Acidification and Calcium Addition Effects on High-Pressure and Thermally Induced Pulse Protein Gels

Modulating the characteristics of pulse protein gels provides opportunities for creating gelled products with unique structures and textures. This work investigates the effects of acidification (pH of 6.3-6.6, 5.5, 4.5), calcium addition (0-30 mg Ca/g protein), and process type (nonthermal vs. thermal) on the structural characteristics of gels made from pea, lentil, and faba bean protein concentrates. Protein concentrate suspensions were processed under conditions that lead to gel formation, either by high-pressure processing (HPP) at 600 MPa, 5 °C for 4 min, or thermal processing at 95 °C for 15 min. The resulting gels were evaluated for rheological properties, texture, water holding capacity, and structure. Both acidification and calcium addition increased protein aggregation due to reduced electrostatic repulsion among protein molecules. Acidification increased the strength of both HPP- and thermally induced gels, while the effect of calcium addition depended on pH and process type. Generally, HPP-induced gels had lower mechanical strength than thermally induced gels, but certain combinations of acidification and calcium addition produced HPP-induced gels stronger than their thermally induced counterparts. These results demonstrate how the structure and mechanical properties of pulse protein gels can be customized through a combination of acidification, calcium addition, and processing. This approach can be used as a foundation for the development of plant protein-based foods of desired structure and texture.