MONITORING LIPID OXIDATION AND ANTIOXIDANT EFFECTS OF PHOSPHOLIPIDS BY HEADSPACE GAS CHROMATOGRAPHIC ANALYSES OF RANCIMAT TRAPPED VOLATILES

Two of the most frequently used techniques to follow oxidation patterns of fats are headspace gas chromatography (HS-GC) and gas chromatography/mass spectrometry (GC/MS). The HS-GC technique offers the advantages of rapidity and multiple sample analyses, whereas GC/MS offers the advantages of GC separation coupled with the ability of MS to identify volatile compounds separated via GC. No previous information exists in the literature on the use of the volatiles trapped in water contained in the measuring vessel of the Rancimat and HS-GC to monitor lipid oxidation, as was the objective of this study. Oxidative secondary breakdown products of fish oil model systems trapped in water contained within the measuring vessel of the Rancimat were subjected to HS-GC analyses for quantitation of individual volatiles. Results from this study showed that oxidation induction time and products of oxidation can be monitored by the combined use of the Rancimat and HS-GC, and that trapped volatiles are representative of typical by-products of lipid oxidation and of oil type being examined. Addition of phospholipids (PL) to salmon and menhaden oils significantly influenced the production of volatile compounds. The molecular weights of the volatiles identified ranged from 30 to 212 daltons. The reproducibility of the method (std. dev. ≈ 2.04) was good but can be greatly improved through the use of a capillary column. PL having antioxidant activity generated lower concentrations of total volatiles than those found to be prooxidants.