Interactions between glycerol monooleate and saturated triacylglycerols interactions at the oil-water interface

Fat crystal-stabilized emulsions are present in products such as tablespreads and cosmetics. They comprise a dispersed aqueous phase stabilized by a matrix of crystallized triacylglycerols (TAGs). Emulsifiers such as glycerol monooleate (GMO) can induce the crystallization of TAGs at the surface of water droplets in water-in-oil emulsions. Still, how emulsifiers induce interfacial crystallization remains poorly understood. Here, we used differential scanning calorimetry and X-ray scattering to obtain information on the phase transitions of TAGs and GMO mixed with small amounts of water. Samples comprised 0 to 2 wt% deionized water dispersed in vegetable oil that contained 5 wt% GMO and 5 wt% fully hydrogenated soybean oil (FHSO). The samples were cooled from 60 °C to 20 °C or -10 °C at 5 °C/min, kept isothermally for 20 min, and heated to 60 °C at 5 °C/min. An increase in water from 0 to 2 wt% decreased the FHSO crystallization onset from 26.2 °C to 24.9 °C, demonstrating that the water possibly altered how the FHSO and GMO were interacting in the presence of water. During the ensuing isothermal hold at 20 °C, an exotherm associated with ongoing FHSO crystallization was detected ~3 min (with no water) and ~11 min (with 2 wt% water), suggesting that association of GMO with water was responsible for the retarded crystallization of the fat. In experiments with an isothermal hold at -10 °C, there were no thermal transitions associated with GMO crystallization when at least 0.5 wt% water was present. This suggested that water presence prevented the lamellar packing of the GMO thereby preventing its crystallization. Together, these results demonstrated that the mixing behaviour of TAGs and surfactants in the presence of small amounts of water is complex and may influence the crystallization kinetics of fats in complex food blends.