The Stability of Palm Oils During Heating in a Rancimat

The crude palm oil (CPO) and refined palm oil (PO) not only have a balance of saturated and unsaturated fatty acids but also have the highest β–carotene and vitamin E compared to others vegetable oils. A series of aliphatic aldehydes starting from hexanal to decanal was identified by LC-MS/MS and quantified as DNPH derivatives. In addition, the total amount of carbonyls was determined based on the calibration with hexanal. Looking at the kinetic profile of the carbonyl formation in crude palm oil and refined palm oil, both of the oils were still stable until 10 h of oxidation with the Ranzimat at 120 °C. The analytical method for quantifying the vitamin E and β–carotene are quick, reliable, precise, economical and suitable for the routine analysis. For both analyses, a simple dilution of the oil was necessary. The quantitative analysis showed that β–carotene in the oxidized crude palm oil decreased from 2.34 mg/g to 0.33mg/g within 7.5 h of oxidation. However, after 7.5 h, no more β–carotene was detected. In addition, β–carotene was not detected in refined palm oil. The HPLC-DAD method developed for the β–carotene in the crude palm oil was validated. The coefficient of determination (0.999) of the linear regression indicates a good correlation between the peak area and the amount of β–carotene. The linearity of the β– carotene analysis was tested in the range 0.00078–0.05 μg/cm3. The limit of detection (LOD) was 2.65 μg/cm3 and the limit of quantification (LOQ) was 8.83 μg/cm3 for β–carotene. Vitamin E in both refined and crude palm oil, δ–tocotrienol and γ–tocotrienol, have the long shelf life compared to α–tocopherol and γ–tocopherol. The δ–tocotrienol is degraded slowly and can be found even after 15 h of oxidation with 0.035 mg/g remaining in the oxidized crude palm oil. However, in refined palm oil, the δ–tocotrienol could be determined until 11 h of oxidation with 0.49 mg/g.