Abstract

Oryzanols are frequently found in rice bran oil but almost completely removed in the neutralization step when the oil is chemically refined. In this way, oryzanols can be recovered from the soapstocks to generate a concentrate. Thereby, they could be used as antioxidants in lipids for specific purposes. In the present work the antioxidant power of oryzanols concentrate (33% purity) was studied together with pure oryzanols and butylhydroxytoulene (BHT). Methyl esters were prepared from regular sunflower oil without antioxidants to which the antioxidants before mentioned were added in an effective concentration of 3x10^-3 M. The samples were oxidized in a heating block with oxygen flow and the hydroperoxides of linoleic acid methyl ester were analyzed. It was observed that all antioxidants were able to protect the sunflower oil methyl esters from oxidation with respect to methyl esters without antioxidants. Oryzanols presented a notoriously lower protection ability compared to BHT. However, the formation of the linoleic acid methyl ester hydroperoxides and their proportion, for the same oxidation stage, did not show differences between the antioxidants used. Therefore, the oxidation kinetics were similar between the different antioxidants studied.

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