Relating crystallization behavior of monoacylglycerols-diacylglycerol mixtures to the strength of their crystalline network in oil

Diacylglycerols (DAGs) are interesting oil structuring molecules as they are structurally similar to triacylgly-cerols (TAGs), but are metabolized differently which results in weight loss and improved blood cholesterol levels upon dietary replacement of TAGs with DAGs. Many commercial products consist of a mixture of mono-acylglycerols (MAGs) and DAGs, yet the effect of MAGs on the crystallization behavior of DAGs is still to be unraveled. Two types of commercial MAGs, one originating from hydrogenated palm stearin and one of hydrogenated rapeseed oil, were added in concentrations 1, 2 and 4% to 20% DAGs derived from hydrogenated soybean oil. Using differential scanning calorimetry, it was shown that the presence of MAGs delayed the onset of DAG crystallization. Rheological analysis revealed that MAGs also hindered crystal network development. Synchrotron X-ray diffraction analysis demonstrated that the addition of MAGs suppressed the formation of the A form and stimulated the development of the beta' form. Likely, MAGs mainly hindered the crystallization of 1,3-DAGs, which are responsible for the development of the beta form, and stimulated the crystallization of the 1,2-DAGs, which can crystallize in the alpha and beta' forms. The presence of two polymorphic forms resulted in a decrease of the crystal network strength, as was derived from oscillatory rheological measurements. This research implies a different effect of monoacylglycerols on both the nucleation and crystal growth of 1,2- and 1,3-DAG isomers. This insight is not only relevant for oleogelation research, but also for emulsifying agents which often contain blends of MAGs, 1,2-DAGs and 1,3-DAGs.