Surface properties of monoglyceride monolayers spread on aqueous glycerol solutions

Surface properties (structural characteristics and stability) of monolayers of monostearin, monopalmitin and monoolein, accepted as food emulsifiers, were studied using an automated Langmuir-type film balance. The monolayers were spread on aqueous glycerol solutions. The glycerol concentration in the subphase was between zero and 0.5 mol l-1. The compression isotherms were obtained over the temperature range 5-40°C. The results show reduced solid structure and increased liquid-condensed structure with glycerol in the subphase for monostearin and monopalmitin. The thermodynamic functions of the liquid-condensed to liquid-expanded transition were obtained. The results can be explained in terms of monolayer-subphase interactions. The monoolein monolayers have a liquid-expanded structure over the entire temperature range. Glycerol in the subphase reduces the monolayer stability with monostearin and monopalmitin, but increases it with monoolein.