Stability determination of soy lecithin-based emulsions by Fourier transform infrared spectroscopy

The stability of soy lecithin-stabilized emulsions was determined by Fourier transform infrared spectroscopy. Oilin-water (o/w) emulsions were prepared with 6% (vol/vol) medium-chain triglycerides (MCT), 94% (vol/vol) water, and 4% (wt/vol) Lecigran and Lecimulthin soy lecithin. There were little or no differences between the 4% Lecigran and 4% Lecimulthin emulsions for all vibrational regions studied (OH at 3348 cm⁻¹, C=O at 1741 cm⁻¹, PO and C−O−C at 1157 cm⁻¹, and P−O−C at 1101 cm⁻¹), but the control emulsion, without emulsifier, had increased vibrations as the emulsion separated. The weaker vibrations of the more stable emulsions were probably due to reduced molecular interaction at the interface. However, added magnesium or calcium chloride enhanced the vibration of these groups, probably by disrupting the lecithin interaction at the emulsion interface.