Determination of mono- and diglycerides in palm oil,olein and stearin

Partial glycerides are important constituents of palm oil and can have significant effects on the physical properties of products containing palm oil or on the fractionation of palm oil. A method is described for their routine determination in palm oil. By analysis of 28 weekly composite samples of crude palm oil the following results were obtained: free fatty acids, mean=3.76%, range 2.4 to 4.5%; monoglycerides, mean=0.28%, range 0.21 to 0.34%; diglycerides, mean=6.30%, range 5.3 to 7.7%. During detergent fractionation of palm oil, diglycerides concentrate in the palm olein, but monoglycerides concentrate in the palm stearin. Palm fatty acid distillate was found to contain approximately 3% each of mono- and diglycerides. Because the refining and fractionation processes are continuous in the refinery, it is not possible to follow a single identifiable batch of crude palm oil through the refinery. To circumvent this problem, crude palm oil, stearin and olein from the refinery were bleached and steam refined in the laboratory and the partial glyceride contents determined at each stage of processing. Except for fractionation, the content of glycerides did not change during processing. For oil, olein and stearin, monoglycerides were reduced significantly both after bleaching and after steam refining.