Lipid oxidation and total lipid content in foods.
Does lipid oxidation determine the decrease of the total fat content determined by the AOAC method (extraction with petroleum ether), or just a qualitative change of lipids?
Thiobarbituric acid reactive substances (TBARS) was negatively correlated with fat content.
Sasaki K, Mitsumoto M and Kawabata K (2001). Relationship between lipid peroxidation and fat content in Japanese Black beef Longissimus muscle during storage. Meat Science, 59 (4): 407-410
Depends on the method you use to determine lipid oxidation
Determining lipid oxidation is not my aim, but I was wondering if it is possible to justify a change in total lipids with lipid oxidation occurring. Oxidation produces hydroperoxides, which should not be extracted by petroleum ether, so this might explain a loss of total lipids... does anyone have evidence for this?
Well, in my opinion the changes in lipids caused by lipid oxidation concern much more their fatty acid composition and not the their quantity. I myself am currently performing research on the changes in the fatty acid composition of lamb and pork as well as their oxidative stability. We are extracting lipids using the method of Bligh and Dyer on the same intervals as we measure the lipid oxidation (TBARS content). I cannot say that the increase of the TBARS content is corresponding every time to a decrease in the total lipid content during storage. Besides sometimes TBARS decrease because they react with other compounds and this does not mean of course that lipid oxidation has stopped. I mean my research is not confirming the negative correlation between the TBARS and total lipid content mentioned above by Dr. Mansour. There are authors which opinion coincide with mine (in poultry), while on the other hand some researchers in Asia do explain that the substantial decrease in the total lipid content in fish subjected to storage is due to oxidative changes in lipids. I'm attaching the two points of view, hoping this helps.
I would think that the change in fat content resulting from lipid oxidation will get lost in the noise of the errors made in the fat extraction itself. Fat extraction is entirely solvent and solvent mixture dependent.
I fully agree with Dr Richard. Lipid oxidation determination is usually for qualitative changes. Simple methods available for quantitative estimation are the best options for determining fat content.
I do agree with Richard. Lipid oxidation may lead to numerous products that could still soluble in petroleum ether. Eventhough some may not be extracted by petroleum ether, their quantity will not be important to significantly change the total lipid content.
I am also wondering whether the oxidation process can change the total lipid content. Since the oxidation process produces volatile compounds, they may be lost upon storage. How much is the quantity of the volatiles is the main thing to be considered. Please share if someone has relevant literature.
- Badges
- Science method