Sugar Alcohol Esters: Peering into the effect of stereoisomerism on their self-assembly, gelation, emulsifying properties and functional performance

Mannitol differs from sorbitol only by virtue of having opposite optical activity through the difference is the orientation of the C2 hydroxyl group. The self-assembly and emulsifying mechanism of supramolecular, stereoisomeric sugar fatty acyl molecular gelators were evaluated. Bio-catalytically enabled mannitol dioctanoate (M8) and sorbitol dioctanoate (S8) were tested. The stereoisomeric difference between the sugar groups significantly affected the gelation and emulsifying properties of the gelators. This difference had shown significant impact on the physical, thermal, and mechanical properties of their resulting oleogels. The effect of such a stereoisomeric molecular difference on assembly and emulsification mechanism of supramolecular assemblies are intriguing. Therefore, a detailed investigation was conducted to evaluate the emulsifying nature of molecular gelators. M8 and S8 formed oleogels at 2% and 3.5% (w/v) and emulsified water up to 30% and 60% (v/v), respectively. Microscopic study showed that the gelator fibers are at the W/O interfaces, demonstrating the solid particle or network mode of stabilization. The long fibers of M8 were unable to completely encompass the water droplets and resulted in poor emulsification. Small, hair-like fibers of S8 showed better emulsification. This study proved that a subtle stereoisomeric difference at the molecular level can greatly alter the supramolecular and emulsifying properties of sugar-fatty acyl compounds.