The supernatant sludge from the palm oil mill was determined to be surface active from surface tension measurement. In crude palm oil (CPO)/ sludge supernatant, the interfacial tension was determined to be 3 mN m^-1 which is favourable for the formation of oil droplets in the CPO slurry.

The refined oil / water systems have higher interfacial tension compared to the CPO / water system. Depending on whether the CPO is chemically or physically refined, the oil/water interfacial tension differs and can be as high as 25.6mN m^-1 and 12.7mN m^-1 respectively compared to an interfacial tension of 8.00 mN m^-1 in the CPO/water system. The higher interfacial tension value indicates more efficient removel of surface active compounds from the chemically refined oil. This may have great implications in the quality and utilization of palm oil in food processing.

The interfacial tension values of the partially refined oils as sampled from various points of refining were found to increase as the oil is processed. In view of this increase, interfacial tension could possibly be used as a process control parameter in the refining of CPO.

Lecithin and monoglycerides were determined to significantly reduce the interfacial tension at the refined palm oil/ water interface. Some of the common minor constituents found in CPO such as carotene, diglycerides, fatty acids and cholesterol did not show surface activity at the refined palm oil /water interface.