Influence of the overall charge and local charge density of pectin on the complex formation between pectin and beta-lactoglobulin

Autor: B.L.H.M. Sperber, Henk A. Schols, Alphons G. J. Voragen, Martien A. Cohen Stuart, Willem Norde
Jazyk: angličtina
Rok vydání: 2009
Předmět:
conformation
STABILIZATION
Pectin
Laboratorium voor Fysische chemie en Kolloïdkunde
State diagrams
General Chemical Engineering
Ionic bonding
Polysaccharide-protein complexes
AQUEOUS-SOLUTION
Colloid
DEPENDENCE
bovine serum-albumin
Organic chemistry
BOVINE SERUM-ALBUMIN
Physical Chemistry and Colloid Science
Food Chemistry
beta-Lactoglobulin
Chemistry
digestive
oral
and skin physiology
food and beverages
Charge density
Electrostatics
Polyelectrolyte
stabilization
CONFORMATION
POLYELECTROLYTES
ACID
carrageenan
acid
aqueous-solution
WHEY PROTEINS
animal structures
food.ingredient
macromolecular substances
complex mixtures
polyelectrolytes
food
Dynamic light scattering
Levensmiddelenchemie
Charge regulation
COACERVATION
VLAG
Electrostatic interactions
CARRAGEENAN
dependence
General Chemistry
Chemical engineering
whey proteins
Ionic strength
coacervation
Food Science
Zdroj: Food hydrocolloids, 23(3), 765-772. ELSEVIER SCI LTD
Food Hydrocolloids, 23(3), 765-772
Food Hydrocolloids 23 (2009) 3
ISSN: 0268-005X
Popis: The complex formation between beta-lactoglobulin (beta-lg) and pectin is studied using pectins with different physicochemical characteristics. Pectin allows for the control of both the overall charge by degree of methyl-esterification as well as local charge density by the degree of blockiness. Varying local charge density, at equal overall charge is a parameter that is not available for synthetic polymers and is of key importance in the complex formation between oppositely charged (bio)polymers. LMP is a pectin with a high overall charge and high local charge density; HMPB arid HMPR are pectins with a low overall charge, but a high and low local charge density, respectively. Dynamic light scattering (DLS) titrations identified pH(c), the pH where soluble complexes of beta-lg and pectin are formed and pH phi, the PH of phase separation, both as a function of ionic strength. pH(c) decreased with increasing ionic strength for all pectins and was used in a theoretical model that showed local charge density of the pectin to control the onset of complex formation. pH phi passed through a maximum with increasing ionic strength for LMP because of shielding of repulsive interactions between beta-lg molecules bound to LMP, while attractive interactions were repressed at higher ionic strength. Potentiometric titrations of homo-molecular solutions and mixtures of beta-lg and pectin showed charge regulation in beta-lg-pectin complexes. Around pH 5.5-5.0 the pK(a)s of beta-lg ionic groups are increased to induce positive charge on the beta-lg molecule; around pH 4.5-3.5 the pK(a) values of the pectin ionic groups are lowered to retain negative charge on the pectin. Since pectins with high local charge density form complexes with beta-lg at higher ionic strength than pectins with low local charge density, pectin with a high local charge density is preferred in food systems where complex formation between protein and pectin is desired. (C) 2008 Elsevier Ltd. All rights reserved.
Databáze: OpenAIRE
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