High Hydrostatic Pressure Improves Protein Solubility and Dispersion Stability of Calcium-Added Soybean Proteins

MANASSERO, CARLOS; VAUDAGNA, SERGIO; ANTON, MARC; DE LAMBALLERIE, MARIE; AÑÓN, MARÍA CRISTINA; SPERONI, FRANCISCO

Nantes

Conferencia; 8th International Conference on High Pressure Bioscience and Biotechnology HPBB2014; 2014

Introduction: Solubility, aggregation and dispersion stability are leading properties of proteins in liquid foods. Ca2+-added soybean proteins are an interesting source of nutrients, but insolubilize and settle under most conditions. Methods: solubility, turbidity, aggregate size and free Ca2+ concentration were evaluated on different soybean protein (SP) samples: pH: 5.9 - 8.0, protein concentration: 0.1 - 9.5% w/w, Ca2+ concentration: 0 - 15 mM, before and after high hydrostatic pressure (HHP) treatments at 200, 400 or 600 MPa.Results and Discussion: HHP reverted Ca2+-induced insolubilization and kinetically improved stability of SP isolates. These effects were verified, with different magnitude, under most of the evaluated conditions of pH, protein and Ca2+ concentration at 400 and 600 MPa. HHP broke up the Ca2+-induced aggregates, leading to soluble aggregates with an intermediate size between those of untreated Ca2+-added (biggest, insoluble) and those without Ca2+ (smallest ones). E.g. at pH 7.0, 1% w/w protein and 5 mM Ca2+, Ca2+-induced insoluble aggregates (1000-5000 nm) were split by 600 MPa to species of 70 - 500 nm. Outstanding, the fraction that remained insoluble after HHP exhibited an increased colloidal stability: turbidity was stable upon time or weak centrifugation. No change in free Ca2+ concentration was observed after HHP treatments. However, Ca2+-protein dissociation may occur during HHP treatment due to electrostriction and reversible HHP-induced pH-decrease. Thus, denaturation may occur on Ca2+-dissociated proteins, with a later re-binding after HHP release. SP isolate at 9.5% w/w treated by HHP and with 15 mM Ca2+ formed transparent gels, suggesting that an ordered gel was made up from soluble protein. The solubilizing and stabilizing effects of HHP were also observed in Ca2+-added soymilk, a more complex system because of lipids and carbohydrate presence. These effects constitute an advantage over those observed after a traditional thermal treatment, encouraging to apply HHP in food processing.