Temperature-Dependent Mixing Behavior of Tristearin and 1,2-Distearoyl-3-oleoyl-rac-glycerol (SSO)

Abstract

We explored the temperature-dependent polymorphism and thermal behavior of binary blends of the triacylglycerols tristearin (SSS) and 1,2-stearoyl-3-oleoyl-rac-glycerol (SSO). We created a kinetic phase diagram based on heating and cooling treatments from 80 to 20 °C at 1 °C/min and back. Under these conditions, SSS dominated SSO–SSS thermal behavior down to a mole fraction (XSSS) of 0.2. The presence of SSO at XSSO = 0.1 to 0.8 promoted the polymorphic transition of SSS from α to β, whereas SSS at XSSS = 0.1 to 0.7 enhanced the transition of SSO from double- and triple-chain length α-crystals to triple-chain length β′-crystals. Results showed that SSS was miscible in molten SSO in the metastable and stable polymorphs at all mole fractions studied. Finally, there was evidence of possible mixed crystal formation between SSO and SSS at XSSO = 0.2 to 0.9, for which we describe a number of possible causes. Outputs from this study provide further insights into the interactions of SSO and SSS as may occur during crystallization, fractionation, and product storage in fat-containing foods.