Methods to determine the extent of lipid oxidation in foods - Oxidation in Foods and Beverages and Antioxidant Applications - page 190

8.6 Research methods to study oxidation in foods and
beverages
Most of the analytical method development in the area of evaluating oxidation
status has been performed and evaluated for the study of neat lipids or lipids
extracted from foods. The extent of oxidation in fats and oils can be evaluated by
different complementary methods, and research questions can be answered fairly
convincingly. On the other hand, methods to study the extent of lipid oxidation
in complex foods and beverages are still in their infancy. Extraction of lipids
from these samples is not only tedious but it also introduces analytical errors
because of the instability of the oxidation products, particularly hydroperoxides,
or co-extractability of other molecules (Velasco et al., 2008).
The two most commonly used methods to extract lipids from complex
matrices are the Folch method (Folch et al., 1957), the Hara and Radin method
(Hara and Radin, 1978), and their modifications. In general, increased extraction
solvent polarity is needed for extracting highly oxidized lipids or oxidized lipids
in difficult matrices because of the binding of lipid oxidation products.
Specifically, the extractability of the volatile oxidation products may be
significantly affected by the food matrix. Moreover, lipid oxidation products are
highly unstable and the reaction mixture is significantly dynamic. Studies on the
effect of extraction conditions and other sample treatments on the oxidation
status are highly warranted.
8.7 Future trends
With the current advances in statistical tools, it is possible to process complex
data such as that generated by analysing lipid oxidation by NMR, IR, or mass
spectrometry, alone or coupled to chromatography. Certain extractions and/or
chemical modifications can be performed to signal particular molecules and the
comprehensive NMR, IR, MS or both can be repeated before chemometrics can
be applied to extract information pertinent to the evolution of molecular species
and the progress of the reaction.
8.8 Sources of further information and advice
Detailed chapters dedicated to the use of common techniques in the analysis of
lipid oxidation can be found in A. Kamal-Eldin and J. Pokorny, eds. 2005,
Analysis of Lipid Oxidation, AOCS Press, Champaign, IL.
8.9 References
AL-ALAWI A, VAN DE VOORT F R and SEDMAN J (2004), `New FTIR method for the
determination of FFA in oils', J. Am. Oil Chem. Soc., 81, 441±446.
AL-ALAWI A, VAN DE VOORT F R and SEDMAN J (2005), `A new FTIR method for the