The effect of sterilisation on palm oil from different degrees of oil palm ripeness was investigated in terms of deterioration of bleachability index (DOBI) value. The experimental treatment was carried out at different temperatures and durations using Response Surface Methodology (RSM). Results showed that DOBI value in this study, ranging from 2.3 to 4.6, were recorded from crude palm oil (CPO) extracted from unripe and underripe fruits, respectively. Improved DOBI value was obtained compared to conventional method where optimum sterilisation process used was 90°C and in not less than 80 min.