Chromatographic Analysis of Secondary Lipid Oxidation Products

Chromatographic Analysis of Secondary Lipid Oxidation Products 

One of the factors responsible for the quality deterioration of foods is lipid oxidation. All foods containing fat are susceptible to oxidative rancidity, which can render the food unacceptable to the senses and also reduce nutritional quality. 

The extent of oxidative deterioration will determine the acceptability of a food product. Because of this, methods for determining the degree of oxidation are very useful to the food industry. There are many possible methods that can be utilized (see Commentary) however, due to the stability of some of the end products, and their direct relationship with rancidity, headspace GC provides a fast and reliable method for oxidation measurement. Headspace techniques include static, dynamic, and solid-phase microextraction (SPME) methods. 

VOLATILE LIPID ANALYSIS UTILIZING STATIC HEADSPACE GAS CHROMATOGRAPHY 

Static headspace GC involves heating the sample in an air-tight environment until the volatile lipids in the food reach an equilibrium with those in the surrounding air. The air above the sample (headspace) is then sampled and analyzed. Flame ionization detection (GC-FID) can be used for quantification and mass-selective detection (GC-MS) can be used for compound identification. This protocol also outlines semiquantitative and quantitative approaches for determination of volatile lipid concentration, and is particularly designed for analysis of a meat sample. 

---

D2.2 Chromatographic Analysis of Secondary Lipid Oxidation Products... 

Lipid oxidation was monitored through analysis of the hydroperoxide content measured via the ferric thiocyanate method [64]. Oil was extracted from an aqueous emulsion prepared from the microcapsules using isooctane/2-propanol 50 50 (v/v). Headspace gas chromatographic analysis of secondary lipid oxidation products was performed in the majority of trials, but since correlation of propanal as a key compound was always very good with the hydroperoxide content, data are not reported in this chapter. 

Many methods have been developed to access the extent of oxidative deterioration, which are related to the measurement of the concentration of primary or secondary oxidation products or of both. The most commonly used are peroxide value (PV) that measures volumetrically the concentration of hydroperoxides, anisidine value (AV), spectrophotometric measurement in the UV region and gas chromatographic (GC) analysis for volatile compounds. Vibrational spectroscopy, because of its high content in molecular structure information, has also been considered to be useful for the fast measurement of lipid oxidation. In contrast to the time consuming chromatographic methods, modem techniques of IR and Raman spectrometry are rapid and do not require any sample preparation steps prior to analysis. These techniques have been used to monitor oil oxidation under moderate and accelerated conditions and the major band changes have been interpreted. ... 

---