The influence of carotenoids and tocopherols on the stability of safflower seed oil during heat-catalyzed oxidation

The stability and antioxidant effects of carotenoids and tocopherols in safflower seed oil were evaluated under thermal (75 degrees C) and oxidative conditions and the oxidative stability index (OSI) determined. The antioxidant capability of butylated hydroxytoluene (BHT) was also compared with that of beta-carotene in a model system. Lycopene and beta-carotene (1 to 2000 ppm) were heated (75 degrees C) and exposed to air (2.5 psi) in an oxidative stability instrument. beta-carotene had no antioxidant effect at concentrations below 500 ppm, because it did not alter the induction time. Lycopene increased the induction time only slightly at low concentrations. However, at concentrations greater than 500 ppm, both beta-carotene and lycopene acted as prooxidants, significantly decreasing the induction period. At the highest concentration, 2000 ppm, lycopene was more prooxidative than beta-carotene. alpha- and gamma-Tocopherol (concentration, 1000 ppm) delayed the induction rime by 16 and 26 h, respectively. There was no cooperative interaction between alpha-tocopherol and beta-carotene in delaying the onset of oxidation. Furthermore, BHT was significantly more antioxidative than beta-carotene. Thus, under thermal and oxidative conditions, beta-carotene could not delay the onset of oxidation. The tocopherols and BHT were effective in suppressing the onset of oxidation, as determined by the oxidative stability measurement.