Study on the gel properties, interactions, and pH stability of pea protein isolate emulsion gels as influenced by inulin

Abstract

The gel properties of underutilized plant proteins, such as pea protein isolate (PPI), can be improved by adding inulin (a prebiotic). Herein, the effects of the inulin concentration (10–70 g/L) on the rheological, mechanical, and microstructural properties, as well as the interactions and pH stability of PPI-based emulsion gels, fabricated by combining high-pressure homogenization and Ca2+-induced gelation, were investigated. The highest gel strength (166 ± 3 N) and water-holding capacity (91.5 ± 0.9 g/100 g) were reached with an inulin concentration of 50 g/L. Scanning electron microscopy revealed that inulin changed the emulsion gel microstructure from porous with a rough surface to dense with a smooth surface. The enhanced gel strength can be explained by the highly cross-linked gel network. The protein solubility results indicated that hydrogen bonding and hydrophobic interactions play important roles in improving the gel properties, and infrared spectroscopy confirmed the important role of hydrogen bonding during PPI–inulin emulsion gel formation. The PPI–inulin emulsion gels were more stable at pH 2.0. These results reveal a possible method for preparing stable and natural carriers with suitable gel properties to deliver lipid-soluble food bioactives.