Effect of pH and high hydrostatic pressure on physicochemical and emulsifying properties of calcium added soybean proteins

MANASSERO, CARLOS A.; DAVID-BRIAND, ELISABETH; DE LAMBALLERIE, MARIE; SPERONI, FRANCISCO; ANTON, MARC; BEAUMAL, VALERIE; VAUDAGNA SERGIO

Nantes

Congreso; Biopolymers 2017: Key Ingredients for the Food Transition; 2017

Calcium addition to vegetable-based foodstuff is important from nutritional and functional points of view. Emulsion stability is sensitive to pH, salts concentration and molecular structure of emulsifier. The aim of this work was to deepen the knowledge about mechanisms involved in the stabilizing and solubilizing effects of high hydrostatic pressure (HHP) on calcium-added soybean protein isolate (SPI) and to evaluate the emulsifying properties of these modified proteins. SPI dispersions were characterized by evaluating the effect of pH (5.9 or 7.0), protein (5 or 10 g L-1) and calcium (1.25 ? 5 mmol L-1) concentrations and HHP level (0.1 or 600 MPa) on protein solubility, colloidal stability, particle size distribution and ζ-potential. Emulsions (o/w, Φ = 0.28) were characterized by evaluating particle size distribution, flocculation index and surface protein concentration. HHP treatment increased the amount of protein that remained in supernatant after centrifugation by splitting aggregates, a fraction of this stabilized protein was insoluble and its size seemed to be the most important factor determining protein content in supernatants. Coalescence and bridging flocculation of emulsions was enhanced by calcium-HHP combination. Increasing protein concentration increased flocculation in pressurized calcium-added samples despite having enhanced interfacial protein concentration (up to 7 mg.m-2). Emulsion behaviors depended on combination of factors: separately and at pH 7.0 calcium and HHP stabilized emulsions, whereas combined calcium and HHP worsened emulsion stability at both pHs. Insoluble aggregates seemed to be responsible for these differences, since soluble protein exhibited similar interfacial activities. Some macroaggregates (ca. 2 ? 4 µm) might be re-structured during homogenization and were prone to sticking to other proteins, increasing the amount of adsorbed protein and the level of flocculation. Therefore, combination of calcium and HHP seemed to be more useful for functional properties where protein-protein association is needed.