Effects of conjugated linoleic acid on the degradation and oxidation stability of model lipids during heating and illumination

The effects of methyl conjugated linoleate (MCLA) on the degradation and oxidative stability of model lipids, methyl linoleate (ML), methyl oleate (MO) and methyl stearate (MS), during heating at 100, 150 or 200 degreesC for 3 h or illumination at 4000 lux for 14 days were studied. Results showed that under either temperature treatment or illumination, MCLA was the most susceptible to degradation, followed by ML, MO and MS. At 100 degreesC, peroxide formation was the main reaction in each model lipid. However, at 150 degreesC, peroxide formation was the main reaction in the initial period of heating, followed by degradation. At 200 degreesC, the degradation was the major reaction. In contrast, peroxide formation was the main reaction for each model lipid during illumination. The addition of MCLA may slow degradation of each model lipid during heating. However, the oxidation stability of the whole system (model lipid plus MCLA) may also be decreased. Under light storage, the effect of MCLA was insignificant. (C) 2001 Elsevier Science Ltd. All rights reserved.