Solid phase behavior of mixture systems based on tripalmitoyl glycerol and monounsaturated triacylglycerols forming a molecular compound

Abstract

Differential scanning calorimetry and X-ray diffraction were used to investigate the mixing behavior of triacylglycerol (TAG) mixtures of PPP/PPO (tripalmitoyl glycerol/1,2-dipalmitoyl-3-oleoyl-rac-glycerol) and PPP/MCPOP/PPO (being MCPOP/PPO the equimolecular blend of 1,3-dipalmitoyl-2-oleoyl-glycerol...

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

“…The presence of X SSS = 0.1 promoted the nucleation of 2L α-SSO based on the increase in peak temperature by ∼1 °C (Figure S2). Overall, this kinetic phase diagram was consistent with monotectic behavior seen in other TAG mixtures. , …”

“…Given the presence of oleic acid in SSO, we presumed that effective fatty acid chain packing in the solid state between SSO and SSS would be sterically hindered, irrespective of polymorphs. Macridachis et al (2022) reported the existence of phase separation in PPO–PPP mixtures due to steric hindrance between the straight palmitic acid chains of PPP and the angled oleic acid moiety of PPO . Two subforms of PPO (2L β′ and 3L β′) were found, depending on the ratio of PPP and PPO, suggesting the possibility of similar partitioning with SSS and SSO.…”

“…Mixed TAG systems in the solid state may associate with three equilibrium states. In a solid solution, structurally similar TAGs are randomly distributed throughout a crystal lattice akin to a liquid solution, with the resulting material having a uniform composition and properties intermediate between those of the individual TAG crystals. , An example is blends of POS and SOS, two common TAGs in cocoa butter. , In eutectics, TAGs mutually inhibit one another’s crystallization when mixed at set ratios, thereby yielding crystals with a lower melting point and enthalpy compared to the pure components. − Eutectics shift toward monotectics when the melting point separating the constituent TAGs increases above a critical value, with the lower-melting point species acting as a solvent for the higher-melting species. For example, the melting point difference of 28 °C in POP–PPP yields monotectic behavior, whereas the melting point difference of 22 °C in SOS–PPP results in a eutectic at 5 to 6% PPP. , Lastly, molecular compounds only form at distinct mole ratios, which results in mixed species with phase behavior different from that of the component TAGs. − Molecular compound traits include the presence of saturated–unsaturated mixed-acid TAGs where oleic acid is present and the conversion from 3L to 2L packing (e.g., SSO–SOS and PPO–POP). ,− …”

“…The term mixed crystal is commonly used in food fat crystallization studies and has different definitions. On the one hand, it is an older term that is synonymous with solid solutions. ,− More broadly, it describes crystals consisting of different compositions that may form distinct lamellae or domains within a TAG crystal lattice, e.g., in POP and PPP or PPO and PPP . Whether these structures are kinetic in nature will be highly dependent on not only TAG ratios but also the thermal treatment and storage conditions.…”

“…18,19 An example is blends of POS and SOS, two common TAGs in cocoa butter. 20,21 In eutectics, TAGs mutually inhibit one another's crystallization when mixed at set ratios, thereby yielding crystals with a lower melting point and enthalpy compared to the pure components. 22−24 Eutectics shift toward monotectics when the melting point separating the constituent TAGs increases above a critical value, with the lower-melting point species acting as a solvent for the higher-melting species.…”