The peroxide index quantifies the hydro-peroxide formed as the initial product of lipid oxidation.
This parameter was determined because the antioxidative treatment applied to fried potatoes cannot only contribute to lowering the concentration of acrylamide, but can also prevent the oxidation of lipids that produces a disagreeable rancid odor in some foods.
Kochhar (2000)mentioned that antioxidants retarded oxidation reactions and inhibited the formation of free radicals by donating hydrogen atoms. It is important to point out that the concentration of the antioxidants present may influence their behavior.
Nogala-Kalucka, Korczak, Elmadfa, and Wagner (2005) found that at high concentrations, tocopherol may act as a pro-oxidant by diminishing the stability of
fats or oils and that this may also be the effect of green tea and thyme extracts.
Moreover, Manzocco et al. (1998) stated that the use of antioxidants in frying processes has the inconvenience of creating low stability in most of them at high temperatures.