Tagatose esters for high internal phase emulsion stabilization: Synthesis and structure-property relationships

Sugar ester emulsifiers incorporating low calorie sugars enhance functional foods with desirable health benefits. Tagatose is a naturally occurring, low calorie hexose with useful functional properties. This study describes the enzymatic synthesis and functional evaluation of tagatose-based fatty acid monoesters with C8–C22 side chains. The new esters have tunable hydrophilic-lipophilic balance (HLB) values (5.8–9.7) and significantly reduce oil-water interfacial tension at 0.05–0.1 wt%, demonstrating their value as emulsifiers. Compounds with C8–C14 side chains effectively stabilize oil-in-water high internal phase emulsions (HIPEs, ϕ = 75 %), with a C10 ester performing best. The formulated HIPEs have high elastic moduli and viscosities, maintaining stability for over 27 days across temperatures ranging from ambient to 65 °C and through three freeze-thaw cycles. The findings reported here highlight the potential for low-calorie tagatose esters to serve as next-generation surfactants in functional food emulsions.