Fatty acid ester surfactants derived from raffinose: Synthesis, characterization and structure-property profiles.

The development of functional and nutritional surfactants for the food industry remains a subject of great interest. Herein, therefore, we report on the design and synthesis of novel trisaccharide (raffinose) monoester-based surfactants in the expectation that they would display functional properties superior to certain disaccharide-based, commercially-deployed emulsifiers and thus have potential for industrial applications. The title esters were prepared by enzymatic methods and their properties as surfactants evaluated through determination of their HLB values, water solubilities, CMCs, foamabilities and foaming stabilities as well as through investigation of their impacts on the stability of oil-in-water emulsions over a range of storage times and under certain other conditions. The emulsifying properties of 6-O-acylraffinose esters are dictated, in large part, by the length of the associated alkyl chains. The results of storage and environmental stress experiments revealed that the increasing length of alkyl chains enhances the stability of the derived emulsions. All the raffinose ester-stabilized oil-in-water emulsions displayed stratification effects under strongly acidic conditions (pH ≤ 4) or at high ionic strength (≥300 mM) while possessing reasonable resistance to variations in temperature. As such, a number of the raffinose monoesters showed greater stability to environmental stress than their commercially-deployed and sucrose-based counterparts. The structure-property profiles established through the present study provide a definitive guide for the development of raffinose esters as novel emulsifiers, particularly in the food industry.