Determination of the pH- and thermal stability mechanism of lipophilic protein–hydroxypropyl methylcellulose oil-in-water emulsion

Abstract

The aim of this study is to investigate the mechanism through which hydroxypropyl methylcellulose (HPMC) addition improves the stability of soybean lipoprotein (LP) under acidic conditions and the thermal stability of LP-HPMC emulsions. Results of SDS-PAGE, Raman spectroscopy, and X-ray diffraction studies reveal that the active sites of the LP-HPMC complexes varied with a change in pH and the amide III bands and the polarity of the microenvironment decrease with increasing HPMC content. The LP-HPMC complex does not form new subunits or crystals, but forms non-covalent bonds exploiting electrostatic and hydrophobic interactions. The addition of HPMC results in a change in the microstructure and droplet size distribution of LP-HPMC emulsions and an increase in the LP denaturation temperature; thus, the thermal stability of the emulsion decreases. This study can help develop non-heated emulsion delivery systems that remain stable in the gastric environment and promote the targeted release in the intestines.