of effectiveness as a CLA promoter was CHA>RME>RA>CA>GA. Chlorogenic acid at 11 ppm showed the greatest increase in CLA yield and a much lower PV than the control. Rosemary extract was less effective than CHA while the CA, GA and RA were ineffective. A balance of polarity/non-polarity and antioxidant concentration seem to be the most important factors in determining CLA yields, oil solubility, and antioxidant performance.