73C-10 |
Kinetic adsorption of the Phaseolus lunatus globulins on aqueous solutions |
G. DÁVILA-ORTÍZ, L. J. Corzo-Rios, and G. F. Gutiérrez-López. Departamento de Graduados e Investigación en Alimentos., Escuela Nacional de Ciencias Biológicas. Instituto Politécnico Nacional, Carpio y Plan de Ayala S/N, Colonia Santo Tomas, México D.F., 11340, Mexico Many of the foods to the available on the market are emulsion and foam based goods. These food systems may be came unstable without the presence of a surfactant agent and phases may separate. Because of protein amphiphilic character, they may act as molecular interface surfactants. Legumes growing in the Mexican southeast include Phaseolus lunatus, also known as lime bean. The vegetable has high protein and carbohydrates content (26% and 60% respectively). In this work kinetics of adsorption of P. lunatus globulins on aqueous solutions were evaluated, aiming to determine its surfactant potential for food applications. Surface tension measurements were carried out with a Digital Analite 2141 tensiometer. 2 ml of protein solutions were added to phosphates buffer 0.05M (pH 8), to get the desired concentration. Studied variables were: concentration of protein (0.01 and 0.1% w/w), sucrose (0 and 0.5M) and NaCl (0 and 0.5 M) in aqueous media. NaCl and sucrose were tested independently. Presence of either compounds decreased final surface tension of globulins in all studied cases. Adsorption follows a first order kinetics, except for NaCl solutions which follow a second order process. Combination of NaCl and sucrose gave place to a synergic effect on surface tension depletion. Unfolding speed (K1) of 0.01% P. lunatus globulins solution decreased under the presence of tested solutes. 0.1% solutions did not showed a significative decreased of this parameter. Structural rearrangement rate (K2) is controlled by NaCl for both tested protein concentrations.
Session 73C, Food Engineering: Transport Processes and Kinetics
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