29B-26 |
Interaction of mesquite gum with milk whey or chitosan in concentrated O/W emulsions and effect on emulsion rheology |
J. O. Ruiz-Ramos1, J. P. PÉREZ-OROZCO2, E. Bosquez-Molina3, F. Cruz-Sosa3, and E. J. Vernon-Carter4. (1) IPH, Universidad Autonoma Metropolitana, San Rafael Atlixco # 186, Mexico City, 09340, Mexico, (2) IPH and DIQBQ, Universidad Autonoma Metropolitana e Instituto Tecnológico Zacatepec, Zacatepec, Mexico, (3) I.B., Universidad Autonoma Metropolitana-Iztapalapa, Mexico, (4) IPH, Universidad Autonoma Metropolitana-Iztapalapa, Mexico City, 09340, Mexico Competitive interactions between polysaccharides and proteins are important in stabilizing dispersed systems. Whey protein (WP) and chitosan (C) have been used as emulsifying agents of O/W emulsions, and an enhanced stability of these systems could be increased if a cooperative competitive adsorption between WP or C and mesquite gum (MG) could be achieved, so as to increase adsorbed layer thickness, and electrostatic and/or covalent complexation. The objective of this investigation was to establish the conditions by which cooperative interactions between MG and WP or C take place, through rheological parameters changes in concentrated O/W emulsions. O/W emulsions were made (45%(w/w) soybean oil and 55%(w/w) aqueous phase, containing 2.75% (w/w) WP or C). Small-deformation dynamic viscoelasticity was studied with a Physica MCR 300 rheometer with a double gap concentric cylinder measuring system. Oscillatory measurements were used to determine the storage (G´) and loss (G´´) moduli, over the frequency range 10-4 to 10 Hz at 25 °C. MG solutions of the appropriate concentration were mixed with the freshly prepared emulsions to give emulsions (40 %(w/w) oil, 2.44%(w/w) WP or C) containing various concentrations of MG. pH had a tremendous effect on biopolymer interactions. Both WP and C emulsions showed an increase in G´ with increasing MG concentration. G´ and G´´ behavior with frequency showed that as MG concentration increased G´>>G´´ so that the viscoelastic behavior changed from weak gel (frequency dependent) to strong gel (frequency independent) up to a frequency of around 6 after which a drop in G´ is observed particularly in C-MG interactions. This behavior is observed at pH 4 where WP is charged positively, and C and MG presumably have equivalent opposite charge densities. MG provides increased stability to O/W emulsions stabilized with WP or C.
Session 29B, Food Chemistry: Lipids, antioxidants and emulsifiers
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