Measurement of Peroxide Value of Fatty Acids by Near Infrared Reflection Spectra and Analysis of Oxidation Rates

Abstract

Oleic, linoleic and linolenic acids were oxidized at 40°C in darkness. The near infrared reflection spectra applied to them were measured in appropriate intervals. At the same time, the peroxide values of fatty acids were measured by a titration method. As a result, a regression equation to presume the peroxide value by using the second derivative values of the spectra was obtained. This regression equation was applicable to the three kinds of fatty acids. The rate constant at each stage of the oxidation (initiation, chain reaction, polymerization, and decomposition period) was obtained by using the kinetic equation of autoxidation of fatty acid. The rate constants of the initiation period of the three fatty acids were almost the same, regardless of the kind of the fatty acid. Those of the chain reaction periods were also the same. However, the rate constants of the polymerization and the decomposition periods increased in relation to the number of double bonds present in the three fatty acids.