Polymorphic transitions of mixed triglycerides, SOS, in the presence of sorbitan monostearate

The polymorphic behavior of 1,3-distearoyl-2-oleo glycerol (SOS) has been investigated in the presence of a selected food emulsifier, sorbitan monostearate. Five polymorphs, named α, γ, pseudo-β′, and β₂, and β₁ were crystallized and identified by both x-rays and DSC. Each polymorph was treated using two selected protocols-the "screen cycle" and the "aging cycle." It has been demonstrated that sorbitan monostearate, when present in the molten fat, will significantly retard the α to γ transition during both the screen cycle and the aging cycle. A retardation effect was not detected for the γ to pseudo-β′ transition (during the screen or the aging cycle). The emulsifier that is inserted into the fat behaves as a conventional impurity, causing significant reduction in the melting temperatures of each polymorph. As a result, the fat tends to melt prior to its transition. The behavior of SOS in the presence of the sorbitan monostearate is therefore different than that of SSS (tristearin), and may explain, in part, the absence of the strong blooming transition to high melting polymorph that occurs when the fat is rich in SOS. This behavior can also shed some light on the behavior of cocoa butter in the presence of sorbitan esters.