In this study, maltoheptaose (G7)-based sugar esters were synthesized from maltoheptaose and fatty acids (C10-C16) using a commercial lipase. With the exception of dimethyl sulfoxide (DMSO; 76.4%, w/v), G7 showed only limited solubility in organic solvents. Among the fatty acids, palmitic acid (PA) was the best substrate for G7-based ester formation. G7-PA ester was successfully synthesized as the monoester structure exclusively in 10% DMSO of t-butanol with a 22% conversion yield. NMR and enzymatic analyses of the purified monoester product revealed that the ester bond in the G7 was located at C-6 of the glucose at the reducing end. The G7-PA monoester showed the melting temperature at 56.3 °C that was 6.5 °C lower than that of the free PA and exhibited a different endothermic pattern from the free G7. The G7-PA monoester exhibited excellent emulsifier potential with more even droplet size distribution compared with the commercial sucrose esters for an oil-in-water emulsion system.
Keywords: Emulsifier; Esterification; Lipase; Maltoheptaose; Sugar esters.
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