Structural modification of lentil protein enhances electrostatic complex formation with pectin and hydrogel particle development

Abstract

Protein–polysaccharide interactions play a crucial role in determining the texture, stability, and functionality of many food systems. However, plant proteins often possess rigid structures that limit their ability to interact with polysaccharides. This study explored how structural modification of lentil protein, through pH-shifting and heat treatment, influences its capacity to form electrostatic complexes with pectin. Confocal microscopy and particle size analysis showed that heat treatment alone was insufficient to promote complex formation. In contrast, pH-shifting (pH 12 → 7) followed by heating treatment at 75 °C led to the formation of uniform and micron-scale protein–polysaccharide complex (i.e., hydrogel particles). Zeta potential measurements confirmed minimal changes in the surface charge of the modified protein after treatment, indicating that the observed complexation was primarily driven by structural modifications rather than changes in electrostatic properties. Hydrophobicity and circular dichroism analysis further revealed that pH-induced unfolding increased molecular flexibility and enhanced protein–polysaccharide interactions while minimizing irreversible aggregation. These findings demonstrate that controlled structural modification of plant proteins, such as lentil protein, can improve their functional performance and promote the complex formation with polysaccharides. Such complexes can be further engineered into particles with tunable texture and rheological properties, making them suitable as fat replacers, texture modifiers, or delivery systems for bioactive compounds in various food applications.