Rheological properties and permeability of soy protein-stabilised emulsion gels made by acidification with glucono-δ-lactone

BACKGROUND: Soy protein, an important efficient emulsifier, is widely used by the food industry for incorporation into milk, yogurts, ice cream, salad dressings, dessert products, etc. The objective of this study was to investigate the rheological and physical properties of soy protein-stabilised emulsion gels as affected by protein concentration and gelation temperature. RESULTS: The rheological properties and permeability were determined using oscillatory rheometry, permeability and whey separation. The modulus (G' and G ''), fracture stress and fracture strain of acid-induced emulsion gels after 20 h of glucono-delta-lactone addition depended strongly on soy protein concentration and gelation temperature. At increasing soy protein concentrations, acid-induced emulsion gels had shorter gelation times but higher storage moduli (G'), fracture stresses and strains. Increasing gelation temperature decreased the gelation time, G', fracture stresses and strains. Permeability and whey separation were significantly affected by the protein concentration and the gelation temperature. A significant positive correlation was observed between whey separation and permeability coefficient in emulsion gels formed at different temperatures. CONCLUSION: The rheological properties and permeability of soy protein-stabilised emulsion gels were significantly influenced by protein concentration and gelation temperature. (C) 2011 Society of Chemical Industry