The progress of hydrogenation of palm stearine using a trans promoting catalyst has been followed by monitoring the chemical composition and the thermal properties by NMR and DSC techniques. The results show that hydrogenation occurs in 2 stages. In the first stage, the formation of the triglyceride, PEP from the lower melting PLP, allows an enhanced mixed crystal formation with the high melting PPP. Although this promotes a greater rate of crystallization in the α form and transformation to the β′ form in tempering, further transformation to the β form is inhibited. Tm is thereby reduced in the early stages even though both the rate of crystallization and the solid fat content at temperatures <40°C are increased. In the later stages of hydrogenation, the conversion of the triglyceride POO to the higher melting POS increases the proportion of the sample which can crystallize in the high melting fraction to at least 80%. Although this still cannot be transformed into the β crystal form, Tm for the overall sample and the solids content at all temperatures are now greater than those of the original palm stearine sample. © 1990 American Oil Chemists' Society.
