Effects of glycerol monooleate and water on fat crystallization

Water and surfactant are critical components in the formulation and stabilization of water-in-oil (W/O) emulsions. Solidified lipids present in the continuous phase are another component often used to modify the rheology and to extend the stability of many W/O emulsions. Yet, surprisingly little is known regarding how the interactions between these three components may be used to structure the continuous oil phase of W/O emulsions. The present study investigated how the admixture of low water amounts and glycerol monooleate (GMO) would alter the phase transitions and rheology of a tristearin-rich hydrogenated fat dissolved in vegetable oil. Samples were cooled 80 °C to -10 °C at 2°C/min where they were held for 10 min and then heated to 80°C at 2°C/min. Under these experimental conditions, the water and GMO increased the stiffness of the hydrogenated fat gel by over two orders of magnitude (from ~ 0.2 kPa to 50-100 kPa), with a clear influence well beyond simple mass effects shown by both the GMO and water. There were corresponding changes in the fat crystallization and polymorphic behaviour induced by the GMO and water. Notably, addition of GMO and water led to greater persistence of the fat’s α-polymorph which may have been associated with the formation of a GMO reverse hexagonal liquid crystalline array. The GMO in oil alone solidified as discrete crystals whereas the added presence of water led to the presence of liquid crystals. Overall, this study showed that the presence and interactions of different constituents added to W/O emulsions can significantly alter their structure and rheology, which is a key criterion in the elaboration of novel emulsion-based foods.