Specific salt effects on the formation and thermal transitions among β-lactoglobulin and pectin electrostatic complexes
Abstract
Factors of ion specificity and ionic strength (I~0-100) were studied in the electrostatic complex formation and protein particle formation by thermal treatment for a β-lactoglobulin and pectin system. &zgr;-potential showed β-lactoglobulin and pectin began to interact near pH 5.50 and interactions were strengthened with decrease in pH. Visible light turbidimetry and light scattering at 90° revealed a trend in critical pH transitions for electrostatic complex formation based on both the ionic strength and the anion of the salt species, while effects of the monovalent cation was insignificant. Critical pH values for complex formation and separation (pHc and pH&PHgr;) decreased with increasing ionic strength, with no significant differences seen between chloride and thiocyanate salts. The ionic strength equivalency of sulfate salts caused significant differences to pHc values, indicating that both ionic strength and specific ion effects influence complex formation. Heat-treatment at 80°C of the β-lactoglobulin/pectin complexes at pH 4.50 led to the creation of particles with a diameter of 200-400. Light scattering revealed particles at pH 4.50 were significantly smaller than those at pH 4.75. Morphological characterization of particles at pH 4.50 with KCl concentrations of 50 mm and greater revealed disruption in particle structure from rounded to more amorphous shapes and possible flocculation of particles. Turbidimetry development of complex and heat-treated particles during heat treatment was significantly different from the protein, alone, demonstrating a specific shielding effect on protein-polysaccharide interactions. Ion effects on particle size of heat-treated complexes is a simple means to reliably control particle formation for purposes of controlled release or modified colloidal flow.
Degree
M.S.
Advisors
Jones, Purdue University.
Subject Area
Food Science|Physical chemistry|Agricultural engineering
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